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

Guenter Roeck
2022-09-08T17:23:03Z

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@gmail.com>

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
>