Bug#815974: Segmentation fault in libresolv triggered by php5-fpm

[Fabian Niepelt <F.Niepelt@mittwald.de>]

Package: libc6
Version: 2.13-38+deb7u10

Dear maintainer,

since the latest update for glibc we keep observing occasional
segmentation faults in libresolv [1]. They are triggered (for us) by
php5-fpm which runs an Owncloud instance when logging in. After the
segfault happens, I can relogin successfuly for about 20 minutes at
which point the segfault happens again. Restarting php5-fpm or
rebooting also does not influence the occurence of it.

We were using the 5.5 packages from the dotdeb repository, but the
segfaults persist in the 5.6 packages and the official wheezy 5.4
packages. 

Attaching to the php5-fpm worker process with GDB yields [2] at
segfault time. (for debugging purposes I set the amount of pool workers
to 1 so I would not attach to the wrong process)

Ubuntu seems to have a similar problem since the update:
https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/1546459

I'll be gladly providing additional info if you require it.

Thank you for your time.

Greetings

[1]
[57348.111866] php5-fpm[20421]: segfault at 200000001 ip
00007fd339eb74fa sp 00007fff9f055700 error 4 in libresolv-
2.13.so[7fd339eaf000+13000]
[62889.617877] php5-fpm[20420]: segfault at 270752f65 ip
00007fd339eb74fa sp 00007fff9f055700 error 4 in libresolv-
2.13.so[7fd339eaf000+13000]
[64717.111099] php5-fpm[20753]: segfault at 270752f65 ip
00007ff6819ef4fa sp 00007fff0d576a90 error 4 in libresolv-
2.13.so[7ff6819e7000+13000]
[66684.547776] php5-fpm[21385]: segfault at 270752f65 ip
00007fd55be4f4fa sp 00007fffe6a3dcd0 error 4 in libresolv-
2.13.so[7fd55be47000+13000]

[2]
[many symbols being loaded messages]
82      ../sysdeps/unix/syscall-template.S: No such file or directory.
Traceback (most recent call last):
  File "/usr/lib/debug/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17-
gdb.py", line 62, in <module>
    from libstdcxx.v6.printers import register_libstdcxx_printers
ImportError: No module named libstdcxx.v6.printers
(gdb) continue
Continuing.
warning: Could not load shared library symbols for
/lib/libnss_dns.so.2.
Do you need "set solib-search-path" or "set sysroot"?

Program received signal SIGSEGV, Segmentation fault.
0x00007f146545e4fa in *__GI___libc_res_nsearch (statp=0x7f14659f7300,
name=<optimized out>, class=<optimized out>, type=<optimized out>,
answer=0x7fff6d6c0df0 "2", anslen=<optimized out>,
answerp=0x7fff6d6c1660,
    answerp2=0x7fff6d6c1658, nanswerp2=0x7fff6d6c167c,
resplen2=0x7fff6d6c1678, answerp2_malloced=0x200000032) at
res_query.c:393
393     res_query.c: No such file or directory.