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

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Message-ID: <20240314101608.6tcgu3myognxxh3j@quack3>
Date: Thu, 14 Mar 2024 11:16:08 +0100
From: Jan Kara <jack@...e.cz>
To: Baokun Li <libaokun1@...wei.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca,
	jack@...e.cz, ritesh.list@...il.com, ojaswin@...ux.ibm.com,
	adobriyan@...il.com, linux-kernel@...r.kernel.org,
	yi.zhang@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH v2 1/9] ext4: avoid overflow when setting values via sysfs

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@...wei.com>

Thanks! The patch looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.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@...e.com>
SUSE Labs, CR