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, 467 insertions, 0 deletions

diff --git a/net/sched/act_skbedit.c b/net/sched/act_skbedit.c
new file mode 100644
index 000000000..bfec6b668
--- /dev/null
+++ b/net/sched/act_skbedit.c
@@ -0,0 +1,467 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2008, Intel Corporation.
+ *
+ * Author: Alexander Duyck <alexander.h.duyck@intel.com>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/skbuff.h>
+#include <linux/rtnetlink.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+#include <net/ip.h>
+#include <net/ipv6.h>
+#include <net/dsfield.h>
+#include <net/pkt_cls.h>
+#include <net/tc_wrapper.h>
+
+#include <linux/tc_act/tc_skbedit.h>
+#include <net/tc_act/tc_skbedit.h>
+
+static struct tc_action_ops act_skbedit_ops;
+
+static u16 tcf_skbedit_hash(struct tcf_skbedit_params *params,
+			    struct sk_buff *skb)
+{
+	u16 queue_mapping = params->queue_mapping;
+
+	if (params->flags & SKBEDIT_F_TXQ_SKBHASH) {
+		u32 hash = skb_get_hash(skb);
+
+		queue_mapping += hash % params->mapping_mod;
+	}
+
+	return netdev_cap_txqueue(skb->dev, queue_mapping);
+}
+
+TC_INDIRECT_SCOPE int tcf_skbedit_act(struct sk_buff *skb,
+				      const struct tc_action *a,
+				      struct tcf_result *res)
+{
+	struct tcf_skbedit *d = to_skbedit(a);
+	struct tcf_skbedit_params *params;
+
+	tcf_lastuse_update(&d->tcf_tm);
+	bstats_update(this_cpu_ptr(d->common.cpu_bstats), skb);
+
+	params = rcu_dereference_bh(d->params);
+
+	if (params->flags & SKBEDIT_F_PRIORITY)
+		skb->priority = params->priority;
+	if (params->flags & SKBEDIT_F_INHERITDSFIELD) {
+		int wlen = skb_network_offset(skb);
+
+		switch (skb_protocol(skb, true)) {
+		case htons(ETH_P_IP):
+			wlen += sizeof(struct iphdr);
+			if (!pskb_may_pull(skb, wlen))
+				goto err;
+			skb->priority = ipv4_get_dsfield(ip_hdr(skb)) >> 2;
+			break;
+
+		case htons(ETH_P_IPV6):
+			wlen += sizeof(struct ipv6hdr);
+			if (!pskb_may_pull(skb, wlen))
+				goto err;
+			skb->priority = ipv6_get_dsfield(ipv6_hdr(skb)) >> 2;
+			break;
+		}
+	}
+	if (params->flags & SKBEDIT_F_QUEUE_MAPPING &&
+	    skb->dev->real_num_tx_queues > params->queue_mapping) {
+#ifdef CONFIG_NET_EGRESS
+		netdev_xmit_skip_txqueue(true);
+#endif
+		skb_set_queue_mapping(skb, tcf_skbedit_hash(params, skb));
+	}
+	if (params->flags & SKBEDIT_F_MARK) {
+		skb->mark &= ~params->mask;
+		skb->mark |= params->mark & params->mask;
+	}
+	if (params->flags & SKBEDIT_F_PTYPE)
+		skb->pkt_type = params->ptype;
+	return params->action;
+
+err:
+	qstats_cpu_drop_inc(d->common.cpu_qstats);
+	return TC_ACT_SHOT;
+}
+
+static void tcf_skbedit_stats_update(struct tc_action *a, u64 bytes,
+				     u64 packets, u64 drops,
