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Avoid returning System Error on clock skew #15

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jhrozek commented Sep 6, 2016

Rather return ERR_NETWORK_IO and at least let the user authenticate offline.

Adds two more return codes to the list of codes we translate to
ERR_NETWORK_IO.

Resolves:
    https://fedorahosted.org/sssd/ticket/3174
@pbrezina pbrezina self-assigned this Sep 6, 2016
@pbrezina pbrezina added the Accepted label Sep 6, 2016
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jhrozek commented Sep 6, 2016

Thanks for the ack, I would also like to ask @sumit-bose if he agrees with the change.

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pbrezina commented Sep 6, 2016

On 09/06/2016 01:51 PM, Jakub Hrozek wrote:

Thanks for the ack, I would also like to ask @sumit-bose
https://github.com/sumit-bose if he agrees with the change.

Btw since clock skew is not fatal anymore, is it possible for us to
actually perform online authentication?

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jhrozek commented Sep 6, 2016

On Tue, Sep 06, 2016 at 05:10:07AM -0700, Pavel Březina wrote:

On 09/06/2016 01:51 PM, Jakub Hrozek wrote:

Thanks for the ack, I would also like to ask @sumit-bose
https://github.com/sumit-bose if he agrees with the change.

Btw since clock skew is not fatal anymore, is it possible for us to
actually perform online authentication?

The TGT times are generated on the server and the error usually happens
only when the client attempts to use the TGT for something like FAST
tunnel establishment or TGT validation. See Sumit's reply here:
https://bugzilla.redhat.com/show_bug.cgi?id=1373427#c4

(that's why I wanted him to confirm this is a good idea)

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pbrezina commented Sep 6, 2016

On 09/06/2016 02:21 PM, Jakub Hrozek wrote:

On Tue, Sep 06, 2016 at 05:10:07AM -0700, Pavel Březina wrote:

On 09/06/2016 01:51 PM, Jakub Hrozek wrote:

Thanks for the ack, I would also like to ask @sumit-bose
https://github.com/sumit-bose if he agrees with the change.

Btw since clock skew is not fatal anymore, is it possible for us to
actually perform online authentication?

The TGT times are generated on the server and the error usually happens
only when the client attempts to use the TGT for something like FAST
tunnel establishment or TGT validation. See Sumit's reply here:
https://bugzilla.redhat.com/show_bug.cgi?id=1373427#c4

(that's why I wanted him to confirm this is a good idea)

AFAIK kinit's magic applies clock skew to the timestamp in the ticket
and compares times within the client's range. I'm just asking if there
is something similar we can do in SSSD:

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sumit-bose commented Sep 6, 2016

On Tue, Sep 06, 2016 at 05:37:14AM -0700, Pavel Březina wrote:

On 09/06/2016 02:21 PM, Jakub Hrozek wrote:

On Tue, Sep 06, 2016 at 05:10:07AM -0700, Pavel Březina wrote:

On 09/06/2016 01:51 PM, Jakub Hrozek wrote:

Thanks for the ack, I would also like to ask @sumit-bose
https://github.com/sumit-bose if he agrees with the change.

Btw since clock skew is not fatal anymore, is it possible for us to
actually perform online authentication?

The TGT times are generated on the server and the error usually happens
only when the client attempts to use the TGT for something like FAST
tunnel establishment or TGT validation. See Sumit's reply here:
https://bugzilla.redhat.com/show_bug.cgi?id=1373427#c4

(that's why I wanted him to confirm this is a good idea)

AFAIK kinit's magic applies clock skew to the timestamp in the ticket
and compares times within the client's range. I'm just asking if there
is something similar we can do in SSSD:

iirc this magic is applied to the timestamps used in the "default"
pre-authentication method where encrypted timestamps are send around.
This does not related to the timestamps in the tickets.

You are receiving this because you were mentioned.
Reply to this email directly or view it on GitHub:
#15 (comment)

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sumit-bose commented Sep 6, 2016

On Tue, Sep 06, 2016 at 04:51:26AM -0700, Jakub Hrozek wrote:

Thanks for the ack, I would also like to ask @sumit-bose if he agrees with the change.

Since we already handle other clock skew related error codes the same
way I think it is ok. But I wonder if a clock-skew is something which
qualifies for a syslog messages to make the admin aware that there is
something which needs fixing?

You are receiving this because you were mentioned.
Reply to this email directly or view it on GitHub:
#15 (comment)

@jhrozek jhrozek added Changes requested and removed Accepted labels Sep 6, 2016
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jhrozek commented Sep 6, 2016

good idea

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jhrozek commented Sep 7, 2016

On Tue, Sep 06, 2016 at 06:09:58AM -0700, Jakub Hrozek wrote:

good idea

ah, only when I started to implement this I realized it's already done :)

See:
https://github.com/SSSD/sssd/blob/master/src/providers/krb5/krb5_child.c#L1364
in the current master, KRB5_CHILD_DEBUG() expands into sss_log() as well
unconditionally.

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lslebodn commented Sep 13, 2016

On (07/09/16 10:13), Jakub Hrozek wrote:

On Tue, Sep 06, 2016 at 06:09:58AM -0700, Jakub Hrozek wrote:

good idea

ah, only when I started to implement this I realized it's already done :)

See:
https://github.com/SSSD/sssd/blob/master/src/providers/krb5/krb5_child.c#L1364
in the current master, KRB5_CHILD_DEBUG() expands into sss_log() as well
unconditionally.

Does it mean that the latest version of patch is Accepted?
Or what is a state of this patch?

LS

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sumit-bose commented Sep 13, 2016

I think it is still an ACK.

