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, 275 insertions, 0 deletions

diff --git a/drivers/leds/leds-max77705.c b/drivers/leds/leds-max77705.c
new file mode 100644
index 000000000..1e2054c1b
--- /dev/null
+++ b/drivers/leds/leds-max77705.c
@@ -0,0 +1,275 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Based on leds-max77650 driver
+ *
+ * LED driver for MAXIM 77705 PMIC.
+ * Copyright (C) 2025 Dzmitry Sankouski <dsankouski@gmail.org>
+ */
+
+#include <linux/i2c.h>
+#include <linux/led-class-multicolor.h>
+#include <linux/leds.h>
+#include <linux/mfd/max77705-private.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define MAX77705_LED_NUM_LEDS			4
+#define MAX77705_LED_EN_MASK			GENMASK(1, 0)
+#define MAX77705_LED_MAX_BRIGHTNESS		0xff
+#define MAX77705_LED_EN_SHIFT(reg)		(reg * MAX77705_RGBLED_EN_WIDTH)
+#define MAX77705_LED_REG_BRIGHTNESS(reg)	(reg + MAX77705_RGBLED_REG_LED0BRT)
+
+struct max77705_led {
+	struct led_classdev cdev;
+	struct led_classdev_mc mcdev;
+	struct regmap *regmap;
+
+	struct mc_subled *subled_info;
+};
+
+static const struct regmap_config max77705_leds_regmap_config = {
+	.reg_base = MAX77705_RGBLED_REG_BASE,
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = MAX77705_LED_REG_END,
+};
+
+static int max77705_rgb_blink(struct led_classdev *cdev,
+				unsigned long *delay_on,
+				unsigned long *delay_off)
+{
+	struct max77705_led *led = container_of(cdev, struct max77705_led, cdev);
+	int value, on_value, off_value;
+
+	if (*delay_on < MAX77705_RGB_DELAY_100_STEP)
+		on_value = 0;
+	else if (*delay_on < MAX77705_RGB_DELAY_100_STEP_LIM)
+		on_value = *delay_on / MAX77705_RGB_DELAY_100_STEP - 1;
+	else if (*delay_on < MAX77705_RGB_DELAY_250_STEP_LIM)
+		on_value = (*delay_on - MAX77705_RGB_DELAY_100_STEP_LIM) /
+				MAX77705_RGB_DELAY_250_STEP +
+				MAX77705_RGB_DELAY_100_STEP_COUNT;
+	else
+		on_value = 15;
+
+	on_value <<= 4;
+
+	if (*delay_off < 1)
+		off_value = 0;
+	else if (*delay_off < MAX77705_RGB_DELAY_500_STEP)
+		off_value = 1;
+	else if (*delay_off < MAX77705_RGB_DELAY_500_STEP_LIM)
+		off_value = *delay_off / MAX77705_RGB_DELAY_500_STEP;
+	else if (*delay_off < MAX77705_RGB_DELAY_1000_STEP_LIM)
+		off_value = (*delay_off - MAX77705_RGB_DELAY_1000_STEP_LIM) /
+				MAX77705_RGB_DELAY_1000_STEP +
+				MAX77705_RGB_DELAY_500_STEP_COUNT;
+	else if (*delay_off < MAX77705_RGB_DELAY_2000_STEP_LIM)
+		off_value = (*delay_off - MAX77705_RGB_DELAY_2000_STEP_LIM) /
+				MAX77705_RGB_DELAY_2000_STEP +
+				MAX77705_RGB_DELAY_1000_STEP_COUNT;
+	else
+		off_value = 15;
+
+	value = on_value | off_value;
+	return regmap_write(led->regmap, MAX77705_RGBLED_REG_LEDBLNK, value);
+}
+
+static int max77705_led_brightness_set(struct regmap *regmap, struct mc_subled *subled,
+				int num_colors)
+{
+	int ret;
+
+	for (int i = 0; i < num_colors; i++) {
+		unsigned int channel, brightness;
+
+		channel = subled[i].channel;
+		brightness = subled[i].brightness;
+
+		if (brightness == LED_OFF) {
+			/* Flash OFF */
+			ret = regmap_update_bits(regmap,
+					MAX77705_RGBLED_REG_LEDEN,
+					MAX77705_LED_EN_MASK << MAX77705_LED_EN_SHIFT(channel), 0);
+		} else {
+			/* Set current */
+			ret = regmap_write(regmap, MAX77705_LED_REG_BRIGHTNESS(channel),
+					brightness);
+			if (ret < 0)
+				return ret;
+
+			ret = regmap_update_bits(regmap,
+					MAX77705_RGBLED_REG_LEDEN,
+					LED_ON << MAX77705_LED_EN_SHIFT(channel),
+					MAX77705_LED_EN_MASK << MAX77705_LED_EN_SHIFT(channel));
+		}
+	}
+
+	return ret;
+}
+
+static int max77705_led_brightness_set_single(struct led_classdev *cdev,
+					enum led_brightness brightness)
+{
+	struct max77705_led *led = container_of(cdev, struct max77705_led, cdev);
+
+	led->subled_info->brightness = brightness;
+
+	return max77705_led_brightness_set(led->regmap, led->subled_info, 1);
+}
+
+static int max77705_led_brightness_set_multi(struct led_classdev *cdev,
+					enum led_brightness brightness)
+{
+	struct led_classdev_mc *mcdev = lcdev_to_mccdev(cdev);
