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 missmatch 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
mount /dev/sdb /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=64K
btrfs dev scan
mount /dev/sdb /btrfs
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
fs/btrfs/volumes.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 45dd0674571b..384e503c83ff 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;
@@ -1177,6 +1178,20 @@ static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
/* align our pointer to the offset of the super block */
*disk_super = p + (bytenr & ~PAGE_MASK);
+ err = btrfs_check_super_csum((char *) *disk_super);
+ if (err) {
+ if (err == -EINVAL)
+ pr_err("BTRFS error (device %pg): "\
+ "unsupported checksum type, bytenr=%llu",
+ bdev, bytenr);
+ else
+ pr_err("BTRFS error (device %pg): "\
+ "superblock checksum failed, bytenr=%llu",
+ bdev, bytenr);
+ btrfs_release_disk_super(*page);
+ return err;
+ }
+
if (btrfs_super_bytenr(*disk_super) != bytenr ||
btrfs_super_magic(*disk_super) != BTRFS_MAGIC) {
btrfs_release_disk_super(*page);
--
2.7.0
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