x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 747 insertions, 0 deletions

diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
new file mode 100644
index 000000000..3b8092999
--- /dev/null
+++ b/net/ipv4/ip_vti.c
@@ -0,0 +1,747 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	Linux NET3: IP/IP protocol decoder modified to support
+ *		    virtual tunnel interface
+ *
+ *	Authors:
+ *		Saurabh Mohan (saurabh.mohan@vyatta.com) 05/07/2012
+ */
+
+/*
+   This version of net/ipv4/ip_vti.c is cloned of net/ipv4/ipip.c
+
+   For comments look at net/ipv4/ip_gre.c --ANK
+ */
+
+
+#include <linux/capability.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/uaccess.h>
+#include <linux/skbuff.h>
+#include <linux/netdevice.h>
+#include <linux/in.h>
+#include <linux/tcp.h>
+#include <linux/udp.h>
+#include <linux/if_arp.h>
+#include <linux/init.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/if_ether.h>
+#include <linux/icmpv6.h>
+
+#include <net/sock.h>
+#include <net/ip.h>
+#include <net/icmp.h>
+#include <net/ip_tunnels.h>
+#include <net/inet_ecn.h>
+#include <net/xfrm.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+static struct rtnl_link_ops vti_link_ops __read_mostly;
+
+static unsigned int vti_net_id __read_mostly;
+static int vti_tunnel_init(struct net_device *dev);
+
+static int vti_input(struct sk_buff *skb, int nexthdr, __be32 spi,
+		     int encap_type, bool update_skb_dev)
+{
+	struct ip_tunnel *tunnel;
+	const struct iphdr *iph = ip_hdr(skb);
+	struct net *net = dev_net(skb->dev);
+	struct ip_tunnel_net *itn = net_generic(net, vti_net_id);
+	IP_TUNNEL_DECLARE_FLAGS(flags) = { };
+
+	__set_bit(IP_TUNNEL_NO_KEY_BIT, flags);
+
+	tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex, flags,
+				  iph->saddr, iph->daddr, 0);
+	if (tunnel) {
+		if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
+			goto drop;
+
+		XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = tunnel;
+
+		if (update_skb_dev)
+			skb->dev = tunnel->dev;
+
+		return xfrm_input(skb, nexthdr, spi, encap_type);
+	}
+
+	return -EINVAL;
+drop:
+	kfree_skb(skb);
+	return 0;
+}
+
+static int vti_input_proto(struct sk_buff *skb, int nexthdr, __be32 spi,
+			   int encap_type)
+{
+	return vti_input(skb, nexthdr, spi, encap_type, false);
+}
+
+static int vti_rcv(struct sk_buff *skb, __be32 spi, bool update_skb_dev)
+{
+	XFRM_SPI_SKB_CB(skb)->family = AF_INET;
+	XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
+
+	return vti_input(skb, ip_hdr(skb)->protocol, spi, 0, update_skb_dev);
+}
+
+static int vti_rcv_proto(struct sk_buff *skb)
+{
+	return vti_rcv(skb, 0, false);
+}
+
+static int vti_rcv_cb(struct sk_buff *skb, int err)
+{
+	unsigned short family;
+	struct net_device *dev;
+	struct xfrm_state *x;
+	const struct xfrm_mode *inner_mode;
+	struct ip_tunnel *tunnel = XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4;
+	u32 orig_mark = skb->mark;
+	int ret;
+
+	if (!tunnel)
+		return 1;
+
+	dev = tunnel->dev;
+
+	if (err) {
+		DEV_STATS_INC(dev, rx_errors);
+		DEV_STATS_INC(dev, rx_dropped);
+
+		return 0;
+	}
+
+	x = xfrm_input_state(skb);
+
+	inner_mode = &x->inner_mode;
+
+	if (x->sel.family == AF_UNSPEC) {
+		inner_mode = xfrm_ip2inner_mode(x, XFRM_MODE_SKB_CB(skb)->protocol);
+		if (inner_mode == NULL) {
+			XFRM_INC_STATS(dev_net(skb->dev),
+				       LINUX_MIB_XFRMINSTATEMODEERROR);
+			return -EINVAL;
+		}
+	}
+
+	family = inner_mode->family;
+
+	skb->mark = be32_to_cpu(tunnel->parms.i_key);
+	ret = xfrm_policy_check(NULL, XFRM_POLICY_IN, skb, family);
+	skb->mark = orig_mark;
+
+	if (!ret)
+		return -EPERM;
+
+	skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(skb->dev)));
+	skb->dev = dev;
+	dev_sw_netstats_rx_add(dev, skb->len);
+
+	return 0;
+}
+
+static bool vti_state_check(const struct xfrm_state *x, __be32 dst, __be32 src)
+{
+	xfrm_address_t *daddr = (xfrm_address_t *)&dst;
+	xfrm_address_t *saddr = (xfrm_address_t *)&src;
+
+	/* if there is no transform then this tunnel is not functional.