+				     u64 lastuse, bool hw)
+{
+	struct tcf_skbedit *d = to_skbedit(a);
+	struct tcf_t *tm = &d->tcf_tm;
+
+	tcf_action_update_stats(a, bytes, packets, drops, hw);
+	tm->lastuse = max_t(u64, tm->lastuse, lastuse);
+}
+
+static const struct nla_policy skbedit_policy[TCA_SKBEDIT_MAX + 1] = {
+	[TCA_SKBEDIT_PARMS]		= { .len = sizeof(struct tc_skbedit) },
+	[TCA_SKBEDIT_PRIORITY]		= { .len = sizeof(u32) },
+	[TCA_SKBEDIT_QUEUE_MAPPING]	= { .len = sizeof(u16) },
+	[TCA_SKBEDIT_MARK]		= { .len = sizeof(u32) },
+	[TCA_SKBEDIT_PTYPE]		= { .len = sizeof(u16) },
+	[TCA_SKBEDIT_MASK]		= { .len = sizeof(u32) },
+	[TCA_SKBEDIT_FLAGS]		= { .len = sizeof(u64) },
+	[TCA_SKBEDIT_QUEUE_MAPPING_MAX]	= { .len = sizeof(u16) },
+};
+
+static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
+			    struct nlattr *est, struct tc_action **a,
+			    struct tcf_proto *tp, u32 act_flags,
+			    struct netlink_ext_ack *extack)
+{
+	struct tc_action_net *tn = net_generic(net, act_skbedit_ops.net_id);
+	bool bind = act_flags & TCA_ACT_FLAGS_BIND;
+	struct tcf_skbedit_params *params_new;
+	struct nlattr *tb[TCA_SKBEDIT_MAX + 1];
+	struct tcf_chain *goto_ch = NULL;
+	struct tc_skbedit *parm;
+	struct tcf_skbedit *d;
+	u32 flags = 0, *priority = NULL, *mark = NULL, *mask = NULL;
+	u16 *queue_mapping = NULL, *ptype = NULL;
+	u32 mapping_mod = 1;
+	bool exists = false;
+	int ret = 0, err;
+	u32 index;
+
+	if (nla == NULL)
+		return -EINVAL;
+
+	err = nla_parse_nested_deprecated(tb, TCA_SKBEDIT_MAX, nla,
+					  skbedit_policy, NULL);
+	if (err < 0)
+		return err;
+
+	if (tb[TCA_SKBEDIT_PARMS] == NULL)
+		return -EINVAL;
+
+	if (tb[TCA_SKBEDIT_PRIORITY] != NULL) {
+		flags |= SKBEDIT_F_PRIORITY;
+		priority = nla_data(tb[TCA_SKBEDIT_PRIORITY]);
+	}
+
+	if (tb[TCA_SKBEDIT_QUEUE_MAPPING] != NULL) {
+		if (is_tcf_skbedit_ingress(act_flags) &&
+		    !(act_flags & TCA_ACT_FLAGS_SKIP_SW)) {
+			NL_SET_ERR_MSG_MOD(extack, "\"queue_mapping\" option on receive side is hardware only, use skip_sw");
+			return -EOPNOTSUPP;
+		}
+		flags |= SKBEDIT_F_QUEUE_MAPPING;
+		queue_mapping = nla_data(tb[TCA_SKBEDIT_QUEUE_MAPPING]);
+	}
+
+	if (tb[TCA_SKBEDIT_PTYPE] != NULL) {
+		ptype = nla_data(tb[TCA_SKBEDIT_PTYPE]);
+		if (!skb_pkt_type_ok(*ptype))
+			return -EINVAL;
+		flags |= SKBEDIT_F_PTYPE;
+	}
+
+	if (tb[TCA_SKBEDIT_MARK] != NULL) {
+		flags |= SKBEDIT_F_MARK;
+		mark = nla_data(tb[TCA_SKBEDIT_MARK]);
+	}
+
+	if (tb[TCA_SKBEDIT_MASK] != NULL) {
+		flags |= SKBEDIT_F_MASK;
+		mask = nla_data(tb[TCA_SKBEDIT_MASK]);
+	}
+
+	if (tb[TCA_SKBEDIT_FLAGS] != NULL) {
+		u64 *pure_flags = nla_data(tb[TCA_SKBEDIT_FLAGS]);
+
+		if (*pure_flags & SKBEDIT_F_TXQ_SKBHASH) {
