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[217.132.244.50]) by smtp.gmail.com with ESMTPSA id sb4sm2596445ejb.1.2021.04.10.05.27.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 Apr 2021 05:27:31 -0700 (PDT) Date: Sat, 10 Apr 2021 15:27:29 +0300 From: Michael Zaidman To: Dan Carpenter Cc: linux-i2c@vger.kernel.org, linux-input@vger.kernel.org, michael.zaidman@gmail.com Subject: Re: [bug report] HID: ft260: add usb hid to i2c host bridge driver Message-ID: <20210410122729.GA6136@michael-VirtualBox> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org 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