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, 1061 insertions, 0 deletions

diff --git a/net/ipv6/ioam6.c b/net/ipv6/ioam6.c
new file mode 100644
index 000000000..943861a55
--- /dev/null
+++ b/net/ipv6/ioam6.c
@@ -0,0 +1,1061 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  IPv6 IOAM implementation
+ *
+ *  Author:
+ *  Justin Iurman <justin.iurman@uliege.be>
+ */
+
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/net.h>
+#include <linux/ioam6.h>
+#include <linux/ioam6_genl.h>
+#include <linux/rhashtable.h>
+#include <linux/netdevice.h>
+
+#include <net/addrconf.h>
+#include <net/genetlink.h>
+#include <net/ioam6.h>
+#include <net/sch_generic.h>
+
+static void ioam6_ns_release(struct ioam6_namespace *ns)
+{
+	kfree_rcu(ns, rcu);
+}
+
+static void ioam6_sc_release(struct ioam6_schema *sc)
+{
+	kfree_rcu(sc, rcu);
+}
+
+static void ioam6_free_ns(void *ptr, void *arg)
+{
+	struct ioam6_namespace *ns = (struct ioam6_namespace *)ptr;
+
+	if (ns)
+		ioam6_ns_release(ns);
+}
+
+static void ioam6_free_sc(void *ptr, void *arg)
+{
+	struct ioam6_schema *sc = (struct ioam6_schema *)ptr;
+
+	if (sc)
+		ioam6_sc_release(sc);
+}
+
+static int ioam6_ns_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
+{
+	const struct ioam6_namespace *ns = obj;
+
+	return (ns->id != *(__be16 *)arg->key);
+}
+
+static int ioam6_sc_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
+{
+	const struct ioam6_schema *sc = obj;
+
+	return (sc->id != *(u32 *)arg->key);
+}
+
+static const struct rhashtable_params rht_ns_params = {
+	.key_len		= sizeof(__be16),
+	.key_offset		= offsetof(struct ioam6_namespace, id),
+	.head_offset		= offsetof(struct ioam6_namespace, head),
+	.automatic_shrinking	= true,
+	.obj_cmpfn		= ioam6_ns_cmpfn,
+};
+
+static const struct rhashtable_params rht_sc_params = {
+	.key_len		= sizeof(u32),
+	.key_offset		= offsetof(struct ioam6_schema, id),
+	.head_offset		= offsetof(struct ioam6_schema, head),
+	.automatic_shrinking	= true,
+	.obj_cmpfn		= ioam6_sc_cmpfn,
+};
+
+static struct genl_family ioam6_genl_family;
+
+static const struct nla_policy ioam6_genl_policy_addns[] = {
+	[IOAM6_ATTR_NS_ID]	= { .type = NLA_U16 },
+	[IOAM6_ATTR_NS_DATA]	= { .type = NLA_U32 },
+	[IOAM6_ATTR_NS_DATA_WIDE] = { .type = NLA_U64 },
+};
+
+static const struct nla_policy ioam6_genl_policy_delns[] = {
+	[IOAM6_ATTR_NS_ID]	= { .type = NLA_U16 },
+};
+
+static const struct nla_policy ioam6_genl_policy_addsc[] = {
+	[IOAM6_ATTR_SC_ID]	= { .type = NLA_U32 },
+	[IOAM6_ATTR_SC_DATA]	= { .type = NLA_BINARY,
+				    .len = IOAM6_MAX_SCHEMA_DATA_LEN },
+};
+
+static const struct nla_policy ioam6_genl_policy_delsc[] = {
+	[IOAM6_ATTR_SC_ID]	= { .type = NLA_U32 },
+};
+
+static const struct nla_policy ioam6_genl_policy_ns_sc[] = {
+	[IOAM6_ATTR_NS_ID]	= { .type = NLA_U16 },
+	[IOAM6_ATTR_SC_ID]	= { .type = NLA_U32 },
+	[IOAM6_ATTR_SC_NONE]	= { .type = NLA_FLAG },
+};
+
+static int ioam6_genl_addns(struct sk_buff *skb, struct genl_info *info)
+{
+	struct ioam6_pernet_data *nsdata;
+	struct ioam6_namespace *ns;
+	u64 data64;
+	u32 data32;
+	__be16 id;
+	int err;
+
+	if (!info->attrs[IOAM6_ATTR_NS_ID])
+		return -EINVAL;
+
+	id = cpu_to_be16(nla_get_u16(info->attrs[IOAM6_ATTR_NS_ID]));
+	nsdata = ioam6_pernet(genl_info_net(info));
+
+	mutex_lock(&nsdata->lock);
+
+	ns = rhashtable_lookup_fast(&nsdata->namespaces, &id, rht_ns_params);
+	if (ns) {
+		err = -EEXIST;
+		goto out_unlock;
+	}
+
+	ns = kzalloc_obj(*ns);
+	if (!ns) {
+		err = -ENOMEM;
+		goto out_unlock;
+	}
+
+	ns->id = id;
+
+	data32 = nla_get_u32_default(info->attrs[IOAM6_ATTR_NS_DATA],
+				     IOAM6_U32_UNAVAILABLE);
+
+	data64 = nla_get_u64_default(info->attrs[IOAM6_ATTR_NS_DATA_WIDE],
+				     IOAM6_U64_UNAVAILABLE);
+
+	ns->data = cpu_to_be32(data32);
+	ns->data_wide = cpu_to_be64(data64);
+
+	err = rhashtable_lookup_insert_fast(&nsdata->namespaces, &ns->head,
+					    rht_ns_params);
+	if (err)
+		kfree(ns);
+
+out_unlock:
+	mutex_unlock(&nsdata->lock);
+	return err;
+}
+
+static int ioam6_genl_delns(struct sk_buff *skb, struct genl_info *info)
+{
+	struct ioam6_pernet_data *nsdata;
+	struct ioam6_namespace *ns;
+	struct ioam6_schema *sc;
+	__be16 id;
+	int err;
+
+	if (!info->attrs[IOAM6_ATTR_NS_ID])
+		return -EINVAL;
+
+	id = cpu_to_be16(nla_get_u16(info->attrs[IOAM6_ATTR_NS_ID]));
+	nsdata = ioam6_pernet(genl_info_net(info));
+
+	mutex_lock(&nsdata->lock);
+
+	ns = rhashtable_lookup_fast(&nsdata->namespaces, &id, rht_ns_params);
+	if (!ns) {
+		err = -ENOENT;
+		goto out_unlock;
+	}
+
+	sc = rcu_dereference_protected(ns->schema,
+				       lockdep_is_held(&nsdata->lock));
+
+	err = rhashtable_remove_fast(&nsdata->namespaces, &ns->head,
+				     rht_ns_params);
+	if (err)
+		goto out_unlock;
+
+	if (sc)
+		rcu_assign_pointer(sc->ns, NULL);
+
+	ioam6_ns_release(ns);
+
+out_unlock:
+	mutex_unlock(&nsdata->lock);
+	return err;
+}
+
+static int __ioam6_genl_dumpns_element(struct ioam6_namespace *ns,
+				       u32 portid,
+				       u32 seq,
+				       u32 flags,
+				       struct sk_buff *skb,
+				       u8 cmd)
+{
+	struct ioam6_schema *sc;
+	u64 data64;
+	u32 data32;
+	void *hdr;
+
+	hdr = genlmsg_put(skb, portid, seq, &ioam6_genl_family, flags, cmd);
+	if (!hdr)
+		return -ENOMEM;
+
+	data32 = be32_to_cpu(ns->data);
+	data64 = be64_to_cpu(ns->data_wide);
+
+	if (nla_put_u16(skb, IOAM6_ATTR_NS_ID, be16_to_cpu(ns->id)) ||
+	    (data32 != IOAM6_U32_UNAVAILABLE &&
+	     nla_put_u32(skb, IOAM6_ATTR_NS_DATA, data32)) ||
+	    (data64 != IOAM6_U64_UNAVAILABLE &&
+	     nla_put_u64_64bit(skb, IOAM6_ATTR_NS_DATA_WIDE,
+			       data64, IOAM6_ATTR_PAD)))
+		goto nla_put_failure;
+
+	rcu_read_lock();
+
+	sc = rcu_dereference(ns->schema);
+	if (sc && nla_put_u32(skb, IOAM6_ATTR_SC_ID, sc->id)) {
+		rcu_read_unlock();
+		goto nla_put_failure;
+	}
+
+	rcu_read_unlock();
+
+	genlmsg_end(skb, hdr);
+	return 0;
+
+nla_put_failure:
+	genlmsg_cancel(skb, hdr);
+	return -EMSGSIZE;
+}
+
+static int ioam6_genl_dumpns_start(struct netlink_callback *cb)
+{
+	struct ioam6_pernet_data *nsdata = ioam6_pernet(sock_net(cb->skb->sk));
+	struct rhashtable_iter *iter = (struct rhashtable_iter *)cb->args[0];
+
+	if (!iter) {
+		iter = kmalloc_obj(*iter);
+		if (!iter)
+			return -ENOMEM;
+
+		cb->args[0] = (long)iter;
+	}
+
