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chan_sip.c: Fix t38id deadlock potential.

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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.

ASTERISK-25023

Change-Id: If595e4456cd059d7171880c7f354e844c21b5f5f
This commit is contained in:
Richard Mudgett
2016-03-10 12:17:09 -06:00
parent 43556b800b
commit 32bd7a64f9
1 changed files with 81 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

103
channels/chan_sip.c
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@@ -1512,6 +1512,7 @@ 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);
static void stop_retrans_pkt(struct sip_pkt *pkt);
static void stop_t38_abort_timer(struct sip_pvt *pvt);
/*! \brief Definition of this channel for PBX channel registration */
struct ast_channel_tech sip_tech = {
@@ -7644,13 +7645,13 @@ static int interpret_t38_parameters(struct sip_pvt *p, const struct ast_control_
/* Negotiation can not take place without a valid max_ifp value. */
if (!parameters->max_ifp) {
if (p->t38.state == T38_PEER_REINVITE) {
AST_SCHED_DEL_UNREF(sched, p->t38id, dialog_unref(p, "when you delete the t38id sched, you should dec the refcount for the stored dialog ptr"));
stop_t38_abort_timer(p);
transmit_response_reliable(p, "488 Not acceptable here", &p->initreq);
}
change_t38_state(p, T38_REJECTED);
break;
} else if (p->t38.state == T38_PEER_REINVITE) {
AST_SCHED_DEL_UNREF(sched, p->t38id, dialog_unref(p, "when you delete the t38id sched, you should dec the refcount for the stored dialog ptr"));
stop_t38_abort_timer(p);
p->t38.our_parms = *parameters;
/* modify our parameters to conform to the peer's parameters,
* based on the rules in the ITU T.38 recommendation
@@ -7684,7 +7685,7 @@ static int interpret_t38_parameters(struct sip_pvt *p, const struct ast_control_
case AST_T38_REFUSED:
case AST_T38_REQUEST_TERMINATE: /* Shutdown T38 */
if (p->t38.state == T38_PEER_REINVITE) {
AST_SCHED_DEL_UNREF(sched, p->t38id, dialog_unref(p, "when you delete the t38id sched, you should dec the refcount for the stored dialog ptr"));
stop_t38_abort_timer(p);
change_t38_state(p, T38_REJECTED);
transmit_response_reliable(p, "488 Not acceptable here", &p->initreq);
} else if (p->t38.state == T38_ENABLED) {
@@ -7696,7 +7697,7 @@ static int interpret_t38_parameters(struct sip_pvt *p, const struct ast_control_
struct ast_control_t38_parameters parameters = p->t38.their_parms;
if (p->t38.state == T38_PEER_REINVITE) {
AST_SCHED_DEL_UNREF(sched, p->t38id, dialog_unref(p, "when you delete the t38id sched, you should dec the refcount for the stored dialog ptr"));
stop_t38_abort_timer(p);
parameters.max_ifp = ast_udptl_get_far_max_ifp(p->udptl);
parameters.request_response = AST_T38_REQUEST_NEGOTIATE;
if (p->owner) {
@@ -25298,27 +25299,89 @@ static int do_magic_pickup(struct ast_channel *channel, const char *extension, c
return 0;
}
/*! \brief Called to deny a T38 reinvite if the core does not respond to our request */
/*!
* \brief Called to deny a T38 reinvite if the core does not respond to our request
*
* \note Run by the sched thread.
*/
static int sip_t38_abort(const void *data)
{
struct sip_pvt *p = (struct sip_pvt *) data;
struct sip_pvt *pvt = (struct sip_pvt *) data;
struct ast_channel *owner;
sip_pvt_lock(p);
/* an application may have taken ownership of the T.38 negotiation on this
* channel while we were waiting to grab the lock... if it did, the scheduler
* id will have been reset to -1, which is our indication that we do *not*
* want to abort the negotiation process
owner = sip_pvt_lock_full(pvt);
pvt->t38id = -1;
/*
* An application may have taken ownership of the T.38 negotiation
* on the channel while we were waiting to grab the lock. If it
* did, the T.38 state will have been changed. This is our
* indication that we do *not* want to abort the negotiation
* process.
*/
if (p->t38id != -1) {
change_t38_state(p, T38_REJECTED);
transmit_response_reliable(p, "488 Not acceptable here", &p->initreq);
p->t38id = -1;
dialog_unref(p, "unref the dialog ptr from sip_t38_abort, because it held a dialog ptr");
if (pvt->t38.state == T38_PEER_REINVITE) {
/* Still waiting for a response on timeout so reject the offer. */
change_t38_state(pvt, T38_REJECTED);
transmit_response_reliable(pvt, "488 Not acceptable here", &pvt->initreq);
}
sip_pvt_unlock(p);
if (owner) {
ast_channel_unlock(owner);
ast_channel_unref(owner);
}
sip_pvt_unlock(pvt);
dialog_unref(pvt, "t38id complete");
return 0;
}
/* Run by the sched thread. */
static int __stop_t38_abort_timer(const void *data)
{
struct sip_pvt *pvt = (void *) data;
AST_SCHED_DEL_UNREF(sched, pvt->t38id,
dialog_unref(pvt, "Stop scheduled t38id"));
dialog_unref(pvt, "Stop t38id action");
return 0;
}
static void stop_t38_abort_timer(struct sip_pvt *pvt)
{
dialog_ref(pvt, "Stop t38id action");
if (ast_sched_add(sched, 0, __stop_t38_abort_timer, pvt) < 0) {
/* Uh Oh. Expect bad behavior. */
dialog_unref(pvt, "Failed to schedule stop t38id action");
}
}
/* Run by the sched thread. */
static int __start_t38_abort_timer(const void *data)
{
struct sip_pvt *pvt = (void *) data;
AST_SCHED_DEL_UNREF(sched, pvt->t38id,
dialog_unref(pvt, "Stop scheduled t38id"));
dialog_ref(pvt, "Schedule t38id");
pvt->t38id = ast_sched_add(sched, 5000, sip_t38_abort, pvt);
if (pvt->t38id < 0) {
/* Uh Oh. Expect bad behavior. */
dialog_unref(pvt, "Failed to schedule t38id");
}
dialog_unref(pvt, "Start t38id action");
return 0;
}
static void start_t38_abort_timer(struct sip_pvt *pvt)
{
dialog_ref(pvt, "Start t38id action");
if (ast_sched_add(sched, 0, __start_t38_abort_timer, pvt) < 0) {
/* Uh Oh. Expect bad behavior. */
dialog_unref(pvt, "Failed to schedule start t38id action");
}
}
/*!
* \brief bare-bones support for SIP UPDATE
*
@@ -26201,11 +26264,7 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, str
transmit_response(p, "100 Trying", req);
if (p->t38.state == T38_PEER_REINVITE) {
if (p->t38id > -1) {
/* reset t38 abort timer */
AST_SCHED_DEL_UNREF(sched, p->t38id, dialog_unref(p, "remove ref for t38id"));
}
p->t38id = ast_sched_add(sched, 5000, sip_t38_abort, dialog_ref(p, "passing dialog ptr into sched structure based on t38id for sip_t38_abort."));
start_t38_abort_timer(p);
} else if (p->t38.state == T38_ENABLED) {
ast_set_flag(&p->flags[1], SIP_PAGE2_DIALOG_ESTABLISHED);
transmit_response_with_t38_sdp(p, "200 OK", req, (reinvite ? XMIT_RELIABLE : (req->ignore ? XMIT_UNRELIABLE : XMIT_CRITICAL)));