logging: multidomain_link: fix crash caused by drop notification

The remote domain may send unsolicited Z_LOG_MULTIDOMAIN_ID_DROPPED IPC
messages, which are not handled in log_multidomain_link_on_recv_cb().
With CONFIG_ASSERT=y, this will cause an assertion failure. With asserts
disabled, this message would be treated as a reply to any in progress
request and cause getter_msg_process() to return early. In turn, this
can cause various kinds of memory corruption when the real reply arrives
and the callback reads/writes stack variables that are no longer valid.

Fix this by explicitly ignoring Z_LOG_MULTIDOMAIN_ID_DROPPED, and also
don't treat unrecognized message types as replies.

Signed-off-by: Ben Wolsieffer <[email protected]>

Author: lopsided98

subsys/logging/log_multidomain_link.c

@@ -76,11 +76,13 @@ void log_multidomain_link_on_recv_cb(struct log_multidomain_link *link_remote,
 	case Z_LOG_MULTIDOMAIN_ID_SET_RUNTIME_LEVEL:
 		link_remote->dst.set_runtime_level.level = msg->data.set_rt_level.runtime_level;
 		break;
+	case Z_LOG_MULTIDOMAIN_ID_DROPPED:
+		return;
 	case Z_LOG_MULTIDOMAIN_ID_READY:
 		break;
 	default:
 		__ASSERT(0, "Unexpected message");
-		break;
+		return;
 	}
 
 exit: