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, 517 insertions, 0 deletions

diff --git a/net/sched/sch_etf.c b/net/sched/sch_etf.c
new file mode 100644
index 000000000..ada87a81d
--- /dev/null
+++ b/net/sched/sch_etf.c
@@ -0,0 +1,517 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/* net/sched/sch_etf.c  Earliest TxTime First queueing discipline.
+ *
+ * Authors:	Jesus Sanchez-Palencia <jesus.sanchez-palencia@intel.com>
+ *		Vinicius Costa Gomes <vinicius.gomes@intel.com>
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/errqueue.h>
+#include <linux/rbtree.h>
+#include <linux/skbuff.h>
+#include <linux/posix-timers.h>
+#include <net/netlink.h>
+#include <net/sch_generic.h>
+#include <net/pkt_sched.h>
+#include <net/sock.h>
+
+#define DEADLINE_MODE_IS_ON(x) ((x)->flags & TC_ETF_DEADLINE_MODE_ON)
+#define OFFLOAD_IS_ON(x) ((x)->flags & TC_ETF_OFFLOAD_ON)
+#define SKIP_SOCK_CHECK_IS_SET(x) ((x)->flags & TC_ETF_SKIP_SOCK_CHECK)
+
+struct etf_sched_data {
+	bool offload;
+	bool deadline_mode;
+	bool skip_sock_check;
+	int clockid;
+	int queue;
+	s32 delta; /* in ns */
+	ktime_t last; /* The txtime of the last skb sent to the netdevice. */
+	struct rb_root_cached head;
+	struct qdisc_watchdog watchdog;
+	ktime_t (*get_time)(void);
+};
+
+static const struct nla_policy etf_policy[TCA_ETF_MAX + 1] = {
+	[TCA_ETF_PARMS]	= { .len = sizeof(struct tc_etf_qopt) },
+};
+
+static inline int validate_input_params(struct tc_etf_qopt *qopt,
+					struct netlink_ext_ack *extack)
+{
+	/* Check if params comply to the following rules:
+	 *	* Clockid and delta must be valid.
+	 *
+	 *	* Dynamic clockids are not supported.
+	 *
+	 *	* Delta must be a positive integer.
+	 *
+	 * Also note that for the HW offload case, we must
+	 * expect that system clocks have been synchronized to PHC.
+	 */
+	if (qopt->clockid < 0) {
+		NL_SET_ERR_MSG(extack, "Dynamic clockids are not supported");
+		return -ENOTSUPP;
+	}
+
+	if (qopt->clockid != CLOCK_TAI) {
+		NL_SET_ERR_MSG(extack, "Invalid clockid. CLOCK_TAI must be used");
+		return -EINVAL;
+	}
+
+	if (qopt->delta < 0) {
+		NL_SET_ERR_MSG(extack, "Delta must be positive");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static bool is_packet_valid(struct Qdisc *sch, struct sk_buff *nskb)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	ktime_t txtime = nskb->tstamp;
+	struct sock *sk = nskb->sk;
+	ktime_t now;
+
+	if (q->skip_sock_check)
+		goto skip;
+
+	if (!sk || !sk_fullsock(sk))
+		return false;
+
+	if (!sock_flag(sk, SOCK_TXTIME))
+		return false;
+
+	/* We don't perform crosstimestamping.
+	 * Drop if packet's clockid differs from qdisc's.
