linux-kernel - Re: [PATCH v2 RESEND] i2c: tegra: check msg length in SMBUS block read

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Message-ID: <j3jxuuwu2joyn6jsfa63lkkuwqazd2mpeki6gamdpktllhpkhv@tfoqnztsa7zw>
Date: Tue, 29 Apr 2025 01:34:23 +0200
From: Andi Shyti <andi.shyti@...nel.org>
To: Akhil R <akhilrajeev@...dia.com>
Cc: ldewangan@...dia.com, digetx@...il.com, thierry.reding@...il.com, 
	jonathanh@...dia.com, wsa@...nel.org, linux-i2c@...r.kernel.org, 
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH v2 RESEND] i2c: tegra: check msg length in SMBUS block
 read

Hi Akhil,

On Thu, Apr 24, 2025 at 11:03:20AM +0530, Akhil R wrote:
> For SMBUS block read, do not continue to read if the message length
> passed from the device is '0' or greater than the maximum allowed bytes.
> 
> Signed-off-by: Akhil R <akhilrajeev@...dia.com>
> Acked-by: Thierry Reding <treding@...dia.com>
> ---
> v1->v2: Add check for the maximum data as well.
> 
>  drivers/i2c/busses/i2c-tegra.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 87976e99e6d0..049b4d154c23 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -1395,6 +1395,11 @@ static int tegra_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
>  			ret = tegra_i2c_xfer_msg(i2c_dev, &msgs[i], MSG_END_CONTINUE);
>  			if (ret)
>  				break;
> +
> +			/* Validate message length before proceeding */
> +			if (msgs[i].buf[0] == 0 || msgs[i].buf[0] > I2C_SMBUS_BLOCK_MAX)
> +				break;
> +

I agree with Thierry, this check is driver independent and it
should be done in the library. Anyway, for now, I'm going to take
this as this check is now left to the drivers and it would be
huge to shift it somewhere else.

Before I merge, I want to know if you have you seen any failure
here? What is the reason you are sending it?

Thanks,
Andi

>  			/* Set the msg length from first byte */
>  			msgs[i].len += msgs[i].buf[0];
>  			dev_dbg(i2c_dev->dev, "reading %d bytes\n", msgs[i].len);
> -- 
> 2.43.2
>