2.6.39-stable review patch. If anyone has any objections, please let us know.
------------------
From: Linus Torvalds <torva...@linux-foundation.org>
Backport of commit 59430262401bec02d415179c43dbe5b8819c09ce
done by Hugh Dickins <hu...@google.com>
Don't update *inode in __follow_mount_rcu() until we'd verified that
there is mountpoint there. Kudos to Hugh Dickins for catching that
one in the first place and eventually figuring out the solution (and
catching a braino in the earlier version of patch).
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Cc: Hugh Dickins <hu...@google.com>
Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
---
fs/namei.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1013,7 +1013,6 @@ static bool __follow_mount_rcu(struct na
* Don't forget we might have a non-mountpoint managed dentry
* that wants to block transit.
*/
- *inode = path->dentry->d_inode;
if (!reverse_transit &&
unlikely(managed_dentry_might_block(path->dentry)))
return false;
@@ -1027,6 +1026,12 @@ static bool __follow_mount_rcu(struct na
path->mnt = mounted;
path->dentry = mounted->mnt_root;
nd->seq = read_seqcount_begin(&path->dentry->d_seq);
+ /*
+ * Update the inode too. We don't need to re-check the
+ * dentry sequence number here after this d_inode read,
+ * because a mount-point is always pinned.
+ */
+ *inode = path->dentry->d_inode;
}
if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
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