res_pjsip_session: segfault on already disconnected session

On heavy loaded system the TCP/TLS incoming calls could be
disconnected by pjproject while these calls are being
processed by asterisk which could use the session's memory pools.
If the session in the disconnected state then the session memory
pools were already freed, so we get segfault.

This patch adds a lifetime control on an INVITE session to pjproject.
The lifetime of the session is manipulated by calling
pjsip_inv_add_ref/pjsip_inv_dec_ref.
This patch uses these functions to inform pjproject that the
session is in use.

This patch adds check if the session state is not disconnected
and also checks if the memory pool is not NULL.

This patch also places tasks 'session_end' and 'session_end_completion'
into session's serializer to avoid race condition.

ASTERISK-26291 #close

Change-Id: I4d28b1fb3b91f0492a911d110049d670fdc3c8d7

2 files changed, 213 insertions, 0 deletions

diff --git a/third-party/pjproject/configure.m4 b/third-party/pjproject/configure.m4
index 67ac04d4d..7a079f657 100644
--- a/third-party/pjproject/configure.m4
+++ b/third-party/pjproject/configure.m4
@@ -45,4 +45,5 @@ AC_DEFUN([PJPROJECT_CONFIGURE],
 	PJPROJECT_SYMBOL_CHECK([PJSIP_EXTERNAL_RESOLVER], [pjsip_endpt_set_ext_resolver], [pjsip.h])
 	AC_DEFINE([HAVE_PJSIP_TLS_TRANSPORT_PROTO], 1, [Define if your system has PJSIP_TLS_TRANSPORT_PROTO])
 	AC_DEFINE([HAVE_PJSIP_EVSUB_GRP_LOCK], 1, [Define if your system has PJSIP_EVSUB_GRP_LOCK])
+	AC_DEFINE([HAVE_PJSIP_INV_SESSION_REF], 1, [Define if your system has PJSIP_INV_SESSION_REF])
 ])
diff --git a/third-party/pjproject/patches/0002-r5435-add-pjsip_inv_session-ref_cnt.patch b/third-party/pjproject/patches/0002-r5435-add-pjsip_inv_session-ref_cnt.patch
new file mode 100644
index 000000000..12ae6a028
--- /dev/null
+++ b/third-party/pjproject/patches/0002-r5435-add-pjsip_inv_session-ref_cnt.patch
@@ -0,0 +1,212 @@
+When a transport error occured on an INVITE session
+the stack calls on_tsx_state_changed with new state
+PJSIP_INV_STATE_DISCONNECTED and immediately destroys
+the INVITE session.
+At the same time this INVITE session could being processed
+on another thread. This thread could use the session's
+memory pools which were already freed, so we get segfault.
+
+This patch adds a reference counter and new functions:
+pjsip_inv_add_ref and pjsip_inv_dec_ref.
+The INVITE session is destroyed only when the reference
+counter has reached zero.
+
+To avoid race condition an application should call
+pjsip_inv_add_ref/pjsip_inv_dec_ref.
+
+Index: pjsip/include/pjsip-ua/sip_inv.h
+===================================================================
+--- a/pjsip/include/pjsip-ua/sip_inv.h	(revision 5434)
++++ b/pjsip/include/pjsip-ua/sip_inv.h	(revision 5435)
+@@ -383,6 +383,11 @@
+  * Other applications that want to use these pools must understand
+  * that the flip-flop pool's lifetimes are synchronized to the
+  * SDP offer-answer negotiation.
++ *
++ * The lifetime of this session is controlled by the reference counter in this
++ * structure, which is manipulated by calling #pjsip_inv_add_ref and
++ * #pjsip_inv_dec_ref. When the reference counter has reached zero, then
++ * this session will be destroyed.
+  */
+ struct pjsip_inv_session
+ {
+@@ -412,6 +417,7 @@
+     struct pjsip_timer	*timer;			    /**< Session Timers.    */
+     pj_bool_t		 following_fork;	    /**< Internal, following
+ 							 forked media?	    */
++    pj_atomic_t		*ref_cnt;		    /**< Reference counter. */
+ };
+ 
+ 
+@@ -631,6 +637,30 @@
+ 
+ 
+ /**
++ * Add reference counter to the INVITE session. The reference counter controls
++ * the life time of the session, ie. when the counter reaches zero, then it 
++ * will be destroyed.
++ *
++ * @param inv       The INVITE session.
++ * @return          PJ_SUCCESS if the INVITE session reference counter
++ *                  was increased.
++ */
++PJ_DECL(pj_status_t) pjsip_inv_add_ref( pjsip_inv_session *inv );
++
++/**
++ * Decrement reference counter of the INVITE session.
++ * When the session is no longer used, it will be destroyed and
++ * caller is informed with PJ_EGONE return status.
++ *
++ * @param inv       The INVITE session.
