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, 755 insertions, 0 deletions

diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
new file mode 100644
index 000000000..5fff52a8c
--- /dev/null
+++ b/net/sched/act_csum.c
@@ -0,0 +1,755 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Checksum updating actions
+ *
+ * Copyright (c) 2010 Gregoire Baron <baronchon@n7mm.org>
+ */
+
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+
+#include <linux/netlink.h>
+#include <net/netlink.h>
+#include <linux/rtnetlink.h>
+
+#include <linux/skbuff.h>
+
+#include <net/ip.h>
+#include <net/ipv6.h>
+#include <net/icmp.h>
+#include <linux/icmpv6.h>
+#include <linux/igmp.h>
+#include <net/tcp.h>
+#include <net/udp.h>
+#include <net/ip6_checksum.h>
+#include <net/sctp/checksum.h>
+
+#include <net/act_api.h>
+#include <net/pkt_cls.h>
+
+#include <linux/tc_act/tc_csum.h>
+#include <net/tc_act/tc_csum.h>
+#include <net/tc_wrapper.h>
+
+static const struct nla_policy csum_policy[TCA_CSUM_MAX + 1] = {
+	[TCA_CSUM_PARMS] = { .len = sizeof(struct tc_csum), },
+};
+
+static struct tc_action_ops act_csum_ops;
+
+static int tcf_csum_init(struct net *net, struct nlattr *nla,
+			 struct nlattr *est, struct tc_action **a,
+			 struct tcf_proto *tp,
+			 u32 flags, struct netlink_ext_ack *extack)
+{
+	struct tc_action_net *tn = net_generic(net, act_csum_ops.net_id);
+	bool bind = flags & TCA_ACT_FLAGS_BIND;
+	struct tcf_csum_params *params_new;
+	struct nlattr *tb[TCA_CSUM_MAX + 1];
+	struct tcf_chain *goto_ch = NULL;
+	struct tc_csum *parm;
+	struct tcf_csum *p;
+	int ret = 0, err;
+	u32 index;
+
+	if (nla == NULL)
+		return -EINVAL;
+
+	err = nla_parse_nested_deprecated(tb, TCA_CSUM_MAX, nla, csum_policy,
+					  NULL);
+	if (err < 0)
+		return err;
+
+	if (tb[TCA_CSUM_PARMS] == NULL)
+		return -EINVAL;
+	parm = nla_data(tb[TCA_CSUM_PARMS]);
+	index = parm->index;
+	err = tcf_idr_check_alloc(tn, &index, a, bind);
+	if (!err) {
+		ret = tcf_idr_create_from_flags(tn, index, est, a,
+						&act_csum_ops, bind, flags);
+		if (ret) {
+			tcf_idr_cleanup(tn, index);
+			return ret;
+		}
+		ret = ACT_P_CREATED;
+	} else if (err > 0) {
+		if (bind) /* dont override defaults */
+			return ACT_P_BOUND;
+		if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
+			tcf_idr_release(*a, bind);
+			return -EEXIST;
+		}
+	} else {
+		return err;
+	}
+
+	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
+	if (err < 0)
+		goto release_idr;
+
+	p = to_tcf_csum(*a);
+
+	params_new = kzalloc_obj(*params_new);
+	if (unlikely(!params_new)) {
+		err = -ENOMEM;
+		goto put_chain;
+	}
+	params_new->update_flags = parm->update_flags;
+	params_new->action = parm->action;
+
+	spin_lock_bh(&p->tcf_lock);
+	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
+	params_new = rcu_replace_pointer(p->params, params_new,
+					 lockdep_is_held(&p->tcf_lock));
+	spin_unlock_bh(&p->tcf_lock);
+
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+	if (params_new)
+		kfree_rcu(params_new, rcu);
+
+	return ret;
+put_chain:
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+release_idr:
+	tcf_idr_release(*a, bind);
+	return err;
+}
+
+/**
+ * tcf_csum_skb_nextlayer - Get next layer pointer
+ * @skb: sk_buff to use
+ * @ihl: previous summed headers length
+ * @ipl: complete packet length
+ * @jhl: next header length
+ *
+ * Check the expected next layer availability in the specified sk_buff.
+ * Return the next layer pointer if pass, NULL otherwise.
