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, 496 insertions, 0 deletions

diff --git a/net/wireless/ibss.c b/net/wireless/ibss.c
new file mode 100644
index 000000000..b1d748bdb
--- /dev/null
+++ b/net/wireless/ibss.c
@@ -0,0 +1,496 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Some IBSS support code for cfg80211.
+ *
+ * Copyright 2009	Johannes Berg <johannes@sipsolutions.net>
+ * Copyright (C) 2020-2026 Intel Corporation
+ */
+
+#include <linux/etherdevice.h>
+#include <linux/if_arp.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <net/cfg80211.h>
+#include "wext-compat.h"
+#include "nl80211.h"
+#include "rdev-ops.h"
+
+
+void __cfg80211_ibss_joined(struct net_device *dev, const u8 *bssid,
+			    struct ieee80211_channel *channel)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct cfg80211_bss *bss;
+#ifdef CONFIG_CFG80211_WEXT
+	union iwreq_data wrqu;
+#endif
+
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_ADHOC))
+		return;
+
+	if (!wdev->u.ibss.ssid_len)
+		return;
+
+	bss = cfg80211_get_bss(wdev->wiphy, channel, bssid, NULL, 0,
+			       IEEE80211_BSS_TYPE_IBSS, IEEE80211_PRIVACY_ANY);
+
+	if (WARN_ON(!bss))
+		return;
+
+	if (wdev->u.ibss.current_bss) {
+		cfg80211_unhold_bss(wdev->u.ibss.current_bss);
+		cfg80211_put_bss(wdev->wiphy, &wdev->u.ibss.current_bss->pub);
+	}
+
+	cfg80211_hold_bss(bss_from_pub(bss));
+	wdev->u.ibss.current_bss = bss_from_pub(bss);
+
+	cfg80211_upload_connect_keys(wdev);
+
+	nl80211_send_ibss_bssid(wiphy_to_rdev(wdev->wiphy), dev, bssid,
+				GFP_KERNEL);
+#ifdef CONFIG_CFG80211_WEXT
+	memset(&wrqu, 0, sizeof(wrqu));
+	memcpy(wrqu.ap_addr.sa_data, bssid, ETH_ALEN);
+	wireless_send_event(dev, SIOCGIWAP, &wrqu, NULL);
+#endif
+}
+
+void cfg80211_ibss_joined(struct net_device *dev, const u8 *bssid,
+			  struct ieee80211_channel *channel, gfp_t gfp)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wdev->wiphy);
+	struct cfg80211_event *ev;
+	unsigned long flags;
+
+	trace_cfg80211_ibss_joined(dev, bssid, channel);
+
+	if (WARN_ON(!channel))
+		return;
+
+	ev = kzalloc_obj(*ev, gfp);
+	if (!ev)
+		return;
+
+	ev->type = EVENT_IBSS_JOINED;
+	memcpy(ev->ij.bssid, bssid, ETH_ALEN);
+	ev->ij.channel = channel;
+
+	spin_lock_irqsave(&wdev->event_lock, flags);
+	list_add_tail(&ev->list, &wdev->event_list);
+	spin_unlock_irqrestore(&wdev->event_lock, flags);
+	queue_work(cfg80211_wq, &rdev->event_work);
+}
+EXPORT_SYMBOL(cfg80211_ibss_joined);
+
+int __cfg80211_join_ibss(struct cfg80211_registered_device *rdev,
+			 struct net_device *dev,
+			 struct cfg80211_ibss_params *params,
+			 struct cfg80211_cached_keys *connkeys)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	int err;
+
+	lockdep_assert_held(&rdev->wiphy.mtx);
+
+	if (wdev->links[0].cac_started)
+		return -EBUSY;
+
+	if (wdev->u.ibss.ssid_len)
+		return -EALREADY;
+
+	if (!params->basic_rates) {
+		/*
+		* If no rates were explicitly configured,
+		* use the mandatory rate set for 11b or
+		* 11a for maximum compatibility.
