Bugzilla – Bug 140512
sshd blocks SIGALRM
Last modified: 2008-06-25 09:53:12 UTC
Gidday everbody, We have just found an interesting issue regarding the sshd daemon on our SuSE system. For some reasons, the /usr/sbin/sshd process blocks SIGALRM as shown in the /proc/pid/status: $ cat /proc/`cat /var/run/sshd.init.pid`/status Name: sshd State: S (sleeping) SleepAVG: 0% [...] SigPnd: 0000000000000000 ShdPnd: 0000000000000000 SigBlk: 0000000000002000 <-- SIGALRM is blocked SigIgn: 0000000000001000 As a result, any descendent processes shall inherit this mask. The bad news is that some commands rely on SIGALRM being unmasked, e.g. those invoking alarm() or similar. If those commands are started from a "ssh shell", then they won't work correctly (e.g. never times out). That's really annoying. Do you have an idea where the problem lies? Below you shall find the relevant information about the system. Thanks in advance! Loic. ******************* System information ****************** * Hardware: HP Proliant, intel PIII 1.4Ghz * SuSE release: SuSE Professional v9.2 * uname -a: Linux mucltpa04 2.6.8-24-smp #1 SMP Wed Oct 6 09:16:23 UTC 2004 i686 i686 i386 GNU/Linux * openssh based on the following RPMs: openssh-3.9p1-3 openssh-askpass-3.9p1-3 * let me know if you need further information
Does this problem really exist within SuSE LINUX 10.0?
I don't know how this problem relates to later SuSE version. We're currently facing this problem with SuSE Pro v9.2. If this is not the right place to report bug with that SuSE version, please redirect me to the appropriate place. Thanks in advance, Loic.
werner: No, problem does not exists on SUSE 10 Loic: get an upgrade and try again... ;-)
Unfortunately, I can't upgrade to SuSE 10 because the system is not tested against that version. Any other suggestions? Thanks, Loic.
In Suse openssh we have patch, which blocks sigalarm, when something is writing to log by syslog (see openssh-3.9p1-blocksigalrm.diff) //snip + /* Prevent a race between the grace_alarm + * which writes a log message and terminates + * and main sshd code that leads to deadlock + * as syslog is not async safe. + */ but after writting we reverted it back to old state.
could you please try fixed openssh from http://beta.suse.com/private/postadal/bug140512/
no respond for a long time, I will add this patch with next security update
mass reopening all SuSE Linux bugs that are set to REMIND+LATER to change the resolution to WONTFIX (adapting to new policy)
Closing old LATER+REMIND bugs as WONTFIX - if you still plan to work on it, feel free to reopen and set to ASSIGNED. In case the report saw repeated reopen comments, it's due to bugzilla timing out on the huge request ;(