mail_crypt crashing randomly during LMTP

[Timo Sirainen]

On 29. Mar 2020, at 15.15, Andi Krischer <ak at michaelpelzer.de> wrote:
> We have a really strange bug with our dovecot setup. After weeks and month of debugging we’re finally reached the point when we ask you for help.
> 
> Our basic setup is quite simple: a single dovecot 2.3.10 (0da0eff44) install on Debian 10 with LDAP as user/passdb and sieve, imap_sieve and mail_crypt as mail_plugins.

Was this happening with old Dovecot versions, or did it start after v2.3.10 upgrade?

> This is what the log says in the moment of crashing:
> dovecot: lmtp(53852): Panic: Module context mail_crypt_user_module missing
> *** backtrace *** (see: https://pastebin.com/YCiFtxmy)

It shows mailbox_free() in the backtrace, so it's probably crashing in mail_crypt_mailbox_close()'s MAIL_CRYPT_CONTEXT(box). But looking at the code, I can't see how that could be possible. Maybe there is some kind of memory corruption or something.

> dovecot: lmtp(53852): Fatal: master: service(lmtp): child 53852 killed with signal 6 (core dumps disabled - https://dovecot.org/bugreport.html#coredumps)

Could you get core dumps enabled? See the link. And from the core dump send at least:

bt full
fr 6 (or maybe 5 or 7, whichever makes the following command work)
p *box

Also please send your doveconf -n output.