+	 * Or if the xfrm is not mode tunnel.
+	 */
+	if (!x || x->props.mode != XFRM_MODE_TUNNEL ||
+	    x->props.family != AF_INET)
+		return false;
+
+	if (!dst)
+		return xfrm_addr_equal(saddr, &x->props.saddr, AF_INET);
+
+	if (!xfrm_state_addr_check(x, daddr, saddr, AF_INET))
+		return false;
+
+	return true;
+}
+
+static netdev_tx_t vti_xmit(struct sk_buff *skb, struct net_device *dev,
+			    struct flowi *fl)
+{
+	struct ip_tunnel *tunnel = netdev_priv(dev);
+	struct ip_tunnel_parm_kern *parms = &tunnel->parms;
+	struct dst_entry *dst = skb_dst(skb);
+	struct net_device *tdev;	/* Device to other host */
+	int pkt_len = skb->len;
+	int err;
+	int mtu;
+
+	if (!dst) {
+		switch (skb->protocol) {
+		case htons(ETH_P_IP): {
+			struct rtable *rt;
+
+			fl->u.ip4.flowi4_oif = dev->ifindex;
+			fl->u.ip4.flowi4_flags |= FLOWI_FLAG_ANYSRC;
+			rt = __ip_route_output_key(dev_net(dev), &fl->u.ip4);
+			if (IS_ERR(rt)) {
+				DEV_STATS_INC(dev, tx_carrier_errors);
+				goto tx_error_icmp;
+			}
+			dst = &rt->dst;
+			skb_dst_set(skb, dst);
+			break;
+		}
+#if IS_ENABLED(CONFIG_IPV6)
+		case htons(ETH_P_IPV6):
+			fl->u.ip6.flowi6_oif = dev->ifindex;
+			fl->u.ip6.flowi6_flags |= FLOWI_FLAG_ANYSRC;
+			dst = ip6_route_output(dev_net(dev), NULL, &fl->u.ip6);
+			if (dst->error) {
+				dst_release(dst);
+				dst = NULL;
+				DEV_STATS_INC(dev, tx_carrier_errors);
+				goto tx_error_icmp;
+			}
+			skb_dst_set(skb, dst);
+			break;
+#endif
+		default:
+			DEV_STATS_INC(dev, tx_carrier_errors);
+			goto tx_error_icmp;
+		}
+	}
+
+	dst_hold(dst);
+	dst = xfrm_lookup_route(tunnel->net, dst, fl, NULL, 0);
+	if (IS_ERR(dst)) {
+		DEV_STATS_INC(dev, tx_carrier_errors);
+		goto tx_error_icmp;
+	}
+
+	if (dst->flags & DST_XFRM_QUEUE)
+		goto xmit;
+
+	if (!vti_state_check(dst->xfrm, parms->iph.daddr, parms->iph.saddr)) {
+		DEV_STATS_INC(dev, tx_carrier_errors);
+		dst_release(dst);
+		goto tx_error_icmp;
+	}
+
+	tdev = dst_dev(dst);
+
+	if (tdev == dev) {
+		dst_release(dst);
+		DEV_STATS_INC(dev, collisions);
+		goto tx_error;
+	}
+
+	mtu = dst_mtu(dst);
+	if (skb->len > mtu) {
+		skb_dst_update_pmtu_no_confirm(skb, mtu);
+		if (skb->protocol == htons(ETH_P_IP)) {
+			if (!(ip_hdr(skb)->frag_off & htons(IP_DF)))
+				goto xmit;
+			icmp_ndo_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
+				      htonl(mtu));
+		} else {
+			if (mtu < IPV6_MIN_MTU)
+				mtu = IPV6_MIN_MTU;
+
+			icmpv6_ndo_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
+		}
+
+		dst_release(dst);
+		goto tx_error;
+	}
+
+xmit:
+	skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(dev)));
