dm table: avoid crash if integrity profile changes

Commit a63a5cf (dm: improve block integrity support) introduced a
two-phase initialization of a DM device's integrity profile.  This
patch avoids dereferencing a NULL 'template_disk' pointer in
blk_integrity_register() if there is an integrity profile mismatch in
dm_table_set_integrity().

This can occur if the integrity profiles for stacked devices in a DM
table are changed between the call to dm_table_prealloc_integrity() and
dm_table_set_integrity().

Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: stable@kernel.org # 2.6.39

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 986b8754bb08..322669807077 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1238,14 +1238,15 @@ 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));
 }
 
 static int device_flush_capable(struct dm_target *ti, struct dm_dev *dev,