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Commit 7ea1e181 authored by Richard Mudgett's avatar Richard Mudgett
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chan_sip.c: Fix waitid deadlock potential. 

This patch is part of a series to resolve deadlocks in chan_sip.c.

Stopping a scheduled event can result in a deadlock if the scheduled event
is running when you try to stop the event.  If you hold a lock needed by
the scheduled event while trying to stop the scheduled event then a
deadlock can happen.  The general strategy for resolving the deadlock
potential is to push the actual starting and stopping of the scheduled
events off onto the scheduler/do_monitor() thread by scheduling an
immediate one shot scheduled event.  Some restructuring may be needed
because the code may assume that the start/stop of the scheduled events is
immediate.

* Made always run check_pendings() under the scheduler thread so scheduler
ids can be checked safely.

ASTERISK-25023

Change-Id: Ia834d6edd5bdb47c163e4ecf884428a4a8b17d52
parent 02458cc6
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with 80 additions and 17 deletions
channels/chan_sip.c
+ 80
− 17
View file @ 7ea1e181
......@@ -1512,6 +1512,7 @@ static int __sip_subscribe_mwi_do(struct sip_subscription_mwi *mwi);
/* Scheduler id start/stop/reschedule functions. */
static void stop_provisional_keepalive(struct sip_pvt *pvt);
static void do_stop_session_timer(struct sip_pvt *pvt);
static void stop_reinvite_retry(struct sip_pvt *pvt);
 
/*! \brief Definition of this channel for PBX channel registration */
struct ast_channel_tech sip_tech = {
......@@ -7223,7 +7224,7 @@ static int sip_hangup(struct ast_channel *ast)
but we can't send one while we have "INVITE" outstanding. */
ast_set_flag(&p->flags[0], SIP_PENDINGBYE);
ast_clear_flag(&p->flags[0], SIP_NEEDREINVITE);
AST_SCHED_DEL_UNREF(sched, p->waitid, dialog_unref(p, "when you delete the waitid sched, you should dec the refcount for the stored dialog ptr"));
stop_reinvite_retry(p);
sip_cancel_destroy(p);
 
/* If we have an ongoing reinvite, there is a chance that we have gotten a provisional
......@@ -22948,10 +22949,13 @@ static void parse_moved_contact(struct sip_pvt *p, struct sip_request *req, char
}
}
 
/*! \brief Check pending actions on SIP call
/*!
* \brief Check pending actions on SIP call
*
* \note both sip_pvt and sip_pvt's owner channel (if present)
* must be locked for this function.
*
* \note Run by the sched thread.
*/
static void check_pendings(struct sip_pvt *p)
{
......@@ -22986,7 +22990,11 @@ static void check_pendings(struct sip_pvt *p)
sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
} else if (ast_test_flag(&p->flags[0], SIP_NEEDREINVITE)) {
/* if we can't REINVITE, hold it for later */
if (p->pendinginvite || p->invitestate == INV_CALLING || p->invitestate == INV_PROCEEDING || p->invitestate == INV_EARLY_MEDIA || p->waitid > -1) {
if (p->pendinginvite
|| p->invitestate == INV_CALLING
|| p->invitestate == INV_PROCEEDING
|| p->invitestate == INV_EARLY_MEDIA
|| p->waitid > -1) {
ast_debug(2, "NOT Sending pending reinvite (yet) on '%s'\n", p->callid);
} else {
ast_debug(2, "Sending pending reinvite on '%s'\n", p->callid);
......@@ -22997,10 +23005,39 @@ static void check_pendings(struct sip_pvt *p)
}
}
 
/*! \brief Reset the NEEDREINVITE flag after waiting when we get 491 on a Re-invite
to avoid race conditions between asterisk servers.
Called from the scheduler.
*/
/* Run by the sched thread. */
static int __sched_check_pendings(const void *data)
{
struct sip_pvt *pvt = (void *) data;
struct ast_channel *owner;
owner = sip_pvt_lock_full(pvt);
check_pendings(pvt);
if (owner) {
ast_channel_unlock(owner);
ast_channel_unref(owner);
}
sip_pvt_unlock(pvt);
dialog_unref(pvt, "Check pending actions action");
return 0;
}
static void sched_check_pendings(struct sip_pvt *pvt)
{
dialog_ref(pvt, "Check pending actions action");
if (ast_sched_add(sched, 0, __sched_check_pendings, pvt) < 0) {
/* Uh Oh. Expect bad behavior. */
dialog_unref(pvt, "Failed to schedule check pending actions action");
}
}
/*!
* \brief Reset the NEEDREINVITE flag after waiting when we get 491 on a Re-invite
* to avoid race conditions between asterisk servers.
*
* \note Run by the sched thread.
*/
static int sip_reinvite_retry(const void *data)
{
struct sip_pvt *p = (struct sip_pvt *) data;
......@@ -23019,10 +23056,30 @@ static int sip_reinvite_retry(const void *data)
if (owner) {
ast_channel_unlock(owner);
}
dialog_unref(p, "unref the dialog ptr from sip_reinvite_retry, because it held a dialog ptr");
dialog_unref(p, "Schedule waitid complete");
return 0;
}
/* Run by the sched thread. */
static int __stop_reinvite_retry(const void *data)
{
struct sip_pvt *pvt = (void *) data;
AST_SCHED_DEL_UNREF(sched, pvt->waitid,
dialog_unref(pvt, "Stop scheduled waitid"));
dialog_unref(pvt, "Stop reinvite retry action");
return 0;
}
 