+	skb_dst_set(skb, dst);
+	skb->dev = skb_dst_dev(skb);
+
+	err = dst_output(tunnel->net, skb->sk, skb);
+	if (net_xmit_eval(err) == 0)
+		err = pkt_len;
+	iptunnel_xmit_stats(dev, err);
+	return NETDEV_TX_OK;
+
+tx_error_icmp:
+	dst_link_failure(skb);
+tx_error:
+	DEV_STATS_INC(dev, tx_errors);
+	kfree_skb(skb);
+	return NETDEV_TX_OK;
+}
+
+/* This function assumes it is being called from dev_queue_xmit()
+ * and that skb is filled properly by that function.
+ */
+static netdev_tx_t vti_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct ip_tunnel *tunnel = netdev_priv(dev);
+	struct flowi fl;
+
+	if (!pskb_inet_may_pull(skb))
+		goto tx_err;
+
+	memset(&fl, 0, sizeof(fl));
+
+	switch (skb->protocol) {
+	case htons(ETH_P_IP):
+		memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
+		xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET);
+		break;
+	case htons(ETH_P_IPV6):
+		memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
+		xfrm_decode_session(dev_net(dev), skb, &fl, AF_INET6);
+		break;
+	default:
+		goto tx_err;
+	}
+
+	/* override mark with tunnel output key */
+	fl.flowi_mark = be32_to_cpu(tunnel->parms.o_key);
+
+	return vti_xmit(skb, dev, &fl);
+
+tx_err:
+	DEV_STATS_INC(dev, tx_errors);
+	kfree_skb(skb);
+	return NETDEV_TX_OK;
+}
+
+static int vti4_err(struct sk_buff *skb, u32 info)
+{
+	__be32 spi;
+	__u32 mark;
+	struct xfrm_state *x;
+	struct ip_tunnel *tunnel;
+	struct ip_esp_hdr *esph;
+	struct ip_auth_hdr *ah ;
+	struct ip_comp_hdr *ipch;
+	struct net *net = dev_net(skb->dev);
+	const struct iphdr *iph = (const struct iphdr *)skb->data;
+	int protocol = iph->protocol;
+	struct ip_tunnel_net *itn = net_generic(net, vti_net_id);
+	IP_TUNNEL_DECLARE_FLAGS(flags) = { };
+
+	__set_bit(IP_TUNNEL_NO_KEY_BIT, flags);
+
+	tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex, flags,
+				  iph->daddr, iph->saddr, 0);
+	if (!tunnel)
+		return -1;
+
+	mark = be32_to_cpu(tunnel->parms.o_key);
+
+	switch (protocol) {
+	case IPPROTO_ESP:
+		esph = (struct ip_esp_hdr *)(skb->data+(iph->ihl<<2));
+		spi = esph->spi;
+		break;
+	case IPPROTO_AH:
+		ah = (struct ip_auth_hdr *)(skb->data+(iph->ihl<<2));
+		spi = ah->spi;
+		break;
+	case IPPROTO_COMP:
+		ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
+		spi = htonl(ntohs(ipch->cpi));
+		break;
+	default:
+		return 0;
+	}
+
+	switch (icmp_hdr(skb)->type) {
+	case ICMP_DEST_UNREACH:
+		if (icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)
+			return 0;
+		break;
+	case ICMP_REDIRECT:
+		break;
+	default:
+		return 0;
+	}
+
