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

commit 3d17adea74a56a4965f7a603d8ed8c66bb9356d9 upstream.

Previous commit a05d3c915314 ("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: a05d3c915314 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 6484f61..2c80fc9 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -202,11 +202,9 @@ 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);
 
@@ -217,7 +215,7 @@ 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))
@@ -3210,7 +3208,7 @@ 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);

diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 9de0c39..718787d 100644 (file)
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -52,6 +52,8 @@ 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);

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index bde5ead..4ff5545 100644 (file)
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2501,6 +2501,7 @@ 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. */
@@ -2515,6 +2516,21 @@ 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)