[asterisk-bugs] [JIRA] (ASTERISK-21297) Segmentation fault on hangup

[German Becker (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-21297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=204370#comment-204370 ] 

German Becker commented on ASTERISK-21297:
------------------------------------------

Here is a backtrace showing the segfault:

Program terminated with signal 11, Segmentation fault.
#0  0x0000000000474356 in ast_bridged_channel (chan=0x7fa22401cdb8) at channel.c:7360
7360		if (bridged && ast_channel_tech(bridged)->bridged_channel)
(gdb) bt
#0  0x0000000000474356 in ast_bridged_channel (chan=0x7fa22401cdb8) at channel.c:7360
#1  0x00007fa237787598 in sip_hangup (ast=0x7fa22401cdb8) at chan_sip.c:6827
#2  0x000000000048824c in ast_hangup (chan=0x7fa22401cdb8) at channel.c:2832
#3  0x00000000005330a2 in __ast_pbx_run (c=0x7fa22401cdb8, args=<value optimized out>) at pbx.c:6268
#4  0x00000000005344bb in pbx_thread (data=0x188f7e8) at pbx.c:6360
#5  0x0000000000574e8b in dummy_start (data=<value optimized out>) at utils.c:1030
#6  0x00007fa24f8039ca in start_thread (arg=<value optimized out>) at pthread_create.c:300
#7  0x00007fa2508c370d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#8  0x0000000000000000 in ?? ()
                
> Segmentation fault on hangup
> ----------------------------
>
>                 Key: ASTERISK-21297
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-21297
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Core/Bridging
>    Affects Versions: 11.0.1
>         Environment: Ubuntu 10.04.2 
> Kernel 2.6.38
>            Reporter: German Becker
>
> Function ast_bridged_channel in main/channel.c generates segmentation fault. It happens seldom, I couldn't reproduce, but I think it happens when releasing call at both channels at the same time, timing issue.
> Here is the function:
> {code}
> struct ast_channel *ast_bridged_channel(struct ast_channel *chan)
> {
>         struct ast_channel *bridged;
>         bridged = ast_channel_internal_bridged_channel(chan);
>         if (bridged && ast_channel_tech(bridged)->bridged_channel)
>                 bridged = ast_channel_tech(bridged)->bridged_channel(chan, bridged);
>         return bridged;
> }
> {code}
> The segfault rises because bridged is not NULL, but ast_channel_tech(bridged) is NULL so the dereference produces a segfault. I'm not sure why it is null, but I think it is related to timing as said before. 
> A possible fix would be to check that ast_channel_tech(bridged) is not null.
> i.e:
> {code}
> struct ast_channel *ast_bridged_channel(struct ast_channel *chan)
> {
>         struct ast_channel *bridged;
>         bridged = ast_channel_internal_bridged_channel(chan);
>         if (bridged && ast_channel_tech(bridged) && 
>            ast_channel_tech(bridged)->bridged_channel)
>                 bridged = ast_channel_tech(bridged)->bridged_channel(chan, bridged);
>         return bridged;
> }
> {code}

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