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, 479 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-r7301.c b/drivers/rtc/rtc-r7301.c
new file mode 100644
index 000000000..6323b7771
--- /dev/null
+++ b/drivers/rtc/rtc-r7301.c
@@ -0,0 +1,479 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * EPSON TOYOCOM RTC-7301SF/DG Driver
+ *
+ * Copyright (c) 2016 Akinobu Mita <akinobu.mita@gmail.com>
+ *
+ * Based on rtc-rp5c01.c
+ *
+ * Datasheet: http://www5.epsondevice.com/en/products/parallel/rtc7301sf.html
+ */
+
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+
+#define DRV_NAME "rtc-r7301"
+
+#define RTC7301_1_SEC		0x0	/* Bank 0 and Band 1 */
+#define RTC7301_10_SEC		0x1	/* Bank 0 and Band 1 */
+#define RTC7301_AE		BIT(3)
+#define RTC7301_1_MIN		0x2	/* Bank 0 and Band 1 */
+#define RTC7301_10_MIN		0x3	/* Bank 0 and Band 1 */
+#define RTC7301_1_HOUR		0x4	/* Bank 0 and Band 1 */
+#define RTC7301_10_HOUR		0x5	/* Bank 0 and Band 1 */
+#define RTC7301_DAY_OF_WEEK	0x6	/* Bank 0 and Band 1 */
+#define RTC7301_1_DAY		0x7	/* Bank 0 and Band 1 */
+#define RTC7301_10_DAY		0x8	/* Bank 0 and Band 1 */
+#define RTC7301_1_MONTH		0x9	/* Bank 0 */
+#define RTC7301_10_MONTH	0xa	/* Bank 0 */
+#define RTC7301_1_YEAR		0xb	/* Bank 0 */
+#define RTC7301_10_YEAR		0xc	/* Bank 0 */
+#define RTC7301_100_YEAR	0xd	/* Bank 0 */
+#define RTC7301_1000_YEAR	0xe	/* Bank 0 */
+#define RTC7301_ALARM_CONTROL	0xe	/* Bank 1 */
+#define RTC7301_ALARM_CONTROL_AIE	BIT(0)
+#define RTC7301_ALARM_CONTROL_AF	BIT(1)
+#define RTC7301_TIMER_CONTROL	0xe	/* Bank 2 */
+#define RTC7301_TIMER_CONTROL_TIE	BIT(0)
+#define RTC7301_TIMER_CONTROL_TF	BIT(1)
+#define RTC7301_CONTROL		0xf	/* All banks */
+#define RTC7301_CONTROL_BUSY		BIT(0)
+#define RTC7301_CONTROL_STOP		BIT(1)
+#define RTC7301_CONTROL_BANK_SEL_0	BIT(2)
+#define RTC7301_CONTROL_BANK_SEL_1	BIT(3)
+
+struct rtc7301_priv {
+	struct regmap *regmap;
+	int irq;
+	spinlock_t lock;
+	u8 bank;
+};
+
+/*
+ * When the device is memory-mapped, some platforms pack the registers into
+ * 32-bit access using the lower 8 bits at each 4-byte stride, while others
+ * expose them as simply consecutive bytes.
