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, 281 insertions, 0 deletions

diff --git a/drivers/leds/leds-ns2.c b/drivers/leds/leds-ns2.c
new file mode 100644
index 000000000..4c6f04a5b
--- /dev/null
+++ b/drivers/leds/leds-ns2.c
@@ -0,0 +1,281 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * leds-ns2.c - Driver for the Network Space v2 (and parents) dual-GPIO LED
+ *
+ * Copyright (C) 2010 LaCie
+ *
+ * Author: Simon Guinot <sguinot@lacie.com>
+ *
+ * Based on leds-gpio.c by Raphael Assenat <raph@8d.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/gpio/consumer.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include "leds.h"
+
+enum ns2_led_modes {
+	NS_V2_LED_OFF,
+	NS_V2_LED_ON,
+	NS_V2_LED_SATA,
+};
+
+/*
+ * If the size of this structure or types of its members is changed,
+ * the filling of array modval in function ns2_led_register must be changed
+ * accordingly.
+ */
+struct ns2_led_modval {
+	u32			mode;
+	u32			cmd_level;
+	u32			slow_level;
+} __packed;
+
+/*
+ * The Network Space v2 dual-GPIO LED is wired to a CPLD. Three different LED
+ * modes are available: off, on and SATA activity blinking. The LED modes are
+ * controlled through two GPIOs (command and slow): each combination of values
+ * for the command/slow GPIOs corresponds to a LED mode.
+ */
+
+struct ns2_led {
+	struct led_classdev	cdev;
+	struct gpio_desc	*cmd;
+	struct gpio_desc	*slow;
+	bool			can_sleep;
+	unsigned char		sata; /* True when SATA mode active. */
+	rwlock_t		rw_lock; /* Lock GPIOs. */
+	int			num_modes;
+	struct ns2_led_modval	*modval;
+};
+
+static int ns2_led_get_mode(struct ns2_led *led, enum ns2_led_modes *mode)
+{
+	int i;
+	int cmd_level;
+	int slow_level;
+
+	cmd_level = gpiod_get_value_cansleep(led->cmd);
+	slow_level = gpiod_get_value_cansleep(led->slow);
+
+	for (i = 0; i < led->num_modes; i++) {
+		if (cmd_level == led->modval[i].cmd_level &&
+		    slow_level == led->modval[i].slow_level) {
+			*mode = led->modval[i].mode;
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+
+static void ns2_led_set_mode(struct ns2_led *led, enum ns2_led_modes mode)
+{
+	int i;
+	unsigned long flags;
+
+	for (i = 0; i < led->num_modes; i++)
+		if (mode == led->modval[i].mode)
+			break;
+
+	if (i == led->num_modes)
+		return;
+
+	write_lock_irqsave(&led->rw_lock, flags);
+
+	if (!led->can_sleep) {
+		gpiod_set_value(led->cmd, led->modval[i].cmd_level);
+		gpiod_set_value(led->slow, led->modval[i].slow_level);
+		goto exit_unlock;
+	}
+
+	gpiod_set_value_cansleep(led->cmd, led->modval[i].cmd_level);
+	gpiod_set_value_cansleep(led->slow, led->modval[i].slow_level);
+
+exit_unlock:
+	write_unlock_irqrestore(&led->rw_lock, flags);
+}
+
+static void ns2_led_set(struct led_classdev *led_cdev,
+			enum led_brightness value)
+{
+	struct ns2_led *led = container_of(led_cdev, struct ns2_led, cdev);
+	enum ns2_led_modes mode;
+
+	if (value == LED_OFF)
+		mode = NS_V2_LED_OFF;
+	else if (led->sata)
+		mode = NS_V2_LED_SATA;
+	else
+		mode = NS_V2_LED_ON;
+
+	ns2_led_set_mode(led, mode);
+}
+
+static int ns2_led_set_blocking(struct led_classdev *led_cdev,
+			enum led_brightness value)
+{
+	ns2_led_set(led_cdev, value);
+	return 0;
+}
+
+static ssize_t ns2_led_sata_store(struct device *dev,
+				  struct device_attribute *attr,
+				  const char *buff, size_t count)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct ns2_led *led = container_of(led_cdev, struct ns2_led, cdev);
+	int ret;
+	unsigned long enable;
+
