appletalk: handle SIOCATALKDIFADDR compat ioctl

We must not have a compat ioctl handler for SIOCATALKDIFADDR
in common code, because the same number is used in other protocols
with different data structures.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

fs/compat_ioctl.c

@@ -2536,7 +2536,6 @@ HANDLE_IOCTL(SIOCSIFHWBROADCAST, dev_ifsioc)
 HANDLE_IOCTL(SIOCSHWTSTAMP, dev_ifsioc)
 
 /* ioctls used by appletalk ddp.c */
-HANDLE_IOCTL(SIOCATALKDIFADDR, dev_ifsioc)
 HANDLE_IOCTL(SIOCDIFADDR, dev_ifsioc)
 HANDLE_IOCTL(SIOCSARP, dev_ifsioc)
 HANDLE_IOCTL(SIOCDARP, dev_ifsioc)

net/appletalk/ddp.c

@@ -1811,12 +1811,14 @@ static int atalk_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 static int atalk_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
 {
 	/*
-	 * All Appletalk ioctls except SIOCATALKDIFADDR are standard.  And
-	 * SIOCATALKDIFADDR is handled by upper layer as well, so there is
-	 * nothing to do.  Eventually SIOCATALKDIFADDR should be moved
-	 * here so there is no generic SIOCPROTOPRIVATE translation in the
-	 * system.
+	 * SIOCATALKDIFADDR is a SIOCPROTOPRIVATE ioctl number, so we
+	 * cannot handle it in common code. The data we access if ifreq
+	 * here is compatible, so we can simply call the native
+	 * handler.
 	 */
+	if (cmd == SIOCATALKDIFADDR)
+		return atalk_ioctl(sock, cmd, (unsigned long)compat_ptr(arg));
+
 	return -ENOIOCTLCMD;
 }
 #endif