netdev - [PATCH net-next v2 06/10] net: IP[V6]_MULTICAST_IF constraint on unbound socket if VRFs present

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Date:   Mon,  1 Oct 2018 09:43:16 +0100
From:   Mike Manning <mmanning@...tta.att-mail.com>
To:     netdev@...r.kernel.org
Cc:     Duncan Eastoe <deastoe@...tta.att-mail.com>
Subject: [PATCH net-next v2 06/10] net: IP[V6]_MULTICAST_IF constraint on unbound socket if VRFs present

From: Duncan Eastoe <deastoe@...tta.att-mail.com>

If setsockopt(IP_MULTICAST_IF) or setsockopt(IPV6_MULTICAST_IF) is
called on a socket which is not bound to a VRF then we should ensure
that the output device chosen is also not bound to a VRF master.

This avoids inadvertently sending traffic out of the wrong interface.
This can be particularly problematic for IP_MULTICAST_IF since the
interface lookup can be performed by address as well as ifindex. If
there are interfaces with the same address, one unbound and one bound
to a VRF, then the interface bound to the VRF may be chosen when the
sockopt is called on an unbound socket.

Signed-off-by: Duncan Eastoe <deastoe@...tta.att-mail.com>
Signed-off-by: Mike Manning <mmanning@...tta.att-mail.com>
---
 net/ipv4/ip_sockglue.c   | 3 +++
 net/ipv6/ipv6_sockglue.c | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index c0fe5ad996f2..026971314c43 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -892,6 +892,9 @@ static int do_ip_setsockopt(struct sock *sk, int level,
 		dev_put(dev);
 
 		err = -EINVAL;
+		if (!sk->sk_bound_dev_if && midx)
+			break;
+
 		if (sk->sk_bound_dev_if &&
 		    mreq.imr_ifindex != sk->sk_bound_dev_if &&
 		    (!midx || midx != sk->sk_bound_dev_if))
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index c0cac9cc3a28..7dfbc797b130 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -626,6 +626,9 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 
 			rcu_read_unlock();
 
+			if (!sk->sk_bound_dev_if && midx)
+				goto e_inval;
+
 			if (sk->sk_bound_dev_if &&
 			    sk->sk_bound_dev_if != val &&
 			    (!midx || midx != sk->sk_bound_dev_if))
-- 
2.11.0