+	x = xfrm_state_lookup(net, mark, (const xfrm_address_t *)&iph->daddr,
+			      spi, protocol, AF_INET);
+	if (!x)
+		return 0;
+
+	if (icmp_hdr(skb)->type == ICMP_DEST_UNREACH)
+		ipv4_update_pmtu(skb, net, info, 0, protocol);
+	else
+		ipv4_redirect(skb, net, 0, protocol);
+	xfrm_state_put(x);
+
+	return 0;
+}
+
+static int
+vti_tunnel_ctl(struct net_device *dev, struct ip_tunnel_parm_kern *p, int cmd)
+{
+	IP_TUNNEL_DECLARE_FLAGS(flags) = { };
+	int err = 0;
+
+	if (cmd == SIOCADDTUNNEL || cmd == SIOCCHGTUNNEL) {
+		if (p->iph.version != 4 || p->iph.protocol != IPPROTO_IPIP ||
+		    p->iph.ihl != 5)
+			return -EINVAL;
+	}
+
+	if (!ip_tunnel_flags_is_be16_compat(p->i_flags) ||
+	    !ip_tunnel_flags_is_be16_compat(p->o_flags))
+		return -EOVERFLOW;
+
+	if (!(ip_tunnel_flags_to_be16(p->i_flags) & GRE_KEY))
+		p->i_key = 0;
+	if (!(ip_tunnel_flags_to_be16(p->o_flags) & GRE_KEY))
+		p->o_key = 0;
+
+	__set_bit(IP_TUNNEL_VTI_BIT, flags);
+	ip_tunnel_flags_copy(p->i_flags, flags);
+
+	err = ip_tunnel_ctl(dev, p, cmd);
+	if (err)
+		return err;
+
+	if (cmd != SIOCDELTUNNEL) {
+		ip_tunnel_flags_from_be16(flags, GRE_KEY);
+		ip_tunnel_flags_or(p->i_flags, p->i_flags, flags);
+		ip_tunnel_flags_or(p->o_flags, p->o_flags, flags);
+	}
+	return 0;
+}
+
+static const struct net_device_ops vti_netdev_ops = {
+	.ndo_init	= vti_tunnel_init,
+	.ndo_uninit	= ip_tunnel_uninit,
+	.ndo_start_xmit	= vti_tunnel_xmit,
+	.ndo_siocdevprivate = ip_tunnel_siocdevprivate,
+	.ndo_change_mtu	= ip_tunnel_change_mtu,
+	.ndo_get_stats64 = dev_get_tstats64,
+	.ndo_get_iflink = ip_tunnel_get_iflink,
+	.ndo_tunnel_ctl	= vti_tunnel_ctl,
+};
+
+static void vti_tunnel_setup(struct net_device *dev)
+{
+	dev->netdev_ops		= &vti_netdev_ops;
+	dev->header_ops		= &ip_tunnel_header_ops;
+	dev->type		= ARPHRD_TUNNEL;
+	ip_tunnel_setup(dev, vti_net_id);
+}
+
+static int vti_tunnel_init(struct net_device *dev)
+{
+	struct ip_tunnel *tunnel = netdev_priv(dev);
+	struct iphdr *iph = &tunnel->parms.iph;
+
+	__dev_addr_set(dev, &iph->saddr, 4);
+	memcpy(dev->broadcast, &iph->daddr, 4);
+
+	dev->flags		= IFF_NOARP;
+	dev->addr_len		= 4;
+	dev->lltx		= true;
+	netif_keep_dst(dev);
+
+	return ip_tunnel_init(dev);
+}
+
+static void __net_init vti_fb_tunnel_init(struct net_device *dev)
+{
+	struct ip_tunnel *tunnel = netdev_priv(dev);
+	struct iphdr *iph = &tunnel->parms.iph;
+
+	iph->version		= 4;
+	iph->protocol		= IPPROTO_IPIP;
+	iph->ihl		= 5;
+}
+
+static struct xfrm4_protocol vti_esp4_protocol __read_mostly = {
+	.handler	=	vti_rcv_proto,
+	.input_handler	=	vti_input_proto,