+	rhashtable_walk_enter(&nsdata->namespaces, iter);
+
+	return 0;
+}
+
+static int ioam6_genl_dumpns_done(struct netlink_callback *cb)
+{
+	struct rhashtable_iter *iter = (struct rhashtable_iter *)cb->args[0];
+
+	rhashtable_walk_exit(iter);
+	kfree(iter);
+
+	return 0;
+}
+
+static int ioam6_genl_dumpns(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	struct rhashtable_iter *iter;
+	struct ioam6_namespace *ns;
+	int err;
+
+	iter = (struct rhashtable_iter *)cb->args[0];
+	rhashtable_walk_start(iter);
+
+	for (;;) {
+		ns = rhashtable_walk_next(iter);
+
+		if (IS_ERR(ns)) {
+			if (PTR_ERR(ns) == -EAGAIN)
+				continue;
+			err = PTR_ERR(ns);
+			goto done;
+		} else if (!ns) {
+			break;
+		}
+
+		err = __ioam6_genl_dumpns_element(ns,
+						  NETLINK_CB(cb->skb).portid,
+						  cb->nlh->nlmsg_seq,
+						  NLM_F_MULTI,
+						  skb,
+						  IOAM6_CMD_DUMP_NAMESPACES);
+		if (err)
+			goto done;
+	}
+
+	err = skb->len;
+
+done:
+	rhashtable_walk_stop(iter);
+	return err;
+}
+
+static int ioam6_genl_addsc(struct sk_buff *skb, struct genl_info *info)
+{
+	struct ioam6_pernet_data *nsdata;
+	int len, len_aligned, err;
+	struct ioam6_schema *sc;
+	u32 id;
+
+	if (!info->attrs[IOAM6_ATTR_SC_ID] || !info->attrs[IOAM6_ATTR_SC_DATA])
+		return -EINVAL;
+
+	id = nla_get_u32(info->attrs[IOAM6_ATTR_SC_ID]);
+	nsdata = ioam6_pernet(genl_info_net(info));
+
+	mutex_lock(&nsdata->lock);
+
+	sc = rhashtable_lookup_fast(&nsdata->schemas, &id, rht_sc_params);
+	if (sc) {
+		err = -EEXIST;
+		goto out_unlock;
+	}
+
+	len = nla_len(info->attrs[IOAM6_ATTR_SC_DATA]);
+	len_aligned = ALIGN(len, 4);
+
+	sc = kzalloc(sizeof(*sc) + len_aligned, GFP_KERNEL);
+	if (!sc) {
+		err = -ENOMEM;
+		goto out_unlock;
+	}
+
+	sc->id = id;
+	sc->len = len_aligned;
+	sc->hdr = cpu_to_be32(sc->id | ((u8)(sc->len / 4) << 24));
+	nla_memcpy(sc->data, info->attrs[IOAM6_ATTR_SC_DATA], len);
+
+	err = rhashtable_lookup_insert_fast(&nsdata->schemas, &sc->head,
+					    rht_sc_params);
+	if (err)
+		goto free_sc;
+
+out_unlock:
+	mutex_unlock(&nsdata->lock);
+	return err;
+free_sc:
+	kfree(sc);
+	goto out_unlock;
+}
+
+static int ioam6_genl_delsc(struct sk_buff *skb, struct genl_info *info)
+{
+	struct ioam6_pernet_data *nsdata;
+	struct ioam6_namespace *ns;
+	struct ioam6_schema *sc;
+	int err;
+	u32 id;
+
+	if (!info->attrs[IOAM6_ATTR_SC_ID])
+		return -EINVAL;
+
+	id = nla_get_u32(info->attrs[IOAM6_ATTR_SC_ID]);
+	nsdata = ioam6_pernet(genl_info_net(info));
+
+	mutex_lock(&nsdata->lock);
+
+	sc = rhashtable_lookup_fast(&nsdata->schemas, &id, rht_sc_params);
+	if (!sc) {
+		err = -ENOENT;
+		goto out_unlock;
+	}
+
+	ns = rcu_dereference_protected(sc->ns, lockdep_is_held(&nsdata->lock));
+
+	err = rhashtable_remove_fast(&nsdata->schemas, &sc->head,
+				     rht_sc_params);
+	if (err)
+		goto out_unlock;
+
+	if (ns)
+		rcu_assign_pointer(ns->schema, NULL);
+
+	ioam6_sc_release(sc);
+
+out_unlock:
+	mutex_unlock(&nsdata->lock);
+	return err;
+}
+
+static int __ioam6_genl_dumpsc_element(struct ioam6_schema *sc,
+				       u32 portid, u32 seq, u32 flags,
+				       struct sk_buff *skb, u8 cmd)
+{
+	struct ioam6_namespace *ns;
