From c0ee60419d622ca87d097b314c5b2741a8b94ce0 Mon Sep 17 00:00:00 2001
From: David Vossel <dvossel@digium.com>
Date: Thu, 8 Oct 2009 22:04:41 +0000
Subject: [PATCH] Deadlock between ast_cel_report_event and ast_do_masquerade
chan_sip calls pbx_exec on a pvt's owner channel while only the
pvt lock is held. Since pbx_exec calls ast_cel_report_event which
attempts to lock the channel, invalid locking order occurs. Channels
should be locked before pvt's.
(closes issue #15512)
Reported by: lmsteffan
Patches:
ast_cel_deadlock_15512.diff uploaded by dvossel (license 671)
git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@222981 65c4cc65-6c06-0410-ace0-fbb531ad65f3
---
channels/chan_sip.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index fee06641f9..80365addd5 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -20117,6 +20117,7 @@ static int sip_uri_cmp(const char *input1, const char *input2)
return sip_uri_params_cmp(params1, params2);
}
+/* \note No channel or pvt locks should be held while calling this function. */
static int do_magic_pickup(struct ast_channel *channel, const char *extension, const char *context)
{
struct ast_str *str = ast_str_alloca(AST_MAX_EXTENSION + AST_MAX_CONTEXT + 2);
@@ -20794,12 +20795,17 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, int
/* Do the pickup itself */
ast_channel_unlock(c);
*nounlock = 1;
- do_magic_pickup(c, pickup.exten, pickup.context);
- /* Now we're either masqueraded or we failed to pickup, in either case we... */
+ /* since p->owner (c) is unlocked, we need to go ahead and unlock pvt for both
+ * magic pickup and ast_hangup. Both of these functions will attempt to lock
+ * p->owner again, which can cause a deadlock if we already hold a lock on p.
+ * Locking order is, channel then pvt. Dead lock avoidance must be used if
+ * called the other way around. */
sip_pvt_unlock(p);
+ do_magic_pickup(c, pickup.exten, pickup.context);
+ /* Now we're either masqueraded or we failed to pickup, in either case we... */
ast_hangup(c);
- sip_pvt_lock(p);
+ sip_pvt_lock(p); /* pvt is expected to remain locked on return, so re-lock it */
return 0;
} else {
--
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