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, 271 insertions, 0 deletions

diff --git a/drivers/input/keyboard/st-keyscan.c b/drivers/input/keyboard/st-keyscan.c
new file mode 100644
index 000000000..e53ef4c67
--- /dev/null
+++ b/drivers/input/keyboard/st-keyscan.c
@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * STMicroelectronics Key Scanning driver
+ *
+ * Copyright (c) 2014 STMicroelectonics Ltd.
+ * Author: Stuart Menefy <stuart.menefy@st.com>
+ *
+ * Based on sh_keysc.c, copyright 2008 Magnus Damm
+ */
+
+#include <linux/clk.h>
+#include <linux/input.h>
+#include <linux/input/matrix_keypad.h>
+#include <linux/io.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#define ST_KEYSCAN_MAXKEYS 16
+
+#define KEYSCAN_CONFIG_OFF		0x0
+#define KEYSCAN_CONFIG_ENABLE		0x1
+#define KEYSCAN_DEBOUNCE_TIME_OFF	0x4
+#define KEYSCAN_MATRIX_STATE_OFF	0x8
+#define KEYSCAN_MATRIX_DIM_OFF		0xc
+#define KEYSCAN_MATRIX_DIM_X_SHIFT	0x0
+#define KEYSCAN_MATRIX_DIM_Y_SHIFT	0x2
+
+struct st_keyscan {
+	void __iomem *base;
+	int irq;
+	struct clk *clk;
+	struct input_dev *input_dev;
+	unsigned long last_state;
+	unsigned int n_rows;
+	unsigned int n_cols;
+	unsigned int debounce_us;
+};
+
+static irqreturn_t keyscan_isr(int irq, void *dev_id)
+{
+	struct st_keyscan *keypad = dev_id;
+	unsigned short *keycode = keypad->input_dev->keycode;
+	unsigned long state, change;
+	int bit_nr;
+
+	state = readl(keypad->base + KEYSCAN_MATRIX_STATE_OFF) & 0xffff;
+	change = keypad->last_state ^ state;
+	keypad->last_state = state;
+
+	for_each_set_bit(bit_nr, &change, BITS_PER_LONG)
+		input_report_key(keypad->input_dev,
+				 keycode[bit_nr], state & BIT(bit_nr));
+
+	input_sync(keypad->input_dev);
+
+	return IRQ_HANDLED;
+}
+
+static int keyscan_start(struct st_keyscan *keypad)
+{
+	int error;
+
+	error = clk_enable(keypad->clk);
+	if (error)
+		return error;
+
+	writel(keypad->debounce_us * (clk_get_rate(keypad->clk) / 1000000),
+	       keypad->base + KEYSCAN_DEBOUNCE_TIME_OFF);
+
+	writel(((keypad->n_cols - 1) << KEYSCAN_MATRIX_DIM_X_SHIFT) |
+	       ((keypad->n_rows - 1) << KEYSCAN_MATRIX_DIM_Y_SHIFT),
+	       keypad->base + KEYSCAN_MATRIX_DIM_OFF);
+
+	writel(KEYSCAN_CONFIG_ENABLE, keypad->base + KEYSCAN_CONFIG_OFF);
+
+	return 0;
+}
+
+static void keyscan_stop(struct st_keyscan *keypad)
+{
+	writel(0, keypad->base + KEYSCAN_CONFIG_OFF);
+
+	clk_disable(keypad->clk);
+}
+
+static int keyscan_open(struct input_dev *dev)
+{
+	struct st_keyscan *keypad = input_get_drvdata(dev);
+
+	return keyscan_start(keypad);
+}
+
+static void keyscan_close(struct input_dev *dev)
+{
+	struct st_keyscan *keypad = input_get_drvdata(dev);
+
+	keyscan_stop(keypad);
+}
+
+static int keypad_matrix_key_parse_dt(struct st_keyscan *keypad_data)
+{
+	struct device *dev = keypad_data->input_dev->dev.parent;
+	struct device_node *np = dev->of_node;
+	int error;
+
+	error = matrix_keypad_parse_properties(dev, &keypad_data->n_rows,
+					       &keypad_data->n_cols);
+	if (error) {
+		dev_err(dev, "failed to parse keypad params\n");
+		return error;
+	}
+
+	of_property_read_u32(np, "st,debounce-us", &keypad_data->debounce_us);
+
+	dev_dbg(dev, "n_rows=%d n_col=%d debounce=%d\n",
+		keypad_data->n_rows, keypad_data->n_cols,
+		keypad_data->debounce_us);
+
+	return 0;
+}
+
+static int keyscan_probe(struct platform_device *pdev)
+{
+	struct st_keyscan *keypad_data;
+	struct input_dev *input_dev;
+	int error;
+
