[Asterisk-code-review] bridge.c: NULL app causes crash during attended transfer (asterisk[certified/13.1])

[Matt Jordan]

Matt Jordan has uploaded a new change for review.

  https://gerrit.asterisk.org/398

Change subject: bridge.c: NULL app causes crash during attended transfer
......................................................................

bridge.c: NULL app causes crash during attended transfer

Due to a race condition there was a chance that during an attended transfer the
channel's application would return NULL. This, of course, would cause a crash
when attempting to access the memory. This patch retrieves the channel's app
at an earlier time in processing in hopes that the app name is available.
However, if it is not then "unknown" is used instead. Since some string value
is now always present the crash can no longer occur.

ASTERISK-24869 #close
Reported by: viniciusfontes
Review:

Change-Id: I5134b84c4524906d8148817719d76ffb306488ac
---
M main/bridge.c
1 file changed, 6 insertions(+), 1 deletion(-)


  git pull ssh://gerrit.asterisk.org:29418/asterisk refs/changes/98/398/1

diff --git a/main/bridge.c b/main/bridge.c
index be4088a..00ea602 100644
--- a/main/bridge.c
+++ b/main/bridge.c
@@ -4486,6 +4486,12 @@
 	chan_bridged = to_transferee_bridge ? to_transferee : to_transfer_target;
 	chan_unbridged = to_transferee_bridge ? to_transfer_target : to_transferee;
 
+	/*
+	 * Race condition makes it possible for app to be NULL, so get the app prior to
+	 * transferring with a fallback of "unknown".
+	 */
+	app = ast_strdupa(ast_channel_appl(chan_unbridged) ?: "unknown");
+
 	{
 		int chan_count;
 		SCOPED_LOCK(lock, the_bridge, ast_bridge_lock, ast_bridge_unlock);
@@ -4527,7 +4533,6 @@
 		goto end;
 	}
 
-	app = ast_strdupa(ast_channel_appl(chan_unbridged));
 	if (bridge_channel_internal_queue_attended_transfer(transferee, chan_unbridged)) {
 		res = AST_BRIDGE_TRANSFER_FAIL;
 		goto end;

-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I5134b84c4524906d8148817719d76ffb306488ac
Gerrit-PatchSet: 1
Gerrit-Project: asterisk
Gerrit-Branch: certified/13.1
Gerrit-Owner: Matt Jordan <mjordan at digium.com>
Gerrit-Reviewer: Kevin Harwell <kharwell at digium.com>