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, 344 insertions, 0 deletions

diff --git a/drivers/auxdisplay/hd44780.c b/drivers/auxdisplay/hd44780.c
new file mode 100644
index 000000000..3383d2fcf
--- /dev/null
+++ b/drivers/auxdisplay/hd44780.c
@@ -0,0 +1,344 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * HD44780 Character LCD driver for Linux
+ *
+ * Copyright (C) 2000-2008, Willy Tarreau <w@1wt.eu>
+ * Copyright (C) 2016-2017 Glider bvba
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+#include "charlcd.h"
+#include "hd44780_common.h"
+
+enum hd44780_pin {
+	/* Order does matter due to writing to GPIO array subsets! */
+	PIN_DATA0,	/* Optional */
+	PIN_DATA1,	/* Optional */
+	PIN_DATA2,	/* Optional */
+	PIN_DATA3,	/* Optional */
+	PIN_DATA4,
+	PIN_DATA5,
+	PIN_DATA6,
+	PIN_DATA7,
+	PIN_CTRL_RS,
+	PIN_CTRL_RW,	/* Optional */
+	PIN_CTRL_E,
+	PIN_CTRL_BL,   /* Optional */
+	PIN_NUM
+};
+
+struct hd44780 {
+	struct gpio_desc *pins[PIN_NUM];
+};
+
+static void hd44780_backlight(struct charlcd *lcd, enum charlcd_onoff on)
+{
+	struct hd44780_common *hdc = lcd->drvdata;
+	struct hd44780 *hd = hdc->hd44780;
+
+	if (hd->pins[PIN_CTRL_BL])
+		gpiod_set_value_cansleep(hd->pins[PIN_CTRL_BL], on);
+}
+
+static void hd44780_strobe_gpio(struct hd44780 *hd)
+{
+	/* Maintain the data during 20 us before the strobe */
+	udelay(20);
+
+	gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 1);
+
+	/* Maintain the strobe during 40 us */
+	udelay(40);
+
+	gpiod_set_value_cansleep(hd->pins[PIN_CTRL_E], 0);
+}
+
+/* write to an LCD panel register in 8 bit GPIO mode */
+static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
+{
+	DECLARE_BITMAP(values, 10); /* for DATA[0-7], RS, RW */
+	unsigned int n;
+
+	values[0] = val;
+	__assign_bit(8, values, rs);
+	n = hd->pins[PIN_CTRL_RW] ? 10 : 9;
+
+	/* Present the data to the port */
+	gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], NULL, values);
+
+	hd44780_strobe_gpio(hd);
+}
+
+/* write to an LCD panel register in 4 bit GPIO mode */
+static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
+{
+	DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
+	unsigned int n;
+
+	/* High nibble + RS, RW */
+	values[0] = val >> 4;
+	__assign_bit(4, values, rs);
+	n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
+
+	/* Present the data to the port */
+	gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
+
+	hd44780_strobe_gpio(hd);
+
+	/* Low nibble */
+	values[0] &= ~0x0fUL;
+	values[0] |= val & 0x0f;
+
+	/* Present the data to the port */
+	gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
+
+	hd44780_strobe_gpio(hd);
+}
+
+/* Send a command to the LCD panel in 8 bit GPIO mode */
+static void hd44780_write_cmd_gpio8(struct hd44780_common *hdc, int cmd)
+{
+	struct hd44780 *hd = hdc->hd44780;
+
+	hd44780_write_gpio8(hd, cmd, 0);
+
+	/* The shortest command takes at least 120 us */
+	udelay(120);
+}
+
+/* Send data to the LCD panel in 8 bit GPIO mode */
