[asterisk-bugs] [Asterisk 0015618]: [patch] Channel not locked when it should in local_attended_transfer

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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https://issues.asterisk.org/view.php?id=15618 
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Reported By:                lmsteffan
Assigned To:                dvossel
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Project:                    Asterisk
Issue ID:                   15618
Category:                   Channels/chan_sip/Transfers
Reproducibility:            always
Severity:                   block
Priority:                   normal
Status:                     ready for testing
Target Version:             1.6.3.0
Asterisk Version:           SVN 
JIRA:                        
Regression:                 No 
Reviewboard Link:            
SVN Branch (only for SVN checkouts, not tarball releases):  trunk 
SVN Revision (number only!): 209615 
Request Review:              
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Date Submitted:             2009-07-30 18:58 CDT
Last Modified:              2009-10-08 15:11 CDT
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Summary:                    [patch] Channel not locked when it should in
local_attended_transfer
Description: 
Right after performing the transfer, the target channel (target.chan1) is
unlocked. It is not locked again before performing the masquerade (although
aa comment says so).

Performing a relock of this channel leads to a deadlock with
&current->chan1. Trying to solve that deadlock led me to a bunch of astobj2
errors.
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---------------------------------------------------------------------- 
 (0112083) svnbot (reporter) - 2009-10-08 15:11
 https://issues.asterisk.org/view.php?id=15618#c112083 
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Repository: asterisk
Revision: 222761

U   trunk/channels/chan_misdn.c
U   trunk/channels/chan_sip.c
U   trunk/include/asterisk/channel.h
U   trunk/main/channel.c
U   trunk/main/features.c
U   trunk/main/pbx.c

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r222761 | dvossel | 2009-10-07 17:58:38 -0500 (Wed, 07 Oct 2009) | 35
lines

Deadlock in channel masquerade handling

Channels are stored in an ao2_container.  When accessing an item within
an ao2_container the proper locking order is to first lock the container,
and then the items within it.

In ast_do_masquerade both the clone and original channel must be locked
for the entire duration of the function.  The problem with this is that
it attemptes to unlink and link these channels back into the ao2_container
when one of the channel's name changes.  This is invalid locking order as
the process of unlinking and linking will lock the ao2_container while
the channels are locked!!! Now, both the channels in do_masquerade are
unlinked from the ao2_container and then locked for the entire function.
At the end of the function both channels are unlocked and linked back
into the container with their new names as hash values.

This new method of requiring all channels and tech pvts to be unlocked
before ast_do_masquerade() or ast_change_name() required several
changes throughout the code base.

(closes issue https://issues.asterisk.org/view.php?id=15911)
Reported by: russell
Patches:
      masq_deadlock_trunk.diff uploaded by dvossel (license 671)
Tested by: dvossel, atis

(closes issue https://issues.asterisk.org/view.php?id=15618)
Reported by: lmsteffan
Patches:
      deadlock_local_attended_transfers_trunk.diff uploaded by dvossel
(license 671)
Tested by: lmsteffan, dvossel

Review: https://reviewboard.asterisk.org/r/387/


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http://svn.digium.com/view/asterisk?view=rev&revision=222761 

Issue History 
Date Modified    Username       Field                    Change               
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2009-10-08 15:11 svnbot         Checkin                                      
2009-10-08 15:11 svnbot         Note Added: 0112083                          
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