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setpgrp appears to have broken sometime between 5.10.1 and 5.18 #14694

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p5pRT opened this issue May 6, 2015 · 6 comments
Open

setpgrp appears to have broken sometime between 5.10.1 and 5.18 #14694

p5pRT opened this issue May 6, 2015 · 6 comments

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@p5pRT
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@p5pRT p5pRT commented May 6, 2015

Migrated from rt.perl.org#125121 (status was 'open')

Searchable as RT125121$

@p5pRT
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@p5pRT p5pRT commented May 6, 2015

From ndavidso@Brocade.com

Created by ndavidso@brocade.com

This is a bug report for perl from ndavidso@​brocade.com,
generated with the help of perlbug 1.39 running under perl 5.18.2.

-----------------------------------------------------------------
Historically setpgrp( $$, $$ ) on linux after a fork would set the process group
of the child process to its process ID. However sometime after perl 5.10.1 the
behaviour changed and it no longer works. Instead strace proves that it attempts
a system call with 1 subsituted for the first argument.

This can be trivially reproduced with the following test script​:

#!/usr/bin/perl
use strict;
use warnings;
my $pid = fork();

if ( $pid == 0 ) {
  my $child_pid = $$;
  print( "Child pid is​: ", $child_pid, "\n" );
  # Child
  if ( $ARGV[0] ) {
  setpgrp( 0, 0 );
  } else {
  setpgrp( $child_pid, $child_pid );
  }

  if ( getpgrp() != $child_pid ) {
  die( 'Failed to set our pgrp to ', $child_pid, "\n" );
  } else {
  print( "Yay set our pgrp to ", $child_pid, "\n" );
  exit 0;
  }
} elsif ( $pid ) {
  waitpid( $pid, -1 );
} else {
  die( "Failed to fork!" );
}

We've also successfully reproduced this on Centos 7.0, Ubuntu 14.04 and our
own locally built version of perl 5.20. The behaviour was correct on Ubuntu
10.04 and centos 5.10.

The work around is to call setpgrp( 0, 0 ) which still works as expected.

Perl Info

Flags:
    category=core
    severity=medium

Site configuration information for perl 5.18.2:

Configured by Debian Project at Thu Mar 27 18:28:21 UTC 2014.

Summary of my perl5 (revision 5 version 18 subversion 2) configuration:

  Platform:
    osname=linux, osvers=3.2.0-58-generic, archname=x86_64-linux-gnu-thread-multi
    uname='linux brownie 3.2.0-58-generic #88-ubuntu smp tue dec 3 17:37:58 utc 2013 x86_64 x86_64 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -D_FORTIFY_SOURCE=2 -g -O2 -fstack-protector --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Dldflags= -Wl,-Bsymbolic-functions -Wl,-z,relro -Dlddlflags=-shared -Wl,-Bsymbolic-functions -Wl,-z,relro -Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.18 -Darchlib=/usr/lib/perl/5.18 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.18.2 -Dsitearch=/usr/local/lib/perl/5.18.2 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Duse64bitint -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio -Uusenm -Ui_libutil -Uversiononly -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib -Dlibperl=libperl.so.5.18.2 -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fstack-protector -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fstack-protector -fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='4.8.2', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -fstack-protector -L/usr/local/lib'
    libpth=/usr/local/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib /usr/lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=, so=so, useshrplib=true, libperl=libperl.so.5.18.2
    gnulibc_version='2.19'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib -fstack-protector'

