linux-kernel - Re: [PATCH] HID: cp2112: prevent a buffer overflow in cp2112

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Date:   Thu, 9 Jun 2022 10:55:57 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
cc:     benjamin.tissoires@...hat.com, eudean@...sta.com,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        dan.carpenter@...cle.com
Subject: Re: [PATCH] HID: cp2112: prevent a buffer overflow in
 cp2112_xfer()

On Wed, 8 Jun 2022, Harshit Mogalapalli wrote:

> Smatch warnings:
> drivers/hid/hid-cp2112.c:793 cp2112_xfer() error: __memcpy()
> 'data->block[1]' too small (33 vs 255)
> drivers/hid/hid-cp2112.c:793 cp2112_xfer() error: __memcpy() 'buf' too
> small (64 vs 255)
> 
> The 'read_length' variable is provided by 'data->block[0]' which comes
> from user and it(read_length) can take a value between 0-255. Add an
> upper bound to 'read_length' variable to prevent a buffer overflow in
> memcpy().
> 
> Fixes: 542134c0375b ("HID: cp2112: Fix I2C_BLOCK_DATA transactions")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
> ---
>  drivers/hid/hid-cp2112.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
> index ece147d1a278..1e16b0fa310d 100644
> --- a/drivers/hid/hid-cp2112.c
> +++ b/drivers/hid/hid-cp2112.c
> @@ -790,6 +790,11 @@ static int cp2112_xfer(struct i2c_adapter *adap, u16 addr,
>  		data->word = le16_to_cpup((__le16 *)buf);
>  		break;
>  	case I2C_SMBUS_I2C_BLOCK_DATA:
> +		if (read_length > I2C_SMBUS_BLOCK_MAX) {
> +			ret = -EINVAL;
> +			goto power_normal;
> +		}
> +
>  		memcpy(data->block + 1, buf, read_length);
>  		break;

Good catch, now applied. Thanks,

-- 
Jiri Kosina
SUSE Labs