+	ret = kstrtoul(buff, 10, &enable);
+	if (ret < 0)
+		return ret;
+
+	enable = !!enable;
+
+	if (led->sata == enable)
+		goto exit;
+
+	led->sata = enable;
+
+	if (!led_get_brightness(led_cdev))
+		goto exit;
+
+	if (enable)
+		ns2_led_set_mode(led, NS_V2_LED_SATA);
+	else
+		ns2_led_set_mode(led, NS_V2_LED_ON);
+
+exit:
+	return count;
+}
+
+static ssize_t ns2_led_sata_show(struct device *dev,
+				 struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct ns2_led *led = container_of(led_cdev, struct ns2_led, cdev);
+
+	return sprintf(buf, "%d\n", led->sata);
+}
+
+static DEVICE_ATTR(sata, 0644, ns2_led_sata_show, ns2_led_sata_store);
+
+static struct attribute *ns2_led_attrs[] = {
+	&dev_attr_sata.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(ns2_led);
+
+static int ns2_led_register(struct device *dev, struct fwnode_handle *node,
+			    struct ns2_led *led)
+{
+	struct led_init_data init_data = {};
+	struct ns2_led_modval *modval;
+	enum ns2_led_modes mode;
+	int nmodes, ret;
+
+	led->cmd = devm_fwnode_gpiod_get_index(dev, node, "cmd", 0, GPIOD_ASIS,
+					       fwnode_get_name(node));
+	if (IS_ERR(led->cmd))
+		return PTR_ERR(led->cmd);
+
+	led->slow = devm_fwnode_gpiod_get_index(dev, node, "slow", 0,
+						GPIOD_ASIS,
+						fwnode_get_name(node));
+	if (IS_ERR(led->slow))
+		return PTR_ERR(led->slow);
+
+	ret = fwnode_property_count_u32(node, "modes-map");
+	if (ret < 0 || ret % 3) {
+		dev_err(dev, "Missing or malformed modes-map for %pfw\n", node);
+		return -EINVAL;
+	}
+
+	nmodes = ret / 3;
+	modval = devm_kcalloc(dev, nmodes, sizeof(*modval), GFP_KERNEL);
+	if (!modval)
+		return -ENOMEM;
+
+	fwnode_property_read_u32_array(node, "modes-map", (void *)modval,
+				       nmodes * 3);
+
+	rwlock_init(&led->rw_lock);
+
+	led->cdev.blink_set = NULL;
+	led->cdev.flags |= LED_CORE_SUSPENDRESUME;
+	led->cdev.groups = ns2_led_groups;
+	led->can_sleep = gpiod_cansleep(led->cmd) || gpiod_cansleep(led->slow);
+	if (led->can_sleep)
+		led->cdev.brightness_set_blocking = ns2_led_set_blocking;
+	else
+		led->cdev.brightness_set = ns2_led_set;
+	led->num_modes = nmodes;
+	led->modval = modval;
+
+	ret = ns2_led_get_mode(led, &mode);
+	if (ret < 0)
+		return ret;
+
+	/* Set LED initial state. */
+	led->sata = (mode == NS_V2_LED_SATA) ? 1 : 0;
+	led->cdev.brightness = (mode == NS_V2_LED_OFF) ? LED_OFF : LED_FULL;
+
+	init_data.fwnode = node;
+
+	ret = devm_led_classdev_register_ext(dev, &led->cdev, &init_data);
+	if (ret)
+		dev_err(dev, "Failed to register LED for node %pfw\n", node);
+
+	return ret;
+}
+
+static int ns2_led_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct ns2_led *leds;
+	int count;
+	int ret;
+
+	count = device_get_child_node_count(dev);
+	if (!count)
+		return -ENODEV;
+
+	leds = devm_kcalloc(dev, count, sizeof(*leds), GFP_KERNEL);
+	if (!leds)
+		return -ENOMEM;
+
+	device_for_each_child_node_scoped(dev, child) {
+		ret = ns2_led_register(dev, child, leds++);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id of_ns2_leds_match[] = {
+	{ .compatible = "lacie,ns2-leds", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_ns2_leds_match);
+
+static struct platform_driver ns2_led_driver = {
+	.probe		= ns2_led_probe,
+	.driver		= {
+		.name		= "leds-ns2",
+		.of_match_table	= of_ns2_leds_match,
+	},
+};
+
+module_platform_driver(ns2_led_driver);
+
+MODULE_AUTHOR("Simon Guinot <sguinot@lacie.com>");
+MODULE_DESCRIPTION("Network Space v2 LED driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:leds-ns2");