Amavis 2.10.1 dies and is unusable when put under moderate load

[Mark Martinec]

The change log to Convert::UUlib 1.50 shows:


   Revision history for Perl extension Convert::UUlib.

   1.5  Sat Jul 11 03:56:06 CEST 2015
   - fix a heap overflow (testcase by Krzysztof Wojtaś).
   - on systems that support it (posix + mmap + map_anonymous),
     allocate all dynamic areas via mmap and put four guard
     pages around them, to catch similar heap overflows
     safely in the future.
   - find a safer way to pass in CC/CFLAGS to uulib.
   - added stability canary support.


The extra protection (guard pages) is probably what is
causing your crashes: previously some heap overflow could
cause corruption and havoc without necessarily being noticed,
bringing down a process. If I understand the changelog
correctly, the new guard pages make it possible to detect
some runaway memory access in uulib and terminate the process
if this occurs, instead of letting a corruption spread.

This is a good step in guarding against security exploits:
better crash than let a leak be exploitable. Unfortunately
the violation cannot be contained, which affects apparent
stability.

   Mark