ipc: fix double sem unlock in semctl error path

Fix another ipc locking buglet introduced by the scalability patches:
when semctl_down() was changed to delay the semaphore locking, one error
path for security_sem_semctl() went through the semaphore unlock logic
even though the semaphore had never been locked.

Introduced by commit 16df367 ("ipc,sem: do not hold ipc lock more
than necessary")

Acked-by: Davidlohr Bueso <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

ipc/sem.c

@@ -1280,7 +1280,7 @@ static int semctl_down(struct ipc_namespace *ns, int semid,
 	err = security_sem_semctl(sma, cmd);
 	if (err) {
 		rcu_read_unlock();
-		goto out_unlock;
+		goto out_up;
 	}
 
 	switch(cmd){