linux-kernel - Re: [PATCH] mfd: mt6360: add bound check in regmap read/write function

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Date:   Wed, 28 Sep 2022 11:30:24 +0100
From:   Lee Jones <lee@...nel.org>
To:     cy_huang <u0084500@...il.com>
Cc:     matthias.bgg@...il.com, gene_chen@...htek.com,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        ChiYuan Huang <cy_huang@...htek.com>, stable@...r.kernel.org
Subject: Re: [PATCH] mfd: mt6360: add bound check in regmap read/write
 function

On Wed, 14 Sep 2022, cy_huang wrote:

> From: ChiYuan Huang <cy_huang@...htek.com>
> 
> Fix the potential risk for null pointer if bank index is over the maximimum.
> 
> Refer to the discussion list for the experiment result on mt6370.
> https://lore.kernel.org/all/20220914013345.GA5802@cyhuang-hp-elitebook-840-g3.rt/
> If not to check the bound, there is the same issue on mt6360.
> 
> Fixes: 3b0850440a06c (mfd: mt6360: Merge different sub-devices I2C read/write)
> Cc: stable@...r.kernel.org
> Signed-off-by: ChiYuan Huang <cy_huang@...htek.com>
> ---
>  drivers/mfd/mt6360-core.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/mfd/mt6360-core.c b/drivers/mfd/mt6360-core.c
> index 6eaa677..d375333 100644
> --- a/drivers/mfd/mt6360-core.c
> +++ b/drivers/mfd/mt6360-core.c
> @@ -410,6 +410,9 @@ static int mt6360_regmap_read(void *context, const void *reg, size_t reg_size,
>  	u8 crc;
>  	int ret;
>  
> +	if (bank >= MT6360_SLAVE_MAX)
> +		return -EINVAL;
> +

It's too late to check bank's value here, we have already used it to
index into an array by this point.  Please fix that.

>  	if (bank == MT6360_SLAVE_PMIC || bank == MT6360_SLAVE_LDO) {
>  		crc_needed = true;
>  		ret = mt6360_xlate_pmicldo_addr(&reg_addr, val_size);
> @@ -460,6 +463,9 @@ static int mt6360_regmap_write(void *context, const void *val, size_t val_size)
>  	int write_size = val_size - MT6360_REGMAP_REG_BYTE_SIZE;
>  	int ret;
>  
> +	if (bank >= MT6360_SLAVE_MAX)
> +		return -EINVAL;
> +
>  	if (bank == MT6360_SLAVE_PMIC || bank == MT6360_SLAVE_LDO) {
>  		crc_needed = true;
>  		ret = mt6360_xlate_pmicldo_addr(&reg_addr, val_size - MT6360_REGMAP_REG_BYTE_SIZE);

-- 
Lee Jones [李琼斯]