[PATCH AUTOSEL 4.4 53/64] fuse: don't check refcount after stealing page

Sasha Levin
2020-09-18T02:18:09Z

From: Miklos Szeredi <mszeredi@redhat.com>

[ Upstream commit 32f98877c57bee6bc27f443a96f49678a2cd6a50 ]

page_count() is unstable. Unless there has been an RCU grace period
between when the page was removed from the page cache and now, a
speculative reference may exist from the page cache.

Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/fuse/dev.c | 1 -
1 file changed, 1 deletion(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 8142f6bf3d310..fc265f4b839ae 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -850,7 +850,6 @@ static int fuse_check_page(struct page *page)
{
if (page_mapcount(page) ||
page->mapping != NULL ||
- page_count(page) != 1 ||
(page->flags & PAGE_FLAGS_CHECK_AT_PREP &
~(1 << PG_locked |
1 << PG_referenced |
--
2.25.1