From 4c0d7cd5c8416b1ef41534d19163cb07ffaa03ab Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 9 Aug 2018 10:15:54 -0400 Subject: make sure that __dentry_kill() always invalidates d_seq, unhashed or not RCU pathwalk relies upon the assumption that anything that changes ->d_inode of a dentry will invalidate its ->d_seq. That's almost true - the one exception is that the final dput() of already unhashed dentry does *not* touch ->d_seq at all. Unhashing does, though, so for anything we'd found by RCU dcache lookup we are fine. Unfortunately, we can *start* with an unhashed dentry or jump into it. We could try and be careful in the (few) places where that could happen. Or we could just make the final dput() invalidate the damn thing, unhashed or not. The latter is much simpler and easier to backport, so let's do it that way. Reported-by: "Dae R. Jeong" Cc: stable@vger.kernel.org Signed-off-by: Al Viro --- fs/dcache.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index d677290b0aca..ceb7b491d1b9 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -358,14 +358,11 @@ static void dentry_unlink_inode(struct dentry * dentry) __releases(dentry->d_inode->i_lock) { struct inode *inode = dentry->d_inode; - bool hashed = !d_unhashed(dentry); - if (hashed) - raw_write_seqcount_begin(&dentry->d_seq); + raw_write_seqcount_begin(&dentry->d_seq); __d_clear_type_and_inode(dentry); hlist_del_init(&dentry->d_u.d_alias); - if (hashed) - raw_write_seqcount_end(&dentry->d_seq); + raw_write_seqcount_end(&dentry->d_seq); spin_unlock(&dentry->d_lock); spin_unlock(&inode->i_lock); if (!inode->i_nlink) -- cgit v1.2.3