[dm-devel] [PATCH] dm table: fix potential NULL pointer in dm_table_set_integrity

[Mike Snitzer]

Commit a63a5cf (dm: improve block integrity support) introduced a
two-phase initialization of a DM device's integrity profile.  The
dm_table_set_integrity() call to blk_integrity_register() may deference
a NULL 'template_disk' due to an integrity profile mismatch.

An integrity profile mismatch can occur if the integrity profile for
devices in a DM table are changed between the call to
dm_table_prealloc_integrity() and dm_table_set_integrity() (possible
via table loads for stacked DM devices with integrity profiles).

Reported-by: Zdenek Kabelac <zkabelac at redhat.com> (coverity run)
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
Cc: stable at kernel.org # >= 2.6.39.y
---
 drivers/md/dm-table.c |   13 +++++++------
 1 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 5e8e2f3..6cd8d95 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1260,14 +1260,15 @@ static void dm_table_set_integrity(struct dm_table *t)
 		return;
 
 	template_disk = dm_table_get_integrity_disk(t, true);
-	if (!template_disk &&
-	    blk_integrity_is_initialized(dm_disk(t->md))) {
+	if (template_disk)
+		blk_integrity_register(dm_disk(t->md),
+				       blk_get_integrity(template_disk));
+	else if (blk_integrity_is_initialized(dm_disk(t->md)))
 		DMWARN("%s: device no longer has a valid integrity profile",
 		       dm_device_name(t->md));
-		return;
-	}
-	blk_integrity_register(dm_disk(t->md),
-			       blk_get_integrity(template_disk));
+	else
+		DMWARN("%s: unable to establish an integrity profile",
+		       dm_device_name(t->md));
 }
 
 void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
-- 
1.7.4.4