dm cache metadata: check the metadata version when reading the superblock

Need to check the version to verify on-disk metadata is supported.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 21 insertions, 3 deletions

diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index 8601425436cd..9ef0752e8a08 100644
--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -20,7 +20,13 @@
 
 #define CACHE_SUPERBLOCK_MAGIC 06142003
 #define CACHE_SUPERBLOCK_LOCATION 0
-#define CACHE_VERSION 1
+
+/*
+ * defines a range of metadata versions that this module can handle.
+ */
+#define MIN_CACHE_VERSION 1
+#define MAX_CACHE_VERSION 1
+
 #define CACHE_METADATA_CACHE_SIZE 64
 
 /*
@@ -134,6 +140,18 @@ static void sb_prepare_for_write(struct dm_block_validator *v,
                                                       SUPERBLOCK_CSUM_XOR));
 }
 
+static int check_metadata_version(struct cache_disk_superblock *disk_super)
+{
+        uint32_t metadata_version = le32_to_cpu(disk_super->version);
+        if (metadata_version < MIN_CACHE_VERSION || metadata_version > MAX_CACHE_VERSION) {
+                DMERR("Cache metadata version %u found, but only versions between %u and %u supported.",
+                      metadata_version, MIN_CACHE_VERSION, MAX_CACHE_VERSION);
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
 static int sb_check(struct dm_block_validator *v,
                     struct dm_block *b,
                     size_t sb_block_size)
@@ -164,7 +182,7 @@ static int sb_check(struct dm_block_validator *v,
                 return -EILSEQ;
         }
 
-        return 0;
+        return check_metadata_version(disk_super);
 }
 
 static struct dm_block_validator sb_validator = {
@@ -270,7 +288,7 @@ static int __write_initial_superblock(struct dm_cache_metadata *cmd)
         disk_super->flags = 0;
         memset(disk_super->uuid, 0, sizeof(disk_super->uuid));
         disk_super->magic = cpu_to_le64(CACHE_SUPERBLOCK_MAGIC);
-        disk_super->version = cpu_to_le32(CACHE_VERSION);
+        disk_super->version = cpu_to_le32(MAX_CACHE_VERSION);
         memset(disk_super->policy_name, 0, sizeof(disk_super->policy_name));
         memset(disk_super->policy_version, 0, sizeof(disk_super->policy_version));
         disk_super->policy_hint_size = 0;