++ * @return          PJ_SUCCESS if the INVITE session reference counter
++ *                  was decreased. A status PJ_EGONE will be returned to 
++ *                  inform that session is destroyed.
++ */
++PJ_DECL(pj_status_t) pjsip_inv_dec_ref( pjsip_inv_session *inv );
++
++
++/**
+  * Forcefully terminate and destroy INVITE session, regardless of
+  * the state of the session. Note that this function should only be used
+  * when there is failure in the INVITE session creation. After the
+Index: pjsip/src/pjsip-ua/sip_inv.c
+===================================================================
+--- a/pjsip/src/pjsip-ua/sip_inv.c	(revision 5434)
++++ b/pjsip/src/pjsip-ua/sip_inv.c	(revision 5435)
+@@ -195,6 +195,65 @@
+ }
+ 
+ /*
++ * Add reference to INVITE session.
++ */
++PJ_DEF(pj_status_t) pjsip_inv_add_ref( pjsip_inv_session *inv )
++{
++    PJ_ASSERT_RETURN(inv && inv->ref_cnt, PJ_EINVAL);
++
++    pj_atomic_inc(inv->ref_cnt);
++
++    return PJ_SUCCESS;
++}
++
++static void inv_session_destroy(pjsip_inv_session *inv)
++{
++    if (inv->last_ack) {
++	pjsip_tx_data_dec_ref(inv->last_ack);
++	inv->last_ack = NULL;
++    }
++    if (inv->invite_req) {
++	pjsip_tx_data_dec_ref(inv->invite_req);
++	inv->invite_req = NULL;
++    }
++    if (inv->pending_bye) {
++	pjsip_tx_data_dec_ref(inv->pending_bye);
++	inv->pending_bye = NULL;
++    }
++    pjsip_100rel_end_session(inv);
++    pjsip_timer_end_session(inv);
++    pjsip_dlg_dec_session(inv->dlg, &mod_inv.mod);
++
++    /* Release the flip-flop pools */
++    pj_pool_release(inv->pool_prov);
++    inv->pool_prov = NULL;
++    pj_pool_release(inv->pool_active);
++    inv->pool_active = NULL;
++
++    pj_atomic_destroy(inv->ref_cnt);
++    inv->ref_cnt = NULL;
++}
++
++/*
++ * Decrease INVITE session reference, destroy it when the reference count
++ * reaches zero.
++ */
++PJ_DEF(pj_status_t) pjsip_inv_dec_ref( pjsip_inv_session *inv )
++{
++    pj_atomic_value_t ref_cnt;
++
++    PJ_ASSERT_RETURN(inv && inv->ref_cnt, PJ_EINVAL);
++
++    ref_cnt = pj_atomic_dec_and_get(inv->ref_cnt);
++    pj_assert( ref_cnt >= 0);
++    if (ref_cnt == 0) {
++        inv_session_destroy(inv);
++        return PJ_EGONE;
++    } 
++    return PJ_SUCCESS;    
++}
++
++/*
+  * Set session state.
+  */
+ static void inv_set_state(pjsip_inv_session *inv, pjsip_inv_state state,
+@@ -261,27 +320,7 @@
+     if (inv->state == PJSIP_INV_STATE_DISCONNECTED &&
+ 	prev_state != PJSIP_INV_STATE_DISCONNECTED) 
+     {
+-	if (inv->last_ack) {
+-	    pjsip_tx_data_dec_ref(inv->last_ack);
+-	    inv->last_ack = NULL;
+-	}
+-	if (inv->invite_req) {
+-	    pjsip_tx_data_dec_ref(inv->invite_req);
+-	    inv->invite_req = NULL;
+-	}
+-	if (inv->pending_bye) {
+-	    pjsip_tx_data_dec_ref(inv->pending_bye);
+-	    inv->pending_bye = NULL;
+-	}
+-	pjsip_100rel_end_session(inv);
+-	pjsip_timer_end_session(inv);
+-	pjsip_dlg_dec_session(inv->dlg, &mod_inv.mod);
+-
+-	/* Release the flip-flop pools */
+-	pj_pool_release(inv->pool_prov);
+-	inv->pool_prov = NULL;
+-	pj_pool_release(inv->pool_active);
+-	inv->pool_active = NULL;
++	pjsip_inv_dec_ref(inv);
+     }
+ }
+ 
+@@ -838,6 +877,12 @@
+     inv = PJ_POOL_ZALLOC_T(dlg->pool, pjsip_inv_session);
+     pj_assert(inv != NULL);
+ 
++    status = pj_atomic_create(dlg->pool, 0, &inv->ref_cnt);
++    if (status != PJ_SUCCESS) {
++	pjsip_dlg_dec_lock(dlg);
++	return status;
++    }
++
+     inv->pool = dlg->pool;
+     inv->role = PJSIP_ROLE_UAC;
+     inv->state = PJSIP_INV_STATE_NULL;
+@@ -881,6 +926,7 @@
+     pjsip_100rel_attach(inv);
+ 
+     /* Done */
++    pjsip_inv_add_ref(inv);
+     *p_inv = inv;
+ 
+     pjsip_dlg_dec_lock(dlg);
+@@ -1471,6 +1517,12 @@
+     inv = PJ_POOL_ZALLOC_T(dlg->pool, pjsip_inv_session);
+     pj_assert(inv != NULL);
+ 
++    status = pj_atomic_create(dlg->pool, 0, &inv->ref_cnt);
++    if (status != PJ_SUCCESS) {
++	pjsip_dlg_dec_lock(dlg);
++	return status;
++    }
++
+     inv->pool = dlg->pool;
+     inv->role = PJSIP_ROLE_UAS;
+     inv->state = PJSIP_INV_STATE_NULL;
+@@ -1540,6 +1592,7 @@
+     }
+ 
+     /* Done */
++    pjsip_inv_add_ref(inv);
+     pjsip_dlg_dec_lock(dlg);
+     *p_inv = inv;
+