Re: [PATCH 1/7] ext4: avoid overflow when setting values via sysfs

Zhang Yi
2024-01-26T09:29:03Z

On 2024/1/26 16:57, Baokun Li wrote:
> When setting values of type unsigned int through sysfs, we use kstrtoul()
> to parse it and then truncate part of it as the final set value, when the
> set value is greater than UINT_MAX, the set value will not match what we
> see because of the truncation. As follows:
>
> $ echo 4294967296 > /sys/fs/ext4/sda/mb_max_linear_groups
> $ cat /sys/fs/ext4/sda/mb_max_linear_groups
> 0
>
> So when the value set is outside the variable type range, -EINVAL is
> returned to avoid the inconsistency described above. In addition, a
> judgment is added to avoid setting s_resv_clusters less than 0.
>
> Signed-off-by: Baokun Li <libaokun1@huawei.com>

Thanks for the patch. Looks good to me.

Reviewed-by: Zhang Yi <yi.zhang@huawei.com>

> ---
> fs/ext4/sysfs.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
> index 6d332dff79dd..3671a8aaf4af 100644
> --- a/fs/ext4/sysfs.c
> +++ b/fs/ext4/sysfs.c
> @@ -104,7 +104,7 @@ static ssize_t reserved_clusters_store(struct ext4_sb_info *sbi,
> int ret;
>
> ret = kstrtoull(skip_spaces(buf), 0, &val);
> - if (ret || val >= clusters)
> + if (ret || val >= clusters || (s64)val < 0)
> return -EINVAL;
>
> atomic64_set(&sbi->s_resv_clusters, val);
> @@ -463,6 +463,8 @@ static ssize_t ext4_attr_store(struct kobject *kobj,
> ret = kstrtoul(skip_spaces(buf), 0, &t);
> if (ret)
> return ret;
> + if (t != (unsigned int)t)
> + return -EINVAL;
> if (a->attr_ptr == ptr_ext4_super_block_offset)
> *((__le32 *) ptr) = cpu_to_le32(t);
> else
>