Subject: [PATCH 17/21] ip6_gre: fix tunnel list corruption for x-netns

From: Olivier Matz <[email-masked]>
Date: Wed, 9 Jan 2019 10:57:21 +0100

[ Upstream commit ab5098fa25b91cb6fe0a0676f17abb64f2bbf024 ]

In changelink ops, the ip6gre_net pointer is retrieved from
dev_net(dev), which is wrong in case of x-netns. Thus, the tunnel is not
unlinked from its current list and is relinked into another net
namespace. This corrupts the tunnel lists and can later trigger a kernel
oops.

Fix this by retrieving the netns from device private area.

Fixes: c8632fc30bb0 ("net: ip6_gre: Split up ip6gre_changelink()")
Cc: Petr Machata <[email-masked]>
Signed-off-by: Olivier Matz <[email-masked]>
Acked-by: Nicolas Dichtel <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/ipv6/ip6_gre.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index c270726b01b0..c0aad1f9ab15 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -2047,9 +2047,9 @@ static int ip6gre_changelink(struct net_device *dev, struct nlattr *tb[],
 			     struct nlattr *data[],
 			     struct netlink_ext_ack *extack)
 {
-	struct ip6gre_net *ign = net_generic(dev_net(dev), ip6gre_net_id);
+	struct ip6_tnl *t = netdev_priv(dev);
+	struct ip6gre_net *ign = net_generic(t->net, ip6gre_net_id);
 	struct __ip6_tnl_parm p;
-	struct ip6_tnl *t;
 
 	t = ip6gre_changelink_common(dev, tb, data, &p, extack);
 	if (IS_ERR(t))
-- 
2.20.1