[lvm-devel] [BISECT] Regression: SEGV: 9156c5d dmeventd rework locking code

[Zdenek Kabelac]

Dne 1.4.2017 v 00:19 Eric Wheeler napsal(a):
> Hello all,
>
> After upgrading from el7.2 to el7.3, we started getting dmeventd segment
> faults immediately after update. A bisect of the lvm2 git tree shows the
> first bad commit below. This bug prevents us from activating our logical
> volumes without disabling lvm2-monitor and setting activation{monitoring =
> 0} in lvm.conf.
>
> I was able to get a git backtrace from a core dump in case that is useful,
> also below.
>
> Please let me know if you need additional information or have a patch that
> I can test with.
>
> Thank you for your help!
>
> -Eric
>
> ===== GDB =====
> Mar 31 12:07:06 server1.localhost kernel: dmeventd[7885]: segfault at 7f753ae4c6a8 ip 00007f7537b69617 sp 00007f753ae4c6b0 error 7 in liblvm2cmd.so.2.02[7f7537ac8000+191000]
>
> ~]# gdb /usr/sbin/dmeventd /var/coredumps/core-dmeventd-sig11-user0-group0-pid20364-time1490987932
> GNU gdb (GDB) Red Hat Enterprise Linux 7.6.1-94.el7
>
> Reading symbols from /usr/sbin/dmeventd...Reading symbols from /usr/lib/debug/usr/sbin/dmeventd.debug...done.
> done.
>
> warning: core file may not match specified executable file.
> [New LWP 20408]
> [New LWP 20364]
> [New LWP 20409]
> [Thread debugging using libthread_db enabled]
> Using host libthread_db library "/lib64/libthread_db.so.1".
> Core was generated by `dmeventd'.
> Program terminated with signal 11, Segmentation fault.
> #0  _touch_memory (size=<optimized out>, mem=<optimized out>) at mm/memlock.c:141
> 141		size_t pagesize = lvm_getpagesize();
> Missing separate debuginfos, use: debuginfo-install bzip2-libs-1.0.6-13.el7.x86_64 elfutils-libelf-0.166-2.el7.x86_64 elfutils-libs-0.166-2.el7.x86_64 glibc-2.17-157.el7_3.1.x86_64 libattr-2.4.46-12.el7.x86_64 libblkid-2.23.2-33.el7.x86_64 libcap-2.22-8.el7.x86_64 libgcc-4.8.5-11.el7.x86_64 libselinux-2.5-6.el7.x86_64 libsepol-2.5-6.el7.x86_64 libuuid-2.23.2-33.el7.x86_64 pcre-8.32-15.el7_2.1.x86_64 systemd-libs-219-30.el7_3.7.x86_64 xz-libs-5.2.2-1.el7.x86_64 zlib-1.2.7-17.el7.x86_64
> (gdb) bt
> #0  _touch_memory (size=<optimized out>, mem=<optimized out>) at mm/memlock.c:141
> #1  _allocate_memory () at mm/memlock.c:163


Hi

Hmm few theories -  from your gdb backtrace it suggests it has failed on libc 
syscall  (getpagesize()) ??
So have you upgraded all related packages ?  (device-mapper*,  kernel*)
or it's some 'mixture' in use ?

Also don't you have some large/changed values of 'reserved_stack'   or 
'reserved_memory' in your lvm.conf ?

Recent version of lvm2 (169) has added 'extra page' for 'stack guard' for 
PPC64le - but since you report suggests you do use 'x86_64'  it should not be 
affecting this arch.

Please open BZ and attach your lvm.conf file in use and all other info
(installed packages)  - selinux enabled/disabled ?
Some non-standard kernel options in use ?

Ragards

Zdenek