[Bug 839] Privilege Separation + PAM locks users out

[bugzilla-daemon at mindrot.org]

http://bugzilla.mindrot.org/show_bug.cgi?id=839

dtucker at zip.com.au changed:

           What    |Removed                     |Added
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 Attachment #600 is|0                           |1
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------- Additional Comments From dtucker at zip.com.au  2004-05-21 13:08 -------
Created an attachment (id=639)
 --> (http://bugzilla.mindrot.org/attachment.cgi?id=639&action=view)
Signal PAM "thread" if SIGCHLD is caused by the privsep slave exitting

Colin Watson pointed out that this may correspond to a Debian bug:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=248125

It appears that what is happening is that the client exits, breaking the TCP
connection.  When that happens, the privsep slave exits too, which causes a
SIGCHLD to be delivered to the monitor.  The monitor then attempts to waitpid()
on the PAM "thread" which is still alive and blissfully unaware of a problem
(because nobody told it to die).  That waitpid hangs the monitor's cleanup.

The attached patch tests adds a test for this case to the signal handler to
shoot the PAM  thread itself if it has to.  It the same as the one I sent to
the Debian bug except it resets SIGCHLD to prevent reentering the signal
handler when the second process exits.



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