[PATCH 4.16 40/55] udp: fix SO_BINDTODEVICE

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.16-stable review patch.  If anyone has any objections, please let me know.

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

From: Paolo Abeni <pabeni@redhat.com>

[ Upstream commit 69678bcd4d2dedbc3e8fcd6d7d99f283d83c531a ]

Damir reported a breakage of SO_BINDTODEVICE for UDP sockets.
In absence of VRF devices, after commit fb74c27735f0 ("net:
ipv4: add second dif to udp socket lookups") the dif mismatch
isn't fatal anymore for UDP socket lookup with non null
sk_bound_dev_if, breaking SO_BINDTODEVICE semantics.

This changeset addresses the issue making the dif match mandatory
again in the above scenario.

Reported-by: Damir Mansurov <dnman@oktetlabs.ru>
Fixes: fb74c27735f0 ("net: ipv4: add second dif to udp socket lookups")
Fixes: 1801b570dd2a ("net: ipv6: add second dif to udp socket lookups")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/udp.c |    4 ++--
 net/ipv6/udp.c |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -407,9 +407,9 @@ static int compute_score(struct sock *sk
 		bool dev_match = (sk->sk_bound_dev_if == dif ||
 				  sk->sk_bound_dev_if == sdif);
 
-		if (exact_dif && !dev_match)
+		if (!dev_match)
 			return -1;
-		if (sk->sk_bound_dev_if && dev_match)
+		if (sk->sk_bound_dev_if)
 			score += 4;
 	}
 
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -148,9 +148,9 @@ static int compute_score(struct sock *sk
 		bool dev_match = (sk->sk_bound_dev_if == dif ||
 				  sk->sk_bound_dev_if == sdif);
 
-		if (exact_dif && !dev_match)
+		if (!dev_match)
 			return -1;
-		if (sk->sk_bound_dev_if && dev_match)
+		if (sk->sk_bound_dev_if)
 			score++;
 	}