linux-kernel - Re: [PATCH 1/1] target: Make sure no zero value in the buffer

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Message-ID: <ddc0f1ab-03bb-2e66-280d-0dcea9042b5c@gmail.com>
Date:   Sun, 6 Dec 2020 19:55:34 +0100
From:   Bodo Stroesser <bostroesser@...il.com>
To:     Xiaohui Zhang <ruc_zhangxiaohui@....com>,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        target-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] target: Make sure no zero value in the buffer

On 03.12.20 12:40, Xiaohui Zhang wrote:
> From: Zhang Xiaohui <ruc_zhangxiaohui@....com>
> 
> The fix makes sure no zero value in the buffer, by comparing the
> strlen() of the original buffer with the size variable.

What problem do you want to fix here?
I think, presently iblock_set_configfs_dev_params() just ignores input after a possible zero byte, which AFAICS is the usual way to handle such 'abnormal' input.

Of course, strictly taken it is a bug to return 'count' without having processed count bytes. OTOH, iblock_set_configfs_dev_params also silently ignores unknown parameter strings.
If you want to have strict error handling in such sys- or config-FS callbacks, you have to do a lot of work ...

> 
> Signed-off-by: Zhang Xiaohui <ruc_zhangxiaohui@....com>
> ---
>   drivers/target/target_core_iblock.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
> index f2bd2e207..b23e92449 100644
> --- a/drivers/target/target_core_iblock.c
> +++ b/drivers/target/target_core_iblock.c
> @@ -537,6 +537,8 @@ static ssize_t iblock_set_configfs_dev_params(struct se_device *dev,
>   	int ret = 0, token;
>   	unsigned long tmp_readonly;
>   
> +	if (strlen(page) < count)
> +		return -EOVERFLOW;
>   	opts = kstrdup(page, GFP_KERNEL);
>   	if (!opts)
>   		return -ENOMEM;
>