+static void hd44780_write_data_gpio8(struct hd44780_common *hdc, int data)
+{
+	struct hd44780 *hd = hdc->hd44780;
+
+	hd44780_write_gpio8(hd, data, 1);
+
+	/* The shortest data takes at least 45 us */
+	udelay(45);
+}
+
+static const struct charlcd_ops hd44780_ops_gpio8 = {
+	.backlight	= hd44780_backlight,
+	.print		= hd44780_common_print,
+	.gotoxy		= hd44780_common_gotoxy,
+	.home		= hd44780_common_home,
+	.clear_display	= hd44780_common_clear_display,
+	.init_display	= hd44780_common_init_display,
+	.shift_cursor	= hd44780_common_shift_cursor,
+	.shift_display	= hd44780_common_shift_display,
+	.display	= hd44780_common_display,
+	.cursor		= hd44780_common_cursor,
+	.blink		= hd44780_common_blink,
+	.fontsize	= hd44780_common_fontsize,
+	.lines		= hd44780_common_lines,
+	.redefine_char	= hd44780_common_redefine_char,
+};
+
+/* Send a command to the LCD panel in 4 bit GPIO mode */
+static void hd44780_write_cmd_gpio4(struct hd44780_common *hdc, int cmd)
+{
+	struct hd44780 *hd = hdc->hd44780;
+
+	hd44780_write_gpio4(hd, cmd, 0);
+
+	/* The shortest command takes at least 120 us */
+	udelay(120);
+}
+
+/* Send 4-bits of a command to the LCD panel in raw 4 bit GPIO mode */
+static void hd44780_write_cmd_raw_gpio4(struct hd44780_common *hdc, int cmd)
+{
+	DECLARE_BITMAP(values, 6); /* for DATA[4-7], RS, RW */
+	struct hd44780 *hd = hdc->hd44780;
+	unsigned int n;
+
+	/* Command nibble + RS, RW */
+	values[0] = cmd & 0x0f;
+	n = hd->pins[PIN_CTRL_RW] ? 6 : 5;
+
+	/* Present the data to the port */
+	gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], NULL, values);
+
+	hd44780_strobe_gpio(hd);
+}
+
+/* Send data to the LCD panel in 4 bit GPIO mode */
+static void hd44780_write_data_gpio4(struct hd44780_common *hdc, int data)
+{
+	struct hd44780 *hd = hdc->hd44780;
+
+	hd44780_write_gpio4(hd, data, 1);
+
+	/* The shortest data takes at least 45 us */
+	udelay(45);
+}
+
+static const struct charlcd_ops hd44780_ops_gpio4 = {
+	.backlight	= hd44780_backlight,
+	.print		= hd44780_common_print,
+	.gotoxy		= hd44780_common_gotoxy,
+	.home		= hd44780_common_home,
+	.clear_display	= hd44780_common_clear_display,
+	.init_display	= hd44780_common_init_display,
+	.shift_cursor	= hd44780_common_shift_cursor,
+	.shift_display	= hd44780_common_shift_display,
+	.display	= hd44780_common_display,
+	.cursor		= hd44780_common_cursor,
+	.blink		= hd44780_common_blink,
+	.fontsize	= hd44780_common_fontsize,
+	.lines		= hd44780_common_lines,
+	.redefine_char	= hd44780_common_redefine_char,
+};
+
+static int hd44780_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	unsigned int i, base;
+	struct charlcd *lcd;
+	struct hd44780_common *hdc;
+	struct hd44780 *hd;
+	int ifwidth, ret = -ENOMEM;
+
+	/* Required pins */
+	ifwidth = gpiod_count(dev, "data");
+	if (ifwidth < 0)
+		return ifwidth;
+
+	switch (ifwidth) {
+	case 4:
+		base = PIN_DATA4;
+		break;
+	case 8:
+		base = PIN_DATA0;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	lcd = hd44780_common_alloc();