+ */
+static void *tcf_csum_skb_nextlayer(struct sk_buff *skb,
+				    unsigned int ihl, unsigned int ipl,
+				    unsigned int jhl)
+{
+	int ntkoff = skb_network_offset(skb);
+	int hl = ihl + jhl;
+
+	if (!pskb_may_pull(skb, ipl + ntkoff) || (ipl < hl) ||
+	    skb_try_make_writable(skb, hl + ntkoff))
+		return NULL;
+	else
+		return (void *)(skb_network_header(skb) + ihl);
+}
+
+static int tcf_csum_ipv4_icmp(struct sk_buff *skb, unsigned int ihl,
+			      unsigned int ipl)
+{
+	struct icmphdr *icmph;
+
+	icmph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*icmph));
+	if (icmph == NULL)
+		return 0;
+
+	icmph->checksum = 0;
+	skb->csum = csum_partial(icmph, ipl - ihl, 0);
+	icmph->checksum = csum_fold(skb->csum);
+
+	skb->ip_summed = CHECKSUM_NONE;
+
+	return 1;
+}
+
+static int tcf_csum_ipv4_igmp(struct sk_buff *skb,
+			      unsigned int ihl, unsigned int ipl)
+{
+	struct igmphdr *igmph;
+
+	igmph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*igmph));
+	if (igmph == NULL)
+		return 0;
+
+	igmph->csum = 0;
+	skb->csum = csum_partial(igmph, ipl - ihl, 0);
+	igmph->csum = csum_fold(skb->csum);
+
+	skb->ip_summed = CHECKSUM_NONE;
+
+	return 1;
+}
+
+static int tcf_csum_ipv6_icmp(struct sk_buff *skb, unsigned int ihl,
+			      unsigned int ipl)
+{
+	struct icmp6hdr *icmp6h;
+	const struct ipv6hdr *ip6h;
+
+	icmp6h = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*icmp6h));
+	if (icmp6h == NULL)
+		return 0;
+
+	ip6h = ipv6_hdr(skb);
+	icmp6h->icmp6_cksum = 0;
+	skb->csum = csum_partial(icmp6h, ipl - ihl, 0);
+	icmp6h->icmp6_cksum = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
+					      ipl - ihl, IPPROTO_ICMPV6,
+					      skb->csum);
+
+	skb->ip_summed = CHECKSUM_NONE;
+
+	return 1;
+}
+
+static int tcf_csum_ipv4_tcp(struct sk_buff *skb, unsigned int ihl,
+			     unsigned int ipl)
+{
+	struct tcphdr *tcph;
+	const struct iphdr *iph;
+
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+		return 1;
+
+	tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
+	if (tcph == NULL)
+		return 0;
+
+	iph = ip_hdr(skb);
+	tcph->check = 0;
+	skb->csum = csum_partial(tcph, ipl - ihl, 0);
+	tcph->check = tcp_v4_check(ipl - ihl,
+				   iph->saddr, iph->daddr, skb->csum);
+
+	skb->ip_summed = CHECKSUM_NONE;
+
+	return 1;
+}
+
+static int tcf_csum_ipv6_tcp(struct sk_buff *skb, unsigned int ihl,
+			     unsigned int ipl)
+{
+	struct tcphdr *tcph;
+	const struct ipv6hdr *ip6h;
+
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+		return 1;
+
+	tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
+	if (tcph == NULL)
+		return 0;
+
+	ip6h = ipv6_hdr(skb);
+	tcph->check = 0;
+	skb->csum = csum_partial(tcph, ipl - ihl, 0);
+	tcph->check = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
+				      ipl - ihl, IPPROTO_TCP,
+				      skb->csum);
+
+	skb->ip_summed = CHECKSUM_NONE;
+
+	return 1;
+}
+
+static int tcf_csum_ipv4_udp(struct sk_buff *skb, unsigned int ihl,
+			     unsigned int ipl, int udplite)
+{
+	struct udphdr *udph;
+	const struct iphdr *iph;
+	u16 ul;
+
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type &
+	    (SKB_GSO_UDP | SKB_GSO_UDP_L4 |
+	     SKB_GSO_UDP_TUNNEL | SKB_GSO_UDP_TUNNEL_CSUM))
+		return 1;
+
+	/*
+	 * Support both UDP and UDPLITE checksum algorithms, Don't use
+	 * udph->len to get the real length without any protocol check,
+	 * UDPLITE uses udph->len for another thing,
+	 * Use iph->tot_len, or just ipl.
