#35894 [Com]: php-imap doesn't trap USR2 when mailbox is locked

From: Date: Sun, 10 Jan 2010 21:45:32 +0000
Subject: #35894 [Com]: php-imap doesn't trap USR2 when mailbox is locked
References: 1  Groups: php.bugs 
Request: Send a blank email to php-bugs+get-146510@lists.php.net to get a copy of this message 
 ID:               35894
 Comment by:       tdfischer at fedoraproject dot org
 Reported By:      jik at kamens dot brookline dot ma dot us
 Status:           Open
 Bug Type:         Feature/Change Request
 Operating System: Linux
 PHP Version:      5.1.2
 New Comment:

This bug is still around and can wreak havok for a drupal site that
lets 
users submit content via machine-local mail. Could someone *please* 
commit it already?


Previous Comments:
------------------------------------------------------------------------

[2006-01-05 15:56:17] jik at kamens dot brookline dot ma dot us

You *don't* want to allow the simultaneous opening of a mailbox by two
processes.  The whole point of locking is to *prevent* the simultaneous
opening of a mailbox by two processes.  What the locking is *supposed*
to do is to make one process *wait* for the other one, but what it does
instead, if you don't catch the USR2 signal, is for the process that got
the lock first to *die* after *being killed* by the other one.  This is
not correct behavior.

Incidentally, I just tested with a newly compiled c-client 2004g and
confirmed that the problem persists there without my patch.

------------------------------------------------------------------------

[2006-01-05 10:07:30] sniper@php.net

Why would you want to allow opening same mailbox by two simultaneous
processes?

------------------------------------------------------------------------

[2006-01-05 04:13:45] jik at kamens dot brookline dot ma dot us

Please look carefully at the output.  The notices are not "harmless". 
Note that the message "successfully opened mailbox" only appears *once*.
 It should appear twice, because there are two processes who both want
to open the mailbox.  It only appears once because one of the two
processes is killed by a USR2 signal as I've described.

I don't know why the patch I sent didn't help for you.  It reliably
solves the problem for me.  Perhaps I picked bad preprocessor symbols
and it's not actually getting compiled into the object code on your
system.  Can you put debugging code in to see if the arm_signal calls
are actually happening?

Thanks.

------------------------------------------------------------------------

[2006-01-05 01:01:06] sniper@php.net

I get the same notices, which seem quite harmless anyway. And your
patch did not make any difference whatsoever.


------------------------------------------------------------------------

[2006-01-04 21:53:23] jik at kamens dot brookline dot ma dot us

libc-client-2002e-18.1 RPM from Fedora Core.  I checked the current
c-client sources from washington.edu and they seem susceptible to this
problem as well, judging from an examination of the source code.  The
USR2 functionality has been in c-client since 1993, as far as I can
tell.

------------------------------------------------------------------------

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the rest of the comments, please view the bug report online at
    http://bugs.php.net/35894

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