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Date: Wed, 29 Mar 2017 17:19:12 +0200
From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: chenwy <chenwy-fnst@cn.fujitsu.com>
Cc: <linux-mtd@lists.infradead.org>, fnstml-fjl@cn.fujitsu.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mtdram: check offs and len where appropriate
Message-ID: <20170329171912.52327b15@bbrezillon>
In-Reply-To: <20170317022939.5511-1-chenwy-fnst@cn.fujitsu.com>
References: <20170317022939.5511-1-chenwy-fnst@cn.fujitsu.com>
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On Fri, 17 Mar 2017 10:29:39 +0800
chenwy <chenwy-fnst@cn.fujitsu.com> wrote:

> We should prevent user to operating mtd device with
> an illegal offset or length.

I realize that all the tests you do here are already done in mtdcore.c.
If one is missing, please patch mtdcore.c instead.

Thanks,

Boris

> 
> Signed-off-by: Chen Wenyong <chenwy-fnst@cn.fujitsu.com>
> ---
>  drivers/mtd/devices/mtdram.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/mtd/devices/mtdram.c b/drivers/mtd/devices/mtdram.c
> index cbd8547..83e1603 100644
> --- a/drivers/mtd/devices/mtdram.c
> +++ b/drivers/mtd/devices/mtdram.c
> @@ -58,6 +58,10 @@ static int ram_erase(struct mtd_info *mtd, struct erase_info *instr)
>  {
>  	if (check_offs_len(mtd, instr->addr, instr->len))
>  		return -EINVAL;
> +	if (mtd->size < (instr->len + instr->addr) || instr->addr < 0
> +		       	|| instr->len < 0)
> +		return -EINVAL;
> +
>  	memset((char *)mtd->priv + instr->addr, 0xff, instr->len);
>  	instr->state = MTD_ERASE_DONE;
>  	mtd_erase_callback(instr);
> @@ -67,6 +71,9 @@ static int ram_erase(struct mtd_info *mtd, struct erase_info *instr)
>  static int ram_point(struct mtd_info *mtd, loff_t from, size_t len,
>  		size_t *retlen, void **virt, resource_size_t *phys)
>  {
> +	if (mtd->size < (len + from) || from < 0 || len < 0)
> +		return -EINVAL;
> +
>  	*virt = mtd->priv + from;
>  	*retlen = len;
>  	return 0;
> @@ -74,6 +81,9 @@ static int ram_point(struct mtd_info *mtd, loff_t from, size_t len,
>  
>  static int ram_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
>  {
> +	if (mtd->size < (len + from) || from < 0 || len < 0)
> +		return -EINVAL;
> +
>  	return 0;
>  }
>  
> @@ -93,6 +103,9 @@ static unsigned long ram_get_unmapped_area(struct mtd_info *mtd,
>  static int ram_read(struct mtd_info *mtd, loff_t from, size_t len,
>  		size_t *retlen, u_char *buf)
>  {
> +	if (mtd->size < (len + from) || from < 0 || len < 0)
> +		return -EINVAL;
> +
>  	memcpy(buf, mtd->priv + from, len);
>  	*retlen = len;
>  	return 0;
> @@ -101,6 +114,9 @@ static int ram_read(struct mtd_info *mtd, loff_t from, size_t len,
>  static int ram_write(struct mtd_info *mtd, loff_t to, size_t len,
>  		size_t *retlen, const u_char *buf)
>  {
> +	if (mtd->size < (len + to) || to < 0 || len < 0)
> +		return -EINVAL;
> +
>  	memcpy((char *)mtd->priv + to, buf, len);
>  	*retlen = len;
>  	return 0;