+	 */
+
+	udph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*udph));
+	if (udph == NULL)
+		return 0;
+
+	iph = ip_hdr(skb);
+	ul = udp_get_len_short(udph);
+
+	if (udplite || udph->check) {
+
+		udph->check = 0;
+
+		if (udplite) {
+			if (ul == 0)
+				skb->csum = csum_partial(udph, ipl - ihl, 0);
+			else if ((ul >= sizeof(*udph)) && (ul <= ipl - ihl))
+				skb->csum = csum_partial(udph, ul, 0);
+			else
+				goto ignore_obscure_skb;
+		} else {
+			if (ul != ipl - ihl)
+				goto ignore_obscure_skb;
+
+			skb->csum = csum_partial(udph, ul, 0);
+		}
+
+		udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr,
+						ul, iph->protocol,
+						skb->csum);
+
+		if (!udph->check)
+			udph->check = CSUM_MANGLED_0;
+	}
+
+	skb->ip_summed = CHECKSUM_NONE;
+
+ignore_obscure_skb:
+	return 1;
+}
+
+static int tcf_csum_ipv6_udp(struct sk_buff *skb, unsigned int ihl,
+			     unsigned int ipl, int udplite)
+{
+	struct udphdr *udph;
+	const struct ipv6hdr *ip6h;
+	u16 ul;
+
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type &
+	    (SKB_GSO_UDP | SKB_GSO_UDP_L4 |
+	     SKB_GSO_UDP_TUNNEL | SKB_GSO_UDP_TUNNEL_CSUM))
+		return 1;
+
+	/*
+	 * Support both UDP and UDPLITE checksum algorithms, Don't use
+	 * udph->len to get the real length without any protocol check,
+	 * UDPLITE uses udph->len for another thing,
+	 * Use ip6h->payload_len + sizeof(*ip6h) ... , or just ipl.
+	 */
+
+	udph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*udph));
+	if (udph == NULL)
+		return 0;
+
+	ip6h = ipv6_hdr(skb);
+	ul = udp_get_len_short(udph);
+
+	udph->check = 0;
+
+	if (udplite) {
+		if (ul == 0)
+			skb->csum = csum_partial(udph, ipl - ihl, 0);
+
+		else if ((ul >= sizeof(*udph)) && (ul <= ipl - ihl))
+			skb->csum = csum_partial(udph, ul, 0);
+
+		else
+			goto ignore_obscure_skb;
+	} else {
+		if (ul != ipl - ihl)
+			goto ignore_obscure_skb;
+
+		skb->csum = csum_partial(udph, ul, 0);
+	}
+
+	udph->check = csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr, ul,
+				      udplite ? IPPROTO_UDPLITE : IPPROTO_UDP,
+				      skb->csum);
+
+	if (!udph->check)
+		udph->check = CSUM_MANGLED_0;
+
+	skb->ip_summed = CHECKSUM_NONE;
+
+ignore_obscure_skb:
+	return 1;
+}
+
+static int tcf_csum_sctp(struct sk_buff *skb, unsigned int ihl,
+			 unsigned int ipl)
+{
+	struct sctphdr *sctph;
+
+	if (skb_is_gso(skb) && skb_is_gso_sctp(skb))
+		return 1;
+
+	sctph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*sctph));
+	if (!sctph)
+		return 0;
+
+	sctph->checksum = sctp_compute_cksum(skb,
+					     skb_network_offset(skb) + ihl);
+	skb_reset_csum_not_inet(skb);
+
+	return 1;
+}
+
+static int tcf_csum_ipv4(struct sk_buff *skb, u32 update_flags)
+{
+	const struct iphdr *iph;
+	int ntkoff;
+
+	ntkoff = skb_network_offset(skb);
+
+	if (!pskb_may_pull(skb, sizeof(*iph) + ntkoff))
+		goto fail;
+
+	iph = ip_hdr(skb);
