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, 252 insertions, 0 deletions

diff --git a/drivers/leds/leds-sunfire.c b/drivers/leds/leds-sunfire.c
new file mode 100644
index 000000000..bd24e7f59
--- /dev/null
+++ b/drivers/leds/leds-sunfire.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* leds-sunfire.c: SUNW,Ultra-Enterprise LED driver.
+ *
+ * Copyright (C) 2008 David S. Miller <davem@davemloft.net>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <asm/fhc.h>
+#include <asm/upa.h>
+
+MODULE_AUTHOR("David S. Miller <davem@davemloft.net>");
+MODULE_DESCRIPTION("Sun Fire LED driver");
+MODULE_LICENSE("GPL");
+
+struct sunfire_led {
+	struct led_classdev	led_cdev;
+	void __iomem		*reg;
+};
+#define	to_sunfire_led(d) container_of(d, struct sunfire_led, led_cdev)
+
+static void __clockboard_set(struct led_classdev *led_cdev,
+			     enum led_brightness led_val, u8 bit)
+{
+	struct sunfire_led *p = to_sunfire_led(led_cdev);
+	u8 reg = upa_readb(p->reg);
+
+	switch (bit) {
+	case CLOCK_CTRL_LLED:
+		if (led_val)
+			reg &= ~bit;
+		else
+			reg |= bit;
+		break;
+
+	default:
+		if (led_val)
+			reg |= bit;
+		else
+			reg &= ~bit;
+		break;
+	}
+	upa_writeb(reg, p->reg);
+}
+
+static void clockboard_left_set(struct led_classdev *led_cdev,
+				enum led_brightness led_val)
+{
+	__clockboard_set(led_cdev, led_val, CLOCK_CTRL_LLED);
+}
+
+static void clockboard_middle_set(struct led_classdev *led_cdev,
+				  enum led_brightness led_val)
+{
+	__clockboard_set(led_cdev, led_val, CLOCK_CTRL_MLED);
+}
+
+static void clockboard_right_set(struct led_classdev *led_cdev,
+				 enum led_brightness led_val)
+{
+	__clockboard_set(led_cdev, led_val, CLOCK_CTRL_RLED);
+}
+
+static void __fhc_set(struct led_classdev *led_cdev,
+			     enum led_brightness led_val, u32 bit)
+{
+	struct sunfire_led *p = to_sunfire_led(led_cdev);
+	u32 reg = upa_readl(p->reg);
+
+	switch (bit) {
+	case FHC_CONTROL_LLED:
+		if (led_val)
+			reg &= ~bit;
+		else
+			reg |= bit;
+		break;
+
+	default:
+		if (led_val)
+			reg |= bit;
+		else
+			reg &= ~bit;
+		break;
+	}
+	upa_writel(reg, p->reg);
+}
+
+static void fhc_left_set(struct led_classdev *led_cdev,
+			 enum led_brightness led_val)
+{
+	__fhc_set(led_cdev, led_val, FHC_CONTROL_LLED);
+}
+
+static void fhc_middle_set(struct led_classdev *led_cdev,
+			   enum led_brightness led_val)
+{
+	__fhc_set(led_cdev, led_val, FHC_CONTROL_MLED);
+}
+
+static void fhc_right_set(struct led_classdev *led_cdev,
+			  enum led_brightness led_val)
+{
+	__fhc_set(led_cdev, led_val, FHC_CONTROL_RLED);
+}
+
+typedef void (*set_handler)(struct led_classdev *, enum led_brightness);
+struct led_type {
+	const char	*name;
+	set_handler	handler;
+	const char	*default_trigger;
+};
+
+#define NUM_LEDS_PER_BOARD	3
+struct sunfire_drvdata {
+	struct sunfire_led	leds[NUM_LEDS_PER_BOARD];
+};
+
+static int sunfire_led_generic_probe(struct platform_device *pdev,
+					       struct led_type *types)
