diff --git a/drivers/firewire/fw-cdev.c b/drivers/firewire/fw-cdev.c
index 7538864..0647130 100644
--- a/drivers/firewire/fw-cdev.c
+++ b/drivers/firewire/fw-cdev.c
@@ -722,10 +722,11 @@
 		buffer_end = 0;
 	}
 
-	if (!access_ok(VERIFY_READ, request->packets, request->size))
+	p = (struct fw_cdev_iso_packet __user *)u64_to_uptr(request->packets);
+
+	if (!access_ok(VERIFY_READ, p, request->size))
 		return -EFAULT;
 
-	p = (struct fw_cdev_iso_packet __user *)u64_to_uptr(request->packets);
 	end = (void __user *)p + request->size;
 	count = 0;
 	while (p < end) {