Subject: [PATCH 14/21] netlink: Do not subscribe to non-existent groups

From: Dmitry Safonov <[email-masked]>
Date: Fri, 27 Jul 2018 16:54:44 +0100

[ 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" <[email-masked]>
Cc: Herbert Xu <[email-masked]>
Cc: Steffen Klassert <[email-masked]>
Cc: [email-masked]
Signed-off-by: Dmitry Safonov <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 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 2e2dd88fc79f..fc5df9598a5a 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1008,6 +1008,7 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
 		if (err)
 			return err;
 	}
+	groups &= (1UL << nlk->ngroups) - 1;
 
 	bound = nlk->bound;
 	if (bound) {
-- 
2.17.1