On 26.03.2018 11:27, Anand Jain wrote:
> 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
Have you considered adding fstests, it will be very easy to test for
this behavior?
>
> Signed-off-by: Anand Jain <anand.j...@oracle.com>
> ---
> 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 < 0)
> + if (err == -EINVAL)
> + pr_err("BTRFS error (device %pg): "\
> + "unsupported checksum type, bytenr=%llu",
> + bdev, bytenr);
Same comment as before regarding string literals splitting across lines.
> + 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);
>
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