[PATCH 3.16 304/366] netlink: Do not subscribe to non-existent groups

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dmitry Safonov <redacted>

commit 7acf9d4237c46894e0fa0492dd96314a41742e84 upstream.

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 <redacted>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <redacted>
---
 net/netlink/af_netlink.c | 1 +
 1 file changed, 1 insertion(+)

--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c

@@ -927,6 +927,7 @@ static int netlink_bind(struct socket *s
 		if (err)
 			return err;
 	}
+	groups &= (1UL << nlk->ngroups) - 1;
 
 	if (nlk->portid)
 		if (nladdr->nl_pid != nlk->portid)