Re: [PATCH v2 1/9] ext4: avoid overflow when setting values via sysfs

Jan Kara
2024-03-14T10:16:10Z

On Tue 27-02-24 17:11:40, 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 we use kstrtouint() to parse the attr_pointer_ui type 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! The patch looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> fs/ext4/sysfs.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c
> index 6d332dff79dd..ca820620b974 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);
> @@ -451,7 +451,8 @@ static ssize_t ext4_attr_store(struct kobject *kobj,
> s_kobj);
> struct ext4_attr *a = container_of(attr, struct ext4_attr, attr);
> void *ptr = calc_ptr(a, sbi);
> - unsigned long t;
> + unsigned int t;
> + unsigned long lt;
> int ret;
>
> switch (a->attr_id) {
> @@ -460,7 +461,7 @@ static ssize_t ext4_attr_store(struct kobject *kobj,
> case attr_pointer_ui:
> if (!ptr)
> return 0;
> - ret = kstrtoul(skip_spaces(buf), 0, &t);
> + ret = kstrtouint(skip_spaces(buf), 0, &t);
> if (ret)
> return ret;
> if (a->attr_ptr == ptr_ext4_super_block_offset)
> @@ -471,10 +472,10 @@ static ssize_t ext4_attr_store(struct kobject *kobj,
> case attr_pointer_ul:
> if (!ptr)
> return 0;
> - ret = kstrtoul(skip_spaces(buf), 0, &t);
> + ret = kstrtoul(skip_spaces(buf), 0, &lt);
> if (ret)
> return ret;
> - *((unsigned long *) ptr) = t;
> + *((unsigned long *) ptr) = lt;
> return len;
> case attr_inode_readahead:
> return inode_readahead_blks_store(sbi, buf, len);
> --
> 2.31.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR