Re: [PATCH 3/3] btrfs: Add sanity check for EXTENT_DATA when reading out leaf

[Nikolay Borisov <nborisov@suse.com>]

On 22.08.2017 10:37, Qu Wenruo wrote:
> Add extra checker for item with EXTENT_DATA type.
> This checks the following thing:
> 1) Item size
>    Plain text inline file extent size must match item size.
>    (compressed inline file extent has no info about its on-disk size)
>    Regular/preallocated file extent size must be a fixed value.
> 
> 2) Every member of regular file extent item
>    Including alignment for bytenr and offset, possible value for
>    compression/encryption/type.
> 
> 3) Type/compression/encode must be one of the valid values.
> 
> This should be the most comprehensive and restrict check in the context
> of btrfs_item for EXTENT_DATA.
> 
> Signed-off-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
> ---
>  fs/btrfs/disk-io.c              | 88 +++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/btrfs_tree.h |  1 +
>  2 files changed, 89 insertions(+)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 59ee7b959bf0..557f9a520e2a 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -549,6 +549,83 @@ static int check_tree_block_fsid(struct btrfs_fs_info *fs_info,
>  		   btrfs_header_level(eb) == 0 ? "leaf" : "node",	\
>  		   reason, btrfs_header_bytenr(eb), root->objectid, slot)
>  
> +static int check_extent_data_item(struct btrfs_root *root,
> +				  struct extent_buffer *leaf, int slot)
> +{
> +	struct btrfs_file_extent_item *fi;
> +	u32 sectorsize = root->fs_info->sectorsize;
> +	u32 item_size = btrfs_item_size_nr(leaf, slot);
> +
> +	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
> +
> +	if (btrfs_file_extent_type(leaf, fi) >= BTRFS_FILE_EXTENT_LAST_TYPE) {
> +		CORRUPT("invalid file extent type", leaf, root, slot);
> +		return -EIO;
> +	}
> +	if (btrfs_file_extent_compression(leaf, fi) >= BTRFS_COMPRESS_LAST) {
> +		CORRUPT("invalid file extent compression", leaf, root, slot);
> +		return -EIO;
> +	}
> +	if (btrfs_file_extent_encryption(leaf, fi)) {
> +		CORRUPT("invalid file extent encryption", leaf, root, slot);
> +		return -EIO;
> +	}
> +	if (btrfs_file_extent_type(leaf, fi) == BTRFS_FILE_EXTENT_INLINE) {
> +		if (btrfs_file_extent_compression(leaf, fi) !=
> +		    BTRFS_COMPRESS_NONE)
> +			return 0;
> +		/* Plaintext inline extent size must match item size */
> +		if (item_size != BTRFS_FILE_EXTENT_INLINE_DATA_START +
> +		    btrfs_file_extent_ram_bytes(leaf, fi)) {
> +			CORRUPT("plaintext inline extent has invalid size",
> +				leaf, root, slot);
> +			return -EIO;
> +		}
> +		return 0;
> +	}
> +
> +
> +	/* regular or preallocated extent has fixed item size */
> +	if (item_size != sizeof(*fi)) {
> +		CORRUPT(
> +		"regluar or preallocated extent data item size is invalid",
> +			leaf, root, slot);
> +		return -EIO;
> +	}
> +	if (!IS_ALIGNED(btrfs_file_extent_ram_bytes(leaf, fi), sectorsize) ||
> +	    !IS_ALIGNED(btrfs_file_extent_disk_bytenr(leaf, fi), sectorsize) ||
> +	    !IS_ALIGNED(btrfs_file_extent_disk_num_bytes(leaf, fi),
> +			sectorsize) ||
> +	    !IS_ALIGNED(btrfs_file_extent_offset(leaf, fi), sectorsize) ||
> +	    !IS_ALIGNED(btrfs_file_extent_num_bytes(leaf, fi), sectorsize)) {
> +		CORRUPT(
> +		"regular or preallocated extent data item has unaligned value",
> +			leaf, root, slot);
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}
> +
> +static int check_leaf_item(struct btrfs_root *root,
> +			   struct extent_buffer *leaf, int slot)
> +{
> +	struct btrfs_key key;
> +	int ret = 0;
> +
> +	btrfs_item_key_to_cpu(leaf, &key, slot);

nit: We already have the key in the proper format in the caller of this
function. Why not just pass in the type as an argument and save a
redundant call for every item in a leaf? Perhaps it's a
microoptimisation but for very densely populated trees the miniature
cost might build up.

> +	/*
> +	 * Considering how overcrowded the code will be inside the switch,
> +	 * complex verification is better to moved its own function.
> +	 */
> +	switch (key.type) {
> +	case BTRFS_EXTENT_DATA_KEY:
> +		ret = check_extent_data_item(root, leaf, slot);
> +		break;
> +	}
> +	return ret;
> +}
> +
>  static noinline int check_leaf(struct btrfs_root *root,
>  			       struct extent_buffer *leaf)
>  {
> @@ -605,9 +682,13 @@ static noinline int check_leaf(struct btrfs_root *root,
>  	 * 1) key order
>  	 * 2) item offset and size
>  	 *    No overlap, no hole, all inside the leaf.
> +	 * 3) item content
> +	 *    If possible, do comprehensive sanity check.
> +	 *    NOTE: All check must only rely on the item data itself.
>  	 */
>  	for (slot = 0; slot < nritems; slot++) {
>  		u32 item_end_expected;
> +		int ret;
>  
>  		btrfs_item_key_to_cpu(leaf, &key, slot);
>  
> @@ -650,6 +731,13 @@ static noinline int check_leaf(struct btrfs_root *root,
>  			return -EIO;
>  		}
>  
> +		/*
> +		 * Check if the item size and content meets other limitation
> +		 */
> +		ret = check_leaf_item(root, leaf, slot);
> +		if (ret < 0)
> +			return ret;
> +
>  		prev_key.objectid = key.objectid;
>  		prev_key.type = key.type;
>  		prev_key.offset = key.offset;
> diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
> index 10689e1fdf11..3aadbb74a024 100644
> --- a/include/uapi/linux/btrfs_tree.h
> +++ b/include/uapi/linux/btrfs_tree.h
> @@ -732,6 +732,7 @@ struct btrfs_balance_item {
>  #define BTRFS_FILE_EXTENT_INLINE 0
>  #define BTRFS_FILE_EXTENT_REG 1
>  #define BTRFS_FILE_EXTENT_PREALLOC 2
> +#define BTRFS_FILE_EXTENT_LAST_TYPE	3
>  
>  struct btrfs_file_extent_item {
>  	/*
>