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, 378 insertions, 0 deletions

diff --git a/net/wireless/wext-sme.c b/net/wireless/wext-sme.c
new file mode 100644
index 000000000..b5914f365
--- /dev/null
+++ b/net/wireless/wext-sme.c
@@ -0,0 +1,378 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * cfg80211 wext compat for managed mode.
+ *
+ * Copyright 2009	Johannes Berg <johannes@sipsolutions.net>
+ * Copyright (C) 2009, 2020-2023 Intel Corporation
+ */
+
+#include <linux/export.h>
+#include <linux/etherdevice.h>
+#include <linux/if_arp.h>
+#include <linux/slab.h>
+#include <net/cfg80211.h>
+#include <net/cfg80211-wext.h>
+#include "wext-compat.h"
+#include "nl80211.h"
+
+int cfg80211_mgd_wext_connect(struct cfg80211_registered_device *rdev,
+			      struct wireless_dev *wdev)
+{
+	struct cfg80211_cached_keys *ck = NULL;
+	const u8 *prev_bssid = NULL;
+	int err, i;
+
+	ASSERT_RTNL();
+	lockdep_assert_wiphy(wdev->wiphy);
+
+	if (!netif_running(wdev->netdev))
+		return 0;
+
+	wdev->wext.connect.ie = wdev->wext.ie;
+	wdev->wext.connect.ie_len = wdev->wext.ie_len;
+
+	/* Use default background scan period */
+	wdev->wext.connect.bg_scan_period = -1;
+
+	if (wdev->wext.keys) {
+		wdev->wext.keys->def = wdev->wext.default_key;
+		if (wdev->wext.default_key != -1)
+			wdev->wext.connect.privacy = true;
+	}
+
+	if (!wdev->wext.connect.ssid_len)
+		return 0;
+
+	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];
+	}
+
+	if (wdev->wext.prev_bssid_valid)
+		prev_bssid = wdev->wext.prev_bssid;
+
+	err = cfg80211_connect(rdev, wdev->netdev,
+			       &wdev->wext.connect, ck, prev_bssid);
+	if (err)
+		kfree_sensitive(ck);
+
+	return err;
+}
+
+int cfg80211_mgd_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 station! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_STATION))
+		return -EINVAL;
+
+	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_DISABLED)
+			return -EINVAL;
+	}
+
+	if (wdev->conn) {
+		bool event = true;
+
+		if (wdev->wext.connect.channel == chan)
+			return 0;
+
+		/* if SSID set, we'll try right again, avoid event */
+		if (wdev->wext.connect.ssid_len)
+			event = false;
+		err = cfg80211_disconnect(rdev, dev,
+					  WLAN_REASON_DEAUTH_LEAVING, event);
+		if (err)
+			return err;
+	}
+
+	wdev->wext.connect.channel = chan;
+	return cfg80211_mgd_wext_connect(rdev, wdev);
+}
+
+int cfg80211_mgd_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 station! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_STATION))
+		return -EINVAL;
+
+	if (wdev->valid_links)
+		return -EOPNOTSUPP;
+
+	if (wdev->links[0].client.current_bss)
+		chan = wdev->links[0].client.current_bss->pub.channel;
+	else if (wdev->wext.connect.channel)
+		chan = wdev->wext.connect.channel;
+
+	if (chan) {
+		freq->m = chan->center_freq;
+		freq->e = 6;
+		return 0;
+	}
+
+	/* no channel if not joining */
+	return -EINVAL;
+}
+
+int cfg80211_mgd_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 station! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_STATION))
+		return -EINVAL;
+
+	if (!data->flags)
+		len = 0;
+
+	/* iwconfig uses nul termination in SSID.. */
+	if (len > 0 && ssid[len - 1] == '\0')
+		len--;
+
+	if (wdev->conn) {
+		bool event = true;
+
+		if (wdev->wext.connect.ssid && len &&
+		    len == wdev->wext.connect.ssid_len &&
+		    memcmp(wdev->wext.connect.ssid, ssid, len) == 0)
+			return 0;
+
+		/* if SSID set now, we'll try to connect, avoid event */
+		if (len)
+			event = false;
+		err = cfg80211_disconnect(rdev, dev,
+					  WLAN_REASON_DEAUTH_LEAVING, event);
+		if (err)
+			return err;
+	}
+
+	wdev->wext.prev_bssid_valid = false;
+	wdev->wext.connect.ssid = wdev->wext.ssid;
+	memcpy(wdev->wext.ssid, ssid, len);
+	wdev->wext.connect.ssid_len = len;
+
+	wdev->wext.connect.crypto.control_port = false;
+	wdev->wext.connect.crypto.control_port_ethertype =
+					cpu_to_be16(ETH_P_PAE);
+
+	return cfg80211_mgd_wext_connect(rdev, wdev);
+}
+
+int cfg80211_mgd_wext_giwessid(struct net_device *dev,
+			       struct iw_request_info *info,
