On Fri, Apr 09, 2021 at 03:32:06PM +0300, Dan Carpenter wrote:
> Hello Michael Zaidman,
>
> The patch 6a82582d9fa4: "HID: ft260: add usb hid to i2c host bridge
> driver" from Feb 19, 2021, leads to the following static checker
> warning:
>
> drivers/hid/hid-ft260.c:441 ft260_smbus_write()
> error: '__memcpy()' '&rep->data[1]' too small (59 vs 255)
>
> drivers/hid/hid-ft260.c
> 423 static int ft260_smbus_write(struct ft260_device *dev, u8 addr, u8 cmd,
> 424 u8 *data, u8 data_len, u8 flag)
> 425 {
> 426 int ret = 0;
> 427 int len = 4;
> 428
> 429 struct ft260_i2c_write_request_report *rep =
> 430 (struct ft260_i2c_write_request_report *)dev->write_buf;
> 431
> 432 rep->address = addr;
> 433 rep->data[0] = cmd;
> 434 rep->length = data_len + 1;
> 435 rep->flag = flag;
> 436 len += rep->length;
> 437
> 438 rep->report = FT260_I2C_DATA_REPORT_ID(len);
> 439
> 440 if (data_len > 0)
> 441 memcpy(&rep->data[1], data, data_len);
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Smatch says that this can be called from the i2cdev_ioctl_smbus()
> function.
Hi Dan,
This is an example of a false-positive static checker warning.
The maximum data size that the i2cdev_ioctl_smbus() can pass to the
i2c_smbus_xfer() is sizeof(data->block) which is (I2C_SMBUS_BLOCK_MAX + 2)
or 34 bytes. Thus, no need to check the data_len against 59 here.
Regrads,
Michael
>
> i2cdev_ioctl_smbus()
> --> i2c_smbus_xfer
> --> __i2c_smbus_xfer
> --> ft260_smbus_xfer
> --> ft260_smbus_write
>
> 442
> 443 ft260_dbg("rep %#02x addr %#02x cmd %#02x datlen %d replen %d\n",
> 444 rep->report, addr, cmd, rep->length, len);
> 445
> 446 ret = ft260_hid_output_report_check_status(dev, (u8 *)rep, len);
> 447
> 448 return ret;
> 449 }
>
> regards,
> dan carpenter
