Patch "dm cache: fix NULL pointer when switching from cleaner policy" has been added to the 4.2-stable tree

Patch "dm cache: fix NULL pointer when switching from cleaner policy" has been added to the 4.2-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    dm cache: fix NULL pointer when switching from cleaner policy

to the 4.2-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-cache-fix-null-pointer-when-switching-from-cleaner-policy.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 2bffa1503c5c06192eb1459180fac4416575a966 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Fri, 9 Oct 2015 14:03:38 +0100
Subject: dm cache: fix NULL pointer when switching from cleaner policy

From: Joe Thornber <ejt@redhat.com>

commit 2bffa1503c5c06192eb1459180fac4416575a966 upstream.

The cleaner policy doesn't make use of the per cache block hint space in
the metadata (unlike the other policies).  When switching from the
cleaner policy to mq or smq a NULL pointer crash (in dm_tm_new_block)
was observed.  The crash was caused by bugs in dm-cache-metadata.c
when trying to skip creation of the hint btree.

The minimal fix is to change hint size for the cleaner policy to 4 bytes
(only hint size supported).

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/md/dm-cache-policy-cleaner.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/dm-cache-policy-cleaner.c
+++ b/drivers/md/dm-cache-policy-cleaner.c
@@ -436,7 +436,7 @@ static struct dm_cache_policy *wb_create
 static struct dm_cache_policy_type wb_policy_type = {
 	.name = "cleaner",
 	.version = {1, 0, 0},
-	.hint_size = 0,
+	.hint_size = 4,
 	.owner = THIS_MODULE,
 	.create = wb_create
 };


Patches currently in stable-queue which might be from ejt@redhat.com are

queue-4.2/dm-cache-fix-null-pointer-when-switching-from-cleaner-policy.patch