openssh-3.8.1p1, with pthreads enabled, hung in pthread_join.

[Darren Tucker]

First, if you're building with USE_POSIX_THREADS then that's an 
unsupported configuration.

Nick Lane-Smith wrote:
> I connect to my OpenSSH 3.8.1p1 server and when the password dialog 
> shoes up I wait a min or so, long enough for the "Timeout before 
> authentication for %s" alarm to trigger. If at that point I enter my 
> password ssh will just sit there:
> 
> debug2: input_userauth_info_req
> debug2: input_userauth_info_req: num_prompts 1
> Password:
> debug3: packet_send2: adding 32 (len 18 padlen 14 extra_pad 64)
> 
> And the sshd will be in this state:
> 
> Attaching to program: `/private/tmp/OpenSSH.roots/OpenSSH~obj/sshd', 
> process 26589.
> Reading symbols for shared libraries ...................... done
> 0x9002cf88 in semaphore_wait_trap ()
> (gdb) bt
> #0  0x9002cf88 in semaphore_wait_trap ()
> #1  0x9006153c in pthread_join ()
> #2  0x00028a50 in sshpam_thread_cleanup () at 
> /tmp/OpenSSH.roots/OpenSSH/openssh/auth-pam.c:417

That line is immediately preceded by:

	pthread_cancel(ctxt->pam_thread);

Maybe pthread_cancel doesn't interrupt the read() syscall?  I don't know 
anything about your thread implementation.

> Shouldn't the sshpam/read thread have an alarm set so if the 
> authentication times out it will exit cleanly?

It shouldn't be necessary (and it's a potential source of races).

-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
     Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.