[asterisk-bugs] [Asterisk 0016678]: [patch] segfault on chanspy due to race in main/channel.c

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
====================================================================== 
https://issues.asterisk.org/view.php?id=16678 
====================================================================== 
Reported By:                tim_ringenbach
Assigned To:                dvossel
====================================================================== 
Project:                    Asterisk
Issue ID:                   16678
Category:                   Applications/app_chanspy
Reproducibility:            random
Severity:                   minor
Priority:                   normal
Status:                     feedback
Target Version:             1.4.31
Asterisk Version:           1.4.29 
JIRA:                       SWP-783 
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
====================================================================== 
Date Submitted:             2010-01-22 17:52 CST
Last Modified:              2010-02-12 16:12 CST
====================================================================== 
Summary:                    [patch] segfault on chanspy due to race in
main/channel.c
Description: 
When channel.c destroys the datastore on the channel, it doesn't hold the
channel lock while calling the destroy callback. It really ought to,
because otherwise it's accessing the datastore list without locking. I've
gotten a segfault trying to lock the mutex in the ds destroy function in
app_chanspy because of this race.

Holding the channel lock during the destroy should be safe because it is
also held during the fixup callback, and app_chanspy has already been
patched to avoid the possible deadlock from that locking order issue.
====================================================================== 

---------------------------------------------------------------------- 
 (0118049) tim_ringenbach (reporter) - 2010-02-12 16:12
 https://issues.asterisk.org/view.php?id=16678#c118049 
---------------------------------------------------------------------- 
I just attached the backtrace I produced while running your patch plus
changing main/channel.c to look like this:

        /* Get rid of each of the data stores on the channel */
        while ((datastore = AST_LIST_REMOVE_HEAD(&chan->datastores,
entry))) {
                sleep(30); //Try to make the race happen
                /* Free the data store */
                ast_channel_datastore_free(datastore);
        }

Is there a good reason not to add the locking my patch adds? 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2010-02-12 16:12 tim_ringenbach Note Added: 0118049                          
======================================================================