[dm-devel] [PATCH] dm-raid: check for zero feature flags in metadata

[heinzm at redhat.com]

From: Heinz Mauelshagen <heinzm at redhat.com>

Because we don't support any feature flags in the dm-raid ondisk
metadata yet (see struct dm_raid_superblock, 'features' member), 
this patch adds a check to ensure no flags are actually set or
reject the activation of the RAID mapping.

This is to prevent possible data corruption in case of a
kernel downgrade when there'll potentially be feature flags
set by a future dm-raid target.


Signed-off-by: Heinz Mauelshagen <heinzm at redhat.com>

---
 drivers/md/dm-raid.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index a090121..5f05ba0 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -1037,6 +1037,10 @@ static int super_validate(struct raid_set *rs, struct md_rdev *rdev)
 	if (!mddev->events && super_init_validation(mddev, rdev))
 		return -EINVAL;
 
+	rs->ti->error = "Unable to assemble array: No feature flags supported yet";
+	if (le32_to_cpu(sb->features)) /* No features supported yet */
+		return -EINVAL;
+
 	/* Enable bitmap creation for RAID levels != 0 */
 	mddev->bitmap_info.offset = (rs->raid_type->level) ? to_sector(4096) : 0;
 	rdev->mddev->bitmap_info.default_offset = mddev->bitmap_info.offset;
-- 
2.5.5