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, 465 insertions, 0 deletions

diff --git a/net/sched/act_vlan.c b/net/sched/act_vlan.c
new file mode 100644
index 000000000..6a375fdc6
--- /dev/null
+++ b/net/sched/act_vlan.c
@@ -0,0 +1,465 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2014 Jiri Pirko <jiri@resnulli.us>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/skbuff.h>
+#include <linux/rtnetlink.h>
+#include <linux/if_vlan.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+#include <net/pkt_cls.h>
+#include <net/tc_wrapper.h>
+
+#include <linux/tc_act/tc_vlan.h>
+#include <net/tc_act/tc_vlan.h>
+
+static struct tc_action_ops act_vlan_ops;
+
+TC_INDIRECT_SCOPE int tcf_vlan_act(struct sk_buff *skb,
+				   const struct tc_action *a,
+				   struct tcf_result *res)
+{
+	struct tcf_vlan *v = to_vlan(a);
+	struct tcf_vlan_params *p;
+	int err;
+	u16 tci;
+
+	tcf_lastuse_update(&v->tcf_tm);
+	tcf_action_update_bstats(&v->common, skb);
+
+	/* Ensure 'data' points at mac_header prior calling vlan manipulating
+	 * functions.
+	 */
+	if (skb_at_tc_ingress(skb))
+		skb_push_rcsum(skb, skb->mac_len);
+
+	p = rcu_dereference_bh(v->vlan_p);
+
+	switch (p->tcfv_action) {
+	case TCA_VLAN_ACT_POP:
+		err = skb_vlan_pop(skb);
+		if (err)
+			goto drop;
+		break;
+	case TCA_VLAN_ACT_PUSH:
+		err = skb_vlan_push(skb, p->tcfv_push_proto, p->tcfv_push_vid |
+				    (p->tcfv_push_prio << VLAN_PRIO_SHIFT));
+		if (err)
+			goto drop;
+		break;
+	case TCA_VLAN_ACT_MODIFY:
+		/* No-op if no vlan tag (either hw-accel or in-payload) */
+		if (!skb_vlan_tagged(skb))
+			goto out;
+		/* extract existing tag (and guarantee no hw-accel tag) */
+		if (skb_vlan_tag_present(skb)) {
+			tci = skb_vlan_tag_get(skb);
+			__vlan_hwaccel_clear_tag(skb);
+		} else {
+			/* in-payload vlan tag, pop it */
+			err = __skb_vlan_pop(skb, &tci);
+			if (err)
+				goto drop;
+		}
+		/* replace the vid */
+		tci = (tci & ~VLAN_VID_MASK) | p->tcfv_push_vid;
+		/* replace prio bits, if tcfv_push_prio specified */
+		if (p->tcfv_push_prio_exists) {
+			tci &= ~VLAN_PRIO_MASK;
+			tci |= p->tcfv_push_prio << VLAN_PRIO_SHIFT;
+		}
+		/* put updated tci as hwaccel tag */
+		__vlan_hwaccel_put_tag(skb, p->tcfv_push_proto, tci);
+		break;
+	case TCA_VLAN_ACT_POP_ETH:
+		err = skb_eth_pop(skb);
+		if (err)
+			goto drop;
+		break;
+	case TCA_VLAN_ACT_PUSH_ETH:
+		err = skb_eth_push(skb, p->tcfv_push_dst, p->tcfv_push_src);
+		if (err)
+			goto drop;
+		break;
+	default:
+		BUG();
+	}
+
+out:
+	if (skb_at_tc_ingress(skb))
+		skb_pull_rcsum(skb, skb->mac_len);
+
+	skb_reset_mac_len(skb);
+	return p->action;
+
+drop:
+	tcf_action_inc_drop_qstats(&v->common);
+	return TC_ACT_SHOT;
+}
+
+static const struct nla_policy vlan_policy[TCA_VLAN_MAX + 1] = {
+	[TCA_VLAN_UNSPEC]		= { .strict_start_type = TCA_VLAN_PUSH_ETH_DST },
+	[TCA_VLAN_PARMS]		= { .len = sizeof(struct tc_vlan) },
+	[TCA_VLAN_PUSH_VLAN_ID]		= { .type = NLA_U16 },
+	[TCA_VLAN_PUSH_VLAN_PROTOCOL]	= { .type = NLA_U16 },
+	[TCA_VLAN_PUSH_VLAN_PRIORITY]	= { .type = NLA_U8 },
+	[TCA_VLAN_PUSH_ETH_DST]		= NLA_POLICY_ETH_ADDR,
+	[TCA_VLAN_PUSH_ETH_SRC]		= NLA_POLICY_ETH_ADDR,
+};
+
+static int tcf_vlan_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_vlan_ops.net_id);
+	bool bind = flags & TCA_ACT_FLAGS_BIND;
+	struct nlattr *tb[TCA_VLAN_MAX + 1];
+	struct tcf_chain *goto_ch = NULL;
+	bool push_prio_exists = false;
+	struct tcf_vlan_params *p;
+	struct tc_vlan *parm;
+	struct tcf_vlan *v;
+	int action;
+	u16 push_vid = 0;
+	__be16 push_proto = 0;
+	u8 push_prio = 0;
+	bool exists = false;
+	int ret = 0, err;
+	u32 index;
+
+	if (!nla)
+		return -EINVAL;
+
+	err = nla_parse_nested_deprecated(tb, TCA_VLAN_MAX, nla, vlan_policy,
+					  NULL);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_VLAN_PARMS])
+		return -EINVAL;
+	parm = nla_data(tb[TCA_VLAN_PARMS]);
+	index = parm->index;
+	err = tcf_idr_check_alloc(tn, &index, a, bind);
+	if (err < 0)
+		return err;
+	exists = err;
+	if (exists && bind)
+		return ACT_P_BOUND;
+
+	switch (parm->v_action) {
+	case TCA_VLAN_ACT_POP:
+		break;
+	case TCA_VLAN_ACT_PUSH:
+	case TCA_VLAN_ACT_MODIFY:
+		if (!tb[TCA_VLAN_PUSH_VLAN_ID]) {
+			if (exists)
+				tcf_idr_release(*a, bind);
+			else
+				tcf_idr_cleanup(tn, index);
+			return -EINVAL;
+		}
+		push_vid = nla_get_u16(tb[TCA_VLAN_PUSH_VLAN_ID]);
+		if (push_vid >= VLAN_VID_MASK) {
+			if (exists)
+				tcf_idr_release(*a, bind);
+			else
+				tcf_idr_cleanup(tn, index);
+			return -ERANGE;
+		}
+
+		if (tb[TCA_VLAN_PUSH_VLAN_PROTOCOL]) {
+			push_proto = nla_get_be16(tb[TCA_VLAN_PUSH_VLAN_PROTOCOL]);
+			switch (push_proto) {
+			case htons(ETH_P_8021Q):
+			case htons(ETH_P_8021AD):
+				break;
+			default:
+				if (exists)
+					tcf_idr_release(*a, bind);
+				else
+					tcf_idr_cleanup(tn, index);
+				return -EPROTONOSUPPORT;
+			}
+		} else {
+			push_proto = htons(ETH_P_8021Q);
+		}
+
+		push_prio_exists = !!tb[TCA_VLAN_PUSH_VLAN_PRIORITY];
+		if (push_prio_exists)
+			push_prio = nla_get_u8(tb[TCA_VLAN_PUSH_VLAN_PRIORITY]);
+		break;
+	case TCA_VLAN_ACT_POP_ETH:
+		break;
+	case TCA_VLAN_ACT_PUSH_ETH:
+		if (!tb[TCA_VLAN_PUSH_ETH_DST] || !tb[TCA_VLAN_PUSH_ETH_SRC]) {
+			if (exists)
+				tcf_idr_release(*a, bind);
+			else
+				tcf_idr_cleanup(tn, index);
+			return -EINVAL;
+		}
+		break;
+	default:
+		if (exists)
+			tcf_idr_release(*a, bind);
+		else
+			tcf_idr_cleanup(tn, index);
+		return -EINVAL;
+	}
+	action = parm->v_action;
+
+	if (!exists) {
+		ret = tcf_idr_create_from_flags(tn, index, est, a,
+						&act_vlan_ops, bind, flags);
+		if (ret) {
+			tcf_idr_cleanup(tn, index);
+			return ret;
+		}
+
+		ret = ACT_P_CREATED;
+	} else if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
+		tcf_idr_release(*a, bind);
+		return -EEXIST;
+	}
+
+	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
+	if (err < 0)
+		goto release_idr;
+
+	v = to_vlan(*a);
+
+	p = kzalloc_obj(*p);
+	if (!p) {
+		err = -ENOMEM;
+		goto put_chain;
+	}
+