+
+	switch (iph->frag_off & htons(IP_OFFSET) ? 0 : iph->protocol) {
+	case IPPROTO_ICMP:
+		if (update_flags & TCA_CSUM_UPDATE_FLAG_ICMP)
+			if (!tcf_csum_ipv4_icmp(skb, iph->ihl * 4,
+						ntohs(iph->tot_len)))
+				goto fail;
+		break;
+	case IPPROTO_IGMP:
+		if (update_flags & TCA_CSUM_UPDATE_FLAG_IGMP)
+			if (!tcf_csum_ipv4_igmp(skb, iph->ihl * 4,
+						ntohs(iph->tot_len)))
+				goto fail;
+		break;
+	case IPPROTO_TCP:
+		if (update_flags & TCA_CSUM_UPDATE_FLAG_TCP)
+			if (!tcf_csum_ipv4_tcp(skb, iph->ihl * 4,
+					       ntohs(iph->tot_len)))
+				goto fail;
+		break;
+	case IPPROTO_UDP:
+		if (update_flags & TCA_CSUM_UPDATE_FLAG_UDP)
+			if (!tcf_csum_ipv4_udp(skb, iph->ihl * 4,
+					       ntohs(iph->tot_len), 0))
+				goto fail;
+		break;
+	case IPPROTO_UDPLITE:
+		if (update_flags & TCA_CSUM_UPDATE_FLAG_UDPLITE)
+			if (!tcf_csum_ipv4_udp(skb, iph->ihl * 4,
+					       ntohs(iph->tot_len), 1))
+				goto fail;
+		break;
+	case IPPROTO_SCTP:
+		if ((update_flags & TCA_CSUM_UPDATE_FLAG_SCTP) &&
+		    !tcf_csum_sctp(skb, iph->ihl * 4, ntohs(iph->tot_len)))
+			goto fail;
+		break;
+	}
+
+	if (update_flags & TCA_CSUM_UPDATE_FLAG_IPV4HDR) {
+		if (skb_try_make_writable(skb, sizeof(*iph) + ntkoff))
+			goto fail;
+
+		ip_send_check(ip_hdr(skb));
+	}
+
+	return 1;
+
+fail:
+	return 0;
+}
+
+static int tcf_csum_ipv6_hopopts(struct ipv6_opt_hdr *ip6xh, unsigned int ixhl,
+				 unsigned int *pl)
+{
+	int off, len, optlen;
+	unsigned char *xh = (void *)ip6xh;
+
+	off = sizeof(*ip6xh);
+	len = ixhl - off;
+
+	while (len > 1) {
+		switch (xh[off]) {
+		case IPV6_TLV_PAD1:
+			optlen = 1;
+			break;
+		case IPV6_TLV_JUMBO:
+			optlen = xh[off + 1] + 2;
+			if (optlen != 6 || len < 6 || (off & 3) != 2)
+				/* wrong jumbo option length/alignment */
+				return 0;
+			*pl = ntohl(*(__be32 *)(xh + off + 2));
+			goto done;
+		default:
+			optlen = xh[off + 1] + 2;
+			if (optlen > len)
+				/* ignore obscure options */
+				goto done;
+			break;
+		}
+		off += optlen;
+		len -= optlen;
+	}
+
+done:
+	return 1;
+}
+
+static int tcf_csum_ipv6(struct sk_buff *skb, u32 update_flags)
+{
+	struct ipv6hdr *ip6h;
+	struct ipv6_opt_hdr *ip6xh;
+	unsigned int hl, ixhl;
+	unsigned int pl;
+	int ntkoff;
+	u8 nexthdr;
+
+	ntkoff = skb_network_offset(skb);
+
+	hl = sizeof(*ip6h);
+
+	if (!pskb_may_pull(skb, hl + ntkoff))
+		goto fail;
+
+	ip6h = ipv6_hdr(skb);
+
+	pl = ntohs(ip6h->payload_len);
+	nexthdr = ip6h->nexthdr;
+
+	do {
+		switch (nexthdr) {
+		case NEXTHDR_FRAGMENT:
+			goto ignore_skb;
+		case NEXTHDR_ROUTING:
+		case NEXTHDR_HOP:
+		case NEXTHDR_DEST:
+			if (!pskb_may_pull(skb, hl + sizeof(*ip6xh) + ntkoff))
+				goto fail;
+			ip6xh = (void *)(skb_network_header(skb) + hl);
+			ixhl = ipv6_optlen(ip6xh);
+			if (!pskb_may_pull(skb, hl + ixhl + ntkoff))
+				goto fail;
+			ip6xh = (void *)(skb_network_header(skb) + hl);
