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

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Message-ID: <b1c09c5b-ec26-e59f-8e13-15b77227ca9a@huawei.com>
Date: Fri, 26 Jan 2024 17:28:59 +0800
From: Zhang Yi <yi.zhang@...wei.com>
To: Baokun Li <libaokun1@...wei.com>, <linux-ext4@...r.kernel.org>
CC: <tytso@....edu>, <adilger.kernel@...ger.ca>, <jack@...e.cz>,
	<ritesh.list@...il.com>, <linux-kernel@...r.kernel.org>,
	<yangerkun@...wei.com>, <chengzhihao1@...wei.com>, <yukuai3@...wei.com>
Subject: Re: [PATCH 1/7] ext4: avoid overflow when setting values via sysfs

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@...wei.com>

Thanks for the patch. Looks good to me.

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