isight_firmware: Avoid crash on loading invalid firmware

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/misc/isight_firmware.c b/drivers/usb/misc/isight_firmware.c
index 390e048855366501a32434b9a85bc54a12f9034d..9f30aa1f8a5da5cdba326d67a80d8a2bf30cb01e 100644 (file)
--- a/drivers/usb/misc/isight_firmware.c
+++ b/drivers/usb/misc/isight_firmware.c
@@ -39,9 +39,12 @@ static int isight_firmware_load(struct usb_interface *intf,
        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 usb_interface *intf,
                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 usb_interface *intf,
                        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 usb_interface *intf,
                                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;
 }