+			       struct iw_point *data, char *ssid)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	int ret = 0;
+
+	/* call only for station! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_STATION))
+		return -EINVAL;
+
+	if (wdev->valid_links)
+		return -EINVAL;
+
+	data->flags = 0;
+
+	if (wdev->links[0].client.current_bss) {
+		const struct element *ssid_elem;
+
+		rcu_read_lock();
+		ssid_elem = ieee80211_bss_get_elem(
+				&wdev->links[0].client.current_bss->pub,
+				WLAN_EID_SSID);
+		if (ssid_elem) {
+			data->flags = 1;
+			data->length = ssid_elem->datalen;
+			if (data->length > IW_ESSID_MAX_SIZE)
+				ret = -EINVAL;
+			else
+				memcpy(ssid, ssid_elem->data, data->length);
+		}
+		rcu_read_unlock();
+	} else if (wdev->wext.connect.ssid && wdev->wext.connect.ssid_len) {
+		data->flags = 1;
+		data->length = wdev->wext.connect.ssid_len;
+		memcpy(ssid, wdev->wext.connect.ssid, data->length);
+	}
+
+	return ret;
+}
+
+int cfg80211_mgd_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 station! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_STATION))
+		return -EINVAL;
+
+	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 (wdev->conn) {
+		/* both automatic */
+		if (!bssid && !wdev->wext.connect.bssid)
+			return 0;
+
+		/* fixed already - and no change */
+		if (wdev->wext.connect.bssid && bssid &&
+		    ether_addr_equal(bssid, wdev->wext.connect.bssid))
+			return 0;
+
+		err = cfg80211_disconnect(rdev, dev,
+					  WLAN_REASON_DEAUTH_LEAVING, false);
+		if (err)
+			return err;
+	}
+
+	if (bssid) {
+		memcpy(wdev->wext.bssid, bssid, ETH_ALEN);
+		wdev->wext.connect.bssid = wdev->wext.bssid;
+	} else
+		wdev->wext.connect.bssid = NULL;
+
+	return cfg80211_mgd_wext_connect(rdev, wdev);
+}
+
+int cfg80211_mgd_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 station! */
+	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_STATION))
+		return -EINVAL;
+
+	ap_addr->sa_family = ARPHRD_ETHER;
+
+	if (wdev->valid_links)
+		return -EOPNOTSUPP;
+
+	if (wdev->links[0].client.current_bss)
+		memcpy(ap_addr->sa_data,
+		       wdev->links[0].client.current_bss->pub.bssid,
+		       ETH_ALEN);
+	else
+		eth_zero_addr(ap_addr->sa_data);
+
+	return 0;
+}
+
+int cfg80211_wext_siwgenie(struct net_device *dev,
+			   struct iw_request_info *info,
+			   union iwreq_data *wrqu, char *extra)
+{
+	struct iw_point *data = &wrqu->data;
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct cfg80211_registered_device *rdev = wiphy_to_rdev(wdev->wiphy);
+	int ie_len = data->length;
+	u8 *ie = extra;
+
+	if (wdev->iftype != NL80211_IFTYPE_STATION)
+		return -EOPNOTSUPP;
+
+	if (!ie_len)
+		ie = NULL;
+
+	guard(wiphy)(wdev->wiphy);
+
+	/* no change */
+	if (wdev->wext.ie_len == ie_len &&
+	    memcmp(wdev->wext.ie, ie, ie_len) == 0)
+		return 0;
+
+	if (ie_len) {
+		const struct element *elem;
+
+		for_each_element(elem, extra, ie_len) {
+			/* nothing */
+		}
+
+		if (!for_each_element_completed(elem, extra, ie_len))
+			return -EINVAL;
+
+		ie = kmemdup(extra, ie_len, GFP_KERNEL);
+		if (!ie)
+			return -ENOMEM;
+	} else {
+		ie = NULL;
+	}
+
+	kfree(wdev->wext.ie);
+	wdev->wext.ie = ie;
+	wdev->wext.ie_len = ie_len;
+
+	if (wdev->conn)
+		return cfg80211_disconnect(rdev, dev,
+					   WLAN_REASON_DEAUTH_LEAVING, false);
+
+	/* userspace better not think we'll reconnect */
+	return 0;
+}
+
+int cfg80211_wext_siwmlme(struct net_device *dev,
+			  struct iw_request_info *info,
+			  union iwreq_data *wrqu, char *extra)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	struct iw_mlme *mlme = (struct iw_mlme *)extra;
+	struct cfg80211_registered_device *rdev;
+
+	if (!wdev)
+		return -EOPNOTSUPP;
+
+	rdev = wiphy_to_rdev(wdev->wiphy);
+
+	if (wdev->iftype != NL80211_IFTYPE_STATION)
+		return -EINVAL;
+
+	if (mlme->addr.sa_family != ARPHRD_ETHER)
+		return -EINVAL;
+
+	guard(wiphy)(&rdev->wiphy);
+
+	switch (mlme->cmd) {
+	case IW_MLME_DEAUTH:
+	case IW_MLME_DISASSOC:
+		return cfg80211_disconnect(rdev, dev, mlme->reason_code, true);
+	default:
+		return -EOPNOTSUPP;
+	}
+}