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    Subject[PATCH 4.9 087/121] fuse: dont check refcount after stealing page
    Date
    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 b99225e117120..f0129c033bd66 100644
    --- a/fs/fuse/dev.c
    +++ b/fs/fuse/dev.c
    @@ -825,7 +825,6 @@ 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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