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lslebodn commented Sep 13, 2016

On (13/09/16 06:07), sumit-bose wrote:

I think it is still an ACK.

master:

LS

@jhrozek jhrozek added Pushed and removed Accepted labels Sep 13, 2016
@jhrozek jhrozek closed this Sep 13, 2016
@jhrozek jhrozek deleted the jhrozek:krb5skew branch Nov 25, 2016
fidencio added a commit to fidencio/sssd that referenced this pull request Dec 12, 2016
While debugging rhbz#1396912 some deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

The removal of those functions we lose some debug messages, which is the
least of problems now. Also instead of re-setting the watchdog timeout
in case of time-shift (please, see b8ceaeb for more info), let's just
re-set the timer's time.

Along with this commit, the function to teardown the watchdog has been
removed as it's not used anymore.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Dec 13, 2016
While debugging rhbz#1396912 some deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

The removal of those functions we lose some debug messages, which is the
least of problems now. Also instead of re-setting the watchdog timeout
in case of time-shift (please, see b8ceaeb for more info), let's just
exit the let the monitor restart the process.

A proper fix for the clock screw situation should be implemented on
samba's side, by having tevent using monotonic (or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Dec 20, 2016
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and a single byte is written to this pipe (which
is an async-signal-safe operation) and the logic currently done by the
timer handler will be done inside the fd handler in a safe way.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Dec 21, 2016
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by _exit(). Personally I don't
think is worth the trouble to try to log those messages properly in this
specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Jan 3, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by _exit(). Personally I don't
think is worth the trouble to try to log those messages properly in this
specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Jan 3, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by _exit(). Personally I don't
think is worth the trouble to try to log those messages properly in this
specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Jan 3, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by kill(-getpgrp(), SIGTERM).
Personally I don't think is worth the trouble to try to log those messages
properly in this specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Jan 5, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by _exit(1). Personally I don't
think is worth the trouble to try to log those messages properly in
this specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Jan 9, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by kill(-getpgrp(), SIGTERM).
Personally I don't think is worth the trouble to try to log those messages
properly in this specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Jan 9, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by kill(-getpgrp(), SIGTERM).
Personally I don't think is worth the trouble to try to log those messages
properly in this specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
fidencio added a commit to fidencio/sssd that referenced this pull request Jan 10, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by kill(-getpgrp(), SIGTERM) (or
_exit(1) considering the cases where setting up the process group during
the server_setup() has failed).
Personally I don't think is worth the trouble to try to log those messages
properly in this specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    SSSD#1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    SSSD#2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    SSSD#3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    SSSD#4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    SSSD#5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    SSSD#6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
jhrozek pushed a commit that referenced this pull request Jan 25, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by kill(-getpgrp(), SIGTERM) (or
_exit(1) considering the cases where setting up the process group during
the server_setup() has failed).
Personally I don't think is worth the trouble to try to log those messages
properly in this specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    #1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    #2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    #3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    #4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    #5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    #6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    #7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    #8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    #9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    #10 <signal handler called>
    #11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    #12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    #13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    #14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    #15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    #16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    #17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    #18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    #19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    #20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    #21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    #22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    #23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    #24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    #25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    #26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    #27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    #28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    #29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    #30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    #31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    #32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    #33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    #34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    #35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    #36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    #37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    #38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    #39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    #40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    #41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    #42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    #43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    #44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    #45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    #46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    #47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    #48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    #49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    #50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    #51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    #52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    #53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    #54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    #55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    #56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    #57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    #58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    #59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    #60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Pavel Březina <pbrezina@redhat.com>
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
jhrozek pushed a commit that referenced this pull request Jan 25, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by kill(-getpgrp(), SIGTERM) (or
_exit(1) considering the cases where setting up the process group during
the server_setup() has failed).
Personally I don't think is worth the trouble to try to log those messages
properly in this specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    #1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    #2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    #3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    #4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    #5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    #6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    #7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    #8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    #9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    #10 <signal handler called>
    #11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    #12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    #13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    #14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    #15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    #16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    #17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    #18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    #19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    #20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    #21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    #22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    #23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    #24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    #25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    #26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    #27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    #28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    #29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    #30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    #31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    #32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    #33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    #34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    #35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    #36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    #37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    #38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    #39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    #40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    #41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    #42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    #43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    #44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    #45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    #46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    #47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    #48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    #49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    #50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    #51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    #52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    #53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    #54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    #55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    #56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    #57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    #58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    #59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    #60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Pavel Březina <pbrezina@redhat.com>
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
(cherry picked from commit e6a5f8c)
jhrozek added a commit to jhrozek/sssd that referenced this pull request Jul 20, 2017
While debugging rhbz#1396912 a deadlock on sssd_be was noticed[0] and
it's been caused by the use of non async-signal-safe functions from the
signal_handler (please, see man 7 signal for more info about which are
the async-signal-safe functions that can be used).

In order to work this situation around a pipe has been added to the
watchdog_ctx structure and, in case of clock screw,  a single byte is
written to this pipe (which is an async-signal-safe operation) and the
logic currently done by the timer handler to reset the watchdog will be
done inside the fd handler in a safe way.

With this patch we ended up losing some debug messages as
orderly_shutdown() has been replaced by kill(-getpgrp(), SIGTERM) (or
_exit(1) considering the cases where setting up the process group during
the server_setup() has failed).
Personally I don't think is worth the trouble to try to log those messages
properly in this specific case.

It's really worth to mention that a proper fix the clock screw situation
should be implemented on samba's side, by having tevent using monotonic
(or boottime) clock.

