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

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

From: Olivier Matz <olivier.m...@6wind.com>

[ 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 <pe...@mellanox.com>
Signed-off-by: Olivier Matz <olivier.m...@6wind.com>
Acked-by: Nicolas Dichtel <nicolas.dich...@6wind.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/ipv6/ip6_gre.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -2029,9 +2029,9 @@ static int ip6gre_changelink(struct net_
                             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))


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