Locally applied patches:
    DEBPKG:debian/cpan_definstalldirs - Provide a sensible INSTALLDIRS default for modules installed from CPAN.
    DEBPKG:debian/db_file_ver - http://bugs.debian.org/340047 Remove overly restrictive DB_File version check.
    DEBPKG:debian/doc_info - Replace generic man(1) instructions with Debian-specific information.
    DEBPKG:debian/enc2xs_inc - http://bugs.debian.org/290336 Tweak enc2xs to follow symlinks and ignore missing @INC directories.
    DEBPKG:debian/errno_ver - http://bugs.debian.org/343351 Remove Errno version check due to upgrade problems with long-running processes.
    DEBPKG:debian/libperl_embed_doc - http://bugs.debian.org/186778 Note that libperl-dev package is required for embedded linking
    DEBPKG:fixes/respect_umask - Respect umask during installation
    DEBPKG:debian/writable_site_dirs - Set umask approproately for site install directories
    DEBPKG:debian/extutils_set_libperl_path - EU:MM: Set location of libperl.a to /usr/lib
    DEBPKG:debian/no_packlist_perllocal - Don't install .packlist or perllocal.pod for perl or vendor
    DEBPKG:debian/prefix_changes - Fiddle with *PREFIX and variables written to the makefile
    DEBPKG:debian/fakeroot - Postpone LD_LIBRARY_PATH evaluation to the binary targets.
    DEBPKG:debian/instmodsh_doc - Debian policy doesn't install .packlist files for core or vendor.
    DEBPKG:debian/ld_run_path - Remove standard libs from LD_RUN_PATH as per Debian policy.
    DEBPKG:debian/libnet_config_path - Set location of libnet.cfg to /etc/perl/Net as /usr may not be writable.
    DEBPKG:debian/mod_paths - Tweak @INC ordering for Debian
    DEBPKG:debian/module_build_man_extensions - http://bugs.debian.org/479460 Adjust Module::Build manual page extensions for the Debian Perl policy
    DEBPKG:debian/prune_libs - http://bugs.debian.org/128355 Prune the list of libraries wanted to what we actually need.
    DEBPKG:fixes/net_smtp_docs - [rt.cpan.org #36038] http://bugs.debian.org/100195 Document the Net::SMTP 'Port' option
    DEBPKG:debian/perlivp - http://bugs.debian.org/510895 Make perlivp skip include directories in /usr/local
    DEBPKG:debian/cpanplus_definstalldirs - http://bugs.debian.org/533707 Configure CPANPLUS to use the site directories by default.
    DEBPKG:debian/cpanplus_config_path - Save local versions of CPANPLUS::Config::System into /etc/perl.
    DEBPKG:debian/deprecate-with-apt - http://bugs.debian.org/702096 Point users to Debian packages of deprecated core modules
    DEBPKG:debian/squelch-locale-warnings - http://bugs.debian.org/508764 Squelch locale warnings in Debian package maintainer scripts
    DEBPKG:debian/skip-upstream-git-tests - Skip tests specific to the upstream Git repository
    DEBPKG:debian/patchlevel - http://bugs.debian.org/567489 List packaged patches for 5.18.2-2ubuntu1 in patchlevel.h
    DEBPKG:debian/skip-kfreebsd-crash - http://bugs.debian.org/628493 [perl #96272] Skip a crashing test case in t/op/threads.t on GNU/kFreeBSD
    DEBPKG:fixes/document_makemaker_ccflags - http://bugs.debian.org/628522 [rt.cpan.org #68613] Document that CCFLAGS should include $Config{ccflags}
    DEBPKG:debian/find_html2text - http://bugs.debian.org/640479 Configure CPAN::Distribution with correct name of html2text
    DEBPKG:debian/hurd_test_skip_stack - http://bugs.debian.org/650175 Disable failing GNU/Hurd tests dist/threads/t/stack.t
    DEBPKG:fixes/manpage_name_Test-Harness - http://bugs.debian.org/650451 [rt.cpan.org #73399] cpan/Test-Harness: add NAME headings in modules with POD
    DEBPKG:debian/makemaker-pasthru - http://bugs.debian.org/660195 [rt.cpan.org #28632] Make EU::MM pass LD through to recursive Makefile.PL invocations
    DEBPKG:debian/perl5db-x-terminal-emulator.patch - http://bugs.debian.org/668490 Invoke x-terminal-emulator rather than xterm in perl5db.pl
    DEBPKG:debian/cpan-missing-site-dirs - http://bugs.debian.org/688842 Fix CPAN::FirstTime defaults with nonexisting site dirs if a parent is writable
    DEBPKG:fixes/memoize_storable_nstore - [rt.cpan.org #77790] http://bugs.debian.org/587650 Memoize::Storable: respect 'nstore' option not respected
    DEBPKG:fixes/net_ftp_failed_command - [rt.cpan.org #37700] http://bugs.debian.org/491062 Net::FTP: cope gracefully with a failed command
    DEBPKG:fixes/perlbug-patchlist - [3541c11] http://bugs.debian.org/710842 [perl #118433] Make perlbug look up the list of local patches at run time
    DEBPKG:fixes/module_metadata_security_doc - [68cdd4b] CVE-2013-1437 documentation fix
    DEBPKG:fixes/module_metadata_taint_fix - [bff978f] http://bugs.debian.org/722210 [rt.cpan.org #88576] untaint version, if needed, in Module::Metadata
    DEBPKG:fixes/IPC-SysV-spelling - http://bugs.debian.org/730558 [rt.cpan.org #86736] Fix spelling of IPC_CREAT in IPC-SysV documentation
    DEBPKG:fixes/fix-undef-source -


@INC for perl 5.18.2:
    /etc/perl
    /usr/local/lib/perl/5.18.2
    /usr/local/share/perl/5.18.2
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.18
    /usr/share/perl/5.18
    /usr/local/lib/site_perl
    .