[0]:
  [root@dusan ~]# pstack 17922
    #0  __lll_lock_wait_private () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
    #1  0x00007fe707d04f93 in _L_lock_14932 () from /lib64/libc.so.6
    #2  0x00007fe707d02013 in __GI___libc_malloc (bytes=140630248638304, bytes@entry=15) at malloc.c:2891
    #3  0x00007fe707d0888a in __GI___strdup (s=0x7fe707dff4f7 "/etc/localtime") at strdup.c:42
    #4  0x00007fe707d31b61 in tzset_internal (always=<optimized out>, explicit=explicit@entry=1) at tzset.c:438
    #5  0x00007fe707d32523 in __tz_convert (timer=timer@entry=0x7ffcd5d2b090, use_localtime=use_localtime@entry=1, tp=tp@entry=0x7fe708041d40 <_tmbuf>) at tzset.c:621
    #6  0x00007fe707d30521 in __GI_localtime (t=t@entry=0x7ffcd5d2b090) at localtime.c:42
    SSSD#7  0x00007fe70886c7b0 in sss_vdebug_fn (file=<optimized out>, line=<optimized out>, function=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=16, flags=flags@entry=0, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n", ap=ap@entry=0x7ffcd5d2b130) at src/util/debug.c:248
    SSSD#8  0x00007fe70886c995 in sss_debug_fn (file=file@entry=0x7fe70bff263b "src/util/util_watchdog.c", line=line@entry=82, function=function@entry=0x7fe70bff27f0 <__FUNCTION__.9379> "watchdog_handler", level=level@entry=16, format=format@entry=0x7fe70bff2760 "Watchdog timer overflow, killing process!\n") at src/util/debug.c:284
    SSSD#9  0x00007fe70bfdb409 in watchdog_handler (sig=<optimized out>) at src/util/util_watchdog.c:81
    SSSD#10 <signal handler called>
    SSSD#11 0x00007fe707cff664 in _int_malloc (av=av@entry=0x7fe70803c760 <main_arena>, bytes=bytes@entry=151) at malloc.c:3494
    SSSD#12 0x00007fe707d01fbc in __GI___libc_malloc (bytes=bytes@entry=151) at malloc.c:2893
    SSSD#13 0x00007fe708450749 in __talloc_with_prefix (prefix_len=0, size=55, context=0x7fe718373210) at ../talloc.c:668
    SSSD#14 __talloc (size=55, context=0x7fe718373210) at ../talloc.c:708
    SSSD#15 _talloc_named_const (name=0x7fe70bb7015d "../common/ldb_pack.c:425", size=55, context=0x7fe718373210) at ../talloc.c:865
    SSSD#16 talloc_named_const (context=<optimized out>, size=size@entry=55, name=name@entry=0x7fe70bb7015d "../common/ldb_pack.c:425") at ../talloc.c:1606
    SSSD#17 0x00007fe70bb61803 in ldb_unpack_data_only_attr_list (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=0x7fe7184aa1e0, list=list@entry=0x0, list_size=list_size@entry=0, nb_elements_in_db=nb_elements_in_db@entry=0x0) at ../common/ldb_pack.c:425
    SSSD#18 0x00007fe70bb61a7d in ldb_unpack_data (ldb=ldb@entry=0x7fe70e4d52c0, data=data@entry=0x7ffcd5d2b990, message=<optimized out>) at ../common/ldb_pack.c:470
    SSSD#19 0x00007fe6fdc29b46 in ltdb_parse_data_unpack (key=..., data=..., private_data=0x7ffcd5d2ba70) at ../ldb_tdb/ldb_search.c:249
    SSSD#20 0x00007fe70a5e0a24 in tdb_parse_data (tdb=tdb@entry=0x7fe70e4eaa10, key=..., offset=15619748, len=414772, parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/io.c:637
    SSSD#21 0x00007fe70a5dc1fc in tdb_parse_record (tdb=0x7fe70e4eaa10, key=..., parser=parser@entry=0x7fe6fdc29b10 <ltdb_parse_data_unpack>, private_data=private_data@entry=0x7ffcd5d2ba70) at ../common/tdb.c:253
    SSSD#22 0x00007fe6fdc29e7b in ltdb_search_dn1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, msg=msg@entry=0x7fe7184aa1e0) at ../ldb_tdb/ldb_search.c:287
    SSSD#23 0x00007fe6fdc2acbb in ltdb_dn_list_load (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183c4940, list=list@entry=0x7fe7183c3a30) at ../ldb_tdb/ldb_index.c:181
    SSSD#24 0x00007fe6fdc2bbbb in ltdb_index_add1 (module=module@entry=0x7fe70e4eab50, dn=dn@entry=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", v_idx=v_idx@entry=0, el=<optimized out>, el=<optimized out>) at ../ldb_tdb/ldb_index.c:1134
    SSSD#25 0x00007fe6fdc2c62c in ltdb_index_add_el (el=0x7fe7184aa3e0, dn=0x7fe7183bf3e0 "name=testuser7045@domain.com,cn=users,cn=DOMAIN.COM,cn=sysdb", module=0x7fe70e4eab50) at ../ldb_tdb/ldb_index.c:1180
    SSSD#26 ltdb_index_add_element (module=module@entry=0x7fe70e4eab50, dn=<optimized out>, el=el@entry=0x7fe7184aa3e0) at ../ldb_tdb/ldb_index.c:1290
    SSSD#27 0x00007fe6fdc290bb in ltdb_modify_internal (module=module@entry=0x7fe70e4eab50, msg=0x7fe7183bf0c0, req=req@entry=0x7fe7183bdc10) at ../ldb_tdb/ldb_tdb.c:903
    SSSD#28 0x00007fe6fdc2958a in ltdb_modify (ctx=0x7fe7183c2950, ctx=0x7fe7183c2950) at ../ldb_tdb/ldb_tdb.c:998
    SSSD#29 ltdb_callback (ev=<optimized out>, te=<optimized out>, t=..., private_data=<optimized out>) at ../ldb_tdb/ldb_tdb.c:1380
    SSSD#30 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4d2890) at ../tevent_timed.c:341
    SSSD#31 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4d2890, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#32 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4d2890, location=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent_standard.c:114