+			u16 *queue_mapping_max;
+
+			if (!tb[TCA_SKBEDIT_QUEUE_MAPPING] ||
+			    !tb[TCA_SKBEDIT_QUEUE_MAPPING_MAX]) {
+				NL_SET_ERR_MSG_MOD(extack, "Missing required range of queue_mapping.");
+				return -EINVAL;
+			}
+
+			queue_mapping_max =
+				nla_data(tb[TCA_SKBEDIT_QUEUE_MAPPING_MAX]);
+			if (*queue_mapping_max < *queue_mapping) {
+				NL_SET_ERR_MSG_MOD(extack, "The range of queue_mapping is invalid, max < min.");
+				return -EINVAL;
+			}
+
+			mapping_mod = *queue_mapping_max - *queue_mapping + 1;
+			if (mapping_mod > U16_MAX) {
+				NL_SET_ERR_MSG_MOD(extack, "The range of queue_mapping is invalid.");
+				return -EINVAL;
+			}
+			flags |= SKBEDIT_F_TXQ_SKBHASH;
+		}
+		if (*pure_flags & SKBEDIT_F_INHERITDSFIELD)
+			flags |= SKBEDIT_F_INHERITDSFIELD;
+	}
+
+	parm = nla_data(tb[TCA_SKBEDIT_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;
+
+	if (!flags) {
+		if (exists)
+			tcf_idr_release(*a, bind);
+		else
+			tcf_idr_cleanup(tn, index);
+		return -EINVAL;
+	}
+
+	if (!exists) {
+		ret = tcf_idr_create(tn, index, est, a,
+				     &act_skbedit_ops, bind, true, act_flags);
+		if (ret) {
+			tcf_idr_cleanup(tn, index);
+			return ret;
+		}
+
+		d = to_skbedit(*a);
+		ret = ACT_P_CREATED;
+	} else {
+		d = to_skbedit(*a);
+		if (!(act_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;
+
+	params_new = kzalloc_obj(*params_new);
+	if (unlikely(!params_new)) {
+		err = -ENOMEM;
+		goto put_chain;
+	}
+
+	params_new->flags = flags;
+	if (flags & SKBEDIT_F_PRIORITY)
+		params_new->priority = *priority;
+	if (flags & SKBEDIT_F_QUEUE_MAPPING) {
+		params_new->queue_mapping = *queue_mapping;
+		params_new->mapping_mod = mapping_mod;
+	}
+	if (flags & SKBEDIT_F_MARK)
+		params_new->mark = *mark;
+	if (flags & SKBEDIT_F_PTYPE)
+		params_new->ptype = *ptype;
+	/* default behaviour is to use all the bits */
+	params_new->mask = 0xffffffff;
+	if (flags & SKBEDIT_F_MASK)
+		params_new->mask = *mask;
+
+	params_new->action = parm->action;
+	spin_lock_bh(&d->tcf_lock);
+	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
+	params_new = rcu_replace_pointer(d->params, params_new,
+					 lockdep_is_held(&d->tcf_lock));
+	spin_unlock_bh(&d->tcf_lock);
+	if (params_new)
+		kfree_rcu(params_new, rcu);
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+
+	return ret;
+put_chain:
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+release_idr:
+	tcf_idr_release(*a, bind);
+	return err;
+}
+
+static int tcf_skbedit_dump(struct sk_buff *skb, struct tc_action *a,
+			    int bind, int ref)
+{
+	const struct tcf_skbedit *d = to_skbedit(a);
+	unsigned char *b = skb_tail_pointer(skb);
+	const struct tcf_skbedit_params *params;
+	struct tc_skbedit opt = {