+			if ((nexthdr == NEXTHDR_HOP) &&
+			    !(tcf_csum_ipv6_hopopts(ip6xh, ixhl, &pl)))
+				goto fail;
+			nexthdr = ip6xh->nexthdr;
+			hl += ixhl;
+			break;
+		case IPPROTO_ICMPV6:
+			if (update_flags & TCA_CSUM_UPDATE_FLAG_ICMP)
+				if (!tcf_csum_ipv6_icmp(skb,
+							hl, pl + sizeof(*ip6h)))
+					goto fail;
+			goto done;
+		case IPPROTO_TCP:
+			if (update_flags & TCA_CSUM_UPDATE_FLAG_TCP)
+				if (!tcf_csum_ipv6_tcp(skb,
+						       hl, pl + sizeof(*ip6h)))
+					goto fail;
+			goto done;
+		case IPPROTO_UDP:
+			if (update_flags & TCA_CSUM_UPDATE_FLAG_UDP)
+				if (!tcf_csum_ipv6_udp(skb, hl,
+						       pl + sizeof(*ip6h), 0))
+					goto fail;
+			goto done;
+		case IPPROTO_UDPLITE:
+			if (update_flags & TCA_CSUM_UPDATE_FLAG_UDPLITE)
+				if (!tcf_csum_ipv6_udp(skb, hl,
+						       pl + sizeof(*ip6h), 1))
+					goto fail;
+			goto done;
+		case IPPROTO_SCTP:
+			if ((update_flags & TCA_CSUM_UPDATE_FLAG_SCTP) &&
+			    !tcf_csum_sctp(skb, hl, pl + sizeof(*ip6h)))
+				goto fail;
+			goto done;
+		default:
+			goto ignore_skb;
+		}
+	} while (pskb_may_pull(skb, hl + 1 + ntkoff));
+
+done:
+ignore_skb:
+	return 1;
+
+fail:
+	return 0;
+}
+
+TC_INDIRECT_SCOPE int tcf_csum_act(struct sk_buff *skb,
+				   const struct tc_action *a,
+				   struct tcf_result *res)
+{
+	struct tcf_csum *p = to_tcf_csum(a);
+	bool orig_vlan_tag_present = false;
+	unsigned int vlan_hdr_count = 0;
+	struct tcf_csum_params *params;
+	u32 update_flags;
+	__be16 protocol;
+	int action;
+
+	params = rcu_dereference_bh(p->params);
+
+	tcf_lastuse_update(&p->tcf_tm);
+	tcf_action_update_bstats(&p->common, skb);
+
+	action = params->action;
+	if (unlikely(action == TC_ACT_SHOT))
+		goto drop;
+
+	update_flags = params->update_flags;
+	protocol = skb_protocol(skb, false);
+again:
+	switch (protocol) {
+	case cpu_to_be16(ETH_P_IP):
+		if (!tcf_csum_ipv4(skb, update_flags))
+			goto drop;
+		break;
+	case cpu_to_be16(ETH_P_IPV6):
+		if (!tcf_csum_ipv6(skb, update_flags))
+			goto drop;
+		break;
+	case cpu_to_be16(ETH_P_8021AD):
+		fallthrough;
+	case cpu_to_be16(ETH_P_8021Q):
+		if (skb_vlan_tag_present(skb) && !orig_vlan_tag_present) {
+			protocol = skb->protocol;
+			orig_vlan_tag_present = true;
+		} else {
+			struct vlan_hdr *vlan;
+
+			if (!pskb_may_pull(skb, VLAN_HLEN))
+				goto drop;
+
+			vlan = (struct vlan_hdr *)skb->data;
+			protocol = vlan->h_vlan_encapsulated_proto;
+			skb_pull(skb, VLAN_HLEN);
+			skb_reset_network_header(skb);
+			vlan_hdr_count++;
+		}
+		goto again;
+	}
+
+out:
+	/* Restore the skb for the pulled VLAN tags */
+	while (vlan_hdr_count--) {
+		skb_push(skb, VLAN_HLEN);
+		skb_reset_network_header(skb);
+	}
+
+	return action;
+
+drop:
+	tcf_action_inc_drop_qstats(&p->common);
+	action = TC_ACT_SHOT;
+	goto out;
+}
+
+static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
