On 2019/2/20 上午11:08, YueHaibing wrote:
> btrfs_item_size_nr return value is u32, convert it to int may result
> in truncation.Also read_extent_buffer expect a unsigned param, so
> min_t should use type u32 to compare.

Btrfs has a up limit on item size, it will never exceed 64K - various
overhead.

Furthermore, btrfs has metadata read time check to exclude such
obviously corrupted tree blocks, thus corrupted tree block will never
reach here.

Thanks,
Qu

> 
> Fixes: 8ea05e3a4262 ("Btrfs: introduce subvol uuids and times")
> Signed-off-by: YueHaibing <yuehaibing@huawei.com>
> ---
>  fs/btrfs/root-tree.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/root-tree.c b/fs/btrfs/root-tree.c
> index 02d1a57af78b..893d12fbfda0 100644
> --- a/fs/btrfs/root-tree.c
> +++ b/fs/btrfs/root-tree.c
> @@ -21,12 +21,12 @@ static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
>  				struct btrfs_root_item *item)
>  {
>  	uuid_le uuid;
> -	int len;
> +	u32 len;
>  	int need_reset = 0;
>  
>  	len = btrfs_item_size_nr(eb, slot);
>  	read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
> -			min_t(int, len, (int)sizeof(*item)));
> +			   min_t(u32, len, sizeof(*item)));
>  	if (len < sizeof(*item))
>  		need_reset = 1;
>  	if (!need_reset && btrfs_root_generation(item)
> 
> 
>