linux-kernel - [PATCH 5.15 097/110] watch_queue: Fix the alloc bitmap size to reflect notes allocated

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Date:   Mon, 14 Mar 2022 12:54:39 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jann Horn <jannh@...gle.com>,
        David Howells <dhowells@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.15 097/110] watch_queue: Fix the alloc bitmap size to reflect notes allocated

From: David Howells <dhowells@...hat.com>

commit 3b4c0371928c17af03e8397ac842346624017ce6 upstream.

Currently, watch_queue_set_size() sets the number of notes available in
wqueue->nr_notes according to the number of notes allocated, but sets
the size of the bitmap to the unrounded number of notes originally asked
for.

Fix this by setting the bitmap size to the number of notes we're
actually going to make available (ie. the number allocated).

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-by: Jann Horn <jannh@...gle.com>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/watch_queue.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -244,6 +244,7 @@ long watch_queue_set_size(struct pipe_in
 		goto error;
 	}
 
+	nr_notes = nr_pages * WATCH_QUEUE_NOTES_PER_PAGE;
 	ret = pipe_resize_ring(pipe, roundup_pow_of_two(nr_notes));
 	if (ret < 0)
 		goto error;
@@ -269,7 +270,7 @@ long watch_queue_set_size(struct pipe_in
 	wqueue->notes = pages;
 	wqueue->notes_bitmap = bitmap;
 	wqueue->nr_pages = nr_pages;
-	wqueue->nr_notes = nr_pages * WATCH_QUEUE_NOTES_PER_PAGE;
+	wqueue->nr_notes = nr_notes;
 	return 0;
 
 error_p: