media: gspca: Add bounds checking to firmware parser

commit aef89c0 upstream.

This sd_init() function reads the firmware.  The firmware data holds a
series of records and the function reads each record and sends the data
to the device.  The request_ihex_firmware() function
calls ihex_validate_fw() which ensures that the total length of all the
records won't read out of bounds of the fw->data[].

However, a potential issue is if there is a single very large
record (larger than PAGE_SIZE) and that would result in memory
corruption.  Generally we trust the firmware, but it's always better to
double check.

Fixes: 49b61ec ("[media] gspca: Add new vicam subdriver")
Cc: stable@vger.kernel.org
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Dan Carpenter

drivers/media/usb/gspca/vicam.c

@@ -227,6 +227,7 @@ static int sd_init(struct gspca_dev *gspca_dev)
 	const struct ihex_binrec *rec;
 	const struct firmware *fw;
 	u8 *firmware_buf;
+	int len;
 
 	ret = request_ihex_firmware(&fw, VICAM_FIRMWARE,
 				    &gspca_dev->dev->dev);
@@ -241,9 +242,14 @@ static int sd_init(struct gspca_dev *gspca_dev)
 		goto exit;
 	}
 	for (rec = (void *)fw->data; rec; rec = ihex_next_binrec(rec)) {
-		memcpy(firmware_buf, rec->data, be16_to_cpu(rec->len));
+		len = be16_to_cpu(rec->len);
+		if (len > PAGE_SIZE) {
+			ret = -EINVAL;
+			break;
+		}
+		memcpy(firmware_buf, rec->data, len);
 		ret = vicam_control_msg(gspca_dev, 0xff, 0, 0, firmware_buf,
-					be16_to_cpu(rec->len));
+					len);
 		if (ret < 0)
 			break;
 	}