4.9-stable review patch. If anyone has any objections, please let me know.
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From: Will Deacon will.deacon@arm.com
[ Upstream commit 8cc07c808c9d595e81cbe5aad419b7769eb2e5c9 ]
i_dir_seq is subject to concurrent modification by a cmpxchg or store-release operation, so ensure that the relaxed access in d_alloc_parallel uses READ_ONCE.
Reported-by: Peter Zijlstra peterz@infradead.org Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/dcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/dcache.c +++ b/fs/dcache.c @@ -2502,7 +2502,7 @@ retry: }
hlist_bl_lock(b); - if (unlikely(parent->d_inode->i_dir_seq != seq)) { + if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) { hlist_bl_unlock(b); rcu_read_unlock(); goto retry;