[nrf fromtree] lib: posix: Fix NULL pointer to strcmp in posix mqueue.

When a queue has been unlinked but not removed the name pointer is set to
NULL. The queue is still in the list when adding new queues and the name
pointer is passed to strcmp.

Signed-off-by: Jari Tervonen <[email protected]>
(cherry picked from commit 3b1e60d)

Author: tervonenja

lib/posix/options/mqueue.c

@@ -424,7 +424,7 @@ static mqueue_object *find_in_list(const char *name)
 
 	while (mq != NULL) {
 		msg_queue = (mqueue_object *)mq;
-		if (strcmp(msg_queue->name, name) == 0) {
+		if ((msg_queue->name != NULL) && (strcmp(msg_queue->name, name) == 0)) {
 			return msg_queue;
 		}
 

tests/posix/xsi_realtime/src/mqueue.c

@@ -271,3 +271,29 @@ ZTEST(xsi_realtime, test_mqueue_notify_errors)
 	zassert_ok(mq_close(mqd), "Unable to close message queue descriptor.");
 	zassert_ok(mq_unlink(queue), "Unable to unlink queue");
 }
+
+ZTEST(xsi_realtime, test_mqueue_open_and_unlink_multiple)
+{
+	const char *q1 = "q1";
+	const char *q2 = "q2";
+
+	mqd_t mqd1, mqd2;
+	struct mq_attr attrs = {
+		.mq_msgsize = MESSAGE_SIZE,
+		.mq_maxmsg = MESG_COUNT_PERMQ,
+	};
+
+	int32_t mode = 0600;
+	int flags = O_RDWR | O_CREAT;
+
+	mqd1 = mq_open(q1, flags, mode, &attrs);
+
+	zassert_ok(mq_unlink(q1), "Unable to unlink q1");
+
+	mqd2 = mq_open(q2, flags, mode, &attrs);
+
+	zassert_ok(mq_unlink(q2), "Unable to unlink q2");
+
+	zassert_ok(mq_close(mqd1), "Unable to close message queue 1 descriptor.");
+	zassert_ok(mq_close(mqd2), "Unable to close message queue 2 descriptor.");
+}