watch_queue: fix IOC_WATCH_QUEUE_SET_SIZE alloc error paths

The watch_queue_set_size() allocation error paths return the ret value
set via the prior pipe_resize_ring() call, which will always be zero.

As a result, IOC_WATCH_QUEUE_SET_SIZE callers such as "keyctl watch"
fail to detect kernel wqueue->notes allocation failures and proceed to
KEYCTL_WATCH_KEY, with any notifications subsequently lost.

Fixes: c73be61c ("pipe: Add general notification queue support")
Signed-off-by: David Disseldorp <ddiss@suse.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>

kernel/watch_queue.c

@@ -273,6 +273,7 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
 	if (ret < 0)
 		goto error;
 
+	ret = -ENOMEM;
 	pages = kcalloc(sizeof(struct page *), nr_pages, GFP_KERNEL);
 	if (!pages)
 		goto error;