[PATCH 4.9 070/101] btrfs: Add checker for EXTENT_CSUM

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Qu Wenruo <quwenruo.btrfs@xxxxxxx>

commit 4b865cab96fe2a30ed512cf667b354bd291b3b0a upstream.

EXTENT_CSUM checker is a relatively easy one, only needs to check:

1) Objectid
   Fixed to BTRFS_EXTENT_CSUM_OBJECTID

2) Key offset alignment
   Must be aligned to sectorsize

3) Item size alignedment
   Must be aligned to csum size

Signed-off-by: Qu Wenruo <quwenruo.btrfs@xxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
[bwh: Backported to 4.9: Use root->sectorsize instead of
 root->fs_info->sectorsize]
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/btrfs/disk-io.c |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -621,6 +621,27 @@ static int check_extent_data_item(struct
 	return 0;
 }
 
+static int check_csum_item(struct btrfs_root *root, struct extent_buffer *leaf,
+			   struct btrfs_key *key, int slot)
+{
+	u32 sectorsize = root->sectorsize;
+	u32 csumsize = btrfs_super_csum_size(root->fs_info->super_copy);
+
+	if (key->objectid != BTRFS_EXTENT_CSUM_OBJECTID) {
+		CORRUPT("invalid objectid for csum item", leaf, root, slot);
+		return -EUCLEAN;
+	}
+	if (!IS_ALIGNED(key->offset, sectorsize)) {
+		CORRUPT("unaligned key offset for csum item", leaf, root, slot);
+		return -EUCLEAN;
+	}
+	if (!IS_ALIGNED(btrfs_item_size_nr(leaf, slot), csumsize)) {
+		CORRUPT("unaligned csum item size", leaf, root, slot);
+		return -EUCLEAN;
+	}
+	return 0;
+}
+
 /*
  * Common point to switch the item-specific validation.
  */
@@ -634,6 +655,9 @@ static int check_leaf_item(struct btrfs_
 	case BTRFS_EXTENT_DATA_KEY:
 		ret = check_extent_data_item(root, leaf, key, slot);
 		break;
+	case BTRFS_EXTENT_CSUM_KEY:
+		ret = check_csum_item(root, leaf, key, slot);
+		break;
 	}
 	return ret;
 }