This is a note to let you know that I've just added the patch titled
vfs: fix race in rcu lookup of pruned dentry
to the 2.6.39-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
vfs-fix-race-in-rcu-lookup-of-pruned-dentry.patch
and it can be found in the queue-2.6.39 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <sta...@kernel.org> know about it.
>From hu...@google.com Mon Aug 1 11:55:24 2011
From: Hugh Dickins <hu...@google.com>
Date: Tue, 26 Jul 2011 13:04:16 -0700 (PDT)
Subject: vfs: fix race in rcu lookup of pruned dentry
To: Stable Kernel <sta...@kernel.org>
Cc: Mike Waychison <mi...@google.com>, Linus Torvalds
<torva...@linux-foundation.org>, Al Viro <v...@zeniv.linux.org.uk>, Ian Kent
<ra...@themaw.net>
Message-ID: <alpine.LSU.2.00.1107261239110.24976@sister.anvils>
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))
Patches currently in stable-queue which might be from hu...@google.com are
queue-2.6.39/vfs-fix-race-in-rcu-lookup-of-pruned-dentry.patch
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