[Dovecot] signal 11 crash, sometimes, during mbox bz2 decompression

Mike Brown mike at skew.org
Tue Aug 16 14:00:24 EEST 2011

Hello again,

I'm running dovecot 1.2.16 from the ports collection on FreeBSD 8.1-STABLE, 

To enable IMAP read-only access to gzip or bzip2 compressed mbox files, I 
added the following to my dovecot.conf, in the protocol imap { ... } section: 
mail_plugins = zlib

My compressed mbox files are all .bz2 files in an 'old' subdirectory of my 
main mail directory. I am trying to access them with Thunderbird. I 
'subscribed' to them just fine, and at first I thought it was working, but I 
just got lucky on the first couple I accessed. Dovecot actually fails to 
decompress them about 90% of the time, seemingly at random; the same box will 
not work a bunch of times, then work once, then not work again and again. When 
it works, sometimes only some of the messages get transmitted.

Most of the failures are accompanied by this pair of messages in my log:

Aug 16 00:25:33 myhost dovecot: dovecot: child 943 (imap) killed with signal 11 (core not dumped - set mail_drop_priv_before_exec=yes)
Aug 16 00:25:33 myhost kernel: pid 943 (imap), uid 1001: exited on signal 11

Some of the failures have only the "exited on signal 11" message.

The very first failure had this:

Aug 16 00:22:47 myhost dovecot: IMAP(mike): Next message unexpectedly lost from mbox file (read-only mbox stream) at 2761 (cached)
Aug 16 00:22:47 myhost dovecot: IMAP(mike): read(mail, uid=2) failed: Invalid argument

Is this a problem with dovecot? Let me know if/how I can help, or what other 
info you need.


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