+		.index   = d->tcf_index,
+		.refcnt  = refcount_read(&d->tcf_refcnt) - ref,
+		.bindcnt = atomic_read(&d->tcf_bindcnt) - bind,
+	};
+	u64 pure_flags = 0;
+	struct tcf_t t;
+
+	rcu_read_lock();
+	params = rcu_dereference(d->params);
+	opt.action = params->action;
+
+	if (nla_put(skb, TCA_SKBEDIT_PARMS, sizeof(opt), &opt))
+		goto nla_put_failure;
+	if ((params->flags & SKBEDIT_F_PRIORITY) &&
+	    nla_put_u32(skb, TCA_SKBEDIT_PRIORITY, params->priority))
+		goto nla_put_failure;
+	if ((params->flags & SKBEDIT_F_QUEUE_MAPPING) &&
+	    nla_put_u16(skb, TCA_SKBEDIT_QUEUE_MAPPING, params->queue_mapping))
+		goto nla_put_failure;
+	if ((params->flags & SKBEDIT_F_MARK) &&
+	    nla_put_u32(skb, TCA_SKBEDIT_MARK, params->mark))
+		goto nla_put_failure;
+	if ((params->flags & SKBEDIT_F_PTYPE) &&
+	    nla_put_u16(skb, TCA_SKBEDIT_PTYPE, params->ptype))
+		goto nla_put_failure;
+	if ((params->flags & SKBEDIT_F_MASK) &&
+	    nla_put_u32(skb, TCA_SKBEDIT_MASK, params->mask))
+		goto nla_put_failure;
+	if (params->flags & SKBEDIT_F_INHERITDSFIELD)
+		pure_flags |= SKBEDIT_F_INHERITDSFIELD;
+	if (params->flags & SKBEDIT_F_TXQ_SKBHASH) {
+		if (nla_put_u16(skb, TCA_SKBEDIT_QUEUE_MAPPING_MAX,
+				params->queue_mapping + params->mapping_mod - 1))
+			goto nla_put_failure;
+
+		pure_flags |= SKBEDIT_F_TXQ_SKBHASH;
+	}
+	if (pure_flags != 0 &&
+	    nla_put(skb, TCA_SKBEDIT_FLAGS, sizeof(pure_flags), &pure_flags))
+		goto nla_put_failure;
+
+	tcf_tm_dump(&t, &d->tcf_tm);
+	if (nla_put_64bit(skb, TCA_SKBEDIT_TM, sizeof(t), &t, TCA_SKBEDIT_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_skbedit_cleanup(struct tc_action *a)
+{
+	struct tcf_skbedit *d = to_skbedit(a);
+	struct tcf_skbedit_params *params;
+
+	params = rcu_dereference_protected(d->params, 1);
+	if (params)
+		kfree_rcu(params, rcu);
+}
+
+static size_t tcf_skbedit_get_fill_size(const struct tc_action *act)
+{
+	return nla_total_size(sizeof(struct tc_skbedit))
+		+ nla_total_size(sizeof(u32)) /* TCA_SKBEDIT_PRIORITY */
+		+ nla_total_size(sizeof(u16)) /* TCA_SKBEDIT_QUEUE_MAPPING */
+		+ nla_total_size(sizeof(u16)) /* TCA_SKBEDIT_QUEUE_MAPPING_MAX */
+		+ nla_total_size(sizeof(u32)) /* TCA_SKBEDIT_MARK */
+		+ nla_total_size(sizeof(u16)) /* TCA_SKBEDIT_PTYPE */
+		+ nla_total_size(sizeof(u32)) /* TCA_SKBEDIT_MASK */
+		+ nla_total_size_64bit(sizeof(u64)); /* TCA_SKBEDIT_FLAGS */
+}
+
+static int tcf_skbedit_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;
+
+		if (is_tcf_skbedit_mark(act)) {
+			entry->id = FLOW_ACTION_MARK;
+			entry->mark = tcf_skbedit_mark(act);
+		} else if (is_tcf_skbedit_ptype(act)) {
+			entry->id = FLOW_ACTION_PTYPE;
+			entry->ptype = tcf_skbedit_ptype(act);