+ */
+static const struct regmap_config rtc7301_regmap_32_config = {
+	.reg_bits = 32,
+	.val_bits = 8,
+	.reg_stride = 4,
+};
+
+static const struct regmap_config rtc7301_regmap_8_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.reg_stride = 1,
+};
+
+static u8 rtc7301_read(struct rtc7301_priv *priv, unsigned int reg)
+{
+	int reg_stride = regmap_get_reg_stride(priv->regmap);
+	unsigned int val;
+
+	regmap_read(priv->regmap, reg_stride * reg, &val);
+
+	return val & 0xf;
+}
+
+static void rtc7301_write(struct rtc7301_priv *priv, u8 val, unsigned int reg)
+{
+	int reg_stride = regmap_get_reg_stride(priv->regmap);
+
+	regmap_write(priv->regmap, reg_stride * reg, val);
+}
+
+static void rtc7301_update_bits(struct rtc7301_priv *priv, unsigned int reg,
+				u8 mask, u8 val)
+{
+	int reg_stride = regmap_get_reg_stride(priv->regmap);
+
+	regmap_update_bits(priv->regmap, reg_stride * reg, mask, val);
+}
+
+static int rtc7301_wait_while_busy(struct rtc7301_priv *priv)
+{
+	int retries = 100;
+
+	while (retries-- > 0) {
+		u8 val;
+
+		val = rtc7301_read(priv, RTC7301_CONTROL);
+		if (!(val & RTC7301_CONTROL_BUSY))
+			return 0;
+
+		udelay(300);
+	}
+
+	return -ETIMEDOUT;
+}
+
+static void rtc7301_stop(struct rtc7301_priv *priv)
+{
+	rtc7301_update_bits(priv, RTC7301_CONTROL, RTC7301_CONTROL_STOP,
+			    RTC7301_CONTROL_STOP);
+}
+
+static void rtc7301_start(struct rtc7301_priv *priv)
+{
+	rtc7301_update_bits(priv, RTC7301_CONTROL, RTC7301_CONTROL_STOP, 0);
+}
+
+static void rtc7301_select_bank(struct rtc7301_priv *priv, u8 bank)
+{
+	u8 val = 0;
+
+	if (bank == priv->bank)
+		return;
+
+	if (bank & BIT(0))
+		val |= RTC7301_CONTROL_BANK_SEL_0;
+	if (bank & BIT(1))
+		val |= RTC7301_CONTROL_BANK_SEL_1;
+
+	rtc7301_update_bits(priv, RTC7301_CONTROL,
+			    RTC7301_CONTROL_BANK_SEL_0 |
+			    RTC7301_CONTROL_BANK_SEL_1, val);
+
+	priv->bank = bank;
+}
+
+static void rtc7301_get_time(struct rtc7301_priv *priv, struct rtc_time *tm,
+			     bool alarm)
+{
+	int year;
+
+	tm->tm_sec = rtc7301_read(priv, RTC7301_1_SEC);
+	tm->tm_sec += (rtc7301_read(priv, RTC7301_10_SEC) & ~RTC7301_AE) * 10;
+	tm->tm_min = rtc7301_read(priv, RTC7301_1_MIN);
+	tm->tm_min += (rtc7301_read(priv, RTC7301_10_MIN) & ~RTC7301_AE) * 10;
+	tm->tm_hour = rtc7301_read(priv, RTC7301_1_HOUR);
+	tm->tm_hour += (rtc7301_read(priv, RTC7301_10_HOUR) & ~RTC7301_AE) * 10;
+	tm->tm_mday = rtc7301_read(priv, RTC7301_1_DAY);
+	tm->tm_mday += (rtc7301_read(priv, RTC7301_10_DAY) & ~RTC7301_AE) * 10;
+
+	if (alarm) {
+		tm->tm_wday = -1;
+		tm->tm_mon = -1;
+		tm->tm_year = -1;
+		tm->tm_yday = -1;
+		tm->tm_isdst = -1;
+		return;
+	}
+
+	tm->tm_wday = (rtc7301_read(priv, RTC7301_DAY_OF_WEEK) & ~RTC7301_AE);
+	tm->tm_mon = rtc7301_read(priv, RTC7301_10_MONTH) * 10 +
+		     rtc7301_read(priv, RTC7301_1_MONTH) - 1;
+	year = rtc7301_read(priv, RTC7301_1000_YEAR) * 1000 +
+	       rtc7301_read(priv, RTC7301_100_YEAR) * 100 +