+	.cb_handler	=	vti_rcv_cb,
+	.err_handler	=	vti4_err,
+	.priority	=	100,
+};
+
+static struct xfrm4_protocol vti_ah4_protocol __read_mostly = {
+	.handler	=	vti_rcv_proto,
+	.input_handler	=	vti_input_proto,
+	.cb_handler	=	vti_rcv_cb,
+	.err_handler	=	vti4_err,
+	.priority	=	100,
+};
+
+static struct xfrm4_protocol vti_ipcomp4_protocol __read_mostly = {
+	.handler	=	vti_rcv_proto,
+	.input_handler	=	vti_input_proto,
+	.cb_handler	=	vti_rcv_cb,
+	.err_handler	=	vti4_err,
+	.priority	=	100,
+};
+
+#if IS_ENABLED(CONFIG_INET_XFRM_TUNNEL)
+static int vti_rcv_tunnel(struct sk_buff *skb)
+{
+	XFRM_SPI_SKB_CB(skb)->family = AF_INET;
+	XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
+
+	return vti_input(skb, IPPROTO_IPIP, ip_hdr(skb)->saddr, 0, false);
+}
+
+static struct xfrm_tunnel vti_ipip_handler __read_mostly = {
+	.handler	=	vti_rcv_tunnel,
+	.cb_handler	=	vti_rcv_cb,
+	.err_handler	=	vti4_err,
+	.priority	=	0,
+};
+
+#if IS_ENABLED(CONFIG_IPV6)
+static struct xfrm_tunnel vti_ipip6_handler __read_mostly = {
+	.handler	=	vti_rcv_tunnel,
+	.cb_handler	=	vti_rcv_cb,
+	.err_handler	=	vti4_err,
+	.priority	=	0,
+};
+#endif
+#endif
+
+static int __net_init vti_init_net(struct net *net)
+{
+	int err;
+	struct ip_tunnel_net *itn;
+
+	err = ip_tunnel_init_net(net, vti_net_id, &vti_link_ops, "ip_vti0");
+	if (err)
+		return err;
+	itn = net_generic(net, vti_net_id);
+	if (itn->fb_tunnel_dev)
+		vti_fb_tunnel_init(itn->fb_tunnel_dev);
+	return 0;
+}
+
+static void __net_exit vti_exit_rtnl(struct net *net,
+				     struct list_head *dev_to_kill)
+{
+	ip_tunnel_delete_net(net, vti_net_id, &vti_link_ops, dev_to_kill);
+}
+
+static struct pernet_operations vti_net_ops = {
+	.init = vti_init_net,
+	.exit_rtnl = vti_exit_rtnl,
+	.id   = &vti_net_id,
+	.size = sizeof(struct ip_tunnel_net),
+};
+
+static int vti_tunnel_validate(struct nlattr *tb[], struct nlattr *data[],
+			       struct netlink_ext_ack *extack)
+{
+	return 0;
+}
+
+static void vti_netlink_parms(struct nlattr *data[],
+			      struct ip_tunnel_parm_kern *parms,
+			      __u32 *fwmark)
+{
+	memset(parms, 0, sizeof(*parms));
+
+	parms->iph.protocol = IPPROTO_IPIP;
+
+	if (!data)
+		return;
+
+	__set_bit(IP_TUNNEL_VTI_BIT, parms->i_flags);
+
+	if (data[IFLA_VTI_LINK])
+		parms->link = nla_get_u32(data[IFLA_VTI_LINK]);
+
+	if (data[IFLA_VTI_IKEY])
+		parms->i_key = nla_get_be32(data[IFLA_VTI_IKEY]);
+
+	if (data[IFLA_VTI_OKEY])
+		parms->o_key = nla_get_be32(data[IFLA_VTI_OKEY]);
+
+	if (data[IFLA_VTI_LOCAL])
+		parms->iph.saddr = nla_get_in_addr(data[IFLA_VTI_LOCAL]);
+