+	if (!lcd)
+		return -ENOMEM;
+
+	hd = kzalloc_obj(*hd);
+	if (!hd)
+		goto fail2;
+
+	hdc = lcd->drvdata;
+	hdc->hd44780 = hd;
+
+	for (i = 0; i < ifwidth; i++) {
+		hd->pins[base + i] = devm_gpiod_get_index(dev, "data", i,
+							  GPIOD_OUT_LOW);
+		if (IS_ERR(hd->pins[base + i])) {
+			ret = PTR_ERR(hd->pins[base + i]);
+			goto fail3;
+		}
+	}
+
+	hd->pins[PIN_CTRL_E] = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
+	if (IS_ERR(hd->pins[PIN_CTRL_E])) {
+		ret = PTR_ERR(hd->pins[PIN_CTRL_E]);
+		goto fail3;
+	}
+
+	hd->pins[PIN_CTRL_RS] = devm_gpiod_get(dev, "rs", GPIOD_OUT_HIGH);
+	if (IS_ERR(hd->pins[PIN_CTRL_RS])) {
+		ret = PTR_ERR(hd->pins[PIN_CTRL_RS]);
+		goto fail3;
+	}
+
+	/* Optional pins */
+	hd->pins[PIN_CTRL_RW] = devm_gpiod_get_optional(dev, "rw",
+							GPIOD_OUT_LOW);
+	if (IS_ERR(hd->pins[PIN_CTRL_RW])) {
+		ret = PTR_ERR(hd->pins[PIN_CTRL_RW]);
+		goto fail3;
+	}
+
+	hd->pins[PIN_CTRL_BL] = devm_gpiod_get_optional(dev, "backlight",
+							GPIOD_OUT_LOW);
+	if (IS_ERR(hd->pins[PIN_CTRL_BL])) {
+		ret = PTR_ERR(hd->pins[PIN_CTRL_BL]);
+		goto fail3;
+	}
+
+	/* Required properties */
+	ret = device_property_read_u32(dev, "display-height-chars",
+				       &lcd->height);
+	if (ret)
+		goto fail3;
+	ret = device_property_read_u32(dev, "display-width-chars", &lcd->width);
+	if (ret)
+		goto fail3;
+
+	/*
+	 * On displays with more than two rows, the internal buffer width is
+	 * usually equal to the display width
+	 */
+	if (lcd->height > 2)
+		hdc->bwidth = lcd->width;
+
+	/* Optional properties */
+	device_property_read_u32(dev, "internal-buffer-width", &hdc->bwidth);
+
+	hdc->ifwidth = ifwidth;
+	if (ifwidth == 8) {
+		lcd->ops = &hd44780_ops_gpio8;
+		hdc->write_data = hd44780_write_data_gpio8;
+		hdc->write_cmd = hd44780_write_cmd_gpio8;
+	} else {
+		lcd->ops = &hd44780_ops_gpio4;
+		hdc->write_data = hd44780_write_data_gpio4;
+		hdc->write_cmd = hd44780_write_cmd_gpio4;
+		hdc->write_cmd_raw4 = hd44780_write_cmd_raw_gpio4;
+	}
+
+	ret = charlcd_register(lcd);
+	if (ret)
+		goto fail3;
+
+	platform_set_drvdata(pdev, lcd);
+	return 0;
+
+fail3:
+	kfree(hd);
+fail2:
+	hd44780_common_free(lcd);
+	return ret;
+}
+
+static void hd44780_remove(struct platform_device *pdev)
+{
+	struct charlcd *lcd = platform_get_drvdata(pdev);
+	struct hd44780_common *hdc = lcd->drvdata;
+
+	charlcd_unregister(lcd);
+	kfree(hdc->hd44780);
+	hd44780_common_free(lcd);
+}
+
+static const struct of_device_id hd44780_of_match[] = {
+	{ .compatible = "hit,hd44780" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, hd44780_of_match);
+
+static struct platform_driver hd44780_driver = {
+	.probe = hd44780_probe,
+	.remove = hd44780_remove,
+	.driver		= {
+		.name	= "hd44780",
+		.of_match_table = hd44780_of_match,
+	},
+};
+
+module_platform_driver(hd44780_driver);
+MODULE_DESCRIPTION("HD44780 Character LCD driver");
+MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
+MODULE_LICENSE("GPL");