+		} else if (is_tcf_skbedit_priority(act)) {
+			entry->id = FLOW_ACTION_PRIORITY;
+			entry->priority = tcf_skbedit_priority(act);
+		} else if (is_tcf_skbedit_tx_queue_mapping(act)) {
+			NL_SET_ERR_MSG_MOD(extack, "Offload not supported when \"queue_mapping\" option is used on transmit side");
+			return -EOPNOTSUPP;
+		} else if (is_tcf_skbedit_rx_queue_mapping(act)) {
+			entry->id = FLOW_ACTION_RX_QUEUE_MAPPING;
+			entry->rx_queue = tcf_skbedit_rx_queue_mapping(act);
+		} else if (is_tcf_skbedit_inheritdsfield(act)) {
+			NL_SET_ERR_MSG_MOD(extack, "Offload not supported when \"inheritdsfield\" option is used");
+			return -EOPNOTSUPP;
+		} else {
+			NL_SET_ERR_MSG_MOD(extack, "Unsupported skbedit option offload");
+			return -EOPNOTSUPP;
+		}
+		*index_inc = 1;
+	} else {
+		struct flow_offload_action *fl_action = entry_data;
+
+		if (is_tcf_skbedit_mark(act))
+			fl_action->id = FLOW_ACTION_MARK;
+		else if (is_tcf_skbedit_ptype(act))
+			fl_action->id = FLOW_ACTION_PTYPE;
+		else if (is_tcf_skbedit_priority(act))
+			fl_action->id = FLOW_ACTION_PRIORITY;
+		else if (is_tcf_skbedit_rx_queue_mapping(act))
+			fl_action->id = FLOW_ACTION_RX_QUEUE_MAPPING;
+		else
+			return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static struct tc_action_ops act_skbedit_ops = {
+	.kind		=	"skbedit",
+	.id		=	TCA_ID_SKBEDIT,
+	.owner		=	THIS_MODULE,
+	.act		=	tcf_skbedit_act,
+	.stats_update	=	tcf_skbedit_stats_update,
+	.dump		=	tcf_skbedit_dump,
+	.init		=	tcf_skbedit_init,
+	.cleanup	=	tcf_skbedit_cleanup,
+	.get_fill_size	=	tcf_skbedit_get_fill_size,
+	.offload_act_setup =	tcf_skbedit_offload_act_setup,
+	.size		=	sizeof(struct tcf_skbedit),
+};
+MODULE_ALIAS_NET_ACT("skbedit");
+
+static __net_init int skbedit_init_net(struct net *net)
+{
+	struct tc_action_net *tn = net_generic(net, act_skbedit_ops.net_id);
+
+	return tc_action_net_init(net, tn, &act_skbedit_ops);
+}
+
+static void __net_exit skbedit_exit_net(struct list_head *net_list)
+{
+	tc_action_net_exit(net_list, act_skbedit_ops.net_id);
+}
+
+static struct pernet_operations skbedit_net_ops = {
+	.init = skbedit_init_net,
+	.exit_batch = skbedit_exit_net,
+	.id   = &act_skbedit_ops.net_id,
+	.size = sizeof(struct tc_action_net),
+};
+
+MODULE_AUTHOR("Alexander Duyck, <alexander.h.duyck@intel.com>");
+MODULE_DESCRIPTION("SKB Editing");
+MODULE_LICENSE("GPL");
+
+static int __init skbedit_init_module(void)
+{
+	return tcf_register_action(&act_skbedit_ops, &skbedit_net_ops);
+}
+
+static void __exit skbedit_cleanup_module(void)
+{
+	tcf_unregister_action(&act_skbedit_ops, &skbedit_net_ops);
+}
+
+module_init(skbedit_init_module);
+module_exit(skbedit_cleanup_module);