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, 203 insertions, 0 deletions

diff --git a/drivers/leds/leds-regulator.c b/drivers/leds/leds-regulator.c
new file mode 100644
index 000000000..5ba0f36b2
--- /dev/null
+++ b/drivers/leds/leds-regulator.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * leds-regulator.c - LED class driver for regulator driven LEDs.
+ *
+ * Copyright (C) 2009 Antonio Ospite <ospite@studenti.unina.it>
+ *
+ * Inspired by leds-wm8350 driver.
+ */
+
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/leds.h>
+#include <linux/leds-regulator.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+
+#define to_regulator_led(led_cdev) \
+	container_of(led_cdev, struct regulator_led, cdev)
+
+struct regulator_led {
+	struct led_classdev cdev;
+	int enabled;
+	struct mutex mutex;
+
+	struct regulator *vcc;
+};
+
+static inline int led_regulator_get_max_brightness(struct regulator *supply)
+{
+	int ret;
+	int voltage = regulator_list_voltage(supply, 0);
+
+	if (voltage <= 0)
+		return 1;
+
+	/* even if regulator can't change voltages,
+	 * we still assume it can change status
+	 * and the LED can be turned on and off.
+	 */
+	ret = regulator_set_voltage(supply, voltage, voltage);
+	if (ret < 0)
+		return 1;
+
+	return regulator_count_voltages(supply);
+}
+
+static int led_regulator_get_voltage(struct regulator *supply,
+		enum led_brightness brightness)
+{
+	if (brightness == 0)
+		return -EINVAL;
+
+	return regulator_list_voltage(supply, brightness - 1);
+}
+
+
+static void regulator_led_enable(struct regulator_led *led)
+{
+	int ret;
+
+	if (led->enabled)
+		return;
+
+	ret = regulator_enable(led->vcc);
+	if (ret != 0) {
+		dev_err(led->cdev.dev, "Failed to enable vcc: %d\n", ret);
+		return;
+	}
+
+	led->enabled = 1;
+}
+
+static void regulator_led_disable(struct regulator_led *led)
+{
+	int ret;
+
+	if (!led->enabled)
+		return;
+
+	ret = regulator_disable(led->vcc);
+	if (ret != 0) {
+		dev_err(led->cdev.dev, "Failed to disable vcc: %d\n", ret);
+		return;
+	}
+
+	led->enabled = 0;
+}
+
+static int regulator_led_brightness_set(struct led_classdev *led_cdev,
+					 enum led_brightness value)
+{
+	struct regulator_led *led = to_regulator_led(led_cdev);
+	int voltage;
+	int ret = 0;
+
+	mutex_lock(&led->mutex);
+
+	if (value == LED_OFF) {
+		regulator_led_disable(led);
+		goto out;
+	}
+
+	if (led->cdev.max_brightness > 1) {
+		voltage = led_regulator_get_voltage(led->vcc, value);
+		dev_dbg(led->cdev.dev, "brightness: %d voltage: %d\n",
+				value, voltage);
+
+		ret = regulator_set_voltage(led->vcc, voltage, voltage);
+		if (ret != 0)
+			dev_err(led->cdev.dev, "Failed to set voltage %d: %d\n",
+				voltage, ret);
+	}
+
+	regulator_led_enable(led);
+
+out:
+	mutex_unlock(&led->mutex);
+	return ret;
+}
+
+static int regulator_led_probe(struct platform_device *pdev)
+{
+	struct led_regulator_platform_data *pdata =
+			dev_get_platdata(&pdev->dev);
+	struct device *dev = &pdev->dev;
+	struct led_init_data init_data = {};
+	struct regulator_led *led;
+	struct regulator *vcc;
+	int ret = 0;
+
+	vcc = devm_regulator_get_exclusive(dev, "vled");
+	if (IS_ERR(vcc)) {
+		dev_err(dev, "Cannot get vcc\n");
+		return PTR_ERR(vcc);
+	}
+
+	led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
+	if (led == NULL)
+		return -ENOMEM;
+
+	init_data.fwnode = dev->fwnode;
+
+	led->cdev.max_brightness = led_regulator_get_max_brightness(vcc);
+	/* Legacy platform data label assignment */
+	if (pdata) {
+		if (pdata->brightness > led->cdev.max_brightness) {
+			dev_err(dev, "Invalid default brightness %d\n",
+				pdata->brightness);
+			return -EINVAL;
+		}
+		led->cdev.brightness = pdata->brightness;
+		init_data.default_label = pdata->name;
+	}
+
+	led->cdev.brightness_set_blocking = regulator_led_brightness_set;
+	led->cdev.flags |= LED_CORE_SUSPENDRESUME;
+	led->vcc = vcc;
+
+	/* to handle correctly an already enabled regulator */
+	if (regulator_is_enabled(led->vcc))
+		led->enabled = 1;
+
+	mutex_init(&led->mutex);
+
+	platform_set_drvdata(pdev, led);
+
+	ret = led_classdev_register_ext(dev, &led->cdev, &init_data);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static void regulator_led_remove(struct platform_device *pdev)
+{
+	struct regulator_led *led = platform_get_drvdata(pdev);
+
+	led_classdev_unregister(&led->cdev);
+	regulator_led_disable(led);
+}
+
+static const struct of_device_id regulator_led_of_match[] = {
+	{ .compatible = "regulator-led", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, regulator_led_of_match);
+
+static struct platform_driver regulator_led_driver = {
+	.driver = {
+		.name  = "leds-regulator",
+		.of_match_table = regulator_led_of_match,
+	},
+	.probe  = regulator_led_probe,
+	.remove = regulator_led_remove,
+};
+
+module_platform_driver(regulator_led_driver);
+
+MODULE_AUTHOR("Antonio Ospite <ospite@studenti.unina.it>");
+MODULE_DESCRIPTION("Regulator driven LED driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:leds-regulator");