[3.11.y.z extended stable] Patch "xfs: fix directory hash ordering bug" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    xfs: fix directory hash ordering bug

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From d7f726a0b549e7c62294527d95f7cbeec44854f5 Mon Sep 17 00:00:00 2001
From: Mark Tinguely <tinguely at sgi.com>
Date: Fri, 4 Apr 2014 07:10:49 +1100
Subject: xfs: fix directory hash ordering bug

commit c88547a8119e3b581318ab65e9b72f27f23e641d upstream.

Commit f5ea1100 ("xfs: add CRCs to dir2/da node blocks") introduced
in 3.10 incorrectly converted the btree hash index array pointer in
xfs_da3_fixhashpath(). It resulted in the the current hash always
being compared against the first entry in the btree rather than the
current block index into the btree block's hash entry array. As a
result, it was comparing the wrong hashes, and so could misorder the
entries in the btree.

For most cases, this doesn't cause any problems as it requires hash
collisions to expose the ordering problem. However, when there are
hash collisions within a directory there is a very good probability
that the entries will be ordered incorrectly and that actually
matters when duplicate hashes are placed into or removed from the
btree block hash entry array.

This bug results in an on-disk directory corruption and that results
in directory verifier functions throwing corruption warnings into
the logs. While no data or directory entries are lost, access to
them may be compromised, and attempts to remove entries from a
directory that has suffered from this corruption may result in a
filesystem shutdown.  xfs_repair will fix the directory hash
ordering without data loss occuring.

[dchinner: wrote useful a commit message]

Reported-by: Hannes Frederic Sowa <hannes at stressinduktion.org>
Signed-off-by: Mark Tinguely <tinguely at sgi.com>
Reviewed-by: Ben Myers <bpm at sgi.com>
Signed-off-by: Dave Chinner <david at fromorbit.com>
[ luis: backported to 3.11: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/xfs/xfs_da_btree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_da_btree.c b/fs/xfs/xfs_da_btree.c
index eca6f9d..79ddbaf 100644
--- a/fs/xfs/xfs_da_btree.c
+++ b/fs/xfs/xfs_da_btree.c
@@ -1334,7 +1334,7 @@ xfs_da3_fixhashpath(
 		node = blk->bp->b_addr;
 		xfs_da3_node_hdr_from_disk(&nodehdr, node);
 		btree = xfs_da3_node_tree_p(node);
-		if (be32_to_cpu(btree->hashval) == lasthash)
+		if (be32_to_cpu(btree[blk->index].hashval) == lasthash)
 			break;
 		blk->hashval = lasthash;
 		btree[blk->index].hashval = cpu_to_be32(lasthash);
--
1.9.1