Fwd: Re: [cyrusimap/cyrus-sasl] PAM auth causes segfault for unknown reason (#547)
dilyan.palauzov at aegee.org
Tue Dec 11 08:45:24 EST 2018
the message below does not show the full backtrace at the very last
moment. One way to create it is to produce a core dump and then open
with gdb the saslauthd executable, the coredump and call "thread apply
all bt f".
More usefull could be to run the process under valgrind/memchech, after
compiling it debug information.
Otherwise it is evident, that the process terminates unexpectedly, but
it is unclear why and where.
On Mon, 2018-12-10 at 11:46 -0800, jan parcel wrote:
> We have seen severe mutex issues with sasl_client init on super-fast machines. We temporarily solved it by patching openldap to ensure it never calls sasl_client_init more than once, but when I get out from under my current non-cyrus-sasl load, I had planned to test and submit changes to sasl_*_init to use a static mutext that is pre-initialized, which is what I found online as the solution for LIBRARY issues with passed in or even local mutexts.
> The issue is that the mutex needs a mutex, which needs a mutex, and it's turtles all the way down unless a static mutex is used at that top level.
> For some reason I have not understood, I've been told to not even THINK of doing anything like that to the mutexes used in gssapi.
> On 12/10/2018 7:53 AM, Alexander Sagen wrote:
> > Trying to set up a temporary shared email server to replace an old server with a dying disk while we move all our customers to a new email solution. Configured saslauthd the same way it was configured on the old server.
> > Somehow, during the authentication process, saslauthd manages to segfault, seemingly due to a mutex lock issue.
> > Installed latest sasl2-bin (version 2.1.27) from APT (source: http://eu-central-1.ec2.archive.ubuntu.com/ubuntu bionic/main amd64 Packages).
> > Running linux kernel 4.15.0-1021-aws.
> > gdb output during crash:
> > root at mail1:~# gdb --args /usr/sbin/saslauthd -a pam -c -m /var/spool/postfix/var/run/saslauthd -r -n 0 -d
> > GNU gdb (Ubuntu 8.1-0ubuntu3) 184.108.40.20680409-git
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> > Reading symbols from /usr/sbin/saslauthd...(no debugging symbols found)...done.
> > (gdb) run
> > Starting program: /usr/sbin/saslauthd -a pam -c -m /var/spool/postfix/var/run/saslauthd -r -n 0 -d
> > [Thread debugging using libthread_db enabled]
> > Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
> > saslauthd :num_procs : 0
> > saslauthd :mech_option: NULL
> > saslauthd :run_path : /var/spool/postfix/var/run/saslauthd
> > saslauthd :auth_mech : pam
> > saslauthd :mmaped shared memory segment on file: /var/spool/postfix/var/run/saslauthd/cache.mmap
> > saslauthd :bucket size: 96 bytes
> > saslauthd :stats size : 36 bytes
> > saslauthd :timeout : 28800 seconds
> > saslauthd :cache table: 985828 total bytes
> > saslauthd :cache table: 1711 slots
> > saslauthd :cache table: 10266 buckets
> > saslauthd :flock file opened at /var/spool/postfix/var/run/saslauthd/cache.flock
> > saslauthd :master pid is: 0
> > saslauthd :listening on socket: /var/spool/postfix/var/run/saslauthd/mux
> > saslauthd :attempting a read lock on slot: 1501
> > saslauthd :[login=someuser at example.com] [service=smtp] [realm=example.com]: not found, update pending
> > saslauthd :attempting to release lock on slot: 1501
> > Program received signal SIGSEGV, Segmentation fault.
> > __GI___pthread_mutex_lock (mutex=0x20) at ../nptl/pthread_mutex_lock.c:65
> > 65 ../nptl/pthread_mutex_lock.c: No such file or directory.
> > (gdb)
> > saslauthd configuration:
> > START=yes
> > DESC="SASL Authentication Daemon"
> > NAME="saslauthd"
> > MECHANISMS="pam"
> > MECH_OPTIONS=""
> > THREADS=0
> > OPTIONS="-c -m /var/spool/postfix/var/run/saslauthd -r"
> > —
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