Date:   Tue, 14 Mar 2023 15:10:36 +0100
From:   Andi Shyti <andi.shyti@kernel.org>
To:     Wei Chen <harperchen1110@gmail.com>
Cc:     linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i2c: xgene-slimpro: Fix out-of-bounds bug in
 xgene_slimpro_i2c_xfer()
Message-ID: <20230314141036.lnwvpputzfcyeiyz@intel.intel>
References: <20230314135734.2792944-1-harperchen1110@gmail.com>
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In-Reply-To: <20230314135734.2792944-1-harperchen1110@gmail.com>
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Hi Wei,

On Tue, Mar 14, 2023 at 01:57:34PM +0000, Wei Chen wrote:
> The data->block[0] variable comes from user and is a number between
> 0-255. Without proper check, the variable may be very large to cause
> an out-of-bounds when performing memcpy in slimpro_i2c_blkwr.
> 
> Fix this bug by checking the value of data->block[0].
> 
> Signed-off-by: Wei Chen <harperchen1110@gmail.com>
> ---
>  drivers/i2c/busses/i2c-xgene-slimpro.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-xgene-slimpro.c b/drivers/i2c/busses/i2c-xgene-slimpro.c
> index 63259b3ea5ab..bc9a3e7e0c96 100644
> --- a/drivers/i2c/busses/i2c-xgene-slimpro.c
> +++ b/drivers/i2c/busses/i2c-xgene-slimpro.c
> @@ -391,6 +391,10 @@ static int xgene_slimpro_i2c_xfer(struct i2c_adapter *adap, u16 addr,
>  						&data->block[0]);
>  
>  		} else {
> +
> +			if (data->block[0] + 1 > I2C_SMBUS_BLOCK_MAX)
> +				return -EINVAL;
> +
>  			ret = slimpro_i2c_blkwr(ctx, addr, command,
>  						SMBUS_CMD_LEN,
>  						SLIMPRO_IIC_SMB_PROTOCOL,
> @@ -408,6 +412,10 @@ static int xgene_slimpro_i2c_xfer(struct i2c_adapter *adap, u16 addr,
>  						IIC_SMB_WITHOUT_DATA_LEN,
>  						&data->block[1]);
>  		} else {
> +
> +			if (data->block[0] > I2C_SMBUS_BLOCK_MAX)
> +				return -EINVAL;
> +

you could eventually put this check inside slimpro_i2c_blkwr() so
that you have it once and for all, for everyone.

Andi

>  			ret = slimpro_i2c_blkwr(ctx, addr, command,
>  						SMBUS_CMD_LEN,
>  						SLIMPRO_IIC_I2C_PROTOCOL,
> -- 
> 2.25.1
>