+	p->tcfv_action = action;
+	p->tcfv_push_vid = push_vid;
+	p->tcfv_push_prio = push_prio;
+	p->tcfv_push_prio_exists = push_prio_exists || action == TCA_VLAN_ACT_PUSH;
+	p->tcfv_push_proto = push_proto;
+
+	if (action == TCA_VLAN_ACT_PUSH_ETH) {
+		nla_memcpy(&p->tcfv_push_dst, tb[TCA_VLAN_PUSH_ETH_DST],
+			   ETH_ALEN);
+		nla_memcpy(&p->tcfv_push_src, tb[TCA_VLAN_PUSH_ETH_SRC],
+			   ETH_ALEN);
+	}
+
+	p->action = parm->action;
+	spin_lock_bh(&v->tcf_lock);
+	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
+	p = rcu_replace_pointer(v->vlan_p, p, lockdep_is_held(&v->tcf_lock));
+	spin_unlock_bh(&v->tcf_lock);
+
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+	if (p)
+		kfree_rcu(p, rcu);
+
+	return ret;
+put_chain:
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+release_idr:
+	tcf_idr_release(*a, bind);
+	return err;
+}
+
+static void tcf_vlan_cleanup(struct tc_action *a)
+{
+	struct tcf_vlan *v = to_vlan(a);
+	struct tcf_vlan_params *p;
+
+	p = rcu_dereference_protected(v->vlan_p, 1);
+	if (p)
+		kfree_rcu(p, rcu);
+}
+
+static int tcf_vlan_dump(struct sk_buff *skb, struct tc_action *a,
+			 int bind, int ref)
+{
+	unsigned char *b = skb_tail_pointer(skb);
+	struct tcf_vlan *v = to_vlan(a);
+	struct tcf_vlan_params *p;
+	struct tc_vlan opt = {
+		.index    = v->tcf_index,
+		.refcnt   = refcount_read(&v->tcf_refcnt) - ref,
+		.bindcnt  = atomic_read(&v->tcf_bindcnt) - bind,
+	};
+	struct tcf_t t;
+
+	rcu_read_lock();
+	p = rcu_dereference(v->vlan_p);
+	opt.action = p->action;
+	opt.v_action = p->tcfv_action;
+	if (nla_put(skb, TCA_VLAN_PARMS, sizeof(opt), &opt))
+		goto nla_put_failure;
+
+	if ((p->tcfv_action == TCA_VLAN_ACT_PUSH ||
+	     p->tcfv_action == TCA_VLAN_ACT_MODIFY) &&
+	    (nla_put_u16(skb, TCA_VLAN_PUSH_VLAN_ID, p->tcfv_push_vid) ||
+	     nla_put_be16(skb, TCA_VLAN_PUSH_VLAN_PROTOCOL,
+			  p->tcfv_push_proto) ||
+	     (p->tcfv_push_prio_exists &&
+	      nla_put_u8(skb, TCA_VLAN_PUSH_VLAN_PRIORITY, p->tcfv_push_prio))))
+		goto nla_put_failure;
+
+	if (p->tcfv_action == TCA_VLAN_ACT_PUSH_ETH) {
+		if (nla_put(skb, TCA_VLAN_PUSH_ETH_DST, ETH_ALEN,
+			    p->tcfv_push_dst))
+			goto nla_put_failure;
+		if (nla_put(skb, TCA_VLAN_PUSH_ETH_SRC, ETH_ALEN,
+			    p->tcfv_push_src))
+			goto nla_put_failure;
+	}
+
+	tcf_tm_dump(&t, &v->tcf_tm);
+	if (nla_put_64bit(skb, TCA_VLAN_TM, sizeof(t), &t, TCA_VLAN_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_vlan_stats_update(struct tc_action *a, u64 bytes, u64 packets,
+				  u64 drops, u64 lastuse, bool hw)
+{
+	struct tcf_vlan *v = to_vlan(a);
+	struct tcf_t *tm = &v->tcf_tm;
+
+	tcf_action_update_stats(a, bytes, packets, drops, hw);
+	tm->lastuse = max_t(u64, tm->lastuse, lastuse);
+}
+
+static size_t tcf_vlan_get_fill_size(const struct tc_action *act)
+{
+	return nla_total_size(sizeof(struct tc_vlan))
+		+ nla_total_size(sizeof(u16)) /* TCA_VLAN_PUSH_VLAN_ID */
+		+ nla_total_size(sizeof(u16)) /* TCA_VLAN_PUSH_VLAN_PROTOCOL */