+{
+	struct sunfire_drvdata *p;
+	int i, err;
+
+	if (pdev->num_resources != 1) {
+		dev_err(&pdev->dev, "Wrong number of resources %d, should be 1\n",
+		       pdev->num_resources);
+		return -EINVAL;
+	}
+
+	p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
+	for (i = 0; i < NUM_LEDS_PER_BOARD; i++) {
+		struct led_classdev *lp = &p->leds[i].led_cdev;
+
+		p->leds[i].reg = (void __iomem *) pdev->resource[0].start;
+		lp->name = types[i].name;
+		lp->brightness = LED_FULL;
+		lp->brightness_set = types[i].handler;
+		lp->default_trigger = types[i].default_trigger;
+
+		err = led_classdev_register(&pdev->dev, lp);
+		if (err) {
+			dev_err(&pdev->dev, "Could not register %s LED\n",
+			       lp->name);
+			for (i--; i >= 0; i--)
+				led_classdev_unregister(&p->leds[i].led_cdev);
+			return err;
+		}
+	}
+
+	platform_set_drvdata(pdev, p);
+
+	return 0;
+}
+
+static void sunfire_led_generic_remove(struct platform_device *pdev)
+{
+	struct sunfire_drvdata *p = platform_get_drvdata(pdev);
+	int i;
+
+	for (i = 0; i < NUM_LEDS_PER_BOARD; i++)
+		led_classdev_unregister(&p->leds[i].led_cdev);
+}
+
+static struct led_type clockboard_led_types[NUM_LEDS_PER_BOARD] = {
+	{
+		.name		= "clockboard-left",
+		.handler	= clockboard_left_set,
+	},
+	{
+		.name		= "clockboard-middle",
+		.handler	= clockboard_middle_set,
+	},
+	{
+		.name		= "clockboard-right",
+		.handler	= clockboard_right_set,
+		.default_trigger = "heartbeat",
+	},
+};
+
+static int sunfire_clockboard_led_probe(struct platform_device *pdev)
+{
+	return sunfire_led_generic_probe(pdev, clockboard_led_types);
+}
+
+static struct led_type fhc_led_types[NUM_LEDS_PER_BOARD] = {
+	{
+		.name		= "fhc-left",
+		.handler	= fhc_left_set,
+	},
+	{
+		.name		= "fhc-middle",
+		.handler	= fhc_middle_set,
+	},
+	{
+		.name		= "fhc-right",
+		.handler	= fhc_right_set,
+		.default_trigger = "heartbeat",
+	},
+};
+
+static int sunfire_fhc_led_probe(struct platform_device *pdev)
+{
+	return sunfire_led_generic_probe(pdev, fhc_led_types);
+}
+
+MODULE_ALIAS("platform:sunfire-clockboard-leds");
+MODULE_ALIAS("platform:sunfire-fhc-leds");
+
+static struct platform_driver sunfire_clockboard_led_driver = {
+	.probe		= sunfire_clockboard_led_probe,
+	.remove		= sunfire_led_generic_remove,
+	.driver		= {
+		.name	= "sunfire-clockboard-leds",
+	},
+};
+
+static struct platform_driver sunfire_fhc_led_driver = {
+	.probe		= sunfire_fhc_led_probe,
+	.remove		= sunfire_led_generic_remove,
+	.driver		= {
+		.name	= "sunfire-fhc-leds",
+	},
+};
+
+static struct platform_driver * const drivers[] = {
+	&sunfire_clockboard_led_driver,
+	&sunfire_fhc_led_driver,
+};
+
+static int __init sunfire_leds_init(void)
+{
+	return platform_register_drivers(drivers, ARRAY_SIZE(drivers));
+}
+
+static void __exit sunfire_leds_exit(void)
+{
+	platform_unregister_drivers(drivers, ARRAY_SIZE(drivers));
+}
+
+module_init(sunfire_leds_init);
+module_exit(sunfire_leds_exit);