Hi Lucas,
On 09/05/2011 10:34 PM, Lukas Czerner wrote:
> In ext4_trim_fs it is possible that start+len might overflow. Fix it by
> decrementing the len so that start+len equals to the file system size in
> the worst case.
Actually start + len can never overflow since they are changed by
start = range->start >> sb->s_blocksize_bits;
len = range->len >> sb->s_blocksize_bits;
range->start and range->len are u64, and after they are shifted with
blocksize_bits, start+len(ext4_fsblk_t is also 64bit) can't overflow.
Thanks
Tao
>
> Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
> ---
> fs/ext4/mballoc.c | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 17a5a57..d86dc14 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4952,14 +4952,18 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
> uint64_t start, len, minlen, trimmed = 0;
> ext4_fsblk_t first_data_blk =
> le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
> + ext4_fsblk_t max_blks = ext4_blocks_count(EXT4_SB(sb)->s_es);
> int ret = 0;
>
> start = range->start >> sb->s_blocksize_bits;
> len = range->len >> sb->s_blocksize_bits;
> minlen = range->minlen >> sb->s_blocksize_bits;
>
> - if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)))
> + if (unlikely(minlen > EXT4_BLOCKS_PER_GROUP(sb)) ||
> + unlikely(start > max_blks))
> return -EINVAL;
> + if (unlikely(len > max_blks))
> + len = max_blks - start;
> if (start + len <= first_data_blk)
> goto out;
> if (start < first_data_blk) {
--
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