+	void *hdr;
+
+	hdr = genlmsg_put(skb, portid, seq, &ioam6_genl_family, flags, cmd);
+	if (!hdr)
+		return -ENOMEM;
+
+	if (nla_put_u32(skb, IOAM6_ATTR_SC_ID, sc->id) ||
+	    nla_put(skb, IOAM6_ATTR_SC_DATA, sc->len, sc->data))
+		goto nla_put_failure;
+
+	rcu_read_lock();
+
+	ns = rcu_dereference(sc->ns);
+	if (ns && nla_put_u16(skb, IOAM6_ATTR_NS_ID, be16_to_cpu(ns->id))) {
+		rcu_read_unlock();
+		goto nla_put_failure;
+	}
+
+	rcu_read_unlock();
+
+	genlmsg_end(skb, hdr);
+	return 0;
+
+nla_put_failure:
+	genlmsg_cancel(skb, hdr);
+	return -EMSGSIZE;
+}
+
+static int ioam6_genl_dumpsc_start(struct netlink_callback *cb)
+{
+	struct ioam6_pernet_data *nsdata = ioam6_pernet(sock_net(cb->skb->sk));
+	struct rhashtable_iter *iter = (struct rhashtable_iter *)cb->args[0];
+
+	if (!iter) {
+		iter = kmalloc_obj(*iter);
+		if (!iter)
+			return -ENOMEM;
+
+		cb->args[0] = (long)iter;
+	}
+
+	rhashtable_walk_enter(&nsdata->schemas, iter);
+
+	return 0;
+}
+
+static int ioam6_genl_dumpsc_done(struct netlink_callback *cb)
+{
+	struct rhashtable_iter *iter = (struct rhashtable_iter *)cb->args[0];
+
+	rhashtable_walk_exit(iter);
+	kfree(iter);
+
+	return 0;
+}
+
+static int ioam6_genl_dumpsc(struct sk_buff *skb, struct netlink_callback *cb)
+{
+	struct rhashtable_iter *iter;
+	struct ioam6_schema *sc;
+	int err;
+
+	iter = (struct rhashtable_iter *)cb->args[0];
+	rhashtable_walk_start(iter);
+
+	for (;;) {
+		sc = rhashtable_walk_next(iter);
+
+		if (IS_ERR(sc)) {
+			if (PTR_ERR(sc) == -EAGAIN)
+				continue;
+			err = PTR_ERR(sc);
+			goto done;
+		} else if (!sc) {
+			break;
+		}
+
+		err = __ioam6_genl_dumpsc_element(sc,
+						  NETLINK_CB(cb->skb).portid,
+						  cb->nlh->nlmsg_seq,
+						  NLM_F_MULTI,
+						  skb,
+						  IOAM6_CMD_DUMP_SCHEMAS);
+		if (err)
+			goto done;
+	}
+
+	err = skb->len;
+
+done:
+	rhashtable_walk_stop(iter);
+	return err;
+}
+
+static int ioam6_genl_ns_set_schema(struct sk_buff *skb, struct genl_info *info)
+{
+	struct ioam6_namespace *ns, *ns_ref;
+	struct ioam6_schema *sc, *sc_ref;
+	struct ioam6_pernet_data *nsdata;
+	__be16 ns_id;
+	u32 sc_id;
+	int err;
+
+	if (!info->attrs[IOAM6_ATTR_NS_ID] ||
+	    (!info->attrs[IOAM6_ATTR_SC_ID] &&
+	     !info->attrs[IOAM6_ATTR_SC_NONE]))
+		return -EINVAL;
+
+	ns_id = cpu_to_be16(nla_get_u16(info->attrs[IOAM6_ATTR_NS_ID]));
+	nsdata = ioam6_pernet(genl_info_net(info));
+
+	mutex_lock(&nsdata->lock);
+
+	ns = rhashtable_lookup_fast(&nsdata->namespaces, &ns_id, rht_ns_params);
+	if (!ns) {
+		err = -ENOENT;
+		goto out_unlock;
+	}
+
+	if (info->attrs[IOAM6_ATTR_SC_NONE]) {
+		sc = NULL;
+	} else {
+		sc_id = nla_get_u32(info->attrs[IOAM6_ATTR_SC_ID]);
+		sc = rhashtable_lookup_fast(&nsdata->schemas, &sc_id,
+					    rht_sc_params);
+		if (!sc) {
+			err = -ENOENT;
+			goto out_unlock;
+		}
+	}
+
+	sc_ref = rcu_dereference_protected(ns->schema,
+					   lockdep_is_held(&nsdata->lock));
+	if (sc_ref)
+		rcu_assign_pointer(sc_ref->ns, NULL);
+	rcu_assign_pointer(ns->schema, sc);
+
+	if (sc) {
+		ns_ref = rcu_dereference_protected(sc->ns,
+						   lockdep_is_held(&nsdata->lock));
+		if (ns_ref)
+			rcu_assign_pointer(ns_ref->schema, NULL);