    SSSD#33 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4d2890, location=location@entry=0x7fe70bb72ec5 "../common/ldb.c:631") at ../tevent.c:533
    SSSD#34 0x00007fe70bb6bc4f in ldb_wait (handle=0x7fe7183c4530, type=<optimized out>) at ../common/ldb.c:631
    SSSD#35 0x00007fe70bb6c793 in ldb_autotransaction_request (ldb=0x7fe70e4d52c0, req=0x7fe7183bdc10) at ../common/ldb.c:573
    SSSD#36 0x00007fe70bb6d263 in ldb_modify (ldb=ldb@entry=0x7fe70e4d52c0, message=<optimized out>) at ../common/ldb.c:1655
    SSSD#37 0x00007fe70bfa2ab5 in sysdb_set_cache_entry_attr (ldb=0x7fe70e4d52c0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bf680, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1159
    SSSD#38 0x00007fe70bfa304d in sysdb_rep_ts_entry_attr (sysdb=0x7fe70e4eadd0, attrs=0x7fe7183bf680, entry_dn=0x7fe7183c4760) at src/db/sysdb_ops.c:1218
    SSSD#39 sysdb_set_ts_entry_attr (sysdb=sysdb@entry=0x7fe70e4eadd0, entry_dn=entry_dn@entry=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1248
    SSSD#40 0x00007fe70bfa4aa9 in sysdb_set_entry_attr (sysdb=0x7fe70e4eadd0, entry_dn=0x7fe7183c4760, attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1199
    SSSD#41 0x00007fe70bfa4b5f in sysdb_set_user_attr (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", attrs=attrs@entry=0x7fe7183bb840, mod_op=mod_op@entry=2) at src/db/sysdb_ops.c:1285
    SSSD#42 0x00007fe70bfa58c3 in sysdb_add_user (domain=domain@entry=0x7fe70e4d62f0, name=name@entry=0x7fe7183c01f0 "testuser7045@domain.com", uid=uid@entry=1415408147, gid=<optimized out>, gid@entry=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:1928
    SSSD#43 0x00007fe70bfab271 in sysdb_store_new_user (now=1481105315, cache_timeout=5400, attrs=0x7fe7183bb840, orig_dn=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", shell=0x0, homedir=0x0, gecos=0x7fe710465d00 "Test User7045", gid=1415400513, uid=1415408147, name=0x7fe7183c01f0 "testuser7045@domain.com", domain=0x7fe70e4d62f0) at src/db/sysdb_ops.c:2549
    SSSD#44 sysdb_store_user (domain=domain@entry=0x7fe70e4d62f0, name=0x7fe7183c01f0 "testuser7045@domain.com", pwd=pwd@entry=0x0, uid=1415408147, gid=1415400513, gecos=gecos@entry=0x7fe710465d00 "Test User7045", homedir=homedir@entry=0x0, shell=shell@entry=0x0, orig_dn=orig_dn@entry=0x7fe710465940 "CN=Test User7045,OU=Sales,DC=DOMAIN,DC=COM", attrs=attrs@entry=0x7fe7183bb840, remove_attrs=0x7fe7183c08a0, cache_timeout=cache_timeout@entry=5400, now=now@entry=1481105315) at src/db/sysdb_ops.c:2499
    SSSD#45 0x00007fe6fba0d9f9 in sdap_save_user (memctx=memctx@entry=0x7fe70e544ee0, opts=opts@entry=0x7fe70e518400, dom=dom@entry=0x7fe70e4d62f0, attrs=<optimized out>, _usn_value=_usn_value@entry=0x7ffcd5d2c260, now=now@entry=1481105315) at src/providers/ldap/sdap_async_users.c:509
    SSSD#46 0x00007fe6fba0df9a in sdap_save_users (memctx=memctx@entry=0x7fe70e544e40, sysdb=0x7fe70e4eadd0, dom=0x7fe70e4d62f0, opts=0x7fe70e518400, users=<optimized out>, num_users=10006, _usn_value=_usn_value@entry=0x7fe70e544e60) at src/providers/ldap/sdap_async_users.c:572
    SSSD#47 0x00007fe6fba0e460 in sdap_get_users_done (subreq=<optimized out>) at src/providers/ldap/sdap_async_users.c:938
    SSSD#48 0x00007fe6fba0c9d5 in sdap_search_user_process (subreq=0x0) at src/providers/ldap/sdap_async_users.c:814
    SSSD#49 0x00007fe6fba07379 in generic_ext_search_handler (subreq=0x0, opts=<optimized out>) at src/providers/ldap/sdap_async.c:1689
    SSSD#50 0x00007fe6fba0991b in sdap_get_generic_op_finished (op=<optimized out>, reply=<optimized out>, error=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:1621
    SSSD#51 0x00007fe6fba083cd in sdap_process_message (ev=<optimized out>, sh=<optimized out>, msg=0x7fe70e5f9ce0) at src/providers/ldap/sdap_async.c:353
    SSSD#52 sdap_process_result (ev=<optimized out>, pvt=<optimized out>) at src/providers/ldap/sdap_async.c:197
    SSSD#53 0x00007fe708664b4f in tevent_common_loop_timer_delay (ev=ev@entry=0x7fe70e4cbc30) at ../tevent_timed.c:341
    SSSD#54 0x00007fe708665b5a in epoll_event_loop_once (ev=0x7fe70e4cbc30, location=<optimized out>) at ../tevent_epoll.c:911
    SSSD#55 0x00007fe708664257 in std_event_loop_once (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:114
    SSSD#56 0x00007fe70866040d in _tevent_loop_once (ev=ev@entry=0x7fe70e4cbc30, location=location@entry=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:533
    SSSD#57 0x00007fe7086605ab in tevent_common_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent.c:637
    SSSD#58 0x00007fe7086641f7 in std_event_loop_wait (ev=0x7fe70e4cbc30, location=0x7fe70bfee8e7 "src/util/server.c:702") at ../tevent_standard.c:140
    SSSD#59 0x00007fe70bfd1993 in server_loop (main_ctx=0x7fe70e4cd080) at src/util/server.c:702
    SSSD#60 0x00007fe70c84cb82 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:587

