From: Matthew Garrett <mjg59@srcf.ucam.org>

Different tools generate slightly different formats of the isight
firmware. Ensure that the firmware buffer is not overrun, while still
ensuring that the correct amount of data is written if trailing data is
present.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Report-by: Justin Mattock <justinmattock@gmail.com>
Tested-by: Justin Mattock <justinmattock@gmail.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/usb/misc/isight_firmware.c |   23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff -puN drivers/usb/misc/isight_firmware.c~isight_firmware-avoid-crash-on-loading-invalid-firmware drivers/usb/misc/isight_firmware.c
--- a/drivers/usb/misc/isight_firmware.c~isight_firmware-avoid-crash-on-loading-invalid-firmware
+++ a/drivers/usb/misc/isight_firmware.c
@@ -39,9 +39,12 @@ static int isight_firmware_load(struct u
 	struct usb_device *dev = interface_to_usbdev(intf);
 	int llen, len, req, ret = 0;
 	const struct firmware *firmware;
-	unsigned char *buf;
+	unsigned char *buf = kmalloc(50, GFP_KERNEL);
 	unsigned char data[4];
-	char *ptr;
+	u8 *ptr;
+
+	if (!buf)
+		return -ENOMEM;
 
 	if (request_firmware(&firmware, "isight.fw", &dev->dev) != 0) {
 		printk(KERN_ERR "Unable to load isight firmware\n");
@@ -59,7 +62,7 @@ static int isight_firmware_load(struct u
 		goto out;
 	}
 
-	while (1) {
+	while (ptr+4 <= firmware->data+firmware->size) {
 		memcpy(data, ptr, 4);
 		len = (data[0] << 8 | data[1]);
 		req = (data[2] << 8 | data[3]);
@@ -71,10 +74,14 @@ static int isight_firmware_load(struct u
 			continue;
 
 		for (; len > 0; req += 50) {
-			llen = len > 50 ? 50 : len;
+			llen = min(len, 50);
 			len -= llen;
-
-			buf = kmalloc(llen, GFP_KERNEL);
+			if (ptr+llen > firmware->data+firmware->size) {
+				printk(KERN_ERR
+				       "Malformed isight firmware");
+				ret = -ENODEV;
+				goto out;
+			}
 			memcpy(buf, ptr, llen);
 
 			ptr += llen;
@@ -89,16 +96,18 @@ static int isight_firmware_load(struct u
 				goto out;
 			}
 
-			kfree(buf);
 		}
 	}
+
 	if (usb_control_msg
 	    (dev, usb_sndctrlpipe(dev, 0), 0xa0, 0x40, 0xe600, 0, "\0", 1,
 	     300) != 1) {
 		printk(KERN_ERR "isight firmware loading completion failed\n");
 		ret = -ENODEV;
 	}
+
 out:
+	kfree(buf);
 	release_firmware(firmware);
 	return ret;
 }
_