+	if (!pdev->dev.of_node) {
+		dev_err(&pdev->dev, "no DT data present\n");
+		return -EINVAL;
+	}
+
+	keypad_data = devm_kzalloc(&pdev->dev, sizeof(*keypad_data),
+				   GFP_KERNEL);
+	if (!keypad_data)
+		return -ENOMEM;
+
+	input_dev = devm_input_allocate_device(&pdev->dev);
+	if (!input_dev) {
+		dev_err(&pdev->dev, "failed to allocate the input device\n");
+		return -ENOMEM;
+	}
+
+	input_dev->name = pdev->name;
+	input_dev->phys = "keyscan-keys/input0";
+	input_dev->dev.parent = &pdev->dev;
+	input_dev->open = keyscan_open;
+	input_dev->close = keyscan_close;
+
+	input_dev->id.bustype = BUS_HOST;
+
+	keypad_data->input_dev = input_dev;
+
+	error = keypad_matrix_key_parse_dt(keypad_data);
+	if (error)
+		return error;
+
+	error = matrix_keypad_build_keymap(NULL, NULL,
+					   keypad_data->n_rows,
+					   keypad_data->n_cols,
+					   NULL, input_dev);
+	if (error) {
+		dev_err(&pdev->dev, "failed to build keymap\n");
+		return error;
+	}
+
+	input_set_drvdata(input_dev, keypad_data);
+
+	keypad_data->base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(keypad_data->base))
+		return PTR_ERR(keypad_data->base);
+
+	keypad_data->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(keypad_data->clk)) {
+		dev_err(&pdev->dev, "cannot get clock\n");
+		return PTR_ERR(keypad_data->clk);
+	}
+
+	error = clk_enable(keypad_data->clk);
+	if (error) {
+		dev_err(&pdev->dev, "failed to enable clock\n");
+		return error;
+	}
+
+	keyscan_stop(keypad_data);
+
+	keypad_data->irq = platform_get_irq(pdev, 0);
+	if (keypad_data->irq < 0)
+		return -EINVAL;
+
+	error = devm_request_irq(&pdev->dev, keypad_data->irq, keyscan_isr, 0,
+				 pdev->name, keypad_data);
+	if (error) {
+		dev_err(&pdev->dev, "failed to request IRQ\n");
+		return error;
+	}
+
+	error = input_register_device(input_dev);
+	if (error) {
+		dev_err(&pdev->dev, "failed to register input device\n");
+		return error;
+	}
+
+	platform_set_drvdata(pdev, keypad_data);
+
+	device_set_wakeup_capable(&pdev->dev, 1);
+
+	return 0;
+}
+
+static int keyscan_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct st_keyscan *keypad = platform_get_drvdata(pdev);
+	struct input_dev *input = keypad->input_dev;
+
+	guard(mutex)(&input->mutex);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(keypad->irq);
+	else if (input_device_enabled(input))
+		keyscan_stop(keypad);
+
+	return 0;
+}
+
+static int keyscan_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct st_keyscan *keypad = platform_get_drvdata(pdev);
+	struct input_dev *input = keypad->input_dev;
+	int error;
+
+	guard(mutex)(&input->mutex);
+
+	if (device_may_wakeup(dev)) {
+		disable_irq_wake(keypad->irq);
+	} else if (input_device_enabled(input)) {
+		error = keyscan_start(keypad);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(keyscan_dev_pm_ops,
+				keyscan_suspend, keyscan_resume);
+
+static const struct of_device_id keyscan_of_match[] = {
+	{ .compatible = "st,sti-keyscan" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, keyscan_of_match);
+
+static struct platform_driver keyscan_device_driver = {
+	.probe		= keyscan_probe,
+	.driver		= {
+		.name	= "st-keyscan",
+		.pm	= pm_sleep_ptr(&keyscan_dev_pm_ops),
+		.of_match_table = keyscan_of_match,
+	}
+};
+
+module_platform_driver(keyscan_device_driver);
+
+MODULE_AUTHOR("Stuart Menefy <stuart.menefy@st.com>");
+MODULE_DESCRIPTION("STMicroelectronics keyscan device driver");
+MODULE_LICENSE("GPL");