From: David Howells <dhowells@redhat.com>
Date: Fri, 11 Mar 2022 13:23:46 +0000 (+0000)
Subject: watch_queue: Fix to release page in ->release()
X-Git-Tag: v5.17-rc8~9^2~8
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=c1853fbadcba1497f4907971e7107888e0714c81;p=people%2Fjgross%2Flinux.git

watch_queue: Fix to release page in ->release()

When a pipe ring descriptor points to a notification message, the
refcount on the backing page is incremented by the generic get function,
but the release function, which marks the bitmap, doesn't drop the page
ref.

Fix this by calling generic_pipe_buf_release() at the end of
watch_queue_pipe_buf_release().

Fixes: c73be61cede5 ("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>
---

diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c
index 427b0318e303..dfb3a7e28280 100644
--- a/kernel/watch_queue.c
+++ b/kernel/watch_queue.c
@@ -54,6 +54,7 @@ static void watch_queue_pipe_buf_release(struct pipe_inode_info *pipe,
 	bit += page->index;
 
 	set_bit(bit, wqueue->notes_bitmap);
+	generic_pipe_buf_release(pipe, buf);
 }
 
 // No try_steal function => no stealing