SIGSEGV in cyrus-imapd 3.0.7 mupdate

[Michael Menge]

Hi Ellie


Quoting ellie timoney <ellie at fastmail.com>:

> Hi,
>
> Are you confident that the backtrace in your earlier email is from  
> the thread that crashed?
>

no, as I had no experience in debugging multithreaded programs before,
but looking at all threads of multiple core dumps DH_free is a
common pattern.


> mupdate is multithreaded, so obtaining the correct backtrace from a  
> crash is a bit of work (but maybe you already did this)

I used Redhats abrtd to collect the coredumps. This program also collects some
other information and produces an core_backtrace json output and  
groups similar
coredumps together. I can provide these if anyone is interested, but they
are to big to mail.

>
> It's been a while since I've done any multithreaded debugging with  
> gcc (since Cyrus is predominantly single-threaded), but my fingers  
> remember using "thread apply all bt" and going from there, if that's  
> any help :)
>

I have attached the output of "thread apply all bt" form three different
core dumps.

>
> On Thu, Jul 5, 2018, at 7:40 PM, Michael Menge wrote:
>> Quoting Michael Menge <michael.menge at zdv.uni-tuebingen.de>:
>>
>> > Hi,
>> >
>> > we are in the process of setting up our new production mailserver with
>> > cyrus-imapd 3.0.7 on RHEL 7.5 Servers.
>> >
>> > At the moment we encounter many crashes (SIGSEGV) of the mupdate  
>> process on
>> > the mupdate master instance. As soon as we issue a command that updates
>> > multiple mailboxes in short time we trigger a SIGSEGV.
>> >
>> >> sam user/zrstes* cyrus all
>> > Setting ACL on user/zrstes1...OK.
>> > Setting ACL on user/zrstes1/Mail...OK.
>> > Setting ACL on user/zrstes1/Mail/drafts...OK.
>> > Setting ACL on user/zrstes1/Mail/s-spam...OK.
>> > Setting ACL on user/zrstes1/Mail/sent...OK.
>> > Setting ACL on user/zrstes1/Mail/trash...OK.
>> > Setting ACL on user/zrstes1/Mail/v-spam...OK.
>> > Setting ACL on user/zrstes2...cyrus: lrswipkxtea: no connection to server
>> >
>> > I suspect that at this time the connection from the backend to the
>> > mupdate master
>> > is lost as the mupdate process received the SIGSEGV
>> >
>> > (gdb) bt
>> > #0  0x00007fb49c000098 in ?? ()
>> > #1  0x00007fb4a9a59a85 in DH_free (r=0x7fb49c1b9600) at dh_lib.c:194
>> > #2  0x00007fb4aa84dbef in tls_shutdown_serverengine () at imap/tls.c:1311
>> > #3  0x0000000000404075 in conn_free (C=0x7fb4840009f0) at  
>> imap/mupdate.c:379
>> > #4  0x00000000004062c0 in thread_main (rock=0x0) at imap/mupdate.c:1330
>> > #5  0x00007fb4a771add5 in start_thread (arg=0x7fb4a22d9700) at
>> > pthread_create.c:308
>> > #6  0x00007fb4a718fb3d in clone () at
>> > ../sysdeps/unix/sysv/linux/x86_64/clone.S:113
>> >
>> >
>> > Further information, as DH_free is in the bt, we have NOT configured
>> > dh_params in
>> > our ssl certificate/key or in the imapd.conf
>> >
>>
>> As a follow up, we did generate dh_params, but the mupdate still crashes
>> with SIGSEGV. Any ideas how to debug/fix this? Is there any
>> information that is missing?
>>
>> Regards
>>
>>     Michael Menge
>>
>>



--------------------------------------------------------------------------------
M.Menge                                Tel.: (49) 7071/29-70316
Universität Tübingen                   Fax.: (49) 7071/29-5912
Zentrum für Datenverarbeitung          mail:  
michael.menge at zdv.uni-tuebingen.de
Wächterstraße 76
72074 Tübingen
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