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btrfs: make thaw time super block check to also verify checksum 

Previous commit a05d3c9153 ("btrfs: check superblock to ensure the fs
was not modified at thaw time") only checks the content of the super
block, but it doesn't really check if the on-disk super block has a
matching checksum.

This patch will add the checksum verification to thaw time superblock
verification.

This involves the following extra changes:

- Export btrfs_check_super_csum()
  As we need to call it in super.c.

- Change the argument list of btrfs_check_super_csum()
  Instead of passing a char *, directly pass struct btrfs_super_block *
  pointer.

- Verify that our checksum type didn't change before checking the
  checksum value, like it's done at mount time

Fixes: a05d3c9153 ("btrfs: check superblock to ensure the fs was not modified at thaw time")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2022-10-18 09:56:38 +08:00 committed by David Sterba
parent 968b715831
commit 3d17adea74
3 changed files with 22 additions and 6 deletions
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10
fs/btrfs/disk-io.c
View File

@ -166,11 +166,9 @@ static bool btrfs_supported_super_csum(u16 csum_type)
* 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(struct btrfs_fs_info *fs_info,
char *raw_disk_sb)
int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
const struct btrfs_super_block *disk_sb)
{
struct btrfs_super_block *disk_sb =
(struct btrfs_super_block *)raw_disk_sb;
char result[BTRFS_CSUM_SIZE];
SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
@ -181,7 +179,7 @@ static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
* BTRFS_SUPER_INFO_SIZE range, we expect that the unused space is
* filled with zeros and is included in the checksum.
*/
crypto_shash_digest(shash, raw_disk_sb + BTRFS_CSUM_SIZE,
crypto_shash_digest(shash, (const u8 *)disk_sb + BTRFS_CSUM_SIZE,
BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE, result);
if (memcmp(disk_sb->csum, result, fs_info->csum_size))
@ -3479,7 +3477,7 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
* 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(fs_info, (u8 *)disk_super)) {
if (btrfs_check_super_csum(fs_info, disk_super)) {
btrfs_err(fs_info, "superblock checksum mismatch");
err = -EINVAL;
btrfs_release_disk_super(disk_super);

2
fs/btrfs/disk-io.h
View File

@ -42,6 +42,8 @@ struct extent_buffer *btrfs_find_create_tree_block(
void btrfs_clean_tree_block(struct extent_buffer *buf);
void btrfs_clear_oneshot_options(struct btrfs_fs_info *fs_info);
int btrfs_start_pre_rw_mount(struct btrfs_fs_info *fs_info);
int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
const struct btrfs_super_block *disk_sb);
int __cold open_ctree(struct super_block *sb,
struct btrfs_fs_devices *fs_devices,
char *options);

16
fs/btrfs/super.c
View File

@ -2555,6 +2555,7 @@ static int check_dev_super(struct btrfs_device *dev)
{
struct btrfs_fs_info *fs_info = dev->fs_info;
struct btrfs_super_block *sb;
u16 csum_type;
int ret = 0;
/* This should be called with fs still frozen. */
@ -2569,6 +2570,21 @@ static int check_dev_super(struct btrfs_device *dev)
if (IS_ERR(sb))
return PTR_ERR(sb);
/* Verify the checksum. */
csum_type = btrfs_super_csum_type(sb);
if (csum_type != btrfs_super_csum_type(fs_info->super_copy)) {
btrfs_err(fs_info, "csum type changed, has %u expect %u",
csum_type, btrfs_super_csum_type(fs_info->super_copy));
ret = -EUCLEAN;
goto out;
}
if (btrfs_check_super_csum(fs_info, sb)) {
btrfs_err(fs_info, "csum for on-disk super block no longer matches");
ret = -EUCLEAN;
goto out;
}
/* Btrfs_validate_super() includes fsid check against super->fsid. */
ret = btrfs_validate_super(fs_info, sb, 0);
if (ret < 0)