[PATCH 3/4] xfs: log recovery needs to validate against sb_meta_uuid

[Dave Chinner <david@xxxxxxxxxxxxx>]

From: Dave Chinner <dchinner@xxxxxxxxxx>

Now that sb_uuid can be changed by the user, we cannot use this to
validate the metadata blocks being recovered belong to this
filesystem. We must check against the sb_meta_uuid as that will
remain unchanged.

There is a complication in this code - the superblock itself. We can
not check the sb_meta_uuid unconditionally, as that may not be set
on disk. Hence we must verify the superblock sb_uuid matches between
the log record and the in-core superblock.

Found by inspection after the previous two problems were found.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/xfs/xfs_log_recover.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index c674b40..6f83d12 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -1895,15 +1895,25 @@ xlog_recover_get_buf_lsn(
                 */
                goto recover_immediately;
        case XFS_SB_MAGIC:
+               /*
+                * superblock uuids are magic. We may or may not have a
+                * sb_meta_uuid on disk, but it will be set in the in-core
+                * superblock. We set the uuid pointer for verification
+                * according to the superblock feature mask to ensure we check
+                * the relevant UUID in the superblock.
+                */
                lsn = be64_to_cpu(((struct xfs_dsb *)blk)->sb_lsn);
-               uuid = &((struct xfs_dsb *)blk)->sb_uuid;
+               if (xfs_sb_version_hasmetauuid(&mp->m_sb))
+                       uuid = &((struct xfs_dsb *)blk)->sb_meta_uuid;
+               else
+                       uuid = &((struct xfs_dsb *)blk)->sb_uuid;
                break;
        default:
                break;
        }
 
        if (lsn != (xfs_lsn_t)-1) {
-               if (!uuid_equal(&mp->m_sb.sb_uuid, uuid))
+               if (!uuid_equal(&mp->m_sb.sb_meta_uuid, uuid))
                        goto recover_immediately;
                return lsn;
        }
-- 
2.1.4