+	struct max77705_led *led = container_of(mcdev, struct max77705_led, mcdev);
+
+	led_mc_calc_color_components(mcdev, brightness);
+
+	return max77705_led_brightness_set(led->regmap, led->mcdev.subled_info, mcdev->num_colors);
+}
+
+static int max77705_parse_subled(struct device *dev, struct fwnode_handle *np,
+				struct mc_subled *info)
+{
+	u32 color = LED_COLOR_ID_GREEN;
+	u32 reg;
+	int ret;
+
+	ret = fwnode_property_read_u32(np, "reg", &reg);
+	if (ret || !reg || reg >= MAX77705_LED_NUM_LEDS)
+		return dev_err_probe(dev, -EINVAL, "invalid \"reg\" of %pOFn\n", np);
+
+	info->channel = reg;
+
+	ret = fwnode_property_read_u32(np, "color", &color);
+	if (ret < 0 && ret != -EINVAL)
+		return dev_err_probe(dev, ret,
+				     "failed to parse \"color\" of %pOF\n", np);
+
+	info->color_index = color;
+
+	return 0;
+}
+
+static int max77705_add_led(struct device *dev, struct regmap *regmap, struct fwnode_handle *np)
+{
+	int ret, i = 0;
+	unsigned int color, reg;
+	struct max77705_led *led;
+	struct led_classdev *cdev;
+	struct mc_subled *info;
+	struct fwnode_handle *child;
+	struct led_init_data init_data = {};
+
+	led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
+	if (!led)
+		return -ENOMEM;
+
+	ret = fwnode_property_read_u32(np, "color", &color);
+	if (ret < 0 && ret != -EINVAL)
+		return dev_err_probe(dev, ret,
+			      "failed to parse \"color\" of %pOF\n", np);
+
+	led->regmap = regmap;
+	init_data.fwnode = np;
+
+	if (color == LED_COLOR_ID_RGB) {
+		int num_channels = of_get_available_child_count(to_of_node(np));
+
+		ret = fwnode_property_read_u32(np, "reg", &reg);
+		if (ret || reg >= MAX77705_LED_NUM_LEDS)
+			return -EINVAL;
+
+		info = devm_kcalloc(dev, num_channels, sizeof(*info), GFP_KERNEL);
+		if (!info)
+			return -ENOMEM;
+
+		cdev = &led->mcdev.led_cdev;
+		cdev->max_brightness = MAX77705_LED_MAX_BRIGHTNESS;
+		cdev->brightness_set_blocking = max77705_led_brightness_set_multi;
+		cdev->blink_set = max77705_rgb_blink;
+
+		fwnode_for_each_child_node(np, child) {
+			ret = max77705_parse_subled(dev, child, &info[i]);
+			if (ret < 0)
+				return ret;
+
+			info[i].intensity = 0;
+			i++;
+		}
+
+		led->mcdev.subled_info = info;
+		led->mcdev.num_colors = num_channels;
+		led->cdev = *cdev;
+
+		ret = devm_led_classdev_multicolor_register_ext(dev, &led->mcdev, &init_data);
+		if (ret)
+			return ret;
+
+		ret = max77705_led_brightness_set_multi(&led->cdev, LED_OFF);
+		if (ret)
+			return ret;
+	} else {
+		info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
+		if (!info)
+			return -ENOMEM;
+
+		max77705_parse_subled(dev, np, info);
+
+		led->subled_info = info;
+		led->cdev.brightness_set_blocking = max77705_led_brightness_set_single;
+		led->cdev.blink_set = max77705_rgb_blink;
+		led->cdev.max_brightness = MAX77705_LED_MAX_BRIGHTNESS;
+
+		ret = devm_led_classdev_register_ext(dev, &led->cdev, &init_data);
+		if (ret)
+			return ret;
+
+		ret = max77705_led_brightness_set_single(&led->cdev, LED_OFF);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int max77705_led_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct i2c_client *i2c = to_i2c_client(pdev->dev.parent);
+	struct regmap *regmap;
+	int ret;
+
+	regmap = devm_regmap_init_i2c(i2c, &max77705_leds_regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap), "Failed to register LEDs regmap\n");
+
+	device_for_each_child_node_scoped(dev, child) {
+		ret = max77705_add_led(dev, regmap, child);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id max77705_led_of_match[] = {
+	{ .compatible = "maxim,max77705-rgb" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, max77705_led_of_match);
+
+static struct platform_driver max77705_led_driver = {
+	.driver = {
+		.name = "max77705-led",
+		.of_match_table = max77705_led_of_match,
+	},
+	.probe = max77705_led_probe,
+};
+module_platform_driver(max77705_led_driver);
+
+MODULE_DESCRIPTION("Maxim MAX77705 LED driver");
+MODULE_AUTHOR("Dzmitry Sankouski <dsankouski@gmail.com>");
+MODULE_LICENSE("GPL");