+		rcu_assign_pointer(sc->ns, ns);
+	}
+
+	err = 0;
+
+out_unlock:
+	mutex_unlock(&nsdata->lock);
+	return err;
+}
+
+static const struct genl_ops ioam6_genl_ops[] = {
+	{
+		.cmd	= IOAM6_CMD_ADD_NAMESPACE,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit	= ioam6_genl_addns,
+		.flags	= GENL_ADMIN_PERM,
+		.policy	= ioam6_genl_policy_addns,
+		.maxattr = ARRAY_SIZE(ioam6_genl_policy_addns) - 1,
+	},
+	{
+		.cmd	= IOAM6_CMD_DEL_NAMESPACE,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit	= ioam6_genl_delns,
+		.flags	= GENL_ADMIN_PERM,
+		.policy	= ioam6_genl_policy_delns,
+		.maxattr = ARRAY_SIZE(ioam6_genl_policy_delns) - 1,
+	},
+	{
+		.cmd	= IOAM6_CMD_DUMP_NAMESPACES,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.start	= ioam6_genl_dumpns_start,
+		.dumpit	= ioam6_genl_dumpns,
+		.done	= ioam6_genl_dumpns_done,
+		.flags	= GENL_ADMIN_PERM,
+	},
+	{
+		.cmd	= IOAM6_CMD_ADD_SCHEMA,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit	= ioam6_genl_addsc,
+		.flags	= GENL_ADMIN_PERM,
+		.policy	= ioam6_genl_policy_addsc,
+		.maxattr = ARRAY_SIZE(ioam6_genl_policy_addsc) - 1,
+	},
+	{
+		.cmd	= IOAM6_CMD_DEL_SCHEMA,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit	= ioam6_genl_delsc,
+		.flags	= GENL_ADMIN_PERM,
+		.policy	= ioam6_genl_policy_delsc,
+		.maxattr = ARRAY_SIZE(ioam6_genl_policy_delsc) - 1,
+	},
+	{
+		.cmd	= IOAM6_CMD_DUMP_SCHEMAS,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.start	= ioam6_genl_dumpsc_start,
+		.dumpit	= ioam6_genl_dumpsc,
+		.done	= ioam6_genl_dumpsc_done,
+		.flags	= GENL_ADMIN_PERM,
+	},
+	{
+		.cmd	= IOAM6_CMD_NS_SET_SCHEMA,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit	= ioam6_genl_ns_set_schema,
+		.flags	= GENL_ADMIN_PERM,
+		.policy	= ioam6_genl_policy_ns_sc,
+		.maxattr = ARRAY_SIZE(ioam6_genl_policy_ns_sc) - 1,
+	},
+};
+
+#define IOAM6_GENL_EV_GRP_OFFSET 0
+
+static const struct genl_multicast_group ioam6_mcgrps[] = {
+	[IOAM6_GENL_EV_GRP_OFFSET] = { .name = IOAM6_GENL_EV_GRP_NAME,
+				       .flags = GENL_MCAST_CAP_NET_ADMIN },
+};
+
+static int ioam6_event_put_trace(struct sk_buff *skb,
+				 struct ioam6_trace_hdr *trace,
+				 unsigned int len)
+{
+	if (nla_put_u16(skb, IOAM6_EVENT_ATTR_TRACE_NAMESPACE,
+			be16_to_cpu(trace->namespace_id)) ||
+	    nla_put_u8(skb, IOAM6_EVENT_ATTR_TRACE_NODELEN, trace->nodelen) ||
+	    nla_put_u32(skb, IOAM6_EVENT_ATTR_TRACE_TYPE,
+			be32_to_cpu(trace->type_be32)) ||
+	    nla_put(skb, IOAM6_EVENT_ATTR_TRACE_DATA,
+		    len - sizeof(struct ioam6_trace_hdr) - trace->remlen * 4,
+		    trace->data + trace->remlen * 4))
+		return 1;
+
+	return 0;
+}
+
+void ioam6_event(enum ioam6_event_type type, struct net *net, gfp_t gfp,
+		 void *opt, unsigned int opt_len)
+{
+	struct nlmsghdr *nlh;
+	struct sk_buff *skb;
+
+	if (!genl_has_listeners(&ioam6_genl_family, net,
+				IOAM6_GENL_EV_GRP_OFFSET))
+		return;
+
+	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, gfp);
+	if (!skb)
+		return;
+
+	nlh = genlmsg_put(skb, 0, 0, &ioam6_genl_family, 0, type);
+	if (!nlh)
+		goto nla_put_failure;
+
+	switch (type) {
+	case IOAM6_EVENT_UNSPEC:
+		WARN_ON_ONCE(1);
+		break;
+	case IOAM6_EVENT_TRACE:
+		if (ioam6_event_put_trace(skb, (struct ioam6_trace_hdr *)opt,
+					  opt_len))
+			goto nla_put_failure;
+		break;
+	}
+
+	genlmsg_end(skb, nlh);
+	genlmsg_multicast_netns(&ioam6_genl_family, net, skb, 0,
+				IOAM6_GENL_EV_GRP_OFFSET, gfp);
+	return;
+
+nla_put_failure:
+	nlmsg_free(skb);
+}
+
+static struct genl_family ioam6_genl_family __ro_after_init = {
+	.name		= IOAM6_GENL_NAME,
+	.version	= IOAM6_GENL_VERSION,
+	.netnsok	= true,
+	.parallel_ops	= true,
+	.ops		= ioam6_genl_ops,
+	.n_ops		= ARRAY_SIZE(ioam6_genl_ops),
+	.resv_start_op	= IOAM6_CMD_NS_SET_SCHEMA + 1,
+	.mcgrps		= ioam6_mcgrps,
+	.n_mcgrps	= ARRAY_SIZE(ioam6_mcgrps),
+	.module		= THIS_MODULE,
+};
+
+struct ioam6_namespace *ioam6_namespace(struct net *net, __be16 id)
+{
+	struct ioam6_pernet_data *nsdata = ioam6_pernet(net);
+
+	return rhashtable_lookup_fast(&nsdata->namespaces, &id, rht_ns_params);
+}
+
+#define IOAM6_MASK_SHORT_FIELDS 0xff1ffc00
+#define IOAM6_MASK_WIDE_FIELDS  0x00e00000
+
+u8 ioam6_trace_compute_nodelen(u32 trace_type)
+{
+	u8 nodelen = hweight32(trace_type & IOAM6_MASK_SHORT_FIELDS)
+				* (sizeof(__be32) / 4);
+
+	nodelen += hweight32(trace_type & IOAM6_MASK_WIDE_FIELDS)
+				* (sizeof(__be64) / 4);
+
+	return nodelen;
+}
+
+static void __ioam6_fill_trace_data(struct sk_buff *skb,
+				    struct ioam6_namespace *ns,
+				    struct ioam6_trace_hdr *trace,
+				    struct ioam6_schema *sc,
+				    unsigned int sclen, bool is_input)
+{
+	/* Note: skb_dst_dev_rcu() can't be NULL at this point. */
+	struct net_device *dev = skb_dst_dev_rcu(skb);
+	struct inet6_dev *i_skb_dev, *idev;
+	struct timespec64 ts;
+	ktime_t tstamp;
+	u64 raw64;
+	u32 raw32;
+	u16 raw16;
+	u8 *data;
+	u8 byte;
+
+	data = trace->data + trace->remlen * 4 - trace->nodelen * 4 - sclen * 4;
+
+	i_skb_dev = skb->dev ? __in6_dev_get(skb->dev) : NULL;
+	idev = __in6_dev_get(dev);
+
+	/* hop_lim and node_id */
+	if (trace->type.bit0) {
+		byte = ipv6_hdr(skb)->hop_limit;
+		if (is_input)
+			byte--;
+
+		raw32 = READ_ONCE(dev_net(dev)->ipv6.sysctl.ioam6_id);
+
+		*(__be32 *)data = cpu_to_be32((byte << 24) | raw32);
+		data += sizeof(__be32);
+	}
+
+	/* ingress_if_id and egress_if_id */
+	if (trace->type.bit1) {
+		if (!i_skb_dev)
+			raw16 = IOAM6_U16_UNAVAILABLE;
+		else
+			raw16 = (__force u16)READ_ONCE(i_skb_dev->cnf.ioam6_id);
+
+		*(__be16 *)data = cpu_to_be16(raw16);
+		data += sizeof(__be16);
+
+		if ((dev->flags & IFF_LOOPBACK) || !idev)
+			raw16 = IOAM6_U16_UNAVAILABLE;
+		else
+			raw16 = (__force u16)READ_ONCE(idev->cnf.ioam6_id);
+
+		*(__be16 *)data = cpu_to_be16(raw16);
+		data += sizeof(__be16);
+	}
+
+	/* timestamp seconds */
+	if (trace->type.bit2) {
+		if (!skb->dev) {
+			*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		} else {
+			tstamp = skb_tstamp_cond(skb, true);
+			ts = ktime_to_timespec64(tstamp);
+
+			*(__be32 *)data = cpu_to_be32((u32)ts.tv_sec);
+		}
+		data += sizeof(__be32);
+	}
+
+	/* timestamp subseconds */
+	if (trace->type.bit3) {
+		if (!skb->dev) {
+			*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		} else {