+		+ nla_total_size(sizeof(u8)); /* TCA_VLAN_PUSH_VLAN_PRIORITY */
+}
+
+static int tcf_vlan_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;
+
+		switch (tcf_vlan_action(act)) {
+		case TCA_VLAN_ACT_PUSH:
+			entry->id = FLOW_ACTION_VLAN_PUSH;
+			entry->vlan.vid = tcf_vlan_push_vid(act);
+			entry->vlan.proto = tcf_vlan_push_proto(act);
+			entry->vlan.prio = tcf_vlan_push_prio(act);
+			break;
+		case TCA_VLAN_ACT_POP:
+			entry->id = FLOW_ACTION_VLAN_POP;
+			break;
+		case TCA_VLAN_ACT_MODIFY:
+			entry->id = FLOW_ACTION_VLAN_MANGLE;
+			entry->vlan.vid = tcf_vlan_push_vid(act);
+			entry->vlan.proto = tcf_vlan_push_proto(act);
+			entry->vlan.prio = tcf_vlan_push_prio(act);
+			break;
+		case TCA_VLAN_ACT_POP_ETH:
+			entry->id = FLOW_ACTION_VLAN_POP_ETH;
+			break;
+		case TCA_VLAN_ACT_PUSH_ETH:
+			entry->id = FLOW_ACTION_VLAN_PUSH_ETH;
+			tcf_vlan_push_eth(entry->vlan_push_eth.src, entry->vlan_push_eth.dst, act);
+			break;
+		default:
+			NL_SET_ERR_MSG_MOD(extack, "Unsupported vlan action mode offload");
+			return -EOPNOTSUPP;
+		}
+		*index_inc = 1;
+	} else {
+		struct flow_offload_action *fl_action = entry_data;
+
+		switch (tcf_vlan_action(act)) {
+		case TCA_VLAN_ACT_PUSH:
+			fl_action->id = FLOW_ACTION_VLAN_PUSH;
+			break;
+		case TCA_VLAN_ACT_POP:
+			fl_action->id = FLOW_ACTION_VLAN_POP;
+			break;
+		case TCA_VLAN_ACT_MODIFY:
+			fl_action->id = FLOW_ACTION_VLAN_MANGLE;
+			break;
+		case TCA_VLAN_ACT_POP_ETH:
+			fl_action->id = FLOW_ACTION_VLAN_POP_ETH;
+			break;
+		case TCA_VLAN_ACT_PUSH_ETH:
+			fl_action->id = FLOW_ACTION_VLAN_PUSH_ETH;
+			break;
+		default:
+			return -EOPNOTSUPP;
+		}
+	}
+
+	return 0;
+}
+
+static struct tc_action_ops act_vlan_ops = {
+	.kind		=	"vlan",
+	.id		=	TCA_ID_VLAN,
+	.owner		=	THIS_MODULE,
+	.act		=	tcf_vlan_act,
+	.dump		=	tcf_vlan_dump,
+	.init		=	tcf_vlan_init,
+	.cleanup	=	tcf_vlan_cleanup,
+	.stats_update	=	tcf_vlan_stats_update,
+	.get_fill_size	=	tcf_vlan_get_fill_size,
+	.offload_act_setup =	tcf_vlan_offload_act_setup,
+	.size		=	sizeof(struct tcf_vlan),
+};
+MODULE_ALIAS_NET_ACT("vlan");
+
+static __net_init int vlan_init_net(struct net *net)
+{
+	struct tc_action_net *tn = net_generic(net, act_vlan_ops.net_id);
+
+	return tc_action_net_init(net, tn, &act_vlan_ops);
+}
+
+static void __net_exit vlan_exit_net(struct list_head *net_list)
+{
+	tc_action_net_exit(net_list, act_vlan_ops.net_id);
+}
+
+static struct pernet_operations vlan_net_ops = {
+	.init = vlan_init_net,
+	.exit_batch = vlan_exit_net,
+	.id   = &act_vlan_ops.net_id,
+	.size = sizeof(struct tc_action_net),
+};
+
+static int __init vlan_init_module(void)
+{
+	return tcf_register_action(&act_vlan_ops, &vlan_net_ops);
+}
+
+static void __exit vlan_cleanup_module(void)
+{
+	tcf_unregister_action(&act_vlan_ops, &vlan_net_ops);
+}
+
+module_init(vlan_init_module);
+module_exit(vlan_cleanup_module);
+
+MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
+MODULE_DESCRIPTION("vlan manipulation actions");
+MODULE_LICENSE("GPL v2");