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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: David Ahern , Kuniyuki Iwashima , Xiao Liang , Steffen Klassert , Herbert Xu , Simon Horman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net v5 4/7] net: ip6_tunnel: require CAP_NET_ADMIN in the device netns for changelink Date: Thu, 11 Jun 2026 14:28:11 +0800 Message-Id: <20260611062814.2528793-5-maoyixie.tju@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260611062814.2528793-1-maoyixie.tju@gmail.com> References: <20260611062814.2528793-1-maoyixie.tju@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 Closes: https://lore.kernel.org/netdev/CABAhCOSzP1vaThGV35_VnsRCb=87_CPjPVsTHbq905k8A+BuUg@mail.gmail.com/ Fixes: 5311a69aaca3 ("net, ip6_tunnel: fix namespaces move") Cc: stable@vger.kernel.org Signed-off-by: Maoyi Xie --- net/ipv6/ip6_tunnel.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c index 9d1037ac082f..922b0feaddf9 100644 --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -2102,6 +2102,9 @@ 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) { if (ip_tunnel_netlink_encap_parms(data, &ipencap)) { /* iproute2 always sets TUNNEL_ENCAP_FLAG_CSUM6, so -- 2.34.1