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net: ip6_tunnel: require CAP_NET_ADMIN in the device netns for changelink

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[ Upstream commit 2496fa0b7d ]

ip6_tnl_changelink() operates on at most two netns, dev_net(dev) and the
tunnel link netns t->net. They differ once the device is created in or
moved to a netns other than the one the request runs in. The rtnl
changelink path checks CAP_NET_ADMIN only against dev_net(dev), so a
caller privileged there but not in t->net can rewrite a tunnel that
lives in t->net.

Gate ip6_tnl_changelink() on rtnl_dev_link_net_capable() at its top,
before any attribute is parsed.

Reported-by: Xiao Liang <shaw.leon@gmail.com>
Closes: https://lore.kernel.org/netdev/CABAhCOSzP1vaThGV35_VnsRCb=87_CPjPVsTHbq905k8A+BuUg@mail.gmail.com/
Fixes: 0bd8762824 ("ip6tnl: add x-netns support")
Cc: stable@vger.kernel.org
Signed-off-by: Maoyi Xie <maoyixie.tju@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260612085941.3158249-5-maoyixie.tju@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Maoyi Xie
2026-08-03 11:15:39 +02:00
committed by Greg Kroah-Hartman
parent e57a4845b0
commit 2636d061bc
1 changed files with 3 additions and 0 deletions
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net/ipv6/ip6_tunnel.c
+3
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@@ -2055,6 +2055,9 @@ static int ip6_tnl_changelink(struct net_device *dev, struct nlattr *tb[],
struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id);
struct ip_tunnel_encap ipencap;
if (!rtnl_dev_link_net_capable(dev, net))
return -EPERM;
if (dev == ip6n->fb_tnl_dev)
return -EINVAL;