Bug#205234: libc6: vsyslog() call hangs su and login
Package: libc6
Version: 2.3.2-2
After upgrading to this version of libc6 and rebooting, su or login do not
work anymore.
su hangs after prompting for password (or right away, if invoked as root),
regardless of whether the '-' option is given.
I am running Debian unstable; I tried this with at least 3 or 4 kernels. For
kernels 2.2.25, 2.4.20, 2.4.21 I was able to successfully login using GDM;
but su hung in all of them.
When I tried booting with the 2.6.0 testing kernel in unstable, I got a
chance to try text console login (X server wouldn't start due to its own
issues) - I could not login through console at all - login hung as well.
I also tried downgrading the login package, but that did not make any
difference.
I ran su using gdb and after it hung and I sent SIGINT to the process, the
backtrace was as follows:
#0 0x401e3b88 in __pthread_sigsuspend () from /lib/libpthread.so.0
#1 0x401e3999 in __pthread_wait_for_restart_signal () from
/lib/libpthread.so.0#2 0x401e5159 in __pthread_alt_lock () from
/lib/libpthread.so.0
#3 0x401e24e6 in pthread_mutex_lock () from /lib/libpthread.so.0
#4 0x4011dead in vsyslog () from /lib/libc.so.6
#5 0x40180289 in _log_err () from /lib/security/pam_unix.so
#6 0x4017ead7 in pam_sm_open_session () from /lib/security/pam_unix.so
#7 0x4004c9c8 in pam_fail_delay () from /lib/libpam.so.0
#8 0x4004cb18 in _pam_dispatch () from /lib/libpam.so.0
#9 0x4004e516 in pam_open_session () from /lib/libpam.so.0
#10 0x0804a780 in ?? ()
#11 0x080568c8 in ?? ()
Googling revealed that the pthread calls look like something to do with an
unitialized mutex, but that's just my guessing.
Downgrading libc6 to 2.3.1 fixed the problem.
This bug seems similar to bug #205099 - that one also involved a syslog call
and a hanging process.
Cheers!
Nick
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