+	if (data[IFLA_VTI_REMOTE])
+		parms->iph.daddr = nla_get_in_addr(data[IFLA_VTI_REMOTE]);
+
+	if (data[IFLA_VTI_FWMARK])
+		*fwmark = nla_get_u32(data[IFLA_VTI_FWMARK]);
+}
+
+static int vti_newlink(struct net_device *dev,
+		       struct rtnl_newlink_params *params,
+		       struct netlink_ext_ack *extack)
+{
+	struct nlattr **data = params->data;
+	struct ip_tunnel_parm_kern parms;
+	struct nlattr **tb = params->tb;
+	__u32 fwmark = 0;
+
+	vti_netlink_parms(data, &parms, &fwmark);
+	return ip_tunnel_newlink(params->link_net ? : dev_net(dev), dev, tb,
+				 &parms, fwmark);
+}
+
+static int vti_changelink(struct net_device *dev, struct nlattr *tb[],
+			  struct nlattr *data[],
+			  struct netlink_ext_ack *extack)
+{
+	struct ip_tunnel *t = netdev_priv(dev);
+	struct ip_tunnel_parm_kern p;
+	__u32 fwmark = t->fwmark;
+
+	if (!rtnl_dev_link_net_capable(dev, t->net))
+		return -EPERM;
+
+	vti_netlink_parms(data, &p, &fwmark);
+	return ip_tunnel_changelink(dev, tb, &p, fwmark);
+}
+
+static size_t vti_get_size(const struct net_device *dev)
+{
+	return
+		/* IFLA_VTI_LINK */
+		nla_total_size(4) +
+		/* IFLA_VTI_IKEY */
+		nla_total_size(4) +
+		/* IFLA_VTI_OKEY */
+		nla_total_size(4) +
+		/* IFLA_VTI_LOCAL */
+		nla_total_size(4) +
+		/* IFLA_VTI_REMOTE */
+		nla_total_size(4) +
+		/* IFLA_VTI_FWMARK */
+		nla_total_size(4) +
+		0;
+}
+
+static int vti_fill_info(struct sk_buff *skb, const struct net_device *dev)
+{
+	struct ip_tunnel *t = netdev_priv(dev);
+	struct ip_tunnel_parm_kern *p = &t->parms;
+
+	if (nla_put_u32(skb, IFLA_VTI_LINK, p->link) ||
+	    nla_put_be32(skb, IFLA_VTI_IKEY, p->i_key) ||
+	    nla_put_be32(skb, IFLA_VTI_OKEY, p->o_key) ||
+	    nla_put_in_addr(skb, IFLA_VTI_LOCAL, p->iph.saddr) ||
+	    nla_put_in_addr(skb, IFLA_VTI_REMOTE, p->iph.daddr) ||
+	    nla_put_u32(skb, IFLA_VTI_FWMARK, t->fwmark))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+static const struct nla_policy vti_policy[IFLA_VTI_MAX + 1] = {
+	[IFLA_VTI_LINK]		= { .type = NLA_U32 },
+	[IFLA_VTI_IKEY]		= { .type = NLA_U32 },
+	[IFLA_VTI_OKEY]		= { .type = NLA_U32 },
+	[IFLA_VTI_LOCAL]	= { .len = sizeof_field(struct iphdr, saddr) },
+	[IFLA_VTI_REMOTE]	= { .len = sizeof_field(struct iphdr, daddr) },
+	[IFLA_VTI_FWMARK]	= { .type = NLA_U32 },
+};
+
+static struct rtnl_link_ops vti_link_ops __read_mostly = {
+	.kind		= "vti",
+	.maxtype	= IFLA_VTI_MAX,
+	.policy		= vti_policy,
+	.priv_size	= sizeof(struct ip_tunnel),
+	.setup		= vti_tunnel_setup,
+	.validate	= vti_tunnel_validate,
+	.newlink	= vti_newlink,
+	.changelink	= vti_changelink,
