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, 204 insertions, 0 deletions

diff --git a/drivers/hid/hid-appletb-bl.c b/drivers/hid/hid-appletb-bl.c
new file mode 100644
index 000000000..bad2aead8
--- /dev/null
+++ b/drivers/hid/hid-appletb-bl.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Apple Touch Bar Backlight Driver
+ *
+ * Copyright (c) 2017-2018 Ronald Tschalär
+ * Copyright (c) 2022-2023 Kerem Karabay <kekrby@gmail.com>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/hid.h>
+#include <linux/backlight.h>
+#include <linux/device.h>
+
+#include "hid-ids.h"
+
+#define APPLETB_BL_ON			1
+#define APPLETB_BL_DIM			3
+#define APPLETB_BL_OFF			4
+
+#define HID_UP_APPLEVENDOR_TB_BL	0xff120000
+
+#define HID_VD_APPLE_TB_BRIGHTNESS	0xff120001
+#define HID_USAGE_AUX1			0xff120020
+#define HID_USAGE_BRIGHTNESS		0xff120021
+
+static int appletb_bl_def_brightness = 2;
+module_param_named(brightness, appletb_bl_def_brightness, int, 0444);
+MODULE_PARM_DESC(brightness, "Default brightness:\n"
+			 "    0 - Touchbar is off\n"
+			 "    1 - Dim brightness\n"
+			 "    [2] - Full brightness");
+
+struct appletb_bl {
+	struct hid_field *aux1_field, *brightness_field;
+	struct backlight_device *bdev;
+
+	bool full_on;
+};
+
+static const u8 appletb_bl_brightness_map[] = {
+	APPLETB_BL_OFF,
+	APPLETB_BL_DIM,
+	APPLETB_BL_ON,
+};
+
+static int appletb_bl_set_brightness(struct appletb_bl *bl, u8 brightness)
+{
+	struct hid_report *report = bl->brightness_field->report;
+	struct hid_device *hdev = report->device;
+	int ret;
+
+	ret = hid_set_field(bl->aux1_field, 0, 1);
+	if (ret) {
+		hid_err(hdev, "Failed to set auxiliary field (%pe)\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	ret = hid_set_field(bl->brightness_field, 0, brightness);
+	if (ret) {
+		hid_err(hdev, "Failed to set brightness field (%pe)\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	if (!bl->full_on) {
+		ret = hid_hw_power(hdev, PM_HINT_FULLON);
+		if (ret < 0) {
+			hid_err(hdev, "Device didn't power on (%pe)\n", ERR_PTR(ret));
+			return ret;
+		}
+
+		bl->full_on = true;
+	}
+
+	hid_hw_request(hdev, report, HID_REQ_SET_REPORT);
+
+	if (brightness == APPLETB_BL_OFF) {
+		hid_hw_power(hdev, PM_HINT_NORMAL);
+		bl->full_on = false;
+	}
+
+	return 0;
+}
+
+static int appletb_bl_update_status(struct backlight_device *bdev)
+{
+	struct appletb_bl *bl = bl_get_data(bdev);
+	u8 brightness;
+
+	if (backlight_is_blank(bdev))
+		brightness = APPLETB_BL_OFF;
+	else
+		brightness = appletb_bl_brightness_map[backlight_get_brightness(bdev)];
+
+	return appletb_bl_set_brightness(bl, brightness);
+}
+
+static const struct backlight_ops appletb_bl_backlight_ops = {
+	.options = BL_CORE_SUSPENDRESUME,
+	.update_status = appletb_bl_update_status,
+};
+
+static int appletb_bl_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	struct hid_field *aux1_field, *brightness_field;
+	struct backlight_properties bl_props = { 0 };
+	struct device *dev = &hdev->dev;
+	struct appletb_bl *bl;
+	int ret;
+
+	ret = hid_parse(hdev);
+	if (ret)
+		return dev_err_probe(dev, ret, "HID parse failed\n");
+
+	aux1_field = hid_find_field(hdev, HID_FEATURE_REPORT,
+				    HID_VD_APPLE_TB_BRIGHTNESS, HID_USAGE_AUX1);
+
+	brightness_field = hid_find_field(hdev, HID_FEATURE_REPORT,
+					  HID_VD_APPLE_TB_BRIGHTNESS, HID_USAGE_BRIGHTNESS);
+
+	if (!aux1_field || !brightness_field)
+		return -ENODEV;
+
+	if (aux1_field->report != brightness_field->report)
+		return dev_err_probe(dev, -ENODEV, "Encountered unexpected report structure\n");
+
+	bl = devm_kzalloc(dev, sizeof(*bl), GFP_KERNEL);
+	if (!bl)
+		return -ENOMEM;
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DRIVER);
+	if (ret)
+		return dev_err_probe(dev, ret, "HID hardware start failed\n");
+
+	ret = hid_hw_open(hdev);
+	if (ret) {
+		dev_err_probe(dev, ret, "HID hardware open failed\n");
+		goto stop_hw;
+	}
+
+	bl->aux1_field = aux1_field;
+	bl->brightness_field = brightness_field;
+
+	ret = appletb_bl_set_brightness(bl,
+		appletb_bl_brightness_map[(appletb_bl_def_brightness > 2) ? 2 : appletb_bl_def_brightness]);
+
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to set default touch bar brightness to %d\n",
+			      appletb_bl_def_brightness);
+		goto close_hw;
+	}
+
+	bl_props.type = BACKLIGHT_RAW;
+	bl_props.max_brightness = ARRAY_SIZE(appletb_bl_brightness_map) - 1;
+
+	bl->bdev = devm_backlight_device_register(dev, "appletb_backlight", dev, bl,
+						  &appletb_bl_backlight_ops, &bl_props);
+	if (IS_ERR(bl->bdev)) {
+		ret = PTR_ERR(bl->bdev);
+		dev_err_probe(dev, ret, "Failed to register backlight device\n");
+		goto close_hw;
+	}
+
+	hid_set_drvdata(hdev, bl);
+
+	return 0;
+
+close_hw:
+	hid_hw_close(hdev);
+stop_hw:
+	hid_hw_stop(hdev);
+
+	return ret;
+}
+
+static void appletb_bl_remove(struct hid_device *hdev)
+{
+	struct appletb_bl *bl = hid_get_drvdata(hdev);
+
+	appletb_bl_set_brightness(bl, APPLETB_BL_OFF);
+
+	hid_hw_close(hdev);
+	hid_hw_stop(hdev);
+}
+
+static const struct hid_device_id appletb_bl_hid_ids[] = {
+	/* MacBook Pro's 2018, 2019, with T2 chip: iBridge DFR Brightness */
+	{ HID_USB_DEVICE(USB_VENDOR_ID_APPLE, USB_DEVICE_ID_APPLE_TOUCHBAR_BACKLIGHT) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, appletb_bl_hid_ids);
+
+static struct hid_driver appletb_bl_hid_driver = {
+	.name = "hid-appletb-bl",
+	.id_table = appletb_bl_hid_ids,
+	.probe = appletb_bl_probe,
+	.remove = appletb_bl_remove,
+};
+module_hid_driver(appletb_bl_hid_driver);
+
+MODULE_AUTHOR("Ronald Tschalär");
+MODULE_AUTHOR("Kerem Karabay <kekrby@gmail.com>");
+MODULE_DESCRIPTION("MacBook Pro Touch Bar Backlight driver");
+MODULE_LICENSE("GPL");