Re: [PATCH v2 3/3] NFC: fdp: Fix possible buffer overflow in WCS4000 NFC driver

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Wed, 2018-05-02 at 23:18 +0530, Amit Pundir wrote:
> From: Suren Baghdasaryan <surenb@google.com>
> 
> Possible buffer overflow when reading next_read_size bytes into
> tmp buffer after next_read_size was extracted from a previous packet.
> 
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
> ---
> v2:
> Remove redundant __func__ from dev_dgb().
> 
>  drivers/nfc/fdp/i2c.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/nfc/fdp/i2c.c b/drivers/nfc/fdp/i2c.c
> index c4da50e..b80d1ad 100644
> --- a/drivers/nfc/fdp/i2c.c
> +++ b/drivers/nfc/fdp/i2c.c
> @@ -176,6 +176,15 @@ static int fdp_nci_i2c_read(struct fdp_i2c_phy
> *phy, struct sk_buff **skb)
>  		/* Packet that contains a length */
>  		if (tmp[0] == 0 && tmp[1] == 0) {
>  			phy->next_read_size = (tmp[2] << 8) + tmp[3]
> + 3;
> +			/*
> +			 * Ensure next_read_size does not exceed
> sizeof(tmp)
> +			 * for reading that many bytes during next
> iteration
> +			 */
> +			if (phy->next_read_size >
> FDP_NCI_I2C_MAX_PAYLOAD) {
> +				dev_dbg(&client->dev, "corrupted
> packet\n");

> +				phy->next_read_size = 5;

Shouldn't be this magic replaced by

	phy->next_read_size = FDP_NCI_I2C_MIN_PAYLOAD;

? 

> +				goto flush;
> +			}
>  		} else {
>  			phy->next_read_size =
> FDP_NCI_I2C_MIN_PAYLOAD;
>  

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy