Fixed crash from orphaned MWI subscriptions in chan_sip

This patch resolves the issue where MWI subscriptions are orphaned
by subsequent SIP SUBSCRIBE messages.  When a peer is removed, either
by pruning realtime SIP peers or by unloading / loading chan_sip, the
MWI subscriptions that were orphaned would still be on the event engine
list of valid subscriptions but have a pointer to a peer that no longer
was valid.  When an MWI event would occur, this would cause a seg fault.

(closes issue ASTERISK-18663)
Reported by: Ross Beer
Tested by: Ross Beer, Matt Jordan
Patches:
  blf_mwi_diff_12_06_11.txt uploaded by Matt Jordan (license 6283)

Review: https://reviewboard.asterisk.org/r/1610/
........

Merged revisions 347058 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 347068 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@347069 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 62 insertions, 32 deletions

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index a10106dc7..ab25f1c46 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -24940,11 +24940,21 @@ static int handle_request_publish(struct sip_pvt *p, struct sip_request *req, st
 	return handler_result;
 }
 
+/*! \internal \brief Subscribe to MWI events for the specified peer
+ * \note The peer cannot be locked during this method.  sip_send_mwi_peer will
+ * attempt to lock the peer after the event subscription lock is held; if the peer is locked during
+ * this method then we will attempt to lock the event subscription lock but after the peer, creating
+ * a locking inversion.
+ */
 static void add_peer_mwi_subs(struct sip_peer *peer)
 {
 	struct sip_mailbox *mailbox;
 
 	AST_LIST_TRAVERSE(&peer->mailboxes, mailbox, entry) {
+		if (mailbox->event_sub) {
+			ast_event_unsubscribe(mailbox->event_sub);
+		}
+
 		mailbox->event_sub = ast_event_subscribe(AST_EVENT_MWI, mwi_event_cb, "SIP mbox event", peer,
 			AST_EVENT_IE_MAILBOX, AST_EVENT_IE_PLTYPE_STR, mailbox->mailbox,
 			AST_EVENT_IE_CONTEXT, AST_EVENT_IE_PLTYPE_STR, S_OR(mailbox->context, "default"),
@@ -25098,7 +25108,7 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 		/* if an authentication response was sent, we are done here */
 		if (res == AUTH_CHALLENGE_SENT)	/* authpeer = NULL here */
 			return 0;
-		if (res < 0) {
+		if (res != AUTH_SUCCESSFUL) {
 			if (res == AUTH_FAKE_AUTH) {
 				ast_log(LOG_NOTICE, "Sending fake auth rejection for device %s\n", sip_get_header(req, "From"));
 				transmit_fake_auth_response(p, SIP_SUBSCRIBE, req, XMIT_UNRELIABLE);
@@ -25112,17 +25122,17 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 		}
 	}
 
-	/* At this point, authpeer cannot be NULL. Remember we hold a reference,
-	 * so we must release it when done.
-	 * XXX must remove all the checks for authpeer == NULL.
+	/* At this point, we hold a reference to authpeer (if not NULL).  It
+	 * must be released when done.
 	 */
 
 	/* Check if this device  is allowed to subscribe at all */
 	if (!ast_test_flag(&p->flags[1], SIP_PAGE2_ALLOWSUBSCRIBE)) {
 		transmit_response(p, "403 Forbidden (policy)", req);
 		pvt_set_needdestroy(p, "subscription not allowed");
-		if (authpeer)
+		if (authpeer) {
 			sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 1)");
+		}
 		return 0;
 	}
 
@@ -25142,8 +25152,9 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 			transmit_response(p, "404 Not Found", req);
 		}
 		pvt_set_needdestroy(p, "subscription target not found");
-		if (authpeer)
+		if (authpeer) {
 			sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 2)");
+		}
 		return 0;
 	}
 
@@ -25158,9 +25169,6 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 		enum subscriptiontype subscribed = NONE;
 		const char *unknown_acceptheader = NULL;
 
-		if (authpeer)	/* We do not need the authpeer any more */
-			authpeer = sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 2)");
-
 		/* Header from Xten Eye-beam Accept: multipart/related, application/rlmi+xml, application/pidf+xml, application/xpidf+xml */
 		accept = __get_header(req, "Accept", &start);
 		while ((subscribed == NONE) && !ast_strlen_zero(accept)) {
@@ -25198,6 +25206,9 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 					p->subscribecontext,
 					p->subscribeuri);
 				pvt_set_needdestroy(p, "no Accept header");
+				if (authpeer) {
+					sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 2)");
+				}
 				return 0;
 			}
 			/* if p->subscribed is non-zero, then accept is not obligatory; according to rfc 3265 section 3.1.3, at least.
@@ -25222,6 +25233,9 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 				p->subscribecontext,
 				p->subscribeuri);
 			pvt_set_needdestroy(p, "unrecognized format");
+			if (authpeer) {
+				sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 2)");
+			}
 			return 0;
 		} else {
 			p->subscribed = subscribed;
@@ -25244,8 +25258,9 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 			transmit_response(p, "406 Not Acceptable", req);
 			ast_debug(2, "Received SIP mailbox subscription for unknown format: %s\n", acceptheader);
 			pvt_set_needdestroy(p, "unknown format");
-			if (authpeer)
+			if (authpeer) {
 				sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 3)");
+			}
 			return 0;
 		}
 		/* Looks like they actually want a mailbox status
@@ -25254,11 +25269,17 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 		  In most devices, this is configurable to the voicemailmain extension you use
 		*/
 		if (!authpeer || AST_LIST_EMPTY(&authpeer->mailboxes)) {
-			transmit_response(p, "404 Not found (no mailbox)", req);
+			if (!authpeer) {
+				transmit_response(p, "404 Not found", req);
+			} else {
+				transmit_response(p, "404 Not found (no mailbox)", req);
+				ast_log(LOG_NOTICE, "Received SIP subscribe for peer without mailbox: %s\n", S_OR(authpeer->name, ""));
+			}
 			pvt_set_needdestroy(p, "received 404 response");
-			ast_log(LOG_NOTICE, "Received SIP subscribe for peer without mailbox: %s\n", S_OR(authpeer->name, ""));
-			if (authpeer)
-				sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 4)");
+
+			if (authpeer) {
+				sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 3)");
+			}
 			return 0;
 		}
 
