During the scan context, we aren't verifying the superblock-
checksum when read.
This patch fixes it by adding the checksum verification function
btrfs_check_super_csum() in the function btrfs_read_disk_super().
And makes device scan to error fail if the primary superblock csum
is wrong, whereas if the copy-superblock csum is wrong it will just
just report mismatch and continue mount/scan as usual. When the
mount is successful We anyway overwrite all superblocks upon unmount.
The context in which this will be called is - device scan, device ready,
and mount -o device option.
Test script:
Corrupt primary superblock and check if device scan and mount
fails:
mkfs.btrfs -fq /dev/sdc
dd if=/dev/urandom of=/dev/sdc ibs=1 obs=1 count=1 seek=64K
btrfs dev scan /dev/sdc
mount /dev/sdc /btrfs
Corrupt secondary superblock and check if device scan and mount
is succcessful, check for the dmesg for errors.
mkfs.btrfs -fq /dev/sdc
dd if=/dev/urandom of=/dev/sdc ibs=1 obs=1 count=1 seek=67108864
btrfs dev scan /dev/sdc
mount /dev/sdc /btrfs
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
---
v3->v4:
Update changelog
v2->v3:
squash 4/8 in here.
4/8: btrfs: make btrfs_check_super_csum() non-static
v1->v2:
changed title.
use explicit (< 0) check for %errr.
Un-split pr_err() string.
Fix typo in the git commit log.
Move the csum check after bytenr and btrfs magic verified.
fs/btrfs/disk-io.c | 2 +-
fs/btrfs/disk-io.h | 1 +
fs/btrfs/volumes.c | 13 +++++++++++++
3 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index c3a9407fc3a5..37b0cf489fdd 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -395,7 +395,7 @@ static int verify_parent_transid(struct extent_io_tree *io_tree,
* Otherwise: -EINVAL if csum type is not found
* -EUCLEAN if csum does not match
*/
-static int btrfs_check_super_csum(char *raw_disk_sb)
+int btrfs_check_super_csum(char *raw_disk_sb)
{
struct btrfs_super_block *disk_sb =
(struct btrfs_super_block *)raw_disk_sb;
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 70a88d61b547..c400cc68f913 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -69,6 +69,7 @@ int write_all_supers(struct btrfs_fs_info *fs_info, int max_mirrors);
struct buffer_head *btrfs_read_dev_super(struct block_device *bdev);
int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,
struct buffer_head **bh_ret);
+int btrfs_check_super_csum(char *raw_disk_sb);
int btrfs_commit_super(struct btrfs_fs_info *fs_info);
struct btrfs_root *btrfs_read_fs_root(struct btrfs_root *tree_root,
struct btrfs_key *location);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 035affa447fa..760c6650e11b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1149,6 +1149,7 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
struct page **page,
struct btrfs_super_block **disk_super)
{
+ int err;
void *p;
pgoff_t index;
@@ -1183,6 +1184,18 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
return -EINVAL;
}
+ err = btrfs_check_super_csum((char *) *disk_super);
+ if (err < 0) {
+ if (err == -EINVAL)
+ pr_err("BTRFS error (device %pg): unsupported checksum type, bytenr=%llu",
+ bdev, bytenr);
+ else if (err == -EUCLEAN)
+ pr_err("BTRFS error (device %pg): superblock checksum failed, bytenr=%llu",
+ bdev, bytenr);
+ btrfs_release_disk_super(*page);
+ return err;
+ }
+
if ((*disk_super)->label[0] &&
(*disk_super)->label[BTRFS_LABEL_SIZE - 1])
(*disk_super)->label[BTRFS_LABEL_SIZE - 1] = '\0';
--
2.7.0
--
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