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SIGSEGV in mosh-server on gentoo #736

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jkolo opened this issue Mar 23, 2016 · 1 comment
Closed

SIGSEGV in mosh-server on gentoo #736

jkolo opened this issue Mar 23, 2016 · 1 comment

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@jkolo
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jkolo commented Mar 23, 2016

Hi,

starting the mosh-server generete SIGSEGV:

[ 1318.007680] grsec: From 10.0.0.100: Segmentation fault occurred at            (nil) in /usr/bin/mosh-server[mosh-server:22655] uid/euid:0/0 gid/egid:0/0, parent /sbin/init[init:1] uid/euid:0/0 gid/egid:0/0

GDB output:

server ~ # gdb \
  -ex "set follow-fork-mode child" \
  -ex "set detach-on-fork off" \
  -ex "set pagination 0" \
  -ex "run" \
  /usr/bin/mosh-server
GNU gdb (Gentoo 7.11 vanilla) 7.11
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://bugs.gentoo.org/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/bin/mosh-server...(no debugging symbols found)...done.
Starting program: /usr/bin/mosh-server
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

MOSH CONNECT 60001 5Rxois4G2G4XslKN0wgLvA
[New process 24150]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

mosh-server (mosh 1.2.5) [build mosh 1.2.5]
Copyright 2012 Keith Winstein <mosh-devel@mit.edu>
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

[mosh-server detached, pid = 24150]

Thread 2.1 "mosh-server" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff7fb0740 (LWP 24150)]
0x0000000000000000 in ?? ()
(gdb) info inferiors
  Num  Description       Executable
  1    process 24142     /usr/bin/mosh-server
* 2    process 24150     /usr/bin/mosh-server
(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x00007ffff6f8562d in forkpty () from /lib64/libutil.so.1
#2  0x000055555555e48c in ?? ()
#3  0x00007ffff5f2d62c in __libc_start_main () from /lib64/libc.so.6
#4  0x0000555555560be9 in ?? ()
(gdb)

GDB on manual build mosh:

server mosh-1.2.5 # gdb \
  -ex "set follow-fork-mode child" \
  -ex "set detach-on-fork off" \
  -ex "set pagination 0" \
  -ex "run" \
  ./src/frontend/mosh-server
GNU gdb (Gentoo 7.11 vanilla) 7.11
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://bugs.gentoo.org/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./src/frontend/mosh-server...done.
Starting program: /root/mosh-1.2.5/src/frontend/mosh-server
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

MOSH CONNECT 60001 7JgiJAZl3VagTWKdjiZ/IA
[New process 29145]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

mosh-server (mosh 1.2.5) [build mosh 1.2.5]
Copyright 2012 Keith Winstein <mosh-devel@mit.edu>
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

[mosh-server detached, pid = 29145]

Thread 2.1 "mosh-server" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff7fb0740 (LWP 29145)]
0x0000000000000000 in ?? ()
(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x00007ffff6d0662d in forkpty () from /lib64/libutil.so.1
#2  0x000055555555e40c in run_server (with_motd=true, verbose=false, colors=0, command_argv=0x7fffffffce60, command_path="/bin/zsh", desired_port=<optimized out>, desired_ip=<optimized out>) at mosh-server.cc:422
#3  main (argc=<optimized out>, argv=<optimized out>) at mosh-server.cc:322
(gdb)

Addational info:

server ~ # uname -a
Linux hell 4.4.5-hardened-r2 #1 SMP Thu Mar 17 13:02:23 CET 2016 x86_64 AMD Opteron(TM) Processor 6234 AuthenticAMD GNU/Linux
server ~ # grep GRKERNSEC /usr/src/linux/.config
CONFIG_GRKERNSEC=y
CONFIG_GRKERNSEC_CONFIG_AUTO=y
# CONFIG_GRKERNSEC_CONFIG_CUSTOM is not set
CONFIG_GRKERNSEC_CONFIG_SERVER=y
# CONFIG_GRKERNSEC_CONFIG_DESKTOP is not set
# CONFIG_GRKERNSEC_CONFIG_VIRT_NONE is not set
# CONFIG_GRKERNSEC_CONFIG_VIRT_GUEST is not set
CONFIG_GRKERNSEC_CONFIG_VIRT_HOST=y
CONFIG_GRKERNSEC_CONFIG_VIRT_EPT=y
# CONFIG_GRKERNSEC_CONFIG_VIRT_SOFT is not set
# CONFIG_GRKERNSEC_CONFIG_VIRT_XEN is not set
# CONFIG_GRKERNSEC_CONFIG_VIRT_VMWARE is not set
CONFIG_GRKERNSEC_CONFIG_VIRT_KVM=y
# CONFIG_GRKERNSEC_CONFIG_VIRT_VIRTUALBOX is not set
# CONFIG_GRKERNSEC_CONFIG_VIRT_HYPERV is not set
CONFIG_GRKERNSEC_CONFIG_PRIORITY_PERF=y
# CONFIG_GRKERNSEC_CONFIG_PRIORITY_SECURITY is not set
CONFIG_GRKERNSEC_PROC_GID=10
CONFIG_GRKERNSEC_TPE_UNTRUSTED_GID=100
CONFIG_GRKERNSEC_SYMLINKOWN_GID=100
CONFIG_GRKERNSEC_KMEM=y
CONFIG_GRKERNSEC_IO=y
CONFIG_GRKERNSEC_BPF_HARDEN=y
CONFIG_GRKERNSEC_PERF_HARDEN=y
CONFIG_GRKERNSEC_KSTACKOVERFLOW=y
CONFIG_GRKERNSEC_BRUTE=y
CONFIG_GRKERNSEC_MODHARDEN=y
CONFIG_GRKERNSEC_HIDESYM=y
CONFIG_GRKERNSEC_RANDSTRUCT=y
CONFIG_GRKERNSEC_RANDSTRUCT_PERFORMANCE=y
CONFIG_GRKERNSEC_KERN_LOCKOUT=y
CONFIG_GRKERNSEC_NO_RBAC=y
CONFIG_GRKERNSEC_ACL_HIDEKERN=y
CONFIG_GRKERNSEC_ACL_MAXTRIES=3
CONFIG_GRKERNSEC_ACL_TIMEOUT=30
CONFIG_GRKERNSEC_PROC=y
# CONFIG_GRKERNSEC_PROC_USER is not set
CONFIG_GRKERNSEC_PROC_USERGROUP=y
CONFIG_GRKERNSEC_PROC_ADD=y
CONFIG_GRKERNSEC_LINK=y
CONFIG_GRKERNSEC_SYMLINKOWN=y
CONFIG_GRKERNSEC_FIFO=y
CONFIG_GRKERNSEC_SYSFS_RESTRICT=y
CONFIG_GRKERNSEC_ROFS=y
CONFIG_GRKERNSEC_DEVICE_SIDECHANNEL=y
# CONFIG_GRKERNSEC_CHROOT is not set
# CONFIG_GRKERNSEC_AUDIT_GROUP is not set
# CONFIG_GRKERNSEC_EXECLOG is not set
CONFIG_GRKERNSEC_RESLOG=y
# CONFIG_GRKERNSEC_CHROOT_EXECLOG is not set
# CONFIG_GRKERNSEC_AUDIT_PTRACE is not set
# CONFIG_GRKERNSEC_AUDIT_CHDIR is not set
# CONFIG_GRKERNSEC_AUDIT_MOUNT is not set
CONFIG_GRKERNSEC_SIGNAL=y
# CONFIG_GRKERNSEC_FORKFAIL is not set
CONFIG_GRKERNSEC_TIME=y
CONFIG_GRKERNSEC_PROC_IPADDR=y
CONFIG_GRKERNSEC_DMESG=y
CONFIG_GRKERNSEC_HARDEN_PTRACE=y
CONFIG_GRKERNSEC_PTRACE_READEXEC=y
CONFIG_GRKERNSEC_SETXID=y
CONFIG_GRKERNSEC_HARDEN_IPC=y
CONFIG_GRKERNSEC_HARDEN_TTY=y
CONFIG_GRKERNSEC_TPE=y
# CONFIG_GRKERNSEC_TPE_ALL is not set
# CONFIG_GRKERNSEC_TPE_INVERT is not set
CONFIG_GRKERNSEC_TPE_GID=100
CONFIG_GRKERNSEC_BLACKHOLE=y
CONFIG_GRKERNSEC_NO_SIMULT_CONNECT=y
# CONFIG_GRKERNSEC_SOCKET is not set
CONFIG_GRKERNSEC_DENYUSB=y
# CONFIG_GRKERNSEC_DENYUSB_FORCE is not set
CONFIG_GRKERNSEC_SYSCTL=y
# CONFIG_GRKERNSEC_SYSCTL_DISTRO is not set
CONFIG_GRKERNSEC_SYSCTL_ON=y
CONFIG_GRKERNSEC_FLOODTIME=10
CONFIG_GRKERNSEC_FLOODBURST=6
@keithw
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keithw commented Mar 23, 2016

Please see #733 and #727 for workaround and diagnosis (and a patch that we think fixes the problem in #733). This is a bug in glibc.

I'd be very grateful if you could let me know if the patch in #733 fixes the problem. Thanks!

@keithw keithw closed this as completed Mar 23, 2016
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@keithw @jkolo