[asterisk-bugs] [Asterisk 0017365]: Race condition causes manager session event list to underflow causing null pointer de-ref and crash.

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=17365 
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Reported By:                davidw
Assigned To:                
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Project:                    Asterisk
Issue ID:                   17365
Category:                   Core/ManagerInterface
Reproducibility:            sometimes
Severity:                   crash
Priority:                   normal
Status:                     new
Asterisk Version:           SVN 
JIRA:                        
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): 1.6.2 
SVN Revision (number only!): 264112 
Request Review:              
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Date Submitted:             2010-05-20 12:26 CDT
Last Modified:              2010-05-20 13:29 CDT
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Summary:                    Race condition causes manager session event list to
underflow causing null pointer de-ref and crash.
Description: 
There is a flaw in the reference count logic for events in manager.c which
means about once in the order of 100,000,000 events, the last event gets
purged, resulting in a trying to dereference a null last_ev pointer at:

0x0811b951 in process_events (s=0xb773819c) at manager.c:2685
2685       while ( (eqe = NEW_EVENT(s)) ) {

Scenario.  Run Asterisk for long enough with a manager logged in and
events being generated.

Expect.  Nothing untoward.

Get. Crash, as above.
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Relationships       ID      Summary
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related to          0017234 [patch] Memory leak in manager.c
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 (0122219) tilghman (administrator) - 2010-05-20 13:29
 https://issues.asterisk.org/view.php?id=17365#c122219 
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Work on the related issue https://issues.asterisk.org/view.php?id=17234 produced
a patch that should fix that
exact race condition. 

Issue History 
Date Modified    Username       Field                    Change               
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2010-05-20 13:29 tilghman       Note Added: 0122219                          
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