watch_queue: Free the alloc bitmap when the watch_queue is torn down

Free the watch_queue note allocation bitmap when the watch_queue is
destroyed.

Fixes: c73be61ced ("pipe: Add general notification queue support")
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/watch_queue.c

@@ -370,6 +370,7 @@ static void __put_watch_queue(struct kref *kref)
 
 	for (i = 0; i < wqueue->nr_pages; i++)
 		__free_page(wqueue->notes[i]);
+	bitmap_free(wqueue->notes_bitmap);
 
 	wfilter = rcu_access_pointer(wqueue->filter);
 	if (wfilter)