+	 */
+	if (sk->sk_clockid != q->clockid)
+		return false;
+
+	if (sk->sk_txtime_deadline_mode != q->deadline_mode)
+		return false;
+
+skip:
+	now = q->get_time();
+	if (ktime_before(txtime, now) || ktime_before(txtime, q->last))
+		return false;
+
+	return true;
+}
+
+static struct sk_buff *etf_peek_timesortedlist(struct Qdisc *sch)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	struct rb_node *p;
+
+	p = rb_first_cached(&q->head);
+	if (!p)
+		return NULL;
+
+	return rb_to_skb(p);
+}
+
+static void reset_watchdog(struct Qdisc *sch)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	struct sk_buff *skb = etf_peek_timesortedlist(sch);
+	ktime_t next;
+
+	if (!skb) {
+		qdisc_watchdog_cancel(&q->watchdog);
+		return;
+	}
+
+	next = ktime_sub_ns(skb->tstamp, q->delta);
+	qdisc_watchdog_schedule_ns(&q->watchdog, ktime_to_ns(next));
+}
+
+static void report_sock_error(struct sk_buff *skb, u32 err, u8 code)
+{
+	struct sock_exterr_skb *serr;
+	struct sk_buff *clone;
+	ktime_t txtime = skb->tstamp;
+	struct sock *sk = skb->sk;
+
+	if (!sk || !sk_fullsock(sk) || !(sk->sk_txtime_report_errors))
+		return;
+
+	clone = skb_clone(skb, GFP_ATOMIC);
+	if (!clone)
+		return;
+
+	serr = SKB_EXT_ERR(clone);
+	serr->ee.ee_errno = err;
+	serr->ee.ee_origin = SO_EE_ORIGIN_TXTIME;
+	serr->ee.ee_type = 0;
+	serr->ee.ee_code = code;
+	serr->ee.ee_pad = 0;
+	serr->ee.ee_data = (txtime >> 32); /* high part of tstamp */
+	serr->ee.ee_info = txtime; /* low part of tstamp */
+
+	if (sock_queue_err_skb(sk, clone))
+		kfree_skb(clone);
+}
+
+static int etf_enqueue_timesortedlist(struct sk_buff *nskb, struct Qdisc *sch,
+				      struct sk_buff **to_free)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	struct rb_node **p = &q->head.rb_root.rb_node, *parent = NULL;
+	ktime_t txtime = nskb->tstamp;
+	bool leftmost = true;
+
+	if (!is_packet_valid(sch, nskb)) {
+		report_sock_error(nskb, EINVAL,
+				  SO_EE_CODE_TXTIME_INVALID_PARAM);
+		return qdisc_drop(nskb, sch, to_free);
+	}
+
+	while (*p) {
+		struct sk_buff *skb;
+
+		parent = *p;
+		skb = rb_to_skb(parent);
+		if (ktime_compare(txtime, skb->tstamp) >= 0) {
+			p = &parent->rb_right;
+			leftmost = false;
+		} else {
+			p = &parent->rb_left;
+		}
+	}
+	rb_link_node(&nskb->rbnode, parent, p);
+	rb_insert_color_cached(&nskb->rbnode, &q->head, leftmost);
+
+	qdisc_qstats_backlog_inc(sch, nskb);
+	qdisc_qlen_inc(sch);
+
+	/* Now we may need to re-arm the qdisc watchdog for the next packet. */
+	reset_watchdog(sch);
+
+	return NET_XMIT_SUCCESS;
+}
+
+static void timesortedlist_drop(struct Qdisc *sch, struct sk_buff *skb,
+				ktime_t now)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	struct sk_buff *to_free = NULL;
+	struct sk_buff *tmp = NULL;
+
+	skb_rbtree_walk_from_safe(skb, tmp) {
+		if (ktime_after(skb->tstamp, now))
+			break;
+
+		rb_erase_cached(&skb->rbnode, &q->head);
+
+		/* The rbnode field in the skb re-uses these fields, now that
+		 * we are done with the rbnode, reset them.
+		 */
+		skb->next = NULL;
+		skb->prev = NULL;
+		skb->dev = qdisc_dev(sch);
+
+		report_sock_error(skb, ECANCELED, SO_EE_CODE_TXTIME_MISSED);
+
+		qdisc_qstats_backlog_dec(sch, skb);
+		qdisc_drop(skb, sch, &to_free);
+		qdisc_qstats_overlimit(sch);
+		qdisc_qlen_dec(sch);
+	}
+
+	kfree_skb_list(to_free);
+}
+
+static void timesortedlist_remove(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+
+	rb_erase_cached(&skb->rbnode, &q->head);
+
+	/* The rbnode field in the skb re-uses these fields, now that
+	 * we are done with the rbnode, reset them.
