batman-adv: bat_socket_read missing checks

commit c00b6856 upstream.

Writing a icmp_packet_rr and then reading icmp_packet can lead to kernel
memory corruption, if __user *buf is just below TASK_SIZE.
Signed-off-by: Paul Kot <pawlkt@gmail.com>
[sven@narfation.org: made it checkpatch clean]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/batman-adv/icmp_socket.c

@@ -136,8 +136,8 @@ static ssize_t bat_socket_read(struct file *file, char __user *buf,
 
 	spin_unlock_bh(&socket_client->lock);
 
-	error = __copy_to_user(buf, &socket_packet->icmp_packet,
-			       socket_packet->icmp_len);
+	error = copy_to_user(buf, &socket_packet->icmp_packet,
+			     socket_packet->icmp_len);
 
 	packet_len = socket_packet->icmp_len;
 	kfree(socket_packet);