[asterisk-dev] [Code Review]: Pickup segfault when multiple pickups of multiple localchan calls

[Alec Davis]

> On Aug. 25, 2011, 4:28 p.m., rmudgett wrote:
> > I don't think this approach is going to work either.

It works, but is it the right approach?


> On Aug. 25, 2011, 4:28 p.m., rmudgett wrote:
> > trunk/main/features.c, lines 6956-6966
> > <https://reviewboard.asterisk.org/r/1353/diff/2/?file=18596#file18596line6956>
> >
> >     Walking this list is dangerous since the list is hopping through ast_channel structs that you don't have the locks on.
> >     
> >     The call to ast_channel_datastore_find() must be called with that channel locked.

Understand regarding locks, first cut.
Is there another way to find the head caller?


> On Aug. 25, 2011, 4:28 p.m., rmudgett wrote:
> > trunk/channels/chan_local.c, lines 1202-1206
> > <https://reviewboard.asterisk.org/r/1353/diff/2/?file=18593#file18593line1202>
> >
> >     This will need to be done for all channel drivers.

I tried to do this in main/channel.c:ast_request() which would then cover all channels, but for the life of me get to the pvt. 


- Alec


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On Aug. 25, 2011, 7:19 a.m., Alec Davis wrote:
> 
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> https://reviewboard.asterisk.org/r/1353/
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> 
> (Updated Aug. 25, 2011, 7:19 a.m.)
> 
> 
> Review request for Asterisk Developers and rmudgett.
> 
> 
> Summary
> -------
> 
> If ast_can_pickup() can pickup the target channel, it also needs to check that the originating parent channel isn't being picked up from one of the other spawned the calls.
> 
> Example dialplan below causes a segfault as ast-hangup removes the same channel as is being picked up.
> 
> How to crash it!
>   dial 801 from 1 phone.
>   from 2 phones simultaneously dial 800.
>   segfault!
> 
> exten => 801,1,NoOp(Local pickup debug: Ring Phones) 
> exten => 801,n,Dial(Local/823 at en-phone&Local/824 at en-phone)
> 
> exten => 800,1,NoOp(Local pickup: Pickup through Localchan call)
> exten => 800,n,Dial(Local/824 at en-pickup&Local/823 at en-pickup)
> 
> [en-pickup]
> exten => _[0-9*#]!, 1, PickupChan(Local/${EXTEN}@en-phone)
> 
> [en-phone]
> exten => _[0-9*#]!, 1, Dial(SIP/gxp-${EXTEN},20,rwt)
> 
> 
> This addresses bugs ASTERISK-18222 and ASTERISK-18273.
>     https://issues.asterisk.org/jira/browse/ASTERISK-18222
>     https://issues.asterisk.org/jira/browse/ASTERISK-18273
> 
> 
> Diffs
> -----
> 
>   trunk/channels/chan_local.c 333199 
>   trunk/channels/chan_sip.c 333199 
>   trunk/include/asterisk/channel.h 333199 
>   trunk/main/features.c 333199 
> 
> Diff: https://reviewboard.asterisk.org/r/1353/diff
> 
> 
> Testing
> -------
> 
> Party A ring in which triggers off 2 internal localchan calls, as per 801 in the example dialplan.
> Party B and Party C, attempt to pickup the same calls, using 800 in the example dialplan.
> 
> There is another senario thats not right, before even applying this patch.
> Party A ring in, which again triggers 2 internal localchan calls as per 801 in dialplan.
> Party B and Party C, use *8 to pickup. We then have a NULL OBJ message on screen, and an orpaned channel.
> 
> 
> Thanks,
> 
> Alec
> 
>

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