segfault when using zlib module with glibc 2.22

[Timo Sirainen]

On 20 Aug 2015, at 01:37, Florian Pritz <bluewind at xinu.at> wrote:
> 
> Hi,
> 
> I'm seeing the following segfault when I run `doveadm search
> mailbox inbox` with the zlib module enabled with dovecot 2.18 and glibc
> 2.22 on Arch Linux. It does not happen with glibc 2.21.
> 
> I've noticed that when I remove "zlib" from the mail_plugins line at
> the beginning of the config file the segfault goes away. I've also
> tested hg tip and the problem does not appear to be fixed yet.
> 
> The segfault also happens with other commands like `doveadm purge`.
> 
> Do you need any more information to reproduce and fix this?

If it only happens with Arch Linux with an updated glibc version, I doubt the problem is with Dovecot's code.

>> 0x00007ffff5eaf1e0 in pthread_mutex_unlock () from /usr/lib/libpthread.so.0
>> #0  0x00007ffff5eaf1e0 in pthread_mutex_unlock () from /usr/lib/libpthread.so.0
>> #1  0x00007ffff7def753 in _dl_close_worker () from /lib64/ld-linux-x86-64.so.2
>> #2  0x00007ffff7defede in _dl_close () from /lib64/ld-linux-x86-64.so.2
>> #3  0x00007ffff7dea124 in _dl_catch_error () from /lib64/ld-linux-x86-64.so.2
>> #4  0x00007ffff6d235e1 in ?? () from /usr/lib/libdl.so.2
>> #5  0x00007ffff6d230bf in dlclose () from /usr/lib/libdl.so.2
>> #6  0x00007ffff739326a in module_free (module=0x69da20) at module-dir.c:67

Looks very much like a non-Dovecot bug.

You could verify by running with valgrind, ideally with glibc debuginfo packages installed. It'll likely point to glibc cod.