Environment for perl 5.18.2:
    HOME=/localhome/ndavidson
    LANG=en_GB.UTF-8
    LANGUAGE=en_GB:en
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/bin:/usr/local/zdev/bin:/usr/sbin:/usr/bin:/opt/ansic/bin:/usr/ccs/bin:/usr/contrib/bin:/opt/aCC/bin:/opt/langtools/bin:/opt/SUNWspro/bin:/bin:/sbin:/localhome/ndavidson/bin/:/opt/rvbd-vpn:/localhome/ndavidson/branches/stm_testperl/scripts
    PERL_BADLANG (unset)
    SHELL=/bin/bash?


@p5pRT
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@p5pRT p5pRT commented May 6, 2015

From @jkeenan

On Wed May 06 09​:35​:06 2015, ndavidso@​Brocade.com wrote​:

This is a bug report for perl from ndavidso@​brocade.com,
generated with the help of perlbug 1.39 running under perl 5.18.2.

-----------------------------------------------------------------
Historically setpgrp( $$, $$ ) on linux after a fork would set the
process group
of the child process to its process ID. However sometime after perl
5.10.1 the
behaviour changed and it no longer works. Instead strace proves that
it attempts
a system call with 1 subsituted for the first argument.

This can be trivially reproduced with the following test script​:

#!/usr/bin/perl
use strict;
use warnings;
my $pid = fork();

if ( $pid == 0 ) {
my $child_pid = $$;
print( "Child pid is​: ", $child_pid, "\n" );
# Child
if ( $ARGV[0] ) {
setpgrp( 0, 0 );
} else {
setpgrp( $child_pid, $child_pid );
}

if ( getpgrp() != $child_pid ) {
die( 'Failed to set our pgrp to ', $child_pid, "\n" );
} else {
print( "Yay set our pgrp to ", $child_pid, "\n" );
exit 0;
}
} elsif ( $pid ) {
waitpid( $pid, -1 );
} else {
die( "Failed to fork!" );
}

We've also successfully reproduced this on Centos 7.0, Ubuntu 14.04
and our
own locally built version of perl 5.20. The behaviour was correct on
Ubuntu
10.04 and centos 5.10.

The work around is to call setpgrp( 0, 0 ) which still works as
expected.

$ perlbrew switch perl-5.14.4

$ perl 125121-setpgrp.pl
Child pid is​: 3376
Yay set our pgrp to 3376

$ perlbrew switch perl-5.16.3

$ perl 125121-setpgrp.pl
Child pid is​: 4098
Failed to set our pgrp to 4098

I tried to use Porting/bisect.pl to bisect between v5.14.4 and v5.16.3, but -- as usually turns out to be the case these days -- I couldn't get meaningful results.

Thank you very much.

--
James E Keenan (jkeenan@​cpan.org)

@p5pRT
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@p5pRT p5pRT commented May 6, 2015

The RT System itself - Status changed from 'new' to 'open'

@p5pRT
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@p5pRT p5pRT commented May 6, 2015

From @Leont

On Thu, May 7, 2015 at 1​:32 AM, James E Keenan via RT <
perlbug-followup@​perl.org> wrote​:

$ perlbrew switch perl-5.14.4

$ perl 125121-setpgrp.pl
Child pid is​: 3376
Yay set our pgrp to 3376

$ perlbrew switch perl-5.16.3

$ perl 125121-setpgrp.pl
Child pid is​: 4098
Failed to set our pgrp to 4098

I tried to use Porting/bisect.pl to bisect between v5.14.4 and v5.16.3,
but -- as usually turns out to be the case these days -- I couldn't get
meaningful results.

Thank you very much.

git-blame only gives one candidate in that codepath for that time-frame​:
92f2ac5.

Leon

@p5pRT
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@p5pRT p5pRT commented May 8, 2015

From @wolfsage

On Wed, May 6, 2015 at 7​:40 PM, Leon Timmermans <fawaka@​gmail.com> wrote​:

git-blame only gives one candidate in that codepath for that time-frame​:
92f2ac5.

I ran a bisect for fun and it led me to that commit as well.

-- Matthew Horsfall (alh)

@p5pRT
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@p5pRT p5pRT commented May 11, 2015

From @tonycoz

On Fri May 08 08​:59​:57 2015, alh wrote​:

On Wed, May 6, 2015 at 7​:40 PM, Leon Timmermans <fawaka@​gmail.com> wrote​:

git-blame only gives one candidate in that codepath for that time-frame​:
92f2ac5.

I ran a bisect for fun and it led me to that commit as well.

Fixed by bae8cfc.

Proposed for backporting to 5.20​:

http​://perl5.git.perl.org/perl.git/commit/749a784c45ecc59e234c853a08f87a8150637a8e

Tony

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