On 2017年11月08日 08:13, Qu Wenruo wrote:
>
>
> On 2017年11月08日 04:50, David Sterba wrote:
>> On Wed, Nov 01, 2017 at 08:22:12PM +0800, Qu Wenruo wrote:
>>> For the following types, we have items with variable length:
>>> (With BTRFS_ prefix and _KEY suffix snipped)
>>>
>>> DIR_ITEM
>>> DIR_INDEX
>>> XATTR_ITEM
>>> INODE_REF
>>> INODE_EXTREF
>>> ROOT_REF
>>> ROOT_BACKREF
>>>
>>> They all use @name_len to indicate their name length, and XATTR_ITEM has
>>> extra @data_len to indicate it data length.
>>>
>>> Despite their variable length, it's also possible to have several such
>>> structure inside one item.
>>>
>>> This patch will add checker to ensure:
>>>
>>> 1) No structure header and its data cross item boundary
>>> 2) Except XATTR_ITEM, no structure should have non-zero @data_len
>>>
>>> This checker is especially useful to avoid possible access beyond
>>> boundary for fuzzed image.
>>>
>>> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
>>> ---
>>> fs/btrfs/tree-checker.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 123 insertions(+)
>>>
>>> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
>>> index 114fc5f0ecc5..f26e86fcbd74 100644
>>> --- a/fs/btrfs/tree-checker.c
>>> +++ b/fs/btrfs/tree-checker.c
>>> @@ -222,6 +222,120 @@ static int check_csum_item(struct btrfs_root *root, struct extent_buffer *leaf,
>>> return 0;
>>> }
>>>
>>> +static u32 get_header_size(u8 type)
>>> +{
>>> + switch (type) {
>>> + case BTRFS_DIR_ITEM_KEY:
>>> + case BTRFS_DIR_INDEX_KEY:
>>> + case BTRFS_XATTR_ITEM_KEY:
>>> + return sizeof(struct btrfs_dir_item);
>>> + case BTRFS_INODE_REF_KEY:
>>> + return sizeof(struct btrfs_inode_ref);
>>> + case BTRFS_INODE_EXTREF_KEY:
>>> + return sizeof(struct btrfs_inode_extref);
>>> + case BTRFS_ROOT_REF_KEY:
>>> + case BTRFS_ROOT_BACKREF_KEY:
>>> + return sizeof(struct btrfs_root_ref);
>>> + }
>>> + WARN_ON(1);
>>
>> The helper name suggests is generic so this warning is there to catch
>> new use, possibly without the matching validation function? If it is so,
>> I'd rather use ASSERT. If you really want a warning, then please replace
>> it with a message. The stacktrace from WARN_ON would not be very useful
>> because we know exactly how we get here, the callchaning starts in the
>> endio handlers.
>
> Please ignore this patch, as there is v2 patch which doesn't use such
> centralized check.
The already submitted patchset is "[PATCH 0/3] tree-checker bug fix and
enhancement."
And patch "[PATCH 2/3] btrfs: tree-checker: Add checker for dir item"
was originally going to replace it.
I'll update the patchset to address the indent comment in v2 patchset.
Thanks,
Qu
>
> Thanks,
> Qu
>
>>
>>> + return 0;
>>> +}
>>> +
>>> +static u16 get_header_namelen(struct extent_buffer *leaf, u8 type,
>>> + u32 header_offset)
>>> +{
>>> + /*
>>> + * @header_offset is offset starts after leaf header, while the
>>> + * accessors expects offset starts from leaf header.
>>> + * Sowe need to adds LEAF_DATA_OFFSET here
>>> + */
>>
>> Can you please rephrase the text? (and fix the typos)
>>
>>> + unsigned long leaf_offset = header_offset + BTRFS_LEAF_DATA_OFFSET;
>>> +
>>> + switch (type) {
>>> + case BTRFS_DIR_ITEM_KEY:
>>> + case BTRFS_DIR_INDEX_KEY:
>>> + case BTRFS_XATTR_ITEM_KEY:
>>> + return btrfs_dir_name_len(leaf, (void *)leaf_offset);
>>> + case BTRFS_INODE_REF_KEY:
>>> + return btrfs_inode_ref_name_len(leaf, (void *)leaf_offset);
>>> + case BTRFS_INODE_EXTREF_KEY:
>>> + return btrfs_inode_extref_name_len(leaf, (void *)leaf_offset);
>>> + case BTRFS_ROOT_REF_KEY:
>>> + case BTRFS_ROOT_BACKREF_KEY:
>>> + return btrfs_root_ref_name_len(leaf, (void *)leaf_offset);
>>> + }
>>> + WARN_ON(1);
>>
>> Similar comment as to the warning above, a message would be more
>> helpful to say which type is unexpected.
