From: Wei Wang <weiwan@google.com>
Date: Mon, 14 Aug 2017 10:44:59 -0700
Subject: ipv6: release rt6->rt6i_idev properly during ifdown
Patch-mainline: v4.13-rc6
Git-commit: e5645f51ba99738b0e5d708edf9c6454f33b9310
References: bsc#1061739

When a dst is created by addrconf_dst_alloc() for a host route or an
anycast route, dst->dev points to loopback dev while rt6->rt6i_idev
points to a real device.
When the real device goes down, the current cleanup code only checks for
dst->dev and assumes rt6->rt6i_idev->dev is the same. This causes the
refcount leak on the real device in the above situation.
This patch makes sure to always release the refcount taken on
rt6->rt6i_idev during dst_dev_put().

Fixes: 587fea741134 ("ipv6: mark DST_NOGC and remove the operation of
dst_free()")
Reported-by: John Stultz <john.stultz@linaro.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Tested-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Wei Wang <weiwan@google.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>

---
 net/ipv6/route.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index c7271ea384d3..97245b2694d6 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -417,14 +417,11 @@ static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
 	struct net_device *loopback_dev =
 		dev_net(dev)->loopback_dev;
 
-	if (dev != loopback_dev) {
-		if (idev && idev->dev == dev) {
-			struct inet6_dev *loopback_idev =
-				in6_dev_get(loopback_dev);
-			if (loopback_idev) {
-				rt->rt6i_idev = loopback_idev;
-				in6_dev_put(idev);
-			}
+	if (idev && idev->dev != loopback_dev) {
+		struct inet6_dev *loopback_idev = in6_dev_get(loopback_dev);
+		if (loopback_idev) {
+			rt->rt6i_idev = loopback_idev;
+			in6_dev_put(idev);
 		}
 	}
 }
-- 
2.14.2