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

[Nikolay Borisov <nborisov@suse.com>]

On 22.08.2017 13:57, Nikolay Borisov wrote:
> 
> 
> 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;
>> +	}

One more thing - don't we really want to use -EUCLEAN rather than -EIO?


>> +
>> +
>> +	/* 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 {
>>  	/*
>>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>