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Miller" , Paolo Abeni , Eric Dumazet , David Ahern Cc: Kuniyuki Iwashima , Steffen Klassert , Shaw Leon , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net v3 1/2] ip6: vti: Use ip6_tnl.net in vti6_changelink(). Date: Tue, 19 May 2026 20:35:46 +0800 Message-Id: <20260519123547.2055911-2-maoyixie.tju@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260519123547.2055911-1-maoyixie.tju@gmail.com> References: <20260519123547.2055911-1-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 From: Kuniyuki Iwashima ip netns add ns1 ip netns add ns2 ip -n ns1 link add vti6_test type vti6 remote ::1 local ::2 key 7 ip -n ns1 link set vti6_test netns ns2 ip -n ns2 link set vti6_test type vti6 remote ::3 local ::4 key 9 ip netns del ns2 ip netns del ns1 [ 132.495484] ------------[ cut here ]------------ [ 132.497609] kernel BUG at net/core/dev.c:12376! After commit 5e72ce3e3980 ("net: ipv6: Use link netns in newlink() of rtnl_link_ops"), vti6_newlink() correctly resolves the per-netns vti6 hash via link_net. vti6_changelink() and vti6_update() were not converted in that series and still read dev_net(dev) / dev_net(t->dev), which diverge from the device's creation netns after IFLA_NET_NS_FD migration. The result is a stale per-netns hash entry; cleanup_net() of the original netns then walks freed memory. Reachable from an unprivileged user namespace ("unshare --user --map-root-user --net"); cross-tenant scope on container hosts. Fixes: 5e72ce3e3980 ("net: ipv6: Use link netns in newlink() of rtnl_link_ops") Reported-by: Maoyi Xie Reviewed-by: Eric Dumazet Cc: stable@vger.kernel.org # v5.15+ Signed-off-by: Kuniyuki Iwashima --- net/ipv6/ip6_vti.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c index ad5290be4..dcb257411 100644 --- a/net/ipv6/ip6_vti.c +++ b/net/ipv6/ip6_vti.c @@ -722,10 +722,11 @@ vti6_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p, static int vti6_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p, bool keep_mtu) { - struct net *net = dev_net(t->dev); - struct vti6_net *ip6n = net_generic(net, vti6_net_id); + struct net *net = t->net; + struct vti6_net *ip6n; int err; + ip6n = net_generic(net, vti6_net_id); vti6_tnl_unlink(ip6n, t); synchronize_net(); err = vti6_tnl_change(t, p, keep_mtu); @@ -1031,11 +1032,12 @@ static int vti6_changelink(struct net_device *dev, struct nlattr *tb[], struct nlattr *data[], struct netlink_ext_ack *extack) { - struct ip6_tnl *t; + struct ip6_tnl *t = netdev_priv(dev); + struct net *net = t->net; struct __ip6_tnl_parm p; - struct net *net = dev_net(dev); - struct vti6_net *ip6n = net_generic(net, vti6_net_id); + struct vti6_net *ip6n; + ip6n = net_generic(net, vti6_net_id); if (dev == ip6n->fb_tnl_dev) return -EINVAL; -- 2.34.1