+	       rtc7301_read(priv, RTC7301_10_YEAR) * 10 +
+	       rtc7301_read(priv, RTC7301_1_YEAR);
+
+	tm->tm_year = year - 1900;
+}
+
+static void rtc7301_write_time(struct rtc7301_priv *priv, struct rtc_time *tm,
+			       bool alarm)
+{
+	int year;
+
+	rtc7301_write(priv, tm->tm_sec % 10, RTC7301_1_SEC);
+	rtc7301_write(priv, tm->tm_sec / 10, RTC7301_10_SEC);
+
+	rtc7301_write(priv, tm->tm_min % 10, RTC7301_1_MIN);
+	rtc7301_write(priv, tm->tm_min / 10, RTC7301_10_MIN);
+
+	rtc7301_write(priv, tm->tm_hour % 10, RTC7301_1_HOUR);
+	rtc7301_write(priv, tm->tm_hour / 10, RTC7301_10_HOUR);
+
+	rtc7301_write(priv, tm->tm_mday % 10, RTC7301_1_DAY);
+	rtc7301_write(priv, tm->tm_mday / 10, RTC7301_10_DAY);
+
+	/* Don't care for alarm register */
+	rtc7301_write(priv, alarm ? RTC7301_AE : tm->tm_wday,
+		      RTC7301_DAY_OF_WEEK);
+
+	if (alarm)
+		return;
+
+	rtc7301_write(priv, (tm->tm_mon + 1) % 10, RTC7301_1_MONTH);
+	rtc7301_write(priv, (tm->tm_mon + 1) / 10, RTC7301_10_MONTH);
+
+	year = tm->tm_year + 1900;
+
+	rtc7301_write(priv, year % 10, RTC7301_1_YEAR);
+	rtc7301_write(priv, (year / 10) % 10, RTC7301_10_YEAR);
+	rtc7301_write(priv, (year / 100) % 10, RTC7301_100_YEAR);
+	rtc7301_write(priv, year / 1000, RTC7301_1000_YEAR);
+}
+
+static void rtc7301_alarm_irq(struct rtc7301_priv *priv, unsigned int enabled)
+{
+	rtc7301_update_bits(priv, RTC7301_ALARM_CONTROL,
+			    RTC7301_ALARM_CONTROL_AF |
+			    RTC7301_ALARM_CONTROL_AIE,
+			    enabled ? RTC7301_ALARM_CONTROL_AIE : 0);
+}
+
+static int rtc7301_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rtc7301_priv *priv = dev_get_drvdata(dev);
+	unsigned long flags;
+	int err;
+
+	spin_lock_irqsave(&priv->lock, flags);
+
+	rtc7301_select_bank(priv, 0);
+
+	err = rtc7301_wait_while_busy(priv);
+	if (!err)
+		rtc7301_get_time(priv, tm, false);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	return err;
+}
+
+static int rtc7301_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rtc7301_priv *priv = dev_get_drvdata(dev);
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->lock, flags);
+
+	rtc7301_stop(priv);
+	udelay(300);
+	rtc7301_select_bank(priv, 0);
+	rtc7301_write_time(priv, tm, false);
+	rtc7301_start(priv);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	return 0;
+}
+
+static int rtc7301_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct rtc7301_priv *priv = dev_get_drvdata(dev);
+	unsigned long flags;
+	u8 alrm_ctrl;
+
+	if (priv->irq <= 0)
+		return -EINVAL;
+
+	spin_lock_irqsave(&priv->lock, flags);
+
+	rtc7301_select_bank(priv, 1);
+	rtc7301_get_time(priv, &alarm->time, true);
+
+	alrm_ctrl = rtc7301_read(priv, RTC7301_ALARM_CONTROL);
+
+	alarm->enabled = !!(alrm_ctrl & RTC7301_ALARM_CONTROL_AIE);
+	alarm->pending = !!(alrm_ctrl & RTC7301_ALARM_CONTROL_AF);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	return 0;
+}
+
