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, 260 insertions, 0 deletions

diff --git a/drivers/input/keyboard/mt6779-keypad.c b/drivers/input/keyboard/mt6779-keypad.c
new file mode 100644
index 000000000..e5eb025c5
--- /dev/null
+++ b/drivers/input/keyboard/mt6779-keypad.c
@@ -0,0 +1,260 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 MediaTek Inc.
+ * Author Fengping Yu <fengping.yu@mediatek.com>
+ */
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/input.h>
+#include <linux/input/matrix_keypad.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define MTK_KPD_NAME		"mt6779-keypad"
+#define MTK_KPD_MEM		0x0004
+#define MTK_KPD_DEBOUNCE	0x0018
+#define MTK_KPD_DEBOUNCE_MASK	GENMASK(13, 0)
+#define MTK_KPD_DEBOUNCE_MAX_MS	256
+#define MTK_KPD_SEL		0x0020
+#define MTK_KPD_SEL_DOUBLE_KP_MODE	BIT(0)
+#define MTK_KPD_SEL_COL	GENMASK(15, 10)
+#define MTK_KPD_SEL_ROW	GENMASK(9, 4)
+#define MTK_KPD_SEL_COLMASK(c)	GENMASK((c) + 9, 10)
+#define MTK_KPD_SEL_ROWMASK(r)	GENMASK((r) + 3, 4)
+#define MTK_KPD_NUM_MEMS	5
+#define MTK_KPD_NUM_BITS	136	/* 4*32+8 MEM5 only use 8 BITS */
+
+struct mt6779_keypad {
+	struct regmap *regmap;
+	struct input_dev *input_dev;
+	struct clk *clk;
+	u32 n_rows;
+	u32 n_cols;
+	void (*calc_row_col)(unsigned int key,
+			     unsigned int *row, unsigned int *col);
+	DECLARE_BITMAP(keymap_state, MTK_KPD_NUM_BITS);
+};
+
+static const struct regmap_config mt6779_keypad_regmap_cfg = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = sizeof(u32),
+	.max_register = 36,
+};
+
+static irqreturn_t mt6779_keypad_irq_handler(int irq, void *dev_id)
+{
+	struct mt6779_keypad *keypad = dev_id;
+	const unsigned short *keycode = keypad->input_dev->keycode;
+	DECLARE_BITMAP(new_state, MTK_KPD_NUM_BITS);
+	DECLARE_BITMAP(change, MTK_KPD_NUM_BITS);
+	unsigned int bit_nr, key;
+	unsigned int row, col;
+	unsigned int scancode;
+	unsigned int row_shift = get_count_order(keypad->n_cols);
+	bool pressed;
+
+	regmap_bulk_read(keypad->regmap, MTK_KPD_MEM,
+			 new_state, MTK_KPD_NUM_MEMS);
+
+	bitmap_xor(change, new_state, keypad->keymap_state, MTK_KPD_NUM_BITS);
+
+	for_each_set_bit(bit_nr, change, MTK_KPD_NUM_BITS) {
+		/*
+		 * Registers are 32bits, but only bits [15:0] are used to
+		 * indicate key status.
+		 */
+		if (bit_nr % 32 >= 16)
+			continue;
+
+		key = bit_nr / 32 * 16 + bit_nr % 32;
+		keypad->calc_row_col(key, &row, &col);
+
+		scancode = MATRIX_SCAN_CODE(row, col, row_shift);
+		/* 1: not pressed, 0: pressed */
+		pressed = !test_bit(bit_nr, new_state);
+		dev_dbg(&keypad->input_dev->dev, "%s",
+			pressed ? "pressed" : "released");
+
+		input_event(keypad->input_dev, EV_MSC, MSC_SCAN, scancode);
+		input_report_key(keypad->input_dev, keycode[scancode], pressed);
+		input_sync(keypad->input_dev);
+
+		dev_dbg(&keypad->input_dev->dev,
+			"report Linux keycode = %d\n", keycode[scancode]);
+	}
+
+	bitmap_copy(keypad->keymap_state, new_state, MTK_KPD_NUM_BITS);
+
+	return IRQ_HANDLED;
+}
+
+static void mt6779_keypad_calc_row_col_single(unsigned int key,
+					      unsigned int *row,
+					      unsigned int *col)
+{
+	*row = key / 9;
+	*col = key % 9;
+}
+
+static void mt6779_keypad_calc_row_col_double(unsigned int key,
+					      unsigned int *row,
+					      unsigned int *col)
+{
+	*row = key / 13;
+	*col = (key % 13) / 2;
+}
+
+static int mt6779_keypad_pdrv_probe(struct platform_device *pdev)
+{
+	struct mt6779_keypad *keypad;
+	void __iomem *base;
+	int irq;
+	u32 debounce;
+	u32 keys_per_group;
+	bool wakeup;
+	int error;
+
+	keypad = devm_kzalloc(&pdev->dev, sizeof(*keypad), GFP_KERNEL);
+	if (!keypad)
+		return -ENOMEM;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	keypad->regmap = devm_regmap_init_mmio(&pdev->dev, base,
