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, 239 insertions, 0 deletions

diff --git a/drivers/video/backlight/locomolcd.c b/drivers/video/backlight/locomolcd.c
new file mode 100644
index 000000000..1b493fb05
--- /dev/null
+++ b/drivers/video/backlight/locomolcd.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backlight control code for Sharp Zaurus SL-5500
+ *
+ * Copyright 2005 John Lenz <lenz@cs.wisc.edu>
+ * Maintainer: Pavel Machek <pavel@ucw.cz> (unless John wants to :-)
+ *
+ * This driver assumes single CPU. That's okay, because collie is
+ * slightly old hardware, and no one is going to retrofit second CPU to
+ * old PDA.
+ */
+
+/* LCD power functions */
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/backlight.h>
+
+#include <asm/hardware/locomo.h>
+#include <asm/irq.h>
+#include <asm/mach/sharpsl_param.h>
+#include <asm/mach-types.h>
+
+#include "../../../arch/arm/mach-sa1100/generic.h"
+
+static struct backlight_device *locomolcd_bl_device;
+static struct locomo_dev *locomolcd_dev;
+static unsigned long locomolcd_flags;
+#define LOCOMOLCD_SUSPENDED     0x01
+
+static void locomolcd_on(int comadj)
+{
+	locomo_gpio_set_dir(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_VSHA_ON, 0);
+	locomo_gpio_write(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_VSHA_ON, 1);
+	mdelay(2);
+
+	locomo_gpio_set_dir(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_VSHD_ON, 0);
+	locomo_gpio_write(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_VSHD_ON, 1);
+	mdelay(2);
+
+	locomo_m62332_senddata(locomolcd_dev, comadj, 0);
+	mdelay(5);
+
+	locomo_gpio_set_dir(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_VEE_ON, 0);
+	locomo_gpio_write(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_VEE_ON, 1);
+	mdelay(10);
+
+	/* TFTCRST | CPSOUT=0 | CPSEN */
+	locomo_writel(0x01, locomolcd_dev->mapbase + LOCOMO_TC);
+
+	/* Set CPSD */
+	locomo_writel(6, locomolcd_dev->mapbase + LOCOMO_CPSD);
+
+	/* TFTCRST | CPSOUT=0 | CPSEN */
+	locomo_writel((0x04 | 0x01), locomolcd_dev->mapbase + LOCOMO_TC);
+	mdelay(10);
+
+	locomo_gpio_set_dir(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_MOD, 0);
+	locomo_gpio_write(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_MOD, 1);
+}
+
+static void locomolcd_off(int comadj)
+{
+	/* TFTCRST=1 | CPSOUT=1 | CPSEN = 0 */
+	locomo_writel(0x06, locomolcd_dev->mapbase + LOCOMO_TC);
+	mdelay(1);
+
+	locomo_gpio_write(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_VSHA_ON, 0);
+	mdelay(110);
+
+	locomo_gpio_write(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_VEE_ON, 0);
+	mdelay(700);
+
+	/* TFTCRST=0 | CPSOUT=0 | CPSEN = 0 */
+	locomo_writel(0, locomolcd_dev->mapbase + LOCOMO_TC);
+	locomo_gpio_write(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_MOD, 0);
+	locomo_gpio_write(locomolcd_dev->dev.parent, LOCOMO_GPIO_LCD_VSHD_ON, 0);
+}
+
+void locomolcd_power(int on)
+{
+	int comadj = sharpsl_param.comadj;
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	if (!locomolcd_dev) {
+		local_irq_restore(flags);
+		return;
+	}
+
+	/* read comadj */
+	if (comadj == -1 && machine_is_collie())
+		comadj = 128;
+
+	if (on)
+		locomolcd_on(comadj);
+	else
+		locomolcd_off(comadj);
+
+	local_irq_restore(flags);
+}
+EXPORT_SYMBOL(locomolcd_power);
+
+static int current_intensity;
+
+static int locomolcd_set_intensity(struct backlight_device *bd)
+{
+	int intensity = backlight_get_brightness(bd);
+
+	if (locomolcd_flags & LOCOMOLCD_SUSPENDED)
+		intensity = 0;
+
+	switch (intensity) {
+	/*
+	 * AC and non-AC are handled differently,
+	 * but produce same results in sharp code?