+		*/
+		struct ieee80211_supported_band *sband;
+		enum nl80211_band band;
+		u32 flag;
+		int j;
+
+		band = params->chandef.chan->band;
+		if (band == NL80211_BAND_5GHZ ||
+		    band == NL80211_BAND_6GHZ)
+			flag = IEEE80211_RATE_MANDATORY_A;
+		else
+			flag = IEEE80211_RATE_MANDATORY_B;
+
+		sband = rdev->wiphy.bands[band];
+		for (j = 0; j < sband->n_bitrates; j++) {
+			if (sband->bitrates[j].flags & flag)
+				params->basic_rates |= BIT(j);
+		}
+	}
+
+	if (WARN_ON(connkeys && connkeys->def < 0))
+		return -EINVAL;
+
+	if (WARN_ON(wdev->connect_keys))
+		kfree_sensitive(wdev->connect_keys);
+	wdev->connect_keys = connkeys;
+
+	wdev->u.ibss.chandef = params->chandef;
+	if (connkeys) {
+		params->wep_keys = connkeys->params;
+		params->wep_tx_key = connkeys->def;
+	}
+
+#ifdef CONFIG_CFG80211_WEXT
+	wdev->wext.ibss.chandef = params->chandef;
+#endif
+	err = rdev_join_ibss(rdev, dev, params);
+	if (err) {
+		wdev->connect_keys = NULL;
+		return err;
+	}
+
+	memcpy(wdev->u.ibss.ssid, params->ssid, params->ssid_len);
+	wdev->u.ibss.ssid_len = params->ssid_len;
+
+	return 0;
+}
+
+void cfg80211_clear_ibss(struct net_device *dev, bool nowext)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wdev->wiphy);
+	int i;
+
+	lockdep_assert_wiphy(wdev->wiphy);
+
+	kfree_sensitive(wdev->connect_keys);
+	wdev->connect_keys = NULL;
+
+	rdev_set_qos_map(rdev, dev, NULL);
+
+	/*
+	 * Delete all the keys ... pairwise keys can't really
+	 * exist any more anyway, but default keys might.
+	 */
+	if (rdev->ops->del_key)
+		for (i = 0; i < 6; i++)
+			rdev_del_key(rdev, wdev, -1, i, false, NULL);
+
+	if (wdev->u.ibss.current_bss) {
+		cfg80211_unhold_bss(wdev->u.ibss.current_bss);
+		cfg80211_put_bss(wdev->wiphy, &wdev->u.ibss.current_bss->pub);
+	}
+
+	wdev->u.ibss.current_bss = NULL;
+	wdev->u.ibss.ssid_len = 0;
+	memset(&wdev->u.ibss.chandef, 0, sizeof(wdev->u.ibss.chandef));
+#ifdef CONFIG_CFG80211_WEXT
+	if (!nowext)
+		wdev->wext.ibss.ssid_len = 0;
+#endif
+	cfg80211_sched_dfs_chan_update(rdev);
+}
+
+int cfg80211_leave_ibss(struct cfg80211_registered_device *rdev,
+			struct net_device *dev, bool nowext)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	int err;
+
+	lockdep_assert_wiphy(wdev->wiphy);
+
+	if (!wdev->u.ibss.ssid_len)
+		return -ENOLINK;
+
+	err = rdev_leave_ibss(rdev, dev);
+
+	if (err)
+		return err;
+
+	wdev->conn_owner_nlportid = 0;
+	cfg80211_clear_ibss(dev, nowext);
+
+	return 0;
+}
+
+#ifdef CONFIG_CFG80211_WEXT
+int cfg80211_ibss_wext_join(struct cfg80211_registered_device *rdev,
+			    struct wireless_dev *wdev)
+{
+	struct cfg80211_cached_keys *ck = NULL;
+	enum nl80211_band band;
+	int i, err;
+
+	lockdep_assert_wiphy(wdev->wiphy);
+
+	if (!wdev->wext.ibss.beacon_interval)
+		wdev->wext.ibss.beacon_interval = 100;
+
+	/* try to find an IBSS channel if none requested ... */
+	if (!wdev->wext.ibss.chandef.chan) {
+		struct ieee80211_channel *new_chan = NULL;
+
+		for (band = 0; band < NUM_NL80211_BANDS; band++) {
+			struct ieee80211_supported_band *sband;
+			struct ieee80211_channel *chan;
+
+			sband = rdev->wiphy.bands[band];
