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, 192 insertions, 0 deletions

diff --git a/drivers/input/misc/max7360-rotary.c b/drivers/input/misc/max7360-rotary.c
new file mode 100644
index 000000000..385831ef3
--- /dev/null
+++ b/drivers/input/misc/max7360-rotary.c
@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2025 Bootlin
+ *
+ * Author: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/device/devres.h>
+#include <linux/dev_printk.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/interrupt.h>
+#include <linux/mfd/max7360.h>
+#include <linux/property.h>
+#include <linux/platform_device.h>
+#include <linux/pm_wakeirq.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+#define MAX7360_ROTARY_DEFAULT_STEPS 24
+
+struct max7360_rotary {
+	struct input_dev *input;
+	struct regmap *regmap;
+	unsigned int debounce_ms;
+
+	unsigned int pos;
+
+	u32 steps;
+	u32 axis;
+	bool relative_axis;
+	bool rollover;
+};
+
+static void max7360_rotary_report_event(struct max7360_rotary *max7360_rotary, int steps)
+{
+	if (max7360_rotary->relative_axis) {
+		input_report_rel(max7360_rotary->input, max7360_rotary->axis, steps);
+	} else {
+		int pos = max7360_rotary->pos;
+		int maxval = max7360_rotary->steps;
+
+		/*
+		 * Add steps to the position.
+		 * Make sure added steps are always in ]-maxval; maxval[
+		 * interval, so (pos + maxval) is always >= 0.
+		 * Then set back pos to the [0; maxval[ interval.
+		 */
+		pos += steps % maxval;
+		if (max7360_rotary->rollover)
+			pos = (pos + maxval) % maxval;
+		else
+			pos = clamp(pos, 0, maxval - 1);
+
+		max7360_rotary->pos = pos;
+		input_report_abs(max7360_rotary->input, max7360_rotary->axis, max7360_rotary->pos);
+	}
+
+	input_sync(max7360_rotary->input);
+}
+
+static irqreturn_t max7360_rotary_irq(int irq, void *data)
+{
+	struct max7360_rotary *max7360_rotary = data;
+	struct device *dev = max7360_rotary->input->dev.parent;
+	unsigned int val;
+	int error;
+
+	error = regmap_read(max7360_rotary->regmap, MAX7360_REG_RTR_CNT, &val);
+	if (error < 0) {
+		dev_err(dev, "Failed to read rotary counter\n");
+		return IRQ_NONE;
+	}
+
+	if (val == 0)
+		return IRQ_NONE;
+
+	max7360_rotary_report_event(max7360_rotary, sign_extend32(val, 7));
+
+	return IRQ_HANDLED;
+}
+
+static int max7360_rotary_hw_init(struct max7360_rotary *max7360_rotary)
+{
+	struct device *dev = max7360_rotary->input->dev.parent;
+	int val;
+	int error;
+
+	val = FIELD_PREP(MAX7360_ROT_DEBOUNCE, max7360_rotary->debounce_ms) |
+	      FIELD_PREP(MAX7360_ROT_INTCNT, 1) | MAX7360_ROT_INTCNT_DLY;
+	error = regmap_write(max7360_rotary->regmap, MAX7360_REG_RTRCFG, val);
+	if (error)
+		dev_err(dev, "Failed to set max7360 rotary encoder configuration\n");
+
+	return error;
+}
+
+static int max7360_rotary_probe(struct platform_device *pdev)
+{
+	struct max7360_rotary *max7360_rotary;
+	struct device *dev = &pdev->dev;
+	struct input_dev *input;
+	struct regmap *regmap;
+	int irq;
+	int error;
+
+	regmap = dev_get_regmap(dev->parent, NULL);
+	if (!regmap)
+		return dev_err_probe(dev, -ENODEV, "Could not get parent regmap\n");
+
+	irq = fwnode_irq_get_byname(dev_fwnode(dev->parent), "inti");
+	if (irq < 0)
+		return dev_err_probe(dev, irq, "Failed to get IRQ\n");
+
+	max7360_rotary = devm_kzalloc(dev, sizeof(*max7360_rotary), GFP_KERNEL);
+	if (!max7360_rotary)
+		return -ENOMEM;
+
+	max7360_rotary->regmap = regmap;
+
+	device_property_read_u32(dev->parent, "linux,axis", &max7360_rotary->axis);
+	max7360_rotary->rollover = device_property_read_bool(dev->parent,
+							     "rotary-encoder,rollover");
+	max7360_rotary->relative_axis =
+		device_property_read_bool(dev->parent, "rotary-encoder,relative-axis");
+
+	error = device_property_read_u32(dev->parent, "rotary-encoder,steps",
+					 &max7360_rotary->steps);
+	if (error)
+		max7360_rotary->steps = MAX7360_ROTARY_DEFAULT_STEPS;
+
+	device_property_read_u32(dev->parent, "rotary-debounce-delay-ms",
+				 &max7360_rotary->debounce_ms);
+	if (max7360_rotary->debounce_ms > MAX7360_ROT_DEBOUNCE_MAX)
+		return dev_err_probe(dev, -EINVAL, "Invalid debounce timing: %u\n",
+				     max7360_rotary->debounce_ms);
+
+	input = devm_input_allocate_device(dev);
+	if (!input)
+		return -ENOMEM;
+
+	max7360_rotary->input = input;
+
+	input->id.bustype = BUS_I2C;
+	input->name = pdev->name;
+
+	if (max7360_rotary->relative_axis)
+		input_set_capability(input, EV_REL, max7360_rotary->axis);
+	else
+		input_set_abs_params(input, max7360_rotary->axis, 0, max7360_rotary->steps, 0, 1);
+
+	error = devm_request_threaded_irq(dev, irq, NULL, max7360_rotary_irq,
+					  IRQF_ONESHOT | IRQF_SHARED,
+					  "max7360-rotary", max7360_rotary);
+	if (error)
+		return dev_err_probe(dev, error, "Failed to register interrupt\n");
+
+	error = input_register_device(input);
+	if (error)
+		return dev_err_probe(dev, error, "Could not register input device\n");
+
+	error = max7360_rotary_hw_init(max7360_rotary);
+	if (error)
+		return dev_err_probe(dev, error, "Failed to initialize max7360 rotary\n");
+
+	device_init_wakeup(dev, true);
+	error = dev_pm_set_wake_irq(dev, irq);
+	if (error)
+		dev_warn(dev, "Failed to set up wakeup irq: %d\n", error);
+
+	return 0;
+}
+
+static void max7360_rotary_remove(struct platform_device *pdev)
+{
+	dev_pm_clear_wake_irq(&pdev->dev);
+	device_init_wakeup(&pdev->dev, false);
+}
+
+static struct platform_driver max7360_rotary_driver = {
+	.driver = {
+		.name	= "max7360-rotary",
+	},
+	.probe		= max7360_rotary_probe,
+	.remove		= max7360_rotary_remove,
+};
+module_platform_driver(max7360_rotary_driver);
+
+MODULE_DESCRIPTION("MAX7360 Rotary driver");
+MODULE_AUTHOR("Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>");
+MODULE_LICENSE("GPL");