Re: [PATCH] i2c: ismt: Fix an out-of-bounds bug in ismt_access()

[Guenter Roeck]

On Fri, Jul 29, 2022 at 07:02:16PM +0800, Zheyu Ma wrote:
> When the driver does not check the data from the user, the variable
> 'data->block[0]' may be very large to cause an out-of-bounds bug.
> 
> The following log can reveal it:
> 
> [   33.995542] i2c i2c-1: ioctl, cmd=0x720, arg=0x7ffcb3dc3a20
> [   33.995978] ismt_smbus 0000:00:05.0: I2C_SMBUS_BLOCK_DATA:  WRITE
> [   33.996475] ==================================================================
> [   33.996995] BUG: KASAN: out-of-bounds in ismt_access.cold+0x374/0x214b
> [   33.997473] Read of size 18446744073709551615 at addr ffff88810efcfdb1 by task ismt_poc/485
> [   33.999450] Call Trace:
> [   34.001849]  memcpy+0x20/0x60
> [   34.002077]  ismt_access.cold+0x374/0x214b
> [   34.003382]  __i2c_smbus_xfer+0x44f/0xfb0
> [   34.004007]  i2c_smbus_xfer+0x10a/0x390
> [   34.004291]  i2cdev_ioctl_smbus+0x2c8/0x710
> [   34.005196]  i2cdev_ioctl+0x5ec/0x74c
> 
> Fix this bug by checking the size of 'data->block[0]' first.
> 
> Fixes: 13f35ac14cd0 ("i2c: Adding support for Intel iSMT SMBus 2.0 host controller")
> Signed-off-by: Zheyu Ma <zheyuma97@xxxxxxxxx>

This patch has not been applied, and I don't see a response to it either.
Is there a problem with it, or did it get lost ?

Thanks,
Guenter

> ---
>  drivers/i2c/busses/i2c-ismt.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-ismt.c b/drivers/i2c/busses/i2c-ismt.c
> index 6078fa0c0d48..63120c41354c 100644
> --- a/drivers/i2c/busses/i2c-ismt.c
> +++ b/drivers/i2c/busses/i2c-ismt.c
> @@ -509,6 +509,9 @@ static int ismt_access(struct i2c_adapter *adap, u16 addr,
>  		if (read_write == I2C_SMBUS_WRITE) {
>  			/* Block Write */
>  			dev_dbg(dev, "I2C_SMBUS_BLOCK_DATA:  WRITE\n");
> +			if (data->block[0] < 1 || data->block[0] > I2C_SMBUS_BLOCK_MAX)
> +				return -EINVAL;
> +
>  			dma_size = data->block[0] + 1;
>  			dma_direction = DMA_TO_DEVICE;
>  			desc->wr_len_cmd = dma_size;
> -- 
> 2.25.1
>