ipc/sem: do not sleep with a spin lock held

We can't call kvfree() with a spin lock held, so defer it.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: fc37a3b ("[PATCH] ipc sem: use kvmalloc for sem_undo allocation")
Reported-by: Zeal Robot <[email protected]>
Signed-off-by: Minghao Chi <[email protected]>
Reviewed-by: Shakeel Butt <[email protected]>
Reviewed-by: Manfred Spraul <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Yang Guang <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Bhaskar Chowdhury <[email protected]>
Cc: Vasily Averin <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Minghao Chi

ipc/sem.c

@@ -1964,6 +1964,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
 	 */
 	un = lookup_undo(ulp, semid);
 	if (un) {
+		spin_unlock(&ulp->lock);
 		kvfree(new);
 		goto success;
 	}
@@ -1976,9 +1977,8 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
 	ipc_assert_locked_object(&sma->sem_perm);
 	list_add(&new->list_id, &sma->list_id);
 	un = new;
-
-success:
 	spin_unlock(&ulp->lock);
+success:
 	sem_unlock(sma, -1);
 out:
 	return un;