>>
>>> + return 0;
>>> +}
>>> +
>>> +static u16 get_header_datalen(struct extent_buffer *leaf, u8 type,
>>> + unsigned long header_offset)
>>> +{
>>> + /* Same as get_header_namelen */
>>> + unsigned long leaf_offset = header_offset + BTRFS_LEAF_DATA_OFFSET;
>>> +
>>> + switch (type) {
>>> + case BTRFS_DIR_ITEM_KEY:
>>> + case BTRFS_DIR_INDEX_KEY:
>>> + case BTRFS_XATTR_ITEM_KEY:
>>> + return btrfs_dir_data_len(leaf, (void *)leaf_offset);
>>> + }
>>> + return 0;
>>> +}
>>> +
>>> +/*
>>> + * For items with variable length, normally with namelen and tailing data.
>>> + * Like INODE_REF or XATTR
>>> + */
>>> +static int check_variable_length_item(struct btrfs_root *root,
>>> + struct extent_buffer *leaf,
>>> + struct btrfs_key *key, int slot)
>>> +{
>>> + u8 type = key->type;
>>> + u32 item_start = btrfs_item_offset_nr(leaf, slot);
>>> + u32 item_end = btrfs_item_end_nr(leaf, slot);
>>> + u32 header_size = get_header_size(type);
>>> + u32 total_size;
>>> + u32 cur = item_start;
>>> +
>>> + while (cur < item_end) {
>>> + u32 namelen;
>>> + u32 datalen;
>>> +
>>> + /* header itself should not cross item boundary */
>>> + if (cur + header_size > item_end) {
>>> + generic_err(root, leaf, slot,
>>> + "structure header crosses item boundary, have %u expect (%u, %u]",
>>
>> Un-indent please. I'm slightly confused by the "(%u, %u]" notation, this
>> reads as an open interval from the left but I don't understand it in
>> this context.
>>
>>> + cur + header_size, cur, item_end);
>>> + return -EUCLEAN;
>>> + }
>>> +
>>> + namelen = get_header_namelen(leaf, type, cur);
>>> + datalen = get_header_datalen(leaf, type, cur);
>>> +
>>> + /* Only XATTR can own data */
>>> + if (type != BTRFS_XATTR_ITEM_KEY && datalen) {
>>> + generic_err(root, leaf, slot,
>>> + "item has invalid data len, have %u expect 0",
>>> + datalen);
>>> + return -EUCLEAN;
>>> + }
>>> +
>>> + total_size = header_size + namelen + datalen;
>>> +
>>> + /* header and name/data should not cross item boundary */
>>> + if (cur + total_size > item_end) {
>>> + generic_err(root, leaf, slot,
>>> + "structure data crosses item boundary, have %u expect (%u, %u]",
>>
>> Same.
>>
>>> + cur + total_size, cur + header_size, item_end);
>>> + return -EUCLEAN;
>>> + }
>>> +
>>> + cur += total_size;
>>> + }
>>> + return 0;
>>> +}
>>> +
>>> /*
>>> * Common point to switch the item-specific validation.
>>> */
>>> @@ -238,6 +352,15 @@ static int check_leaf_item(struct btrfs_root *root,
>>> case BTRFS_EXTENT_CSUM_KEY:
>>> ret = check_csum_item(root, leaf, key, slot);
>>> break;
>>> + case BTRFS_DIR_ITEM_KEY:
>>> + case BTRFS_XATTR_ITEM_KEY:
>>> + case BTRFS_DIR_INDEX_KEY:
>>> + case BTRFS_INODE_REF_KEY:
>>> + case BTRFS_INODE_EXTREF_KEY:
>>> + case BTRFS_ROOT_REF_KEY:
>>> + case BTRFS_ROOT_BACKREF_KEY:
>>> + ret = check_variable_length_item(root, leaf, key, slot);
>>> + break;
>>> }
>>> return ret;
>>> }
>>
>> Otherwise ok.
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
>> the body of a message to majordomo@xxxxxxxxxxxxxxx
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>
Attachment:
signature.asc
Description: OpenPGP digital signature
