[asterisk-bugs] [Asterisk 0015617]: [patch] crash in LOCAL() if Gosub stack is allocated but empty

[Asterisk Bug Tracker]

The following issue has been SUBMITTED. 
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https://issues.asterisk.org/view.php?id=15617 
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Reported By:                rain
Assigned To:                tilghman
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Project:                    Asterisk
Issue ID:                   15617
Category:                   Applications/app_stack
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     assigned
Asterisk Version:           Older 1.6.0 
Regression:                 No 
SVN Branch (only for SVN checkouts, not tarball releases): N/A 
SVN Revision (number only!):  
Request Review:              
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Date Submitted:             2009-07-30 14:45 CDT
Last Modified:              2009-07-30 14:45 CDT
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Summary:                    [patch] crash in LOCAL() if Gosub stack is allocated
but empty
Description: 
If the Gosub stack is allocated but empty (e.g. outside of a Gosub, but
after a previous call to Gosub on the current channel), local_read() will
crash because it blindly dereferences frame = AST_LIST_FIRST(oldlist),
which will be NULL.

The attached patch (against trunk) ensures that the stack is not empty in
local_read() and deallocates the datastore in return_exec() if the stack is
empty.  The latter might not be desirable, but each change is in a separate
hunk in the patch should you only want one of them.  The patch applies
cleanly against 1.6.x as well.
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Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2009-07-30 14:45 rain           New Issue                                    
2009-07-30 14:45 rain           Status                   new => assigned     
2009-07-30 14:45 rain           Assigned To               => tilghman        
2009-07-30 14:45 rain           Asterisk Version          => Older 1.6.0     
2009-07-30 14:45 rain           Regression                => No              
2009-07-30 14:45 rain           SVN Branch (only for SVN checkouts, not tarball
releases) => N/A             
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