Thread (393 messages) 393 messages, 5 authors, 2020-09-30
STALE2112d

[PATCH 5.4 264/388] fuse: dont check refcount after stealing page

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2020-09-29 11:41:47
Also in: lkml
Subsystem: filesystems (vfs and infrastructure), fuse filesystem [core], the rest · Maintainers: Alexander Viro, Christian Brauner, Miklos Szeredi, Linus Torvalds

From: Miklos Szeredi <redacted>

[ 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 <redacted>
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 06dd38e76c62a..f9022b7028754 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -764,7 +764,6 @@ 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


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