+			if (!sband)
+				continue;
+
+			for (i = 0; i < sband->n_channels; i++) {
+				chan = &sband->channels[i];
+				if (chan->flags & IEEE80211_CHAN_NO_IR)
+					continue;
+				if (chan->flags & IEEE80211_CHAN_DISABLED)
+					continue;
+				new_chan = chan;
+				break;
+			}
+
+			if (new_chan)
+				break;
+		}
+
+		if (!new_chan)
+			return -EINVAL;
+
+		cfg80211_chandef_create(&wdev->wext.ibss.chandef, new_chan,
+					NL80211_CHAN_NO_HT);
+	}
+
+	/* don't join -- SSID is not there */
+	if (!wdev->wext.ibss.ssid_len)
+		return 0;
+
+	if (!netif_running(wdev->netdev))
+		return 0;
+
+	if (wdev->wext.keys)
+		wdev->wext.keys->def = wdev->wext.default_key;
+
+	wdev->wext.ibss.privacy = wdev->wext.default_key != -1;
+
+	if (wdev->wext.keys && wdev->wext.keys->def != -1) {
+		ck = kmemdup(wdev->wext.keys, sizeof(*ck), GFP_KERNEL);
+		if (!ck)
+			return -ENOMEM;
+		for (i = 0; i < 4; i++)
+			ck->params[i].key = ck->data[i];
+	}
+	err = __cfg80211_join_ibss(rdev, wdev->netdev,
+				   &wdev->wext.ibss, ck);
+	if (err)
+		kfree(ck);
+
+	return err;
+}
+
+int cfg80211_ibss_wext_siwfreq(struct net_device *dev,
+			       struct iw_request_info *info,
+			       struct iw_freq *wextfreq, char *extra)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wdev->wiphy);
+	struct ieee80211_channel *chan = NULL;
+	int err, freq;
+
+	/* call only for ibss! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_ADHOC))
+		return -EINVAL;
+
+	if (!rdev->ops->join_ibss)
+		return -EOPNOTSUPP;
+
+	freq = cfg80211_wext_freq(wextfreq);
+	if (freq < 0)
+		return freq;
+
+	if (freq) {
+		chan = ieee80211_get_channel(wdev->wiphy, freq);
+		if (!chan)
+			return -EINVAL;
+		if (chan->flags & IEEE80211_CHAN_NO_IR ||
+		    chan->flags & IEEE80211_CHAN_DISABLED)
+			return -EINVAL;
+	}
+
+	if (wdev->wext.ibss.chandef.chan == chan)
+		return 0;
+
+	err = 0;
+	if (wdev->u.ibss.ssid_len)
+		err = cfg80211_leave_ibss(rdev, dev, true);
+
+	if (err)
+		return err;
+
+	if (chan) {
+		cfg80211_chandef_create(&wdev->wext.ibss.chandef, chan,
+					NL80211_CHAN_NO_HT);
+		wdev->wext.ibss.channel_fixed = true;
+	} else {
+		/* cfg80211_ibss_wext_join will pick one if needed */
+		wdev->wext.ibss.channel_fixed = false;
+	}
+
+	return cfg80211_ibss_wext_join(rdev, wdev);
+}
+
+int cfg80211_ibss_wext_giwfreq(struct net_device *dev,
+			       struct iw_request_info *info,
+			       struct iw_freq *freq, char *extra)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct ieee80211_channel *chan = NULL;
+
+	/* call only for ibss! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_ADHOC))
+		return -EINVAL;
+
+	if (wdev->u.ibss.current_bss)
+		chan = wdev->u.ibss.current_bss->pub.channel;
+	else if (wdev->wext.ibss.chandef.chan)
+		chan = wdev->wext.ibss.chandef.chan;
+
+	if (chan) {
+		freq->m = chan->center_freq;
+		freq->e = 6;
+		return 0;
+	}
+
+	/* no channel if not joining */
+	return -EINVAL;
+}
+
+int cfg80211_ibss_wext_siwessid(struct net_device *dev,
+				struct iw_request_info *info,
+				struct iw_point *data, char *ssid)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wdev->wiphy);
