Re: [PATCH] check: check so offset is not bigger then the leaf

[Josef Bacik <jbacik@fb.com>]

On 06/25/2015 09:06 AM, David Sterba wrote:
> On Thu, Jun 18, 2015 at 10:16:54AM -0700, Josef Bacik wrote:
>> On 06/18/2015 09:44 AM, David Sterba wrote:
>>> On Thu, Jun 18, 2015 at 01:59:13AM +0200, Robert Marklund wrote:
>>>> This could crash before because of dangerous dangling
>>>> offset of pointer.
>>>
>>> That's right, this can happen. There are more btrfs_item_ptr that would
>>> be good to validate that way, namely in the checker as it's most likely
>>> to see corrupted data.
>>>
>>
>> The check_block stuff should be doing this, if it isn't that's where we
>> need to fix it.  Thanks,
>
> Something like that?
>
> --- a/ctree.c
> +++ b/ctree.c
> @@ -521,6 +521,19 @@ btrfs_check_leaf(struct btrfs_root *root, struct btrfs_disk_key *parent_key,
>                          goto fail;
>                  }
>          }
> +
> +       for (i = 0; i < nritems; i++) {
> +               void *tmp;
> +
> +               tmp = btrfs_item_ptr(buf, i, void);
> +               if ((long)tmp >= BTRFS_LEAF_DATA_SIZE(root)) {
> +                       ret = BTRFS_TREE_BLOCK_INVALID_OFFSETS;
> +                       fprintf(stderr, "bad item pointer %lu\n",
> +                               (long)tmp);
> +                       goto fail;
> +               }
> +       }

I'd just do

if (btrfs_item_end_nr(buf, i) >= BTRFS_LEAF_DATA_SIZE(root))

that way you catch problems with offset and size.  Thanks,

Josef