+			 int ref)
+{
+	const struct tcf_csum *p = to_tcf_csum(a);
+	unsigned char *b = skb_tail_pointer(skb);
+	const struct tcf_csum_params *params;
+	struct tc_csum opt = {
+		.index   = p->tcf_index,
+		.refcnt  = refcount_read(&p->tcf_refcnt) - ref,
+		.bindcnt = atomic_read(&p->tcf_bindcnt) - bind,
+	};
+	struct tcf_t t;
+
+	rcu_read_lock();
+	params = rcu_dereference(p->params);
+	opt.action = params->action;
+	opt.update_flags = params->update_flags;
+
+	if (nla_put(skb, TCA_CSUM_PARMS, sizeof(opt), &opt))
+		goto nla_put_failure;
+
+	tcf_tm_dump(&t, &p->tcf_tm);
+	if (nla_put_64bit(skb, TCA_CSUM_TM, sizeof(t), &t, TCA_CSUM_PAD))
+		goto nla_put_failure;
+	rcu_read_unlock();
+
+	return skb->len;
+
+nla_put_failure:
+	rcu_read_unlock();
+	nlmsg_trim(skb, b);
+	return -1;
+}
+
+static void tcf_csum_cleanup(struct tc_action *a)
+{
+	struct tcf_csum *p = to_tcf_csum(a);
+	struct tcf_csum_params *params;
+
+	params = rcu_dereference_protected(p->params, 1);
+	if (params)
+		kfree_rcu(params, rcu);
+}
+
+static size_t tcf_csum_get_fill_size(const struct tc_action *act)
+{
+	return nla_total_size(sizeof(struct tc_csum));
+}
+
+static int tcf_csum_offload_act_setup(struct tc_action *act, void *entry_data,
+				      u32 *index_inc, bool bind,
+				      struct netlink_ext_ack *extack)
+{
+	if (bind) {
+		struct flow_action_entry *entry = entry_data;
+
+		entry->id = FLOW_ACTION_CSUM;
+		entry->csum_flags = tcf_csum_update_flags(act);
+		*index_inc = 1;
+	} else {
+		struct flow_offload_action *fl_action = entry_data;
+
+		fl_action->id = FLOW_ACTION_CSUM;
+	}
+
+	return 0;
+}
+
+static struct tc_action_ops act_csum_ops = {
+	.kind		= "csum",
+	.id		= TCA_ID_CSUM,
+	.owner		= THIS_MODULE,
+	.act		= tcf_csum_act,
+	.dump		= tcf_csum_dump,
+	.init		= tcf_csum_init,
+	.cleanup	= tcf_csum_cleanup,
+	.get_fill_size  = tcf_csum_get_fill_size,
+	.offload_act_setup = tcf_csum_offload_act_setup,
+	.size		= sizeof(struct tcf_csum),
+};
+MODULE_ALIAS_NET_ACT("csum");
+
+static __net_init int csum_init_net(struct net *net)
+{
+	struct tc_action_net *tn = net_generic(net, act_csum_ops.net_id);
+
+	return tc_action_net_init(net, tn, &act_csum_ops);
+}
+
+static void __net_exit csum_exit_net(struct list_head *net_list)
+{
+	tc_action_net_exit(net_list, act_csum_ops.net_id);
+}
+
+static struct pernet_operations csum_net_ops = {
+	.init = csum_init_net,
+	.exit_batch = csum_exit_net,
+	.id   = &act_csum_ops.net_id,
+	.size = sizeof(struct tc_action_net),
+};
+
+MODULE_DESCRIPTION("Checksum updating actions");
+MODULE_LICENSE("GPL");
+
+static int __init csum_init_module(void)
+{
+	return tcf_register_action(&act_csum_ops, &csum_net_ops);
+}
+
+static void __exit csum_cleanup_module(void)
+{
+	tcf_unregister_action(&act_csum_ops, &csum_net_ops);
+}
+
+module_init(csum_init_module);
+module_exit(csum_cleanup_module);