[gnutls-devel] Possible dereferencing error on pthread mutexes in 3.6.0

[Nikos Mavrogiannopoulos]

On Fri, 2017-09-29 at 20:47 +0200, Svein Olav Bjerkeset wrote:
> Hi,
> 
> During an attempt to build libmicrohttpd on RHEL5, I tried a
> combination 
> of libmicrohttpd-0.9.55 and GnuTLS 3.6.0. It consistantly core
> dumped 
> with a segfault when trying to increment at mutex value 
> (gnutls_atomic_uint_st) during https connections. The increment
> occurs 
> at lib/priority.c:563:
> 
> gnutls_atomic_increment(&priority->usage_cnt);
> 
> Running the test https server through gdb, I find that the reason
> for 
> the crash, is that pthread_mutex_lock is eventually called with a
> null 
> pointer argument from gnutls_system_mutex_lock.
> 
> Debuging seems to show that the mutex initialization works as
> intended, 
> but not lock and unlock.

Thank you. That seems to be the same case as the issue fixed by the
following merge request:
https://gitlab.com/gnutls/gnutls/merge_requests/491

It is triggered on older systems without atomic integers. The fix will
be included in the 3.6.1 release.

regards,
Nikos