chan_sip: Fix theoretical leak of p->refer.

If transmit_refer is called when p->refer is already allocated,
it leaks the previous allocation.  Updated code to always free
previous allocation during a new allocation.  Also instead of
checking if we have a previous allocation, always create a
clean record.

ASTERISK-15242 #close
Reported by: David Woolley
Review: https://reviewboard.asterisk.org/r/4160/


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@428117 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -1431,6 +1431,7 @@ static int dialog_find_multiple(void *obj, void *arg, int flags);
 static struct ast_channel *sip_pvt_lock_full(struct sip_pvt *pvt);
 /* static int sip_addrcmp(char *name, struct sockaddr_in *sin);	Support for peer matching */
 static int sip_refer_alloc(struct sip_pvt *p);
+static void sip_refer_destroy(struct sip_pvt *p);
 static int sip_notify_alloc(struct sip_pvt *p);
 static void ast_quiet_chan(struct ast_channel *chan);
 static int attempt_transfer(struct sip_dual *transferer, struct sip_dual *target);
@@ -6405,14 +6406,7 @@ void __sip_destroy(struct sip_pvt *p, int lockowner, int lockdialoglist)
 		ast_udptl_destroy(p->udptl);
 		p->udptl = NULL;
 	}
-	if (p->refer) {
-		if (p->refer->refer_call) {
-			p->refer->refer_call = dialog_unref(p->refer->refer_call, "unref dialog p->refer->refer_call");
-		}
-		ast_string_field_free_memory(p->refer);
-		ast_free(p->refer);
-		p->refer = NULL;
-	}
+	sip_refer_destroy(p);
 	if (p->route) {
 		free_old_route(p->route);
 		p->route = NULL;
@@ -15374,10 +15368,24 @@ static int transmit_message(struct sip_pvt *p, int init, int auth)
 /*! \brief Allocate SIP refer structure */
 static int sip_refer_alloc(struct sip_pvt *p)
 {
+	sip_refer_destroy(p);
 	p->refer = ast_calloc_with_stringfields(1, struct sip_refer, 512);
 	return p->refer ? 1 : 0;
 }
 
+/*! \brief Destroy SIP refer structure */
+static void sip_refer_destroy(struct sip_pvt *p)
+{
+	if (p->refer) {
+		if (p->refer->refer_call) {
+			p->refer->refer_call = dialog_unref(p->refer->refer_call, "unref dialog p->refer->refer_call");
+		}
+		ast_string_field_free_memory(p->refer);
+		ast_free(p->refer);
+		p->refer = NULL;
+	}
+}
+
 /*! \brief Allocate SIP refer structure */
 static int sip_notify_alloc(struct sip_pvt *p)
 {
@@ -17862,8 +17870,9 @@ static int get_also_info(struct sip_pvt *p, struct sip_request *oreq)
 	struct sip_refer *refer = NULL;
 	const char *transfer_context = NULL;
 
-	if (!p->refer && !sip_refer_alloc(p))
+	if (!sip_refer_alloc(p)) {
 		return -1;
+	}
 
 	refer = p->refer;
 
@@ -25342,7 +25351,7 @@ static int handle_request_invite(struct sip_pvt *p, struct sip_request *req, str
 		replace_id = ast_strdupa(p_replaces);
 		ast_uri_decode(replace_id, ast_uri_sip_user);
 
-		if (!p->refer && !sip_refer_alloc(p)) {
+		if (!sip_refer_alloc(p)) {
 			transmit_response_reliable(p, "500 Server Internal Error", req);
 			append_history(p, "Xfer", "INVITE/Replace Failed. Out of memory.");
 			sip_scheddestroy(p, DEFAULT_TRANS_TIMEOUT);
@@ -26302,7 +26311,7 @@ static int handle_request_refer(struct sip_pvt *p, struct sip_request *req, uint
 	}
 
 	/* Allocate memory for call transfer data */
-	if (!p->refer && !sip_refer_alloc(p)) {
+	if (!sip_refer_alloc(p)) {
 		transmit_response(p, "500 Internal Server Error", req);
 		append_history(p, "Xfer", "Refer failed. Memory allocation error.");
 		res = -3;