On Thu, 30 Jun 2011, Tao Ma wrote:
> From: Tao Ma <boyu.mt@xxxxxxxxxx>
>
> In 0f0a25b, we adjust 'len' with s_first_data_block - start, but
> it could underflow in case blocksize=1K, fstrim_range.len=512 and
> fstrim_range.start = 0. In this case, when we run the code:
> len -= first_data_blk - start; len will be underflow to -1ULL.
> In the end, although we are safe that last_group check later will limit
> the trim to the whole volume, but that isn't what the user really want.
>
> So this patch fix it. It also adds the check for 'start' like ext3 so that
> we can break immediately if the start is invalid.
Hi Tao,
thanks for the resend!
>
> Signed-off-by: Tao Ma <boyu.mt@xxxxxxxxxx>
> ---
> fs/ext4/mballoc.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 6ed859d..2336424 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4904,6 +4904,9 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
>
> if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)))
> return -EINVAL;
> + if (start >= ext4_blocks_count(EXT4_SB(sb)->s_es) ||
> + start + len <= first_data_blk)
> + goto out;
We should really return -EINVAL in case that start is beyond the
filesystem. However we can not return -EINVAL in case that start+len is
before the first data block, because it would require user to know fs
internals.
So simply doing this, should be enough:
if (start + len <= first_data_blk)
goto out;
and the code later
if (first_group > last_group)
return -EINVAL;
will handle the rest.
Thanks!
-Lukas
> if (start < first_data_blk) {
> len -= first_data_blk - start;
> start = first_data_blk;
> @@ -4952,5 +4955,6 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
> }
> range->len = trimmed * sb->s_blocksize;
>
> +out:
> return ret;
> }
>
--
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