+	 */
+	skb->next = NULL;
+	skb->prev = NULL;
+	skb->dev = qdisc_dev(sch);
+
+	qdisc_qstats_backlog_dec(sch, skb);
+
+	qdisc_bstats_update(sch, skb);
+
+	q->last = skb->tstamp;
+
+	qdisc_qlen_dec(sch);
+}
+
+static struct sk_buff *etf_dequeue_timesortedlist(struct Qdisc *sch)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	struct sk_buff *skb;
+	ktime_t now, next;
+
+	skb = etf_peek_timesortedlist(sch);
+	if (!skb)
+		return NULL;
+
+	now = q->get_time();
+
+	/* Drop if packet has expired while in queue. */
+	if (ktime_before(skb->tstamp, now)) {
+		timesortedlist_drop(sch, skb, now);
+		skb = NULL;
+		goto out;
+	}
+
+	/* When in deadline mode, dequeue as soon as possible and change the
+	 * txtime from deadline to (now + delta).
+	 */
+	if (q->deadline_mode) {
+		timesortedlist_remove(sch, skb);
+		skb->tstamp = now;
+		goto out;
+	}
+
+	next = ktime_sub_ns(skb->tstamp, q->delta);
+
+	/* Dequeue only if now is within the [txtime - delta, txtime] range. */
+	if (ktime_after(now, next))
+		timesortedlist_remove(sch, skb);
+	else
+		skb = NULL;
+
+out:
+	/* Now we may need to re-arm the qdisc watchdog for the next packet. */
+	reset_watchdog(sch);
+
+	return skb;
+}
+
+static void etf_disable_offload(struct net_device *dev,
+				struct etf_sched_data *q)
+{
+	struct tc_etf_qopt_offload etf = { };
+	const struct net_device_ops *ops;
+	int err;
+
+	if (!q->offload)
+		return;
+
+	ops = dev->netdev_ops;
+	if (!ops->ndo_setup_tc)
+		return;
+
+	etf.queue = q->queue;
+	etf.enable = 0;
+
+	err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_ETF, &etf);
+	if (err < 0)
+		pr_warn("Couldn't disable ETF offload for queue %d\n",
+			etf.queue);
+}
+
+static int etf_enable_offload(struct net_device *dev, struct etf_sched_data *q,
+			      struct netlink_ext_ack *extack)
+{
+	const struct net_device_ops *ops = dev->netdev_ops;
+	struct tc_etf_qopt_offload etf = { };
+	int err;
+
+	if (!ops->ndo_setup_tc) {
+		NL_SET_ERR_MSG(extack, "Specified device does not support ETF offload");
+		return -EOPNOTSUPP;
+	}
+
+	etf.queue = q->queue;
+	etf.enable = 1;
+
+	err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_ETF, &etf);
+	if (err < 0) {
+		NL_SET_ERR_MSG(extack, "Specified device failed to setup ETF hardware offload");
+		return err;
+	}
+
+	return 0;
+}
+
+static int etf_init(struct Qdisc *sch, struct nlattr *opt,
+		    struct netlink_ext_ack *extack)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	struct net_device *dev = qdisc_dev(sch);
+	struct nlattr *tb[TCA_ETF_MAX + 1];
+	struct tc_etf_qopt *qopt;
+	int err;
+
+	if (!opt) {
+		NL_SET_ERR_MSG(extack,
+			       "Missing ETF qdisc options which are mandatory");
+		return -EINVAL;
+	}
+
+	err = nla_parse_nested_deprecated(tb, TCA_ETF_MAX, opt, etf_policy,
+					  extack);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_ETF_PARMS]) {
+		NL_SET_ERR_MSG(extack, "Missing mandatory ETF parameters");
+		return -EINVAL;
+	}
+
+	qopt = nla_data(tb[TCA_ETF_PARMS]);
+
+	pr_debug("delta %d clockid %d offload %s deadline %s\n",
+		 qopt->delta, qopt->clockid,
+		 OFFLOAD_IS_ON(qopt) ? "on" : "off",
+		 DEADLINE_MODE_IS_ON(qopt) ? "on" : "off");
+
+	err = validate_input_params(qopt, extack);
+	if (err < 0)
+		return err;
+
+	q->queue = sch->dev_queue - netdev_get_tx_queue(dev, 0);
+
