usb: iowarrior: don't trust report_size for buffer size

commit 3ed7801 upstream.

If the iowarrior devices in this case statement support more than 8 bytes
per report, it is possible to write past the end of a kernel heap allocation.
This will probably never be possible, but change the allocation to be more
defensive anyway.

Signed-off-by: Kees Cook <kees.cook@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Brandon Philips <bphilips@suse.de>

drivers/usb/misc/iowarrior.c

@@ -373,7 +373,7 @@ static ssize_t iowarrior_write(struct file *file,
 	case USB_DEVICE_ID_CODEMERCS_IOWPV2:
 	case USB_DEVICE_ID_CODEMERCS_IOW40:
 		/* IOW24 and IOW40 use a synchronous call */
-		buf = kmalloc(8, GFP_KERNEL);	/* 8 bytes are enough for both products */
+		buf = kmalloc(count, GFP_KERNEL);
 		if (!buf) {
 			retval = -ENOMEM;
 			goto exit;