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Mon, 12 Apr 2021 09:12:00 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3020.oracle.com with ESMTP id 37unwx3dww-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 12 Apr 2021 09:12:00 +0000 Received: from abhmp0010.oracle.com (abhmp0010.oracle.com [141.146.116.16]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 13C9BweC031359; Mon, 12 Apr 2021 09:11:58 GMT Received: from kadam (/102.36.221.92) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 12 Apr 2021 02:11:57 -0700 Date: Mon, 12 Apr 2021 12:11:51 +0300 From: Dan Carpenter To: Michael Zaidman Cc: Jiri Kosina , Benjamin Tissoires , linux-i2c@vger.kernel.org, linux-input@vger.kernel.org Subject: Re: [bug report] HID: ft260: add usb hid to i2c host bridge driver Message-ID: <20210412091151.GV6048@kadam> References: <20210410122729.GA6136@michael-VirtualBox> <20210410153712.GQ6048@kadam> <20210410210425.GA4073@michael-VirtualBox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210410210425.GA4073@michael-VirtualBox> User-Agent: Mutt/1.9.4 (2018-02-28) X-Proofpoint-IMR: 1 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9951 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 suspectscore=0 mlxscore=0 malwarescore=0 adultscore=0 bulkscore=0 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104120061 X-Proofpoint-GUID: DuN6qnFhiNejlye4IJG2eFkmPgql03eb X-Proofpoint-ORIG-GUID: DuN6qnFhiNejlye4IJG2eFkmPgql03eb X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9951 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 mlxlogscore=999 spamscore=0 impostorscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 bulkscore=0 phishscore=0 suspectscore=0 malwarescore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104120061 Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org On Sun, Apr 11, 2021 at 12:04:25AM +0300, Michael Zaidman wrote: > On Sat, Apr 10, 2021 at 06:37:13PM +0300, Dan Carpenter wrote: > > On Sat, Apr 10, 2021 at 03:27:29PM +0300, Michael Zaidman wrote: > > > 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. > > > > > > > > > > > i2cdev_ioctl_smbus() > > > > --> i2c_smbus_xfer > > > > --> __i2c_smbus_xfer > > > > --> ft260_smbus_xfer > > > > --> ft260_smbus_write > > > > It's actually me who misunderstood the Smatch warning. Smatch is not > > complaining about data_len, it's data->block[0] which is user > > controlled and only for the I2C_SMBUS_I2C_BLOCK_DATA command. > > > > The call tree is the same. I've looked at it again. Here is how > > i2cdev_ioctl_smbus() looks like: > > > > drivers/i2c/i2c-dev.c > > 355 return -EINVAL; > > 356 } > > 357 > > 358 if ((size == I2C_SMBUS_BYTE_DATA) || > > 359 (size == I2C_SMBUS_BYTE)) > > 360 datasize = sizeof(data->byte); > > 361 else if ((size == I2C_SMBUS_WORD_DATA) || > > 362 (size == I2C_SMBUS_PROC_CALL)) > > 363 datasize = sizeof(data->word); > > 364 else /* size == smbus block, i2c block, or block proc. call */ > > 365 datasize = sizeof(data->block); > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > 366 > > 367 if ((size == I2C_SMBUS_PROC_CALL) || > > 368 (size == I2C_SMBUS_BLOCK_PROC_CALL) || > > 369 (size == I2C_SMBUS_I2C_BLOCK_DATA) || > > ^^^^^^^^^^^^^^^^^^^^^^^^ > > 370 (read_write == I2C_SMBUS_WRITE)) { > > 371 if (copy_from_user(&temp, data, datasize)) > > ^^^^ > > temp.block[0] is user controlled. > > > > 372 return -EFAULT; > > 373 } > > 374 if (size == I2C_SMBUS_I2C_BLOCK_BROKEN) { > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > > 375 /* Convert old I2C block commands to the new > > 376 convention. This preserves binary compatibility. */ > > 377 size = I2C_SMBUS_I2C_BLOCK_DATA; > > 378 if (read_write == I2C_SMBUS_READ) > > 379 temp.block[0] = I2C_SMBUS_BLOCK_MAX; > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > Except for size BROKEN > > > > 380 } > > 381 res = i2c_smbus_xfer(client->adapter, client->addr, client->flags, > > 382 read_write, command, size, &temp); > > ^^^^^ > > > > 383 if (!res && ((size == I2C_SMBUS_PROC_CALL) || > > 384 (size == I2C_SMBUS_BLOCK_PROC_CALL) || > > 385 (read_write == I2C_SMBUS_READ))) { > > 386 if (copy_to_user(data, &temp, datasize)) > > 387 return -EFAULT; > > 388 } > > > > The rest of the call tree seems straight forward but it's possible I > > have missed somewhere that checks data[0]. Here is how ft260_smbus_xfer() > > looks like. > > Oh, you are right. Despite that the SMbus block transaction limits the maximum > number of bytes to 32, nothing prevents a user from specifying via ioctl a larger > data size than the ft260 can handle in a single transfer. > > I am going to fix it in the ft260_smbus_write (with your Signed-off-by), but > perhaps we should fix it in the first place, in the i2cdev_ioctl_smbus routine? > What do you think? Could you just give me a Reported-by tag? Thanks! regards, dan carpenter