+	if (OFFLOAD_IS_ON(qopt)) {
+		err = etf_enable_offload(dev, q, extack);
+		if (err < 0)
+			return err;
+	}
+
+	/* Everything went OK, save the parameters used. */
+	q->delta = qopt->delta;
+	q->clockid = qopt->clockid;
+	q->offload = OFFLOAD_IS_ON(qopt);
+	q->deadline_mode = DEADLINE_MODE_IS_ON(qopt);
+	q->skip_sock_check = SKIP_SOCK_CHECK_IS_SET(qopt);
+
+	switch (q->clockid) {
+	case CLOCK_REALTIME:
+		q->get_time = ktime_get_real;
+		break;
+	case CLOCK_MONOTONIC:
+		q->get_time = ktime_get;
+		break;
+	case CLOCK_BOOTTIME:
+		q->get_time = ktime_get_boottime;
+		break;
+	case CLOCK_TAI:
+		q->get_time = ktime_get_clocktai;
+		break;
+	default:
+		NL_SET_ERR_MSG(extack, "Clockid is not supported");
+		return -ENOTSUPP;
+	}
+
+	qdisc_watchdog_init_clockid(&q->watchdog, sch, q->clockid);
+
+	return 0;
+}
+
+static void timesortedlist_clear(struct Qdisc *sch)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	struct rb_node *p = rb_first_cached(&q->head);
+
+	while (p) {
+		struct sk_buff *skb = rb_to_skb(p);
+
+		p = rb_next(p);
+
+		rb_erase_cached(&skb->rbnode, &q->head);
+		rtnl_kfree_skbs(skb, skb);
+		qdisc_qlen_dec(sch);
+	}
+}
+
+static void etf_reset(struct Qdisc *sch)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+
+	/* Only cancel watchdog if it's been initialized. */
+	if (q->watchdog.qdisc == sch)
+		qdisc_watchdog_cancel(&q->watchdog);
+
+	/* No matter which mode we are on, it's safe to clear both lists. */
+	timesortedlist_clear(sch);
+	__qdisc_reset_queue(&sch->q);
+
+	q->last = 0;
+}
+
+static void etf_destroy(struct Qdisc *sch)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	struct net_device *dev = qdisc_dev(sch);
+
+	/* Only cancel watchdog if it's been initialized. */
+	if (q->watchdog.qdisc == sch)
+		qdisc_watchdog_cancel(&q->watchdog);
+
+	etf_disable_offload(dev, q);
+}
+
+static int etf_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct etf_sched_data *q = qdisc_priv(sch);
+	struct tc_etf_qopt opt = { };
+	struct nlattr *nest;
+
+	nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
+	if (!nest)
+		goto nla_put_failure;
+
+	opt.delta = READ_ONCE(q->delta);
+	opt.clockid = READ_ONCE(q->clockid);
+	if (READ_ONCE(q->offload))
+		opt.flags |= TC_ETF_OFFLOAD_ON;
+
+	if (READ_ONCE(q->deadline_mode))
+		opt.flags |= TC_ETF_DEADLINE_MODE_ON;
+
+	if (READ_ONCE(q->skip_sock_check))
+		opt.flags |= TC_ETF_SKIP_SOCK_CHECK;
+
+	if (nla_put(skb, TCA_ETF_PARMS, sizeof(opt), &opt))
+		goto nla_put_failure;
+
+	return nla_nest_end(skb, nest);
+
+nla_put_failure:
+	nla_nest_cancel(skb, nest);
+	return -1;
+}
+
+static struct Qdisc_ops etf_qdisc_ops __read_mostly = {
+	.id		=	"etf",
+	.priv_size	=	sizeof(struct etf_sched_data),
+	.enqueue	=	etf_enqueue_timesortedlist,
+	.dequeue	=	etf_dequeue_timesortedlist,
+	.peek		=	etf_peek_timesortedlist,
+	.init		=	etf_init,
+	.reset		=	etf_reset,
+	.destroy	=	etf_destroy,
+	.dump		=	etf_dump,
+	.owner		=	THIS_MODULE,
+};
+MODULE_ALIAS_NET_SCH("etf");
+
+static int __init etf_module_init(void)
+{
+	return register_qdisc(&etf_qdisc_ops);
+}
+
+static void __exit etf_module_exit(void)
+{
+	unregister_qdisc(&etf_qdisc_ops);
+}
+module_init(etf_module_init)
+module_exit(etf_module_exit)
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Earliest TxTime First (ETF) qdisc");