This is a note to let you know that I've just added the patch titled
dm array: fix a reference counting bug in shadow_ablock
to the 3.12-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:
dm-array-fix-a-reference-counting-bug-in-shadow_ablock.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ed9571f0cf1fe09d3506302610f3ccdfa1d22c4a Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@xxxxxxxxxx>
Date: Fri, 13 Dec 2013 14:55:55 +0000
Subject: dm array: fix a reference counting bug in shadow_ablock
From: Joe Thornber <ejt@xxxxxxxxxx>
commit ed9571f0cf1fe09d3506302610f3ccdfa1d22c4a upstream.
An old array block could have its reference count decremented below
zero when it is being replaced in the btree by a new array block.
The fix is to increment the old ablock's reference count just before
inserting a new ablock into the btree.
Signed-off-by: Joe Thornber <ejt@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/persistent-data/dm-array.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
--- a/drivers/md/persistent-data/dm-array.c
+++ b/drivers/md/persistent-data/dm-array.c
@@ -317,8 +317,16 @@ static int shadow_ablock(struct dm_array
* The shadow op will often be a noop. Only insert if it really
* copied data.
*/
- if (dm_block_location(*block) != b)
+ if (dm_block_location(*block) != b) {
+ /*
+ * dm_tm_shadow_block will have already decremented the old
+ * block, but it is still referenced by the btree. We
+ * increment to stop the insert decrementing it below zero
+ * when overwriting the old value.
+ */
+ dm_tm_inc(info->btree_info.tm, b);
r = insert_ablock(info, index, *block, root);
+ }
return r;
}
Patches currently in stable-queue which might be from ejt@xxxxxxxxxx are
queue-3.12/dm-array-fix-a-reference-counting-bug-in-shadow_ablock.patch
queue-3.12/dm-thin-always-fallback-the-pool-mode-if-commit-fails.patch
queue-3.12/dm-thin-allow-pool-in-read-only-mode-to-transition-to-read-write-mode.patch
queue-3.12/dm-space-map-metadata-return-on-failure-in-sm_metadata_new_block.patch
queue-3.12/dm-thin-re-establish-read-only-state-when-switching-to-fail-mode.patch
queue-3.12/dm-thin-switch-to-read-only-mode-if-a-mapping-insert-fails.patch
queue-3.12/dm-thin-switch-to-read-only-mode-if-metadata-space-is-exhausted.patch
queue-3.12/dm-space-map-disallow-decrementing-a-reference-count-below-zero.patch
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