linux-kernel - [PATCH 3.11 156/233] dm space map metadata: fix bug in resizing of thin metadata

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1391773652-25214-157-git-send-email-luis.henriques@canonical.com>
Date:	Fri,  7 Feb 2014 11:46:15 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Joe Thornber <ejt@...hat.com>, Mike Snitzer <snitzer@...hat.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.11 156/233] dm space map metadata: fix bug in resizing of thin metadata

3.11.10.4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joe Thornber <ejt@...hat.com>

commit fca028438fb903852beaf7c3fe1cd326651af57d upstream.

This bug was introduced in commit 7e664b3dec431e ("dm space map metadata:
fix extending the space map").

When extending a dm-thin metadata volume we:

- Switch the space map into a simple bootstrap mode, which allocates
  all space linearly from the newly added space.
- Add new bitmap entries for the new space
- Increment the reference counts for those newly allocated bitmap
  entries
- Commit changes to disk
- Switch back out of bootstrap mode.

But, the disk commit may allocate space itself, if so this fact will be
lost when switching out of bootstrap mode.

The bug exhibited itself as an error when the bitmap_root, with an
erroneous ref count of 0, was subsequently decremented as part of a
later disk commit.  This would cause the disk commit to fail, and thinp
to enter read_only mode.  The metadata was not damaged (thin_check
passed).

The fix is to put the increments + commit into a loop, running until
the commit has not allocated extra space.  In practise this loop only
runs twice.

With this fix the following device mapper testsuite test passes:
 dmtest run --suite thin-provisioning -n thin_remove_works_after_resize

Signed-off-by: Joe Thornber <ejt@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/md/persistent-data/dm-space-map-metadata.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/md/persistent-data/dm-space-map-metadata.c b/drivers/md/persistent-data/dm-space-map-metadata.c
index f04d92f..afb419e 100644
--- a/drivers/md/persistent-data/dm-space-map-metadata.c
+++ b/drivers/md/persistent-data/dm-space-map-metadata.c
@@ -617,13 +617,23 @@ static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
 	if (r)
 		goto out;
 
-	for (i = old_len; !r && i < smm->begin; i++) {
-		r = sm_ll_inc(&smm->ll, i, &ev);
+	/*
+	 * We repeatedly increment then commit until the commit doesn't
+	 * allocate any new blocks.
+	 */
+	do {
+		for (i = old_len; !r && i < smm->begin; i++) {
+			r = sm_ll_inc(&smm->ll, i, &ev);
+			if (r)
+				goto out;
+		}
+		old_len = smm->begin;
+
+		r = sm_ll_commit(&smm->ll);
 		if (r)
 			goto out;
-	}
 
-	r = sm_metadata_commit(sm);
+	} while (old_len != smm->begin);
 
 out:
 	/*
-- 
1.8.3.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/