Subject: [PATCH v2 net-next] net/ipv6: Do not allow route add with a device that is down

From: David Ahern <[email-masked]>
Date: Wed, 24 Jan 2018 08:29:24 -0800

IPv6 allows routes to be installed when the device is not up (admin up).
Worse, it does not mark it as LINKDOWN. IPv4 does not allow it and really
there is no reason for IPv6 to allow it, so check the flags and deny if
device is admin down.

Signed-off-by: David Ahern <[email-masked]>
---
v2
- missed setting err to -ENETDOWN (thanks for catching that Roopa)

 net/ipv6/route.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f85da2f1e729..4e8fab766018 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2734,6 +2734,12 @@ static struct rt6_info *ip6_route_info_create(struct fib6_config *cfg,
 	if (!dev)
 		goto out;
 
+	err = -ENETDOWN;
+	if (!(dev->flags & IFF_UP)) {
+		NL_SET_ERR_MSG(extack, "Nexthop device is not up");
+		goto out;
+	}
+
 	if (!ipv6_addr_any(&cfg->fc_prefsrc)) {
 		if (!ipv6_chk_addr(net, &cfg->fc_prefsrc, dev, 0)) {
 			NL_SET_ERR_MSG(extack, "Invalid source address");
-- 
2.11.0