static void stop_reinvite_retry(struct sip_pvt *pvt)
{
dialog_ref(pvt, "Stop reinvite retry action");
if (ast_sched_add(sched, 0, __stop_reinvite_retry, pvt) < 0) {
/* Uh Oh. Expect bad behavior. */
dialog_unref(pvt, "Failed to schedule stop reinvite retry action");
}
}
/*!
* \brief Handle authentication challenge for SIP UPDATE
*
......@@ -23247,7 +23304,7 @@ static void handle_response_invite(struct sip_pvt *p, int resp, const char *rest
if (!req->ignore && p->invitestate != INV_CANCELLED) {
sip_cancel_destroy(p);
}
check_pendings(p);
sched_check_pendings(p);
break;
 
case 180: /* 180 Ringing */
......@@ -23305,7 +23362,7 @@ static void handle_response_invite(struct sip_pvt *p, int resp, const char *rest
}
ast_rtp_instance_activate(p->rtp);
}
check_pendings(p);
sched_check_pendings(p);
break;
 
case 181: /* Call Is Being Forwarded */
......@@ -23338,7 +23395,7 @@ static void handle_response_invite(struct sip_pvt *p, int resp, const char *rest
ast_party_redirecting_free(&redirecting);
sip_handle_cc(p, req, AST_CC_CCNR);
}
check_pendings(p);
sched_check_pendings(p);
break;
 
case 183: /* Session progress */
......@@ -23399,7 +23456,7 @@ static void handle_response_invite(struct sip_pvt *p, int resp, const char *rest
ast_queue_control(p->owner, AST_CONTROL_RINGING);
}
}
check_pendings(p);
sched_check_pendings(p);
break;
 
case 200: /* 200 OK on invite - someone's answering our call */
......@@ -23550,7 +23607,7 @@ static void handle_response_invite(struct sip_pvt *p, int resp, const char *rest
p->invitestate = INV_TERMINATED;
ast_set_flag(&p->flags[1], SIP_PAGE2_DIALOG_ESTABLISHED);
xmitres = transmit_request(p, SIP_ACK, seqno, XMIT_UNRELIABLE, TRUE);
check_pendings(p);
sched_check_pendings(p);
break;
 
case 407: /* Proxy authentication */
......@@ -23662,7 +23719,7 @@ static void handle_response_invite(struct sip_pvt *p, int resp, const char *rest
update_call_counter(p, DEC_CALL_LIMIT);
append_history(p, "Hangup", "Got 487 on CANCEL request from us on call without owner. Killing this dialog.");
}
check_pendings(p);
sched_check_pendings(p);
sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
break;
case 415: /* Unsupported media type */
......@@ -23694,6 +23751,7 @@ static void handle_response_invite(struct sip_pvt *p, int resp, const char *rest
/* Reset the flag after a while
*/
int wait;
/* RFC 3261, if owner of call, wait between 2.1 to 4 seconds,
* if not owner of call, wait 0 to 2 seconds */
if (p->outgoing_call) {
......@@ -23701,7 +23759,12 @@ static void handle_response_invite(struct sip_pvt *p, int resp, const char *rest
} else {
wait = ast_random() % 2000;
}
p->waitid = ast_sched_add(sched, wait, sip_reinvite_retry, dialog_ref(p, "passing dialog ptr into sched structure based on waitid for sip_reinvite_retry."));
dialog_ref(p, "Schedule waitid for sip_reinvite_retry.");
p->waitid = ast_sched_add(sched, wait, sip_reinvite_retry, p);
if (p->waitid < 0) {
/* Uh Oh. Expect bad behavior. */
dialog_ref(p, "Failed to schedule waitid");
}
ast_debug(2, "Reinvite race. Scheduled sip_reinvite_retry in %d secs in handle_response_invite (waitid %d, dialog '%s')\n",
wait, p->waitid, p->callid);
}
......@@ -26914,7 +26977,7 @@ static int handle_request_bye(struct sip_pvt *p, struct sip_request *req)
 
/* Destroy any pending invites so we won't try to do another
* scheduled reINVITE. */
AST_SCHED_DEL_UNREF(sched, p->waitid, dialog_unref(p, "decrement refcount from sip_destroy because waitid won't be scheduled"));
stop_reinvite_retry(p);
 
return 1;
}
......@@ -28446,7 +28509,7 @@ static int handle_incoming(struct sip_pvt *p, struct sip_request *req, struct as
ast_queue_control(p->owner, AST_CONTROL_SRCCHANGE);
}
}
check_pendings(p);
sched_check_pendings(p);
} else if (p->glareinvite == seqno) {
/* handle ack for the 491 pending sent for glareinvite */
p->glareinvite = 0;
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