+			if (!trace->type.bit2) {
+				tstamp = skb_tstamp_cond(skb, true);
+				ts = ktime_to_timespec64(tstamp);
+			}
+
+			*(__be32 *)data = cpu_to_be32((u32)(ts.tv_nsec / NSEC_PER_USEC));
+		}
+		data += sizeof(__be32);
+	}
+
+	/* transit delay */
+	if (trace->type.bit4) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* namespace data */
+	if (trace->type.bit5) {
+		*(__be32 *)data = ns->data;
+		data += sizeof(__be32);
+	}
+
+	/* queue depth */
+	if (trace->type.bit6) {
+		struct netdev_queue *queue;
+		const struct Qdisc *qdisc;
+		__u32 qlen, backlog;
+
+		if (dev->flags & IFF_LOOPBACK ||
+		    skb_get_queue_mapping(skb) >= dev->num_tx_queues) {
+			*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		} else {
+			queue = skb_get_tx_queue(dev, skb);
+			qdisc = rcu_dereference(queue->qdisc);
+
+			qdisc_qstats_qlen_backlog(qdisc, &qlen, &backlog);
+
+			*(__be32 *)data = cpu_to_be32(backlog);
+		}
+		data += sizeof(__be32);
+	}
+
+	/* checksum complement */
+	if (trace->type.bit7) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* hop_lim and node_id (wide) */
+	if (trace->type.bit8) {
+		byte = ipv6_hdr(skb)->hop_limit;
+		if (is_input)
+			byte--;
+
+		raw64 = READ_ONCE(dev_net(dev)->ipv6.sysctl.ioam6_id_wide);
+
+		*(__be64 *)data = cpu_to_be64(((u64)byte << 56) | raw64);
+		data += sizeof(__be64);
+	}
+
+	/* ingress_if_id and egress_if_id (wide) */
+	if (trace->type.bit9) {
+		if (!i_skb_dev)
+			raw32 = IOAM6_U32_UNAVAILABLE;
+		else
+			raw32 = READ_ONCE(i_skb_dev->cnf.ioam6_id_wide);
+
+		*(__be32 *)data = cpu_to_be32(raw32);
+		data += sizeof(__be32);
+
+		if ((dev->flags & IFF_LOOPBACK) || !idev)
+			raw32 = IOAM6_U32_UNAVAILABLE;
+		else
+			raw32 = READ_ONCE(idev->cnf.ioam6_id_wide);
+
+		*(__be32 *)data = cpu_to_be32(raw32);
+		data += sizeof(__be32);
+	}
+
+	/* namespace data (wide) */
+	if (trace->type.bit10) {
+		*(__be64 *)data = ns->data_wide;
+		data += sizeof(__be64);
+	}
+
+	/* buffer occupancy */
+	if (trace->type.bit11) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit12 undefined: filled with empty value */
+	if (trace->type.bit12) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit13 undefined: filled with empty value */
+	if (trace->type.bit13) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit14 undefined: filled with empty value */
+	if (trace->type.bit14) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit15 undefined: filled with empty value */
+	if (trace->type.bit15) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit16 undefined: filled with empty value */
+	if (trace->type.bit16) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit17 undefined: filled with empty value */
+	if (trace->type.bit17) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit18 undefined: filled with empty value */
+	if (trace->type.bit18) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit19 undefined: filled with empty value */
+	if (trace->type.bit19) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit20 undefined: filled with empty value */
+	if (trace->type.bit20) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* bit21 undefined: filled with empty value */