+	size_t len = data->length;
+	int err;
+
+	/* call only for ibss! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_ADHOC))
+		return -EINVAL;
+
+	if (!rdev->ops->join_ibss)
+		return -EOPNOTSUPP;
+
+	err = 0;
+	if (wdev->u.ibss.ssid_len)
+		err = cfg80211_leave_ibss(rdev, dev, true);
+
+	if (err)
+		return err;
+
+	/* iwconfig uses nul termination in SSID.. */
+	if (len > 0 && ssid[len - 1] == '\0')
+		len--;
+
+	memcpy(wdev->u.ibss.ssid, ssid, len);
+	wdev->wext.ibss.ssid = wdev->u.ibss.ssid;
+	wdev->wext.ibss.ssid_len = len;
+
+	return cfg80211_ibss_wext_join(rdev, wdev);
+}
+
+int cfg80211_ibss_wext_giwessid(struct net_device *dev,
+				struct iw_request_info *info,
+				struct iw_point *data, char *ssid)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+
+	/* call only for ibss! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_ADHOC))
+		return -EINVAL;
+
+	data->flags = 0;
+
+	if (wdev->u.ibss.ssid_len) {
+		data->flags = 1;
+		data->length = wdev->u.ibss.ssid_len;
+		memcpy(ssid, wdev->u.ibss.ssid, data->length);
+	} else if (wdev->wext.ibss.ssid && wdev->wext.ibss.ssid_len) {
+		data->flags = 1;
+		data->length = wdev->wext.ibss.ssid_len;
+		memcpy(ssid, wdev->wext.ibss.ssid, data->length);
+	}
+
+	return 0;
+}
+
+int cfg80211_ibss_wext_siwap(struct net_device *dev,
+			     struct iw_request_info *info,
+			     struct sockaddr *ap_addr, char *extra)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wdev->wiphy);
+	u8 *bssid = ap_addr->sa_data;
+	int err;
+
+	/* call only for ibss! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_ADHOC))
+		return -EINVAL;
+
+	if (!rdev->ops->join_ibss)
+		return -EOPNOTSUPP;
+
+	if (ap_addr->sa_family != ARPHRD_ETHER)
+		return -EINVAL;
+
+	/* automatic mode */
+	if (is_zero_ether_addr(bssid) || is_broadcast_ether_addr(bssid))
+		bssid = NULL;
+
+	if (bssid && !is_valid_ether_addr(bssid))
+		return -EINVAL;
+
+	/* both automatic */
+	if (!bssid && !wdev->wext.ibss.bssid)
+		return 0;
+
+	/* fixed already - and no change */
+	if (wdev->wext.ibss.bssid && bssid &&
+	    ether_addr_equal(bssid, wdev->wext.ibss.bssid))
+		return 0;
+
+	err = 0;
+	if (wdev->u.ibss.ssid_len)
+		err = cfg80211_leave_ibss(rdev, dev, true);
+
+	if (err)
+		return err;
+
+	if (bssid) {
+		memcpy(wdev->wext.bssid, bssid, ETH_ALEN);
+		wdev->wext.ibss.bssid = wdev->wext.bssid;
+	} else
+		wdev->wext.ibss.bssid = NULL;
+
+	return cfg80211_ibss_wext_join(rdev, wdev);
+}
+
+int cfg80211_ibss_wext_giwap(struct net_device *dev,
+			     struct iw_request_info *info,
+			     struct sockaddr *ap_addr, char *extra)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+
+	/* call only for ibss! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_ADHOC))
+		return -EINVAL;
+
+	ap_addr->sa_family = ARPHRD_ETHER;
+
+	if (wdev->u.ibss.current_bss)
+		memcpy(ap_addr->sa_data, wdev->u.ibss.current_bss->pub.bssid,
+		       ETH_ALEN);
+	else if (wdev->wext.ibss.bssid)
+		memcpy(ap_addr->sa_data, wdev->wext.ibss.bssid, ETH_ALEN);
+	else
+		eth_zero_addr(ap_addr->sa_data);
+
+	return 0;
+}
+#endif