Resolves:
https://fedorahosted.org/sssd/ticket/3266

Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Pavel Březina <pbrezina@redhat.com>
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
(cherry picked from commit e6a5f8c)
(cherry picked from commit 0606a71)
lslebodn pushed a commit to lslebodn/sssd that referenced this pull request Jun 28, 2019
The function remove_duplicate_group_members might return EOK also in the middle
of function but return parameter was not set with right data.
Processing continued in the function save_group but there was a
dereference of NULL pointer.

Introduced in: https://pagure.io/SSSD/sssd/issue/3931

Crash:
  (gdb) bt
  #0  0x00007fb4ce4a9ac5 in save_group (sysdb=sysdb@entry=0x55c9a0efb230, dom=dom@entry=0x55c9a0efb420, grp=grp@entry=0x55c9a0f370f0, real_name=0x55c9a0f47340 "nobody@ldap",
      alias=alias@entry=0x0) at src/providers/proxy/proxy_id.c:748
  #1  0x00007fb4ce4aa600 in get_gr_gid (mem_ctx=mem_ctx@entry=0x55c9a0f38be0, sysdb=sysdb@entry=0x55c9a0efb230, dom=dom@entry=0x55c9a0efb420, gid=99, now=<optimized out>,
      ctx=<optimized out>) at src/providers/proxy/proxy_id.c:1160
  SSSD#2  0x00007fb4ce4ac9e5 in get_initgr_groups_process (pwd=0x55c9a0f384a0, pwd=0x55c9a0f384a0, dom=0x55c9a0efb420, sysdb=0x55c9a0efb230, ctx=0x55c9a0f048e0, memctx=0x55c9a0f38be0)
      at src/providers/proxy/proxy_id.c:1553
  SSSD#3  get_initgr (i_name=<optimized out>, dom=0x55c9a0efb420, sysdb=<optimized out>, ctx=0x55c9a0f048e0, mem_ctx=0x55c9a0f38b70) at src/providers/proxy/proxy_id.c:1461
  SSSD#4  proxy_account_info (domain=0x55c9a0efb420, be_ctx=<optimized out>, data=<optimized out>, ctx=0x55c9a0f048e0, mem_ctx=0x55c9a0f38b70) at src/providers/proxy/proxy_id.c:1659
  SSSD#5  proxy_account_info_handler_send (mem_ctx=<optimized out>, id_ctx=0x55c9a0f048e0, data=<optimized out>, params=0x55c9a0f39790) at src/providers/proxy/proxy_id.c:1758
  SSSD#6  0x000055c99fc67677 in file_dp_request (_dp_req=<synthetic pointer>, req=0x55c9a0f39470, request_data=<optimized out>, dp_flags=1, method=DPM_ACCOUNT_HANDLER, target=DPT_ID,
      name=<optimized out>, domainname=0x55c9a0f39190 "LDAP", provider=0x55c9a0efe0e0, mem_ctx=<optimized out>) at src/providers/data_provider/dp_request.c:250
  SSSD#7  dp_req_send (mem_ctx=0x55c9a0f37b60, provider=provider@entry=0x55c9a0efe0e0, domain=domain@entry=0x55c9a0f39190 "LDAP", name=<optimized out>, target=target@entry=DPT_ID,
      method=method@entry=DPM_ACCOUNT_HANDLER, dp_flags=dp_flags@entry=1, request_data=0x55c9a0f37c00, _request_name=0x55c9a0f37b60) at src/providers/data_provider/dp_request.c:295
  SSSD#8  0x000055c99fc6a132 in dp_get_account_info_send (mem_ctx=<optimized out>, ev=0x55c9a0eddbc0, sbus_req=<optimized out>, provider=0x55c9a0efe0e0, dp_flags=1,
      entry_type=<optimized out>, filter=0x55c9a0f358d0 "name=nobody@ldap", domain=0x55c9a0f39190 "LDAP", extra=0x55c9a0f354a0 "") at src/providers/data_provider/dp_target_id.c:528
  SSSD#9  0x00007fb4da35265b in _sbus_sss_invoke_in_uusss_out_qus_step (ev=0x55c9a0eddbc0, te=<optimized out>, tv=..., private_data=<optimized out>) at src/sss_iface/sbus_sss_invokers.c:2847
  SSSD#10 0x00007fb4d9cfb1cf in tevent_common_invoke_timer_handler () from /lib64/libtevent.so.0
  SSSD#11 0x00007fb4d9cfb339 in tevent_common_loop_timer_delay () from /lib64/libtevent.so.0
  SSSD#12 0x00007fb4d9cfc2f9 in epoll_event_loop_once () from /lib64/libtevent.so.0
  SSSD#13 0x00007fb4d9cfa7b7 in std_event_loop_once () from /lib64/libtevent.so.0
  SSSD#14 0x00007fb4d9cf5b5d in _tevent_loop_once () from /lib64/libtevent.so.0
  SSSD#15 0x00007fb4d9cf5d8b in tevent_common_loop_wait () from /lib64/libtevent.so.0
  SSSD#16 0x00007fb4d9cfa757 in std_event_loop_wait () from /lib64/libtevent.so.0
  SSSD#17 0x00007fb4dd955ac3 in server_loop (main_ctx=0x55c9a0edf090) at src/util/server.c:724
  SSSD#18 0x000055c99fc59760 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:747
  (gdb) l
  (gdb) bt
  #0  0x00007fb4ce4a9ac5 in save_group (sysdb=sysdb@entry=0x55c9a0efb230, dom=dom@entry=0x55c9a0efb420, grp=grp@entry=0x55c9a0f370f0, real_name=0x55c9a0f47340 "nobody@ldap",
      alias=alias@entry=0x0) at src/providers/proxy/proxy_id.c:748
  #1  0x00007fb4ce4aa600 in get_gr_gid (mem_ctx=mem_ctx@entry=0x55c9a0f38be0, sysdb=sysdb@entry=0x55c9a0efb230, dom=dom@entry=0x55c9a0efb420, gid=99, now=<optimized out>,
      ctx=<optimized out>) at src/providers/proxy/proxy_id.c:1160
