[Bug 1692] New: sshd sometimes dies when sent multiple SIGHUPs in quick succession

bugzilla-daemon at bugzilla.mindrot.org bugzilla-daemon at bugzilla.mindrot.org
Wed Jan 6 01:41:12 EST 2010


https://bugzilla.mindrot.org/show_bug.cgi?id=1692

           Summary: sshd sometimes dies when sent multiple SIGHUPs in
                    quick succession
           Product: Portable OpenSSH
           Version: 5.3p1
          Platform: Other
               URL: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug
                    /497781
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: sshd
        AssignedTo: unassigned-bugs at mindrot.org
        ReportedBy: cjwatson at debian.org


Created an attachment (id=1766)
 --> (https://bugzilla.mindrot.org/attachment.cgi?id=1766)
ignore SIGHUP across sshd re-exec window

In Ubuntu bug #497781, "PierreF" reported that it's sometimes possible
to end up with no sshd running if you send it two SIGHUP signals in
quick succession, which can sometimes happen due to configuration of
networking scripts. Although I haven't been able to reproduce this
myself so far, I think this is because SIGHUP is reset to the default
action by execve(), and sshd's handler isn't reinstalled until shortly
after the exec, so there's a window when it's simply set to the default
action of terminating the process.

If this hypothesis is correct, which I think is likely, then the
attached patch should fix it by ignoring SIGHUP across the exec window.

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