linux-kernel - Re: [PATCH] mtd: mtdram: check offs and len in mtdram->erase

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Date:	Fri, 2 Oct 2015 17:39:02 +0800
From:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>
CC:	<linux-kernel@...r.kernel.org>, <linux-mtd@...ts.infradead.org>
Subject: Re: [PATCH] mtd: mtdram: check offs and len in mtdram->erase

On 10/01/2015 12:41 AM, Sudip Mukherjee wrote:
> We should prevent user to erasing mtd device with an unaligned offset
> or length.
>
> Signed-off-by: Sudip Mukherjee <sudip@...torindia.org>
> ---
>
> I am not sure if I should add the Signed-off-by of
> Dongsheng Yang <yangds.fnst@...fujitsu.com> . He is the original author
> and he should get the credit for that.

But I had sent a a patch out to fix this problem before your v1.

http://lists.infradead.org/pipermail/linux-mtd/2015-September/062234.html

Yang
>
>   drivers/mtd/devices/mtdram.c | 27 +++++++++++++++++++++++++++
>   1 file changed, 27 insertions(+)
>
> diff --git a/drivers/mtd/devices/mtdram.c b/drivers/mtd/devices/mtdram.c
> index 8e28508..21b6a05 100644
> --- a/drivers/mtd/devices/mtdram.c
> +++ b/drivers/mtd/devices/mtdram.c
> @@ -32,8 +32,35 @@ MODULE_PARM_DESC(erase_size, "Device erase block size in KiB");
>   // We could store these in the mtd structure, but we only support 1 device..
>   static struct mtd_info *mtd_info;
>
> +static int check_offs_len(struct mtd_info *mtd, loff_t ofs, uint64_t len)
> +{
> +	int ret = 0;
> +	uint64_t temp_len, rem;
> +
> +	/* Start address must align on block boundary */
> +	temp_len = ofs;
> +	rem = do_div(temp_len, mtd->erasesize);
> +	if (rem) {
> +		pr_debug("%s: unaligned address\n", __func__);
> +		ret = -EINVAL;
> +	}
> +
> +	/* Length must align on block boundary */
> +	temp_len = len;
> +	rem = do_div(temp_len, mtd->erasesize);
> +
> +	if (rem) {
> +		pr_debug("%s: length not block aligned\n", __func__);
> +		ret = -EINVAL;
> +	}
> +
> +	return ret;
> +}
> +
>   static int ram_erase(struct mtd_info *mtd, struct erase_info *instr)
>   {
> +	if (check_offs_len(mtd, instr->addr, instr->len))
> +		return -EINVAL;
>   	memset((char *)mtd->priv + instr->addr, 0xff, instr->len);
>   	instr->state = MTD_ERASE_DONE;
>   	mtd_erase_callback(instr);
>

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