+	.dellink        = ip_tunnel_dellink,
+	.get_size	= vti_get_size,
+	.fill_info	= vti_fill_info,
+	.get_link_net	= ip_tunnel_get_link_net,
+};
+
+static int __init vti_init(void)
+{
+	const char *msg;
+	int err;
+
+	pr_info("IPv4 over IPsec tunneling driver\n");
+
+	msg = "tunnel device";
+	err = register_pernet_device(&vti_net_ops);
+	if (err < 0)
+		goto pernet_dev_failed;
+
+	msg = "tunnel protocols";
+	err = xfrm4_protocol_register(&vti_esp4_protocol, IPPROTO_ESP);
+	if (err < 0)
+		goto xfrm_proto_esp_failed;
+	err = xfrm4_protocol_register(&vti_ah4_protocol, IPPROTO_AH);
+	if (err < 0)
+		goto xfrm_proto_ah_failed;
+	err = xfrm4_protocol_register(&vti_ipcomp4_protocol, IPPROTO_COMP);
+	if (err < 0)
+		goto xfrm_proto_comp_failed;
+
+#if IS_ENABLED(CONFIG_INET_XFRM_TUNNEL)
+	msg = "ipip tunnel";
+	err = xfrm4_tunnel_register(&vti_ipip_handler, AF_INET);
+	if (err < 0)
+		goto xfrm_tunnel_ipip_failed;
+#if IS_ENABLED(CONFIG_IPV6)
+	err = xfrm4_tunnel_register(&vti_ipip6_handler, AF_INET6);
+	if (err < 0)
+		goto xfrm_tunnel_ipip6_failed;
+#endif
+#endif
+
+	msg = "netlink interface";
+	err = rtnl_link_register(&vti_link_ops);
+	if (err < 0)
+		goto rtnl_link_failed;
+
+	return err;
+
+rtnl_link_failed:
+#if IS_ENABLED(CONFIG_INET_XFRM_TUNNEL)
+#if IS_ENABLED(CONFIG_IPV6)
+	xfrm4_tunnel_deregister(&vti_ipip6_handler, AF_INET6);
+xfrm_tunnel_ipip6_failed:
+#endif
+	xfrm4_tunnel_deregister(&vti_ipip_handler, AF_INET);
+xfrm_tunnel_ipip_failed:
+#endif
+	xfrm4_protocol_deregister(&vti_ipcomp4_protocol, IPPROTO_COMP);
+xfrm_proto_comp_failed:
+	xfrm4_protocol_deregister(&vti_ah4_protocol, IPPROTO_AH);
+xfrm_proto_ah_failed:
+	xfrm4_protocol_deregister(&vti_esp4_protocol, IPPROTO_ESP);
+xfrm_proto_esp_failed:
+	unregister_pernet_device(&vti_net_ops);
+pernet_dev_failed:
+	pr_err("vti init: failed to register %s\n", msg);
+	return err;
+}
+
+static void __exit vti_fini(void)
+{
+	rtnl_link_unregister(&vti_link_ops);
+#if IS_ENABLED(CONFIG_INET_XFRM_TUNNEL)
+#if IS_ENABLED(CONFIG_IPV6)
+	xfrm4_tunnel_deregister(&vti_ipip6_handler, AF_INET6);
+#endif
+	xfrm4_tunnel_deregister(&vti_ipip_handler, AF_INET);
+#endif
+	xfrm4_protocol_deregister(&vti_ipcomp4_protocol, IPPROTO_COMP);
+	xfrm4_protocol_deregister(&vti_ah4_protocol, IPPROTO_AH);
+	xfrm4_protocol_deregister(&vti_esp4_protocol, IPPROTO_ESP);
+	unregister_pernet_device(&vti_net_ops);
+}
+
+module_init(vti_init);
+module_exit(vti_fini);
+MODULE_DESCRIPTION("Virtual (secure) IP tunneling library");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_RTNL_LINK("vti");
+MODULE_ALIAS_NETDEV("ip_vti0");