+					       &mt6779_keypad_regmap_cfg);
+	if (IS_ERR(keypad->regmap)) {
+		dev_err(&pdev->dev,
+			"regmap init failed:%pe\n", keypad->regmap);
+		return PTR_ERR(keypad->regmap);
+	}
+
+	bitmap_fill(keypad->keymap_state, MTK_KPD_NUM_BITS);
+
+	keypad->input_dev = devm_input_allocate_device(&pdev->dev);
+	if (!keypad->input_dev) {
+		dev_err(&pdev->dev, "Failed to allocate input dev\n");
+		return -ENOMEM;
+	}
+
+	keypad->input_dev->name = MTK_KPD_NAME;
+	keypad->input_dev->id.bustype = BUS_HOST;
+
+	error = matrix_keypad_parse_properties(&pdev->dev, &keypad->n_rows,
+					       &keypad->n_cols);
+	if (error) {
+		dev_err(&pdev->dev, "Failed to parse keypad params\n");
+		return error;
+	}
+
+	if (device_property_read_u32(&pdev->dev, "debounce-delay-ms",
+				     &debounce))
+		debounce = 16;
+
+	if (debounce > MTK_KPD_DEBOUNCE_MAX_MS) {
+		dev_err(&pdev->dev,
+			"Debounce time exceeds the maximum allowed time %dms\n",
+			MTK_KPD_DEBOUNCE_MAX_MS);
+		return -EINVAL;
+	}
+
+	if (device_property_read_u32(&pdev->dev, "mediatek,keys-per-group",
+				     &keys_per_group))
+		keys_per_group = 1;
+
+	switch (keys_per_group) {
+	case 1:
+		keypad->calc_row_col = mt6779_keypad_calc_row_col_single;
+		break;
+	case 2:
+		keypad->calc_row_col = mt6779_keypad_calc_row_col_double;
+		break;
+	default:
+		dev_err(&pdev->dev,
+			"Invalid keys-per-group: %d\n", keys_per_group);
+		return -EINVAL;
+	}
+
+	wakeup = device_property_read_bool(&pdev->dev, "wakeup-source");
+
+	dev_dbg(&pdev->dev, "n_row=%d n_col=%d debounce=%d\n",
+		keypad->n_rows, keypad->n_cols, debounce);
+
+	error = matrix_keypad_build_keymap(NULL, NULL,
+					   keypad->n_rows, keypad->n_cols,
+					   NULL, keypad->input_dev);
+	if (error) {
+		dev_err(&pdev->dev, "Failed to build keymap\n");
+		return error;
+	}
+
+	input_set_capability(keypad->input_dev, EV_MSC, MSC_SCAN);
+
+	regmap_write(keypad->regmap, MTK_KPD_DEBOUNCE,
+		     (debounce * (1 << 5)) & MTK_KPD_DEBOUNCE_MASK);
+
+	if (keys_per_group == 2)
+		regmap_update_bits(keypad->regmap, MTK_KPD_SEL,
+				   MTK_KPD_SEL_DOUBLE_KP_MODE,
+				   MTK_KPD_SEL_DOUBLE_KP_MODE);
+
+	regmap_update_bits(keypad->regmap, MTK_KPD_SEL, MTK_KPD_SEL_ROW,
+			   MTK_KPD_SEL_ROWMASK(keypad->n_rows));
+	regmap_update_bits(keypad->regmap, MTK_KPD_SEL, MTK_KPD_SEL_COL,
+			   MTK_KPD_SEL_COLMASK(keypad->n_cols));
+
+	keypad->clk = devm_clk_get_enabled(&pdev->dev, "kpd");
+	if (IS_ERR(keypad->clk))
+		return PTR_ERR(keypad->clk);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	error = devm_request_threaded_irq(&pdev->dev, irq,
+					  NULL, mt6779_keypad_irq_handler,
+					  IRQF_ONESHOT, MTK_KPD_NAME, keypad);
+	if (error) {
+		dev_err(&pdev->dev, "Failed to request IRQ#%d: %d\n",
+			irq, error);
+		return error;
+	}
+
+	error = input_register_device(keypad->input_dev);
+	if (error) {
+		dev_err(&pdev->dev, "Failed to register device\n");
+		return error;
+	}
+
+	error = device_init_wakeup(&pdev->dev, wakeup);
+	if (error)
+		dev_warn(&pdev->dev, "device_init_wakeup() failed: %d\n",
+			 error);
+
+	return 0;
+}
+
+static const struct of_device_id mt6779_keypad_of_match[] = {
+	{ .compatible = "mediatek,mt6779-keypad" },
+	{ .compatible = "mediatek,mt6873-keypad" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mt6779_keypad_of_match);
+
+static struct platform_driver mt6779_keypad_pdrv = {
+	.probe = mt6779_keypad_pdrv_probe,
+	.driver = {
+		   .name = MTK_KPD_NAME,
+		   .of_match_table = mt6779_keypad_of_match,
+	},
+};
+module_platform_driver(mt6779_keypad_pdrv);
+
+MODULE_AUTHOR("Mediatek Corporation");
+MODULE_DESCRIPTION("MTK Keypad (KPD) Driver");
+MODULE_LICENSE("GPL");