From e208cda5f10e131f149e59d7de4ceb943382f4c6 Mon Sep 17 00:00:00 2001
From: Dmitry Safonov <dima@arista.com>
Date: Fri, 27 Jul 2018 16:54:44 +0100
Subject: [PATCH] netlink: Do not subscribe to non-existent groups

[ Upstream commit 7acf9d4237c46894e0fa0492dd96314a41742e84 ]

Make ABI more strict about subscribing to group > ngroups.
Code doesn't check for that and it looks bogus.
(one can subscribe to non-existing group)
Still, it's possible to bind() to all possible groups with (-1)

Cc: "David S. Miller" <davem@davemloft.net>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: netdev@vger.kernel.org
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/netlink/af_netlink.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index b3932846f6c4..143d9001e87d 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -976,6 +976,7 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
 		if (err)
 			return err;
 	}
+	groups &= (1UL << nlk->ngroups) - 1;
 
 	bound = nlk->bound;
 	if (bound) {
-- 
2.20.1