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, 294 insertions, 0 deletions

diff --git a/drivers/leds/leds-max8997.c b/drivers/leds/leds-max8997.c
new file mode 100644
index 000000000..c8d7f55c9
--- /dev/null
+++ b/drivers/leds/leds-max8997.c
@@ -0,0 +1,294 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * leds-max8997.c - LED class driver for MAX8997 LEDs.
+ *
+ * Copyright (C) 2011 Samsung Electronics
+ * Donggeun Kim <dg77.kim@samsung.com>
+ */
+
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/leds.h>
+#include <linux/mfd/max8997.h>
+#include <linux/mfd/max8997-private.h>
+#include <linux/platform_device.h>
+
+#define MAX8997_LED_FLASH_SHIFT			3
+#define MAX8997_LED_FLASH_CUR_MASK		0xf8
+#define MAX8997_LED_MOVIE_SHIFT			4
+#define MAX8997_LED_MOVIE_CUR_MASK		0xf0
+
+#define MAX8997_LED_FLASH_MAX_BRIGHTNESS	0x1f
+#define MAX8997_LED_MOVIE_MAX_BRIGHTNESS	0xf
+#define MAX8997_LED_NONE_MAX_BRIGHTNESS		0
+
+#define MAX8997_LED0_FLASH_MASK			0x1
+#define MAX8997_LED0_FLASH_PIN_MASK		0x5
+#define MAX8997_LED0_MOVIE_MASK			0x8
+#define MAX8997_LED0_MOVIE_PIN_MASK		0x28
+
+#define MAX8997_LED1_FLASH_MASK			0x2
+#define MAX8997_LED1_FLASH_PIN_MASK		0x6
+#define MAX8997_LED1_MOVIE_MASK			0x10
+#define MAX8997_LED1_MOVIE_PIN_MASK		0x30
+
+#define MAX8997_LED_BOOST_ENABLE_MASK		(1 << 6)
+
+struct max8997_led {
+	struct max8997_dev *iodev;
+	struct led_classdev cdev;
+	bool enabled;
+	int id;
+	enum max8997_led_mode led_mode;
+	struct mutex mutex;
+};
+
+static void max8997_led_set_mode(struct max8997_led *led,
+			enum max8997_led_mode mode)
+{
+	int ret;
+	struct i2c_client *client = led->iodev->i2c;
+	u8 mask = 0, val;
+
+	switch (mode) {
+	case MAX8997_FLASH_MODE:
+		mask = MAX8997_LED1_FLASH_MASK | MAX8997_LED0_FLASH_MASK;
+		val = led->id ?
+		      MAX8997_LED1_FLASH_MASK : MAX8997_LED0_FLASH_MASK;
+		led->cdev.max_brightness = MAX8997_LED_FLASH_MAX_BRIGHTNESS;
+		break;
+	case MAX8997_MOVIE_MODE:
+		mask = MAX8997_LED1_MOVIE_MASK | MAX8997_LED0_MOVIE_MASK;
+		val = led->id ?
+		      MAX8997_LED1_MOVIE_MASK : MAX8997_LED0_MOVIE_MASK;
+		led->cdev.max_brightness = MAX8997_LED_MOVIE_MAX_BRIGHTNESS;
+		break;
+	case MAX8997_FLASH_PIN_CONTROL_MODE:
+		mask = MAX8997_LED1_FLASH_PIN_MASK |
+		       MAX8997_LED0_FLASH_PIN_MASK;
+		val = led->id ?
+		      MAX8997_LED1_FLASH_PIN_MASK : MAX8997_LED0_FLASH_PIN_MASK;
+		led->cdev.max_brightness = MAX8997_LED_FLASH_MAX_BRIGHTNESS;
+		break;
+	case MAX8997_MOVIE_PIN_CONTROL_MODE:
+		mask = MAX8997_LED1_MOVIE_PIN_MASK |
+		       MAX8997_LED0_MOVIE_PIN_MASK;
+		val = led->id ?
+		      MAX8997_LED1_MOVIE_PIN_MASK : MAX8997_LED0_MOVIE_PIN_MASK;
+		led->cdev.max_brightness = MAX8997_LED_MOVIE_MAX_BRIGHTNESS;
+		break;
+	default:
+		led->cdev.max_brightness = MAX8997_LED_NONE_MAX_BRIGHTNESS;
+		break;
+	}
+
+	if (mask) {
+		ret = max8997_update_reg(client, MAX8997_REG_LEN_CNTL, val,
+					 mask);
+		if (ret)
+			dev_err(led->iodev->dev,
+				"failed to update register(%d)\n", ret);
+	}
+
+	led->led_mode = mode;
+}
+
+static void max8997_led_enable(struct max8997_led *led, bool enable)
+{
+	int ret;
+	struct i2c_client *client = led->iodev->i2c;
+	u8 val = 0, mask = MAX8997_LED_BOOST_ENABLE_MASK;
+
+	if (led->enabled == enable)
+		return;
+
+	val = enable ? MAX8997_LED_BOOST_ENABLE_MASK : 0;
+
+	ret = max8997_update_reg(client, MAX8997_REG_BOOST_CNTL, val, mask);
+	if (ret)
+		dev_err(led->iodev->dev,
+			"failed to update register(%d)\n", ret);
+
+	led->enabled = enable;
+}
+
+static void max8997_led_set_current(struct max8997_led *led,
+				enum led_brightness value)
+{
+	int ret;
+	struct i2c_client *client = led->iodev->i2c;
+	u8 val = 0, mask = 0, reg = 0;
+
+	switch (led->led_mode) {
+	case MAX8997_FLASH_MODE:
+	case MAX8997_FLASH_PIN_CONTROL_MODE:
+		val = value << MAX8997_LED_FLASH_SHIFT;
+		mask = MAX8997_LED_FLASH_CUR_MASK;
+		reg = led->id ? MAX8997_REG_FLASH2_CUR : MAX8997_REG_FLASH1_CUR;
+		break;
+	case MAX8997_MOVIE_MODE:
+	case MAX8997_MOVIE_PIN_CONTROL_MODE:
+		val = value << MAX8997_LED_MOVIE_SHIFT;
+		mask = MAX8997_LED_MOVIE_CUR_MASK;
+		reg = MAX8997_REG_MOVIE_CUR;
+		break;
+	default:
+		break;
+	}
+
+	if (mask) {
+		ret = max8997_update_reg(client, reg, val, mask);
+		if (ret)
+			dev_err(led->iodev->dev,
+				"failed to update register(%d)\n", ret);
+	}
+}
+
+static void max8997_led_brightness_set(struct led_classdev *led_cdev,
+				enum led_brightness value)
+{
+	struct max8997_led *led =
+			container_of(led_cdev, struct max8997_led, cdev);
+
+	if (value) {
+		max8997_led_set_current(led, value);
+		max8997_led_enable(led, true);
+	} else {
+		max8997_led_set_current(led, value);
+		max8997_led_enable(led, false);
+	}
+}
+
+static ssize_t mode_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct max8997_led *led =
+			container_of(led_cdev, struct max8997_led, cdev);
+	ssize_t ret = 0;
+
+	mutex_lock(&led->mutex);
+
+	switch (led->led_mode) {
+	case MAX8997_FLASH_MODE:
+		ret += sprintf(buf, "FLASH\n");
+		break;
+	case MAX8997_MOVIE_MODE:
+		ret += sprintf(buf, "MOVIE\n");
+		break;
+	case MAX8997_FLASH_PIN_CONTROL_MODE:
+		ret += sprintf(buf, "FLASH_PIN_CONTROL\n");
+		break;
+	case MAX8997_MOVIE_PIN_CONTROL_MODE:
+		ret += sprintf(buf, "MOVIE_PIN_CONTROL\n");
+		break;
+	default:
+		ret += sprintf(buf, "NONE\n");
+		break;
+	}
+
+	mutex_unlock(&led->mutex);
+
+	return ret;
+}
+
+static ssize_t mode_store(struct device *dev,
+			  struct device_attribute *attr,
+			  const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct max8997_led *led =
+			container_of(led_cdev, struct max8997_led, cdev);
+	enum max8997_led_mode mode;
+
+	mutex_lock(&led->mutex);
+
+	if (!strncmp(buf, "FLASH_PIN_CONTROL", 17))
+		mode = MAX8997_FLASH_PIN_CONTROL_MODE;
+	else if (!strncmp(buf, "MOVIE_PIN_CONTROL", 17))
+		mode = MAX8997_MOVIE_PIN_CONTROL_MODE;
+	else if (!strncmp(buf, "FLASH", 5))
+		mode = MAX8997_FLASH_MODE;
+	else if (!strncmp(buf, "MOVIE", 5))
+		mode = MAX8997_MOVIE_MODE;
+	else
+		mode = MAX8997_NONE;
+
+	max8997_led_set_mode(led, mode);
+
+	mutex_unlock(&led->mutex);
+
+	return size;
+}
+
+static DEVICE_ATTR_RW(mode);
+
+static struct attribute *max8997_attrs[] = {
+	&dev_attr_mode.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(max8997);
+
+static int max8997_led_probe(struct platform_device *pdev)
+{
+	struct max8997_dev *iodev = dev_get_drvdata(pdev->dev.parent);
+	struct max8997_platform_data *pdata = dev_get_platdata(iodev->dev);
+	struct max8997_led *led;
+	char name[20];
+	int ret = 0;
+
+	led = devm_kzalloc(&pdev->dev, sizeof(*led), GFP_KERNEL);
+	if (led == NULL)
+		return -ENOMEM;
+
+	led->id = pdev->id;
+	snprintf(name, sizeof(name), "max8997-led%d", pdev->id);
+
+	led->cdev.name = name;
+	led->cdev.brightness_set = max8997_led_brightness_set;
+	led->cdev.flags |= LED_CORE_SUSPENDRESUME;
+	led->cdev.brightness = 0;
+	led->cdev.groups = max8997_groups;
+	led->iodev = iodev;
+
+	/* initialize mode and brightness according to platform_data */
+	if (pdata && pdata->led_pdata) {
+		u8 mode = 0, brightness = 0;
+
+		mode = pdata->led_pdata->mode[led->id];
+		brightness = pdata->led_pdata->brightness[led->id];
+
+		max8997_led_set_mode(led, mode);
+
+		if (brightness > led->cdev.max_brightness)
+			brightness = led->cdev.max_brightness;
+		max8997_led_set_current(led, brightness);
+		led->cdev.brightness = brightness;
+	} else {
+		max8997_led_set_mode(led, MAX8997_NONE);
+		max8997_led_set_current(led, 0);
+	}
+
+	mutex_init(&led->mutex);
+
+	ret = devm_led_classdev_register(&pdev->dev, &led->cdev);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static struct platform_driver max8997_led_driver = {
+	.driver = {
+		.name  = "max8997-led",
+	},
+	.probe  = max8997_led_probe,
+};
+
+module_platform_driver(max8997_led_driver);
+
+MODULE_AUTHOR("Donggeun Kim <dg77.kim@samsung.com>");
+MODULE_DESCRIPTION("MAX8997 LED driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:max8997-led");