+static int rtc7301_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct rtc7301_priv *priv = dev_get_drvdata(dev);
+	unsigned long flags;
+
+	if (priv->irq <= 0)
+		return -EINVAL;
+
+	spin_lock_irqsave(&priv->lock, flags);
+
+	rtc7301_select_bank(priv, 1);
+	rtc7301_write_time(priv, &alarm->time, true);
+	rtc7301_alarm_irq(priv, alarm->enabled);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	return 0;
+}
+
+static int rtc7301_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct rtc7301_priv *priv = dev_get_drvdata(dev);
+	unsigned long flags;
+
+	if (priv->irq <= 0)
+		return -EINVAL;
+
+	spin_lock_irqsave(&priv->lock, flags);
+
+	rtc7301_select_bank(priv, 1);
+	rtc7301_alarm_irq(priv, enabled);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	return 0;
+}
+
+static const struct rtc_class_ops rtc7301_rtc_ops = {
+	.read_time	= rtc7301_read_time,
+	.set_time	= rtc7301_set_time,
+	.read_alarm	= rtc7301_read_alarm,
+	.set_alarm	= rtc7301_set_alarm,
+	.alarm_irq_enable = rtc7301_alarm_irq_enable,
+};
+
+static irqreturn_t rtc7301_irq_handler(int irq, void *dev_id)
+{
+	struct rtc_device *rtc = dev_id;
+	struct rtc7301_priv *priv = dev_get_drvdata(rtc->dev.parent);
+	irqreturn_t ret = IRQ_NONE;
+	u8 alrm_ctrl;
+
+	spin_lock(&priv->lock);
+
+	rtc7301_select_bank(priv, 1);
+
+	alrm_ctrl = rtc7301_read(priv, RTC7301_ALARM_CONTROL);
+	if (alrm_ctrl & RTC7301_ALARM_CONTROL_AF) {
+		ret = IRQ_HANDLED;
+		rtc7301_alarm_irq(priv, false);
+		rtc_update_irq(rtc, 1, RTC_IRQF | RTC_AF);
+	}
+
+	spin_unlock(&priv->lock);
+
+	return ret;
+}
+
+static void rtc7301_init(struct rtc7301_priv *priv)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&priv->lock, flags);
+
+	rtc7301_select_bank(priv, 2);
+	rtc7301_write(priv, 0, RTC7301_TIMER_CONTROL);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+}
+
+static int __init rtc7301_rtc_probe(struct platform_device *dev)
+{
+	void __iomem *regs;
+	struct rtc7301_priv *priv;
+	struct rtc_device *rtc;
+	static const struct regmap_config *mapconf;
+	int ret;
+	u32 val;
+
+	priv = devm_kzalloc(&dev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	regs = devm_platform_ioremap_resource(dev, 0);
+	if (IS_ERR(regs))
+		return PTR_ERR(regs);
+
+	ret = device_property_read_u32(&dev->dev, "reg-io-width", &val);
+	if (ret)
+		/* Default to 32bit accesses */
+		val = 4;
+
+	switch (val) {
+	case 1:
+		mapconf = &rtc7301_regmap_8_config;
+		break;
+	case 4:
+		mapconf = &rtc7301_regmap_32_config;
+		break;
+	default:
+		dev_err(&dev->dev, "invalid reg-io-width %d\n", val);
+		return -EINVAL;
+	}
+
+	priv->regmap = devm_regmap_init_mmio(&dev->dev, regs,
+					     mapconf);
+	if (IS_ERR(priv->regmap))
+		return PTR_ERR(priv->regmap);
+
+	priv->irq = platform_get_irq(dev, 0);
+
+	spin_lock_init(&priv->lock);
+	priv->bank = -1;
+
+	rtc7301_init(priv);
+
+	platform_set_drvdata(dev, priv);
+
+	rtc = devm_rtc_device_register(&dev->dev, DRV_NAME, &rtc7301_rtc_ops,
+				