From 0c45fc4edacf324926c85774ab0e2ca466f1e7e6 Mon Sep 17 00:00:00 2001 From: Russell Bryant Date: Sat, 6 Mar 2010 14:16:20 +0000 Subject: [PATCH] Fix a crash in SIP blind transfer handling found by an automated external test. The first real test added to the external test suite found a pretty nasty crash that occurred in Asterisk trunk. The crash was due to a race condition between the REFER handling and channel destruction in the channel thread. After the transfer has been completed, we go back to the transferrer channel and try to lock it so we can fire off a CEL event. However, there was no guarantee that the channel was still around at that point since it's racing against the channel thread. Since ast_channel is a reference counted object, the fix is simple. The code unlocks the transferrer channel before finally completing the transfer with an async goto. At this point the channel thread is going to start call tear down and the channel will eventually be destroyed. To ensure that the channel is valid when we want to fire off the CEL event, increase the channel's reference count. git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@251137 65c4cc65-6c06-0410-ace0-fbb531ad65f3 --- channels/chan_sip.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/channels/chan_sip.c b/channels/chan_sip.c index 793a31b3cf..b8f93b5835 100644 --- a/channels/chan_sip.c +++ b/channels/chan_sip.c @@ -20089,6 +20089,11 @@ static int handle_request_refer(struct sip_pvt *p, struct sip_request *req, int /* Must release lock now, because it will not longer be accessible after the transfer! */ *nounlock = 1; + /* + * Increase ref count so that we can delay channel destruction until after + * we get a chance to fire off some events. + */ + ast_channel_ref(current.chan1); ast_channel_unlock(current.chan1); /* Connect the call */ @@ -20113,6 +20118,7 @@ static int handle_request_refer(struct sip_pvt *p, struct sip_request *req, int transmit_notify_with_sipfrag(p, seqno, "503 Service Unavailable (can't handle one-legged xfers)", TRUE); ast_clear_flag(&p->flags[0], SIP_GOTREFER); append_history(p, "Xfer", "Refer failed (only bridged calls)."); + ast_channel_unref(current.chan1); return -1; } ast_set_flag(&p->flags[0], SIP_DEFER_BYE_ON_TRANSFER); /* Delay hangup */ @@ -20163,6 +20169,9 @@ static int handle_request_refer(struct sip_pvt *p, struct sip_request *req, int ast_clear_flag(&p->flags[0], SIP_GOTREFER); res = -1; } + + ast_channel_unref(current.chan1); + return res; }