btrfs: enhance superblock checks
The superblock checksum is not verified upon mount. <awkward silence>
Add that check and also reorder existing checks to a more logical
order.
Current mkfs.btrfs does not calculate the correct checksum of
super_block and thus a freshly created filesytem will fail to mount when
this patch is applied.
First transaction commit calculates correct superblock checksum and
saves it to disk.
Reproducer:
$ mfks.btrfs /dev/sda
$ mount /dev/sda /mnt
$ btrfs scrub start /mnt
$ sleep 5
$ btrfs scrub status /mnt
... super:2 ...
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 78b9d45..63c328a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2793,8 +2793,10 @@
static inline int btrfs_super_csum_size(struct btrfs_super_block *s)
{
- int t = btrfs_super_csum_type(s);
- BUG_ON(t >= ARRAY_SIZE(btrfs_csum_sizes));
+ u16 t = btrfs_super_csum_type(s);
+ /*
+ * csum type is validated at mount time
+ */
return btrfs_csum_sizes[t];
}
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 2bc1ecf..bc423f7e 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -357,6 +357,44 @@
}
/*
+ * Return 0 if the superblock checksum type matches the checksum value of that
+ * algorithm. Pass the raw disk superblock data.
+ */
+static int btrfs_check_super_csum(char *raw_disk_sb)
+{
+ struct btrfs_super_block *disk_sb =
+ (struct btrfs_super_block *)raw_disk_sb;
+ u16 csum_type = btrfs_super_csum_type(disk_sb);
+ int ret = 0;
+
+ if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
+ u32 crc = ~(u32)0;
+ const int csum_size = sizeof(crc);
+ char result[csum_size];
+
+ /*
+ * The super_block structure does not span the whole
+ * BTRFS_SUPER_INFO_SIZE range, we expect that the unused space
+ * is filled with zeros and is included in the checkum.
+ */
+ crc = btrfs_csum_data(raw_disk_sb + BTRFS_CSUM_SIZE,
+ crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+ btrfs_csum_final(crc, result);
+
+ if (memcmp(raw_disk_sb, result, csum_size))
+ ret = 1;
+ }
+
+ if (csum_type >= ARRAY_SIZE(btrfs_csum_sizes)) {
+ printk(KERN_ERR "btrfs: unsupported checksum algorithm %u\n",
+ csum_type);
+ ret = 1;
+ }
+
+ return ret;
+}
+
+/*
* helper to read a given tree block, doing retries as required when
* the checksums don't match and we have alternate mirrors to try.
*/
@@ -2249,12 +2287,31 @@
fs_info, BTRFS_ROOT_TREE_OBJECTID);
invalidate_bdev(fs_devices->latest_bdev);
+
+ /*
+ * Read super block and check the signature bytes only
+ */
bh = btrfs_read_dev_super(fs_devices->latest_bdev);
if (!bh) {
err = -EINVAL;
goto fail_alloc;
}
+ /*
+ * We want to check superblock checksum, the type is stored inside.
+ * Pass the whole disk block of size BTRFS_SUPER_INFO_SIZE (4k).
+ */
+ if (btrfs_check_super_csum(bh->b_data)) {
+ printk(KERN_ERR "btrfs: superblock checksum mismatch\n");
+ err = -EINVAL;
+ goto fail_alloc;
+ }
+
+ /*
+ * super_copy is zeroed at allocation time and we never touch the
+ * following bytes up to INFO_SIZE, the checksum is calculated from
+ * the whole block of INFO_SIZE
+ */
memcpy(fs_info->super_copy, bh->b_data, sizeof(*fs_info->super_copy));
memcpy(fs_info->super_for_commit, fs_info->super_copy,
sizeof(*fs_info->super_for_commit));
@@ -2262,6 +2319,13 @@
memcpy(fs_info->fsid, fs_info->super_copy->fsid, BTRFS_FSID_SIZE);
+ ret = btrfs_check_super_valid(fs_info, sb->s_flags & MS_RDONLY);
+ if (ret) {
+ printk(KERN_ERR "btrfs: superblock contains fatal errors\n");
+ err = -EINVAL;
+ goto fail_alloc;
+ }
+
disk_super = fs_info->super_copy;
if (!btrfs_super_root(disk_super))
goto fail_alloc;
@@ -2270,13 +2334,6 @@
if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_ERROR)
set_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state);
- ret = btrfs_check_super_valid(fs_info, sb->s_flags & MS_RDONLY);
- if (ret) {
- printk(KERN_ERR "btrfs: superblock contains fatal errors\n");
- err = ret;
- goto fail_alloc;
- }
-
/*
* run through our array of backup supers and setup
* our ring pointer to the oldest one
@@ -3561,14 +3618,9 @@
static int btrfs_check_super_valid(struct btrfs_fs_info *fs_info,
int read_only)
{
- if (btrfs_super_csum_type(fs_info->super_copy) >= ARRAY_SIZE(btrfs_csum_sizes)) {
- printk(KERN_ERR "btrfs: unsupported checksum algorithm\n");
- return -EINVAL;
- }
-
- if (read_only)
- return 0;
-
+ /*
+ * Placeholder for checks
+ */
return 0;
}