+	 */
+	case 0:
+		locomo_frontlight_set(locomolcd_dev, 0, 0, 161);
+		break;
+	case 1:
+		locomo_frontlight_set(locomolcd_dev, 117, 0, 161);
+		break;
+	case 2:
+		locomo_frontlight_set(locomolcd_dev, 163, 0, 148);
+		break;
+	case 3:
+		locomo_frontlight_set(locomolcd_dev, 194, 0, 161);
+		break;
+	case 4:
+		locomo_frontlight_set(locomolcd_dev, 194, 1, 161);
+		break;
+	default:
+		return -ENODEV;
+	}
+	current_intensity = intensity;
+	return 0;
+}
+
+static int locomolcd_get_intensity(struct backlight_device *bd)
+{
+	return current_intensity;
+}
+
+static const struct backlight_ops locomobl_data = {
+	.get_brightness = locomolcd_get_intensity,
+	.update_status  = locomolcd_set_intensity,
+};
+
+#ifdef CONFIG_PM_SLEEP
+static int locomolcd_suspend(struct device *dev)
+{
+	locomolcd_flags |= LOCOMOLCD_SUSPENDED;
+	locomolcd_set_intensity(locomolcd_bl_device);
+	return 0;
+}
+
+static int locomolcd_resume(struct device *dev)
+{
+	locomolcd_flags &= ~LOCOMOLCD_SUSPENDED;
+	locomolcd_set_intensity(locomolcd_bl_device);
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(locomolcd_pm_ops, locomolcd_suspend, locomolcd_resume);
+
+static int locomolcd_probe(struct locomo_dev *ldev)
+{
+	struct backlight_properties props;
+	unsigned long flags;
+
+	local_irq_save(flags);
+	locomolcd_dev = ldev;
+
+	locomo_gpio_set_dir(ldev->dev.parent, LOCOMO_GPIO_FL_VR, 0);
+
+	local_irq_restore(flags);
+
+	memset(&props, 0, sizeof(struct backlight_properties));
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = 4;
+	locomolcd_bl_device = backlight_device_register("locomo-bl",
+							&ldev->dev, NULL,
+							&locomobl_data, &props);
+
+	if (IS_ERR(locomolcd_bl_device))
+		return PTR_ERR(locomolcd_bl_device);
+
+	/* Set up frontlight so that screen is readable */
+	locomolcd_bl_device->props.brightness = 2;
+	locomolcd_set_intensity(locomolcd_bl_device);
+
+	return 0;
+}
+
+static void locomolcd_remove(struct locomo_dev *dev)
+{
+	unsigned long flags;
+
+	locomolcd_bl_device->props.brightness = 0;
+	locomolcd_bl_device->props.power = 0;
+	locomolcd_set_intensity(locomolcd_bl_device);
+
+	backlight_device_unregister(locomolcd_bl_device);
+	local_irq_save(flags);
+	locomolcd_dev = NULL;
+	local_irq_restore(flags);
+}
+
+static struct locomo_driver poodle_lcd_driver = {
+	.drv = {
+		.name	= "locomo-backlight",
+		.pm	= &locomolcd_pm_ops,
+	},
+	.devid	= LOCOMO_DEVID_BACKLIGHT,
+	.probe	= locomolcd_probe,
+	.remove	= locomolcd_remove,
+};
+
+static int __init locomolcd_init(void)
+{
+	return locomo_driver_register(&poodle_lcd_driver);
+}
+
+static void __exit locomolcd_exit(void)
+{
+	locomo_driver_unregister(&poodle_lcd_driver);
+}
+
+module_init(locomolcd_init);
+module_exit(locomolcd_exit);
+
+MODULE_AUTHOR("John Lenz <lenz@cs.wisc.edu>, Pavel Machek <pavel@ucw.cz>");
+MODULE_DESCRIPTION("Collie LCD driver");
+MODULE_LICENSE("GPL");