@@ -25268,18 +25289,21 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 			add_peer_mwi_subs(authpeer);
 			ao2_lock(p);
 		}
-		if (authpeer->mwipvt && authpeer->mwipvt != p) {	/* Destroy old PVT if this is a new one */
+		if (authpeer->mwipvt != p) {	/* Destroy old PVT if this is a new one */
 			/* We only allow one subscription per peer */
-			dialog_unlink_all(authpeer->mwipvt);
-			authpeer->mwipvt = dialog_unref(authpeer->mwipvt, "unref dialog authpeer->mwipvt");
-			/* sip_destroy(authpeer->mwipvt); */
-		}
-		if (authpeer->mwipvt)
-			dialog_unref(authpeer->mwipvt, "Unref previously stored mwipvt dialog pointer");
-		authpeer->mwipvt = dialog_ref(p, "setting peers' mwipvt to p");		/* Link from peer to pvt UH- should this be dialog_ref()? */
-		if (p->relatedpeer)
-			sip_unref_peer(p->relatedpeer, "Unref previously stored relatedpeer ptr");
-		p->relatedpeer = sip_ref_peer(authpeer, "setting dialog's relatedpeer pointer");	/* already refcounted...Link from pvt to peer UH- should this be dialog_ref()? */
+			if (authpeer->mwipvt) {
+				dialog_unlink_all(authpeer->mwipvt);
+				authpeer->mwipvt = dialog_unref(authpeer->mwipvt, "unref dialog authpeer->mwipvt");
+			}
+			authpeer->mwipvt = dialog_ref(p, "setting peers' mwipvt to p");
+		}
+
+		if (p->relatedpeer != authpeer) {
+			if (p->relatedpeer) {
+				sip_unref_peer(p->relatedpeer, "Unref previously stored relatedpeer ptr");
+			}
+			p->relatedpeer = sip_ref_peer(authpeer, "setting dialog's relatedpeer pointer");
+		}
 		/* Do not release authpeer here */
 	} else if (!strcmp(event, "call-completion")) {
 		handle_cc_subscribe(p, req);
@@ -25287,16 +25311,12 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 		transmit_response(p, "489 Bad Event", req);
 		ast_debug(2, "Received SIP subscribe for unknown event package: %s\n", event);
 		pvt_set_needdestroy(p, "unknown event package");
-		if (authpeer)
+		if (authpeer) {
 			sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 5)");
+		}
 		return 0;
 	}
 
-	/* At this point, if we have an authpeer we should unref it. */
-	if (authpeer) {
-		authpeer = sip_unref_peer(authpeer, "unref pointer into (*authpeer)");
-	}
-
 	/* Add subscription for extension state from the PBX core */
 	if (p->subscribed != MWI_NOTIFICATION  && p->subscribed != CALL_COMPLETION && !resubscribe) {
 		if (p->stateid > -1) {
@@ -25321,6 +25341,9 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 				"with Expire header less that 'minexpire' limit. Received \"Expire: %d\" min is %d\n",
 				p->exten, p->context, p->expiry, min_expiry);
 			pvt_set_needdestroy(p, "Expires is less that the min expires allowed.");
+			if (authpeer) {
+				sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 6)");
+			}
 			return 0;
 		}
 
@@ -25356,6 +25379,9 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 				ast_log(LOG_NOTICE, "Got SUBSCRIBE for extension %s@%s from %s, but there is no hint for that extension.\n", p->exten, p->context, ast_sockaddr_stringify(&p->sa));
 				transmit_response(p, "404 Not found", req);
 				pvt_set_needdestroy(p, "no extension for SUBSCRIBE");
+				if (authpeer) {
+					sip_unref_peer(authpeer, "sip_unref_peer, from handle_request_subscribe (authpeer 6)");
+				}
 				return 0;
 			}
 			ast_set_flag(&p->flags[1], SIP_PAGE2_DIALOG_ESTABLISHED);
@@ -25371,6 +25397,10 @@ static int handle_request_subscribe(struct sip_pvt *p, struct sip_request *req,
 			pvt_set_needdestroy(p, "forcing expiration");
 		}
 	}
+
+	if (authpeer) {
+		sip_unref_peer(authpeer, "unref pointer into (*authpeer)");
+	}
 	return 1;
 }
 
@@ -26088,7 +26118,7 @@ static int get_cached_mwi(struct sip_peer *peer, int *new, int *old)
  */
 static int sip_send_mwi_to_peer(struct sip_peer *peer, int cache_only)
 {
-	/* Called with peerl lock, but releases it */
+	/* Called with peer lock, but releases it */
 	struct sip_pvt *p;
 	int newmsgs = 0, oldmsgs = 0;
 	const char *vmexten = NULL;