  SSSD#2  0x00007fb4ce4ac9e5 in get_initgr_groups_process (pwd=0x55c9a0f384a0, pwd=0x55c9a0f384a0, dom=0x55c9a0efb420, sysdb=0x55c9a0efb230, ctx=0x55c9a0f048e0, memctx=0x55c9a0f38be0)
      at src/providers/proxy/proxy_id.c:1553
  SSSD#3  get_initgr (i_name=<optimized out>, dom=0x55c9a0efb420, sysdb=<optimized out>, ctx=0x55c9a0f048e0, mem_ctx=0x55c9a0f38b70) at src/providers/proxy/proxy_id.c:1461
  SSSD#4  proxy_account_info (domain=0x55c9a0efb420, be_ctx=<optimized out>, data=<optimized out>, ctx=0x55c9a0f048e0, mem_ctx=0x55c9a0f38b70) at src/providers/proxy/proxy_id.c:1659
  SSSD#5  proxy_account_info_handler_send (mem_ctx=<optimized out>, id_ctx=0x55c9a0f048e0, data=<optimized out>, params=0x55c9a0f39790) at src/providers/proxy/proxy_id.c:1758
  SSSD#6  0x000055c99fc67677 in file_dp_request (_dp_req=<synthetic pointer>, req=0x55c9a0f39470, request_data=<optimized out>, dp_flags=1, method=DPM_ACCOUNT_HANDLER, target=DPT_ID,
      name=<optimized out>, domainname=0x55c9a0f39190 "LDAP", provider=0x55c9a0efe0e0, mem_ctx=<optimized out>) at src/providers/data_provider/dp_request.c:250
  SSSD#7  dp_req_send (mem_ctx=0x55c9a0f37b60, provider=provider@entry=0x55c9a0efe0e0, domain=domain@entry=0x55c9a0f39190 "LDAP", name=<optimized out>, target=target@entry=DPT_ID,
      method=method@entry=DPM_ACCOUNT_HANDLER, dp_flags=dp_flags@entry=1, request_data=0x55c9a0f37c00, _request_name=0x55c9a0f37b60) at src/providers/data_provider/dp_request.c:295
  SSSD#8  0x000055c99fc6a132 in dp_get_account_info_send (mem_ctx=<optimized out>, ev=0x55c9a0eddbc0, sbus_req=<optimized out>, provider=0x55c9a0efe0e0, dp_flags=1,
      entry_type=<optimized out>, filter=0x55c9a0f358d0 "name=nobody@ldap", domain=0x55c9a0f39190 "LDAP", extra=0x55c9a0f354a0 "") at src/providers/data_provider/dp_target_id.c:528
  SSSD#9  0x00007fb4da35265b in _sbus_sss_invoke_in_uusss_out_qus_step (ev=0x55c9a0eddbc0, te=<optimized out>, tv=..., private_data=<optimized out>) at src/sss_iface/sbus_sss_invokers.c:2847
  SSSD#10 0x00007fb4d9cfb1cf in tevent_common_invoke_timer_handler () from /lib64/libtevent.so.0
  SSSD#11 0x00007fb4d9cfb339 in tevent_common_loop_timer_delay () from /lib64/libtevent.so.0
  SSSD#12 0x00007fb4d9cfc2f9 in epoll_event_loop_once () from /lib64/libtevent.so.0
  SSSD#13 0x00007fb4d9cfa7b7 in std_event_loop_once () from /lib64/libtevent.so.0
  SSSD#14 0x00007fb4d9cf5b5d in _tevent_loop_once () from /lib64/libtevent.so.0
  SSSD#15 0x00007fb4d9cf5d8b in tevent_common_loop_wait () from /lib64/libtevent.so.0
  SSSD#16 0x00007fb4d9cfa757 in std_event_loop_wait () from /lib64/libtevent.so.0
  SSSD#17 0x00007fb4dd955ac3 in server_loop (main_ctx=0x55c9a0edf090) at src/util/server.c:724
  SSSD#18 0x000055c99fc59760 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:747
  (gdb) l
  733         ret = remove_duplicate_group_members(tmp_ctx, grp, &ngroup);
  734         if (ret != EOK) {
  735             DEBUG(SSSDBG_CRIT_FAILURE, "Failed to remove duplicate group member     s\n");
  736             goto done;
  737         }
  738
  739         DEBUG_GR_MEM(SSSDBG_TRACE_LIBS, ngroup);
  740
  741         ret = sysdb_transaction_start(sysdb);
  742         if (ret != EOK) {
  743             DEBUG(SSSDBG_CRIT_FAILURE, "Failed to start transaction\n");
  744             goto done;
  745         }
  746         in_transaction = true;
  747
  748         if (ngroup->gr_mem && ngroup->gr_mem[0]) {
  749             attrs = sysdb_new_attrs(tmp_ctx);
  750             if (!attrs) {
  751                 DEBUG(SSSDBG_CRIT_FAILURE, "Allocation error?!\n");
  752                 ret = ENOMEM;
  (gdb) p ngroup
  $1 = (struct group *) 0x0
  743             DEBUG(SSSDBG_CRIT_FAILURE, "Failed to start transaction\n");
  744             goto done;
  745         }
  746         in_transaction = true;
  747
  748         if (ngroup->gr_mem && ngroup->gr_mem[0]) {
  749             attrs = sysdb_new_attrs(tmp_ctx);
  750             if (!attrs) {
  751                 DEBUG(SSSDBG_CRIT_FAILURE, "Allocation error?!\n");
  752                 ret = ENOMEM;
  (gdb) p ngroup
  $1 = (struct group *) 0x0

Merges: https://pagure.io/SSSD/sssd/pull-request/4036

Resolves:
https://pagure.io/SSSD/sssd/issue/XXXX
jhrozek added a commit that referenced this pull request Jun 28, 2019
The function remove_duplicate_group_members might return EOK also in the middle
of function but return parameter was not set with right data.
Processing continued in the function save_group but there was a
dereference of NULL pointer.

