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authorAl Viro <viro@zeniv.linux.org.uk>2018-08-09 10:15:54 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2018-08-09 18:07:15 -0400
commit4c0d7cd5c8416b1ef41534d19163cb07ffaa03ab (patch)
tree1271fc0ec0ee812900750b246c90afd807efabac
parent119e1ef80ecfe0d1deb6378d4ab41f5b71519de1 (diff)
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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" <threeearcat@gmail.com> Cc: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/dcache.c7
1 files changed, 2 insertions, 5 deletions
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)