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, 226 insertions, 0 deletions

diff --git a/drivers/input/input-leds.c b/drivers/input/input-leds.c
new file mode 100644
index 000000000..b08d1d08d
--- /dev/null
+++ b/drivers/input/input-leds.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * LED support for the input layer
+ *
+ * Copyright 2010-2015 Samuel Thibault <samuel.thibault@ens-lyon.org>
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+#include <linux/input.h>
+
+#if IS_ENABLED(CONFIG_VT)
+#define VT_TRIGGER(_name)	.trigger = _name
+#else
+#define VT_TRIGGER(_name)	.trigger = NULL
+#endif
+
+#if IS_ENABLED(CONFIG_SND_CTL_LED)
+#define AUDIO_TRIGGER(_name)	.trigger = _name
+#else
+#define AUDIO_TRIGGER(_name)	.trigger = NULL
+#endif
+
+static const struct {
+	const char *name;
+	const char *trigger;
+} input_led_info[LED_CNT] = {
+	[LED_NUML]	= { "numlock", VT_TRIGGER("kbd-numlock") },
+	[LED_CAPSL]	= { "capslock", VT_TRIGGER("kbd-capslock") },
+	[LED_SCROLLL]	= { "scrolllock", VT_TRIGGER("kbd-scrolllock") },
+	[LED_COMPOSE]	= { "compose" },
+	[LED_KANA]	= { "kana", VT_TRIGGER("kbd-kanalock") },
+	[LED_SLEEP]	= { "sleep" } ,
+	[LED_SUSPEND]	= { "suspend" },
+	[LED_MUTE]	= { "mute", AUDIO_TRIGGER("audio-mute") },
+	[LED_MISC]	= { "misc" },
+	[LED_MAIL]	= { "mail" },
+	[LED_CHARGING]	= { "charging" },
+};
+
+struct input_led {
+	struct led_classdev cdev;
+	struct input_handle *handle;
+	unsigned int code; /* One of LED_* constants */
+};
+
+struct input_leds {
+	struct input_handle handle;
+	unsigned int num_leds;
+	struct input_led leds[] __counted_by(num_leds);
+};
+
+static enum led_brightness input_leds_brightness_get(struct led_classdev *cdev)
+{
+	struct input_led *led = container_of(cdev, struct input_led, cdev);
+	struct input_dev *input = led->handle->dev;
+
+	return test_bit(led->code, input->led) ? cdev->max_brightness : 0;
+}
+
+static void input_leds_brightness_set(struct led_classdev *cdev,
+				      enum led_brightness brightness)
+{
+	struct input_led *led = container_of(cdev, struct input_led, cdev);
+
+	input_inject_event(led->handle, EV_LED, led->code, !!brightness);
+}
+
+static void input_leds_event(struct input_handle *handle, unsigned int type,
+			     unsigned int code, int value)
+{
+}
+
+static int input_leds_get_count(struct input_dev *dev)
+{
+	unsigned int led_code;
+	int count = 0;
+
+	for_each_set_bit(led_code, dev->ledbit, LED_CNT)
+		if (input_led_info[led_code].name)
+			count++;
+
+	return count;
+}
+
+static int input_leds_connect(struct input_handler *handler,
+			      struct input_dev *dev,
+			      const struct input_device_id *id)
+{
+	struct input_leds *leds;
+	struct input_led *led;
+	unsigned int num_leds;
+	unsigned int led_code;
+	int led_no;
+	int error;
+
+	num_leds = input_leds_get_count(dev);
+	if (!num_leds)
+		return -ENXIO;
+
+	leds = kzalloc_flex(*leds, leds, num_leds);
+	if (!leds)
+		return -ENOMEM;
+
+	leds->num_leds = num_leds;
+
+	leds->handle.dev = dev;
+	leds->handle.handler = handler;
+	leds->handle.name = "leds";
+	leds->handle.private = leds;
+
+	error = input_register_handle(&leds->handle);
+	if (error)
+		goto err_free_mem;
+
+	error = input_open_device(&leds->handle);
+	if (error)
+		goto err_unregister_handle;
+
+	led_no = 0;
+	for_each_set_bit(led_code, dev->ledbit, LED_CNT) {
+		if (!input_led_info[led_code].name)
+			continue;
+
+		led = &leds->leds[led_no];
+		led->handle = &leds->handle;
+		led->code = led_code;
+
+		led->cdev.name = kasprintf(GFP_KERNEL, "%s::%s",
+					   dev_name(&dev->dev),
+					   input_led_info[led_code].name);
+		if (!led->cdev.name) {
+			error = -ENOMEM;
+			goto err_unregister_leds;
+		}
+
+		led->cdev.max_brightness = 1;
+		led->cdev.brightness_get = input_leds_brightness_get;
+		led->cdev.brightness_set = input_leds_brightness_set;
+		led->cdev.default_trigger = input_led_info[led_code].trigger;
+
+		error = led_classdev_register(&dev->dev, &led->cdev);
+		if (error) {
+			dev_err(&dev->dev, "failed to register LED %s: %d\n",
+				led->cdev.name, error);
+			kfree(led->cdev.name);
+			goto err_unregister_leds;
+		}
+
+		led_no++;
+	}
+
+	return 0;
+
+err_unregister_leds:
+	while (--led_no >= 0) {
+		struct input_led *led = &leds->leds[led_no];
+
+		led_classdev_unregister(&led->cdev);
+		kfree(led->cdev.name);
+	}
+
+	input_close_device(&leds->handle);
+
+err_unregister_handle:
+	input_unregister_handle(&leds->handle);
+
+err_free_mem:
+	kfree(leds);
+	return error;
+}
+
+static void input_leds_disconnect(struct input_handle *handle)
+{
+	struct input_leds *leds = handle->private;
+	int i;
+
+	for (i = 0; i < leds->num_leds; i++) {
+		struct input_led *led = &leds->leds[i];
+
+		led_classdev_unregister(&led->cdev);
+		kfree(led->cdev.name);
+	}
+
+	input_close_device(handle);
+	input_unregister_handle(handle);
+
+	kfree(leds);
+}
+
+static const struct input_device_id input_leds_ids[] = {
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+		.evbit = { BIT_MASK(EV_LED) },
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(input, input_leds_ids);
+
+static struct input_handler input_leds_handler = {
+	.event =	input_leds_event,
+	.connect =	input_leds_connect,
+	.disconnect =	input_leds_disconnect,
+	.name =		"leds",
+	.id_table =	input_leds_ids,
+};
+
+static int __init input_leds_init(void)
+{
+	return input_register_handler(&input_leds_handler);
+}
+module_init(input_leds_init);
+
+static void __exit input_leds_exit(void)
+{
+	input_unregister_handler(&input_leds_handler);
+}
+module_exit(input_leds_exit);
+
+MODULE_AUTHOR("Samuel Thibault <samuel.thibault@ens-lyon.org>");
+MODULE_AUTHOR("Dmitry Torokhov <dmitry.torokhov@gmail.com>");
+MODULE_DESCRIPTION("Input -> LEDs Bridge");
+MODULE_LICENSE("GPL v2");