+	if (trace->type.bit21) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* opaque state snapshot */
+	if (trace->type.bit22) {
+		if (!sc) {
+			*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE >> 8);
+		} else {
+			*(__be32 *)data = sc->hdr;
+			data += sizeof(__be32);
+
+			memcpy(data, sc->data, sc->len);
+		}
+	}
+}
+
+/* called with rcu_read_lock() */
+void ioam6_fill_trace_data(struct sk_buff *skb,
+			   struct ioam6_namespace *ns,
+			   struct ioam6_trace_hdr *trace,
+			   bool is_input)
+{
+	struct ioam6_schema *sc;
+	unsigned int sclen = 0;
+
+	/* Skip if Overflow flag is set
+	 */
+	if (trace->overflow)
+		return;
+
+	/* NodeLen does not include Opaque State Snapshot length. We need to
+	 * take it into account if the corresponding bit is set (bit 22) and
+	 * if the current IOAM namespace has an active schema attached to it
+	 */
+	sc = rcu_dereference(ns->schema);
+	if (trace->type.bit22) {
+		sclen = sizeof_field(struct ioam6_schema, hdr) / 4;
+
+		if (sc)
+			sclen += sc->len / 4;
+	}
+
+	/* If there is no space remaining, we set the Overflow flag and we
+	 * skip without filling the trace
+	 */
+	if (!trace->remlen || trace->remlen < trace->nodelen + sclen) {
+		trace->overflow = 1;
+		return;
+	}
+
+	__ioam6_fill_trace_data(skb, ns, trace, sc, sclen, is_input);
+	trace->remlen -= trace->nodelen + sclen;
+}
+
+static int __net_init ioam6_net_init(struct net *net)
+{
+	struct ioam6_pernet_data *nsdata;
+	int err = -ENOMEM;
+
+	nsdata = kzalloc_obj(*nsdata);
+	if (!nsdata)
+		goto out;
+
+	mutex_init(&nsdata->lock);
+	net->ipv6.ioam6_data = nsdata;
+
+	err = rhashtable_init(&nsdata->namespaces, &rht_ns_params);
+	if (err)
+		goto free_nsdata;
+
+	err = rhashtable_init(&nsdata->schemas, &rht_sc_params);
+	if (err)
+		goto free_rht_ns;
+
+out:
+	return err;
+free_rht_ns:
+	rhashtable_destroy(&nsdata->namespaces);
+free_nsdata:
+	kfree(nsdata);
+	net->ipv6.ioam6_data = NULL;
+	goto out;
+}
+
+static void __net_exit ioam6_net_exit(struct net *net)
+{
+	struct ioam6_pernet_data *nsdata = ioam6_pernet(net);
+
+	rhashtable_free_and_destroy(&nsdata->namespaces, ioam6_free_ns, NULL);
+	rhashtable_free_and_destroy(&nsdata->schemas, ioam6_free_sc, NULL);
+
+	kfree(nsdata);
+}
+
+static struct pernet_operations ioam6_net_ops = {
+	.init = ioam6_net_init,
+	.exit = ioam6_net_exit,
+};
+
+int __init ioam6_init(void)
+{
+	int err = register_pernet_subsys(&ioam6_net_ops);
+	if (err)
+		goto out;
+
+	err = genl_register_family(&ioam6_genl_family);
+	if (err)
+		goto out_unregister_pernet_subsys;
+
+#ifdef CONFIG_IPV6_IOAM6_LWTUNNEL
+	err = ioam6_iptunnel_init();
+	if (err)
+		goto out_unregister_genl;
+#endif
+
+	pr_info("In-situ OAM (IOAM) with IPv6\n");
+
+out:
+	return err;
+#ifdef CONFIG_IPV6_IOAM6_LWTUNNEL
+out_unregister_genl:
+	genl_unregister_family(&ioam6_genl_family);
+#endif
+out_unregister_pernet_subsys:
+	unregister_pernet_subsys(&ioam6_net_ops);
+	goto out;
+}
+
+void ioam6_exit(void)
+{
+#ifdef CONFIG_IPV6_IOAM6_LWTUNNEL
+	ioam6_iptunnel_exit();
+#endif
+	genl_unregister_family(&ioam6_genl_family);
+	unregister_pernet_subsys(&ioam6_net_ops);
+}