Introduced in: https://pagure.io/SSSD/sssd/issue/3931

Crash:
  (gdb) bt
  #0  0x00007fb4ce4a9ac5 in save_group (sysdb=sysdb@entry=0x55c9a0efb230, dom=dom@entry=0x55c9a0efb420, grp=grp@entry=0x55c9a0f370f0, real_name=0x55c9a0f47340 "nobody@ldap",
      alias=alias@entry=0x0) at src/providers/proxy/proxy_id.c:748
  #1  0x00007fb4ce4aa600 in get_gr_gid (mem_ctx=mem_ctx@entry=0x55c9a0f38be0, sysdb=sysdb@entry=0x55c9a0efb230, dom=dom@entry=0x55c9a0efb420, gid=99, now=<optimized out>,
      ctx=<optimized out>) at src/providers/proxy/proxy_id.c:1160
  #2  0x00007fb4ce4ac9e5 in get_initgr_groups_process (pwd=0x55c9a0f384a0, pwd=0x55c9a0f384a0, dom=0x55c9a0efb420, sysdb=0x55c9a0efb230, ctx=0x55c9a0f048e0, memctx=0x55c9a0f38be0)
      at src/providers/proxy/proxy_id.c:1553
  #3  get_initgr (i_name=<optimized out>, dom=0x55c9a0efb420, sysdb=<optimized out>, ctx=0x55c9a0f048e0, mem_ctx=0x55c9a0f38b70) at src/providers/proxy/proxy_id.c:1461
  #4  proxy_account_info (domain=0x55c9a0efb420, be_ctx=<optimized out>, data=<optimized out>, ctx=0x55c9a0f048e0, mem_ctx=0x55c9a0f38b70) at src/providers/proxy/proxy_id.c:1659
  #5  proxy_account_info_handler_send (mem_ctx=<optimized out>, id_ctx=0x55c9a0f048e0, data=<optimized out>, params=0x55c9a0f39790) at src/providers/proxy/proxy_id.c:1758
  #6  0x000055c99fc67677 in file_dp_request (_dp_req=<synthetic pointer>, req=0x55c9a0f39470, request_data=<optimized out>, dp_flags=1, method=DPM_ACCOUNT_HANDLER, target=DPT_ID,
      name=<optimized out>, domainname=0x55c9a0f39190 "LDAP", provider=0x55c9a0efe0e0, mem_ctx=<optimized out>) at src/providers/data_provider/dp_request.c:250
  #7  dp_req_send (mem_ctx=0x55c9a0f37b60, provider=provider@entry=0x55c9a0efe0e0, domain=domain@entry=0x55c9a0f39190 "LDAP", name=<optimized out>, target=target@entry=DPT_ID,
      method=method@entry=DPM_ACCOUNT_HANDLER, dp_flags=dp_flags@entry=1, request_data=0x55c9a0f37c00, _request_name=0x55c9a0f37b60) at src/providers/data_provider/dp_request.c:295
  #8  0x000055c99fc6a132 in dp_get_account_info_send (mem_ctx=<optimized out>, ev=0x55c9a0eddbc0, sbus_req=<optimized out>, provider=0x55c9a0efe0e0, dp_flags=1,
      entry_type=<optimized out>, filter=0x55c9a0f358d0 "name=nobody@ldap", domain=0x55c9a0f39190 "LDAP", extra=0x55c9a0f354a0 "") at src/providers/data_provider/dp_target_id.c:528
  #9  0x00007fb4da35265b in _sbus_sss_invoke_in_uusss_out_qus_step (ev=0x55c9a0eddbc0, te=<optimized out>, tv=..., private_data=<optimized out>) at src/sss_iface/sbus_sss_invokers.c:2847
  #10 0x00007fb4d9cfb1cf in tevent_common_invoke_timer_handler () from /lib64/libtevent.so.0
  #11 0x00007fb4d9cfb339 in tevent_common_loop_timer_delay () from /lib64/libtevent.so.0
  #12 0x00007fb4d9cfc2f9 in epoll_event_loop_once () from /lib64/libtevent.so.0
  #13 0x00007fb4d9cfa7b7 in std_event_loop_once () from /lib64/libtevent.so.0
  #14 0x00007fb4d9cf5b5d in _tevent_loop_once () from /lib64/libtevent.so.0
  #15 0x00007fb4d9cf5d8b in tevent_common_loop_wait () from /lib64/libtevent.so.0
  #16 0x00007fb4d9cfa757 in std_event_loop_wait () from /lib64/libtevent.so.0
  #17 0x00007fb4dd955ac3 in server_loop (main_ctx=0x55c9a0edf090) at src/util/server.c:724
  #18 0x000055c99fc59760 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:747
  (gdb) l
  (gdb) bt
  #0  0x00007fb4ce4a9ac5 in save_group (sysdb=sysdb@entry=0x55c9a0efb230, dom=dom@entry=0x55c9a0efb420, grp=grp@entry=0x55c9a0f370f0, real_name=0x55c9a0f47340 "nobody@ldap",
      alias=alias@entry=0x0) at src/providers/proxy/proxy_id.c:748
  #1  0x00007fb4ce4aa600 in get_gr_gid (mem_ctx=mem_ctx@entry=0x55c9a0f38be0, sysdb=sysdb@entry=0x55c9a0efb230, dom=dom@entry=0x55c9a0efb420, gid=99, now=<optimized out>,
      ctx=<optimized out>) at src/providers/proxy/proxy_id.c:1160
  #2  0x00007fb4ce4ac9e5 in get_initgr_groups_process (pwd=0x55c9a0f384a0, pwd=0x55c9a0f384a0, dom=0x55c9a0efb420, sysdb=0x55c9a0efb230, ctx=0x55c9a0f048e0, memctx=0x55c9a0f38be0)
      at src/providers/proxy/proxy_id.c:1553
