fs/btrfs: Integer overflow in btrfs_ioctl_resize()

The local variable 'new_size' comes from userspace. If a large number
was passed, there would be an integer overflow in the following line:
	new_size = old_size + new_size;

Signed-off-by: Wenliang Fan <fanwlexca@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/ioctl.c

@@ -1474,6 +1474,10 @@ static noinline int btrfs_ioctl_resize(struct file *file,
 		}
 		new_size = old_size - new_size;
 	} else if (mod > 0) {
+		if (new_size > ULLONG_MAX - old_size) {
+			ret = -EINVAL;
+			goto out_free;
+		}
 		new_size = old_size + new_size;
 	}