  #3  get_initgr (i_name=<optimized out>, dom=0x55c9a0efb420, sysdb=<optimized out>, ctx=0x55c9a0f048e0, mem_ctx=0x55c9a0f38b70) at src/providers/proxy/proxy_id.c:1461
  #4  proxy_account_info (domain=0x55c9a0efb420, be_ctx=<optimized out>, data=<optimized out>, ctx=0x55c9a0f048e0, mem_ctx=0x55c9a0f38b70) at src/providers/proxy/proxy_id.c:1659
  #5  proxy_account_info_handler_send (mem_ctx=<optimized out>, id_ctx=0x55c9a0f048e0, data=<optimized out>, params=0x55c9a0f39790) at src/providers/proxy/proxy_id.c:1758
  #6  0x000055c99fc67677 in file_dp_request (_dp_req=<synthetic pointer>, req=0x55c9a0f39470, request_data=<optimized out>, dp_flags=1, method=DPM_ACCOUNT_HANDLER, target=DPT_ID,
      name=<optimized out>, domainname=0x55c9a0f39190 "LDAP", provider=0x55c9a0efe0e0, mem_ctx=<optimized out>) at src/providers/data_provider/dp_request.c:250
  #7  dp_req_send (mem_ctx=0x55c9a0f37b60, provider=provider@entry=0x55c9a0efe0e0, domain=domain@entry=0x55c9a0f39190 "LDAP", name=<optimized out>, target=target@entry=DPT_ID,
      method=method@entry=DPM_ACCOUNT_HANDLER, dp_flags=dp_flags@entry=1, request_data=0x55c9a0f37c00, _request_name=0x55c9a0f37b60) at src/providers/data_provider/dp_request.c:295
  #8  0x000055c99fc6a132 in dp_get_account_info_send (mem_ctx=<optimized out>, ev=0x55c9a0eddbc0, sbus_req=<optimized out>, provider=0x55c9a0efe0e0, dp_flags=1,
      entry_type=<optimized out>, filter=0x55c9a0f358d0 "name=nobody@ldap", domain=0x55c9a0f39190 "LDAP", extra=0x55c9a0f354a0 "") at src/providers/data_provider/dp_target_id.c:528
  #9  0x00007fb4da35265b in _sbus_sss_invoke_in_uusss_out_qus_step (ev=0x55c9a0eddbc0, te=<optimized out>, tv=..., private_data=<optimized out>) at src/sss_iface/sbus_sss_invokers.c:2847
  #10 0x00007fb4d9cfb1cf in tevent_common_invoke_timer_handler () from /lib64/libtevent.so.0
  #11 0x00007fb4d9cfb339 in tevent_common_loop_timer_delay () from /lib64/libtevent.so.0
  #12 0x00007fb4d9cfc2f9 in epoll_event_loop_once () from /lib64/libtevent.so.0
  #13 0x00007fb4d9cfa7b7 in std_event_loop_once () from /lib64/libtevent.so.0
  #14 0x00007fb4d9cf5b5d in _tevent_loop_once () from /lib64/libtevent.so.0
  #15 0x00007fb4d9cf5d8b in tevent_common_loop_wait () from /lib64/libtevent.so.0
  #16 0x00007fb4d9cfa757 in std_event_loop_wait () from /lib64/libtevent.so.0
  #17 0x00007fb4dd955ac3 in server_loop (main_ctx=0x55c9a0edf090) at src/util/server.c:724
  #18 0x000055c99fc59760 in main (argc=8, argv=<optimized out>) at src/providers/data_provider_be.c:747
  (gdb) l
  733         ret = remove_duplicate_group_members(tmp_ctx, grp, &ngroup);
  734         if (ret != EOK) {
  735             DEBUG(SSSDBG_CRIT_FAILURE, "Failed to remove duplicate group member     s\n");
  736             goto done;
  737         }
  738
  739         DEBUG_GR_MEM(SSSDBG_TRACE_LIBS, ngroup);
  740
  741         ret = sysdb_transaction_start(sysdb);
  742         if (ret != EOK) {
  743             DEBUG(SSSDBG_CRIT_FAILURE, "Failed to start transaction\n");
  744             goto done;
  745         }
  746         in_transaction = true;
  747
  748         if (ngroup->gr_mem && ngroup->gr_mem[0]) {
  749             attrs = sysdb_new_attrs(tmp_ctx);
  750             if (!attrs) {
  751                 DEBUG(SSSDBG_CRIT_FAILURE, "Allocation error?!\n");
  752                 ret = ENOMEM;
  (gdb) p ngroup
  $1 = (struct group *) 0x0
  743             DEBUG(SSSDBG_CRIT_FAILURE, "Failed to start transaction\n");
  744             goto done;
  745         }
  746         in_transaction = true;
  747
  748         if (ngroup->gr_mem && ngroup->gr_mem[0]) {
  749             attrs = sysdb_new_attrs(tmp_ctx);
  750             if (!attrs) {
  751                 DEBUG(SSSDBG_CRIT_FAILURE, "Allocation error?!\n");
  752                 ret = ENOMEM;
  (gdb) p ngroup
  $1 = (struct group *) 0x0

Merges: https://pagure.io/SSSD/sssd/pull-request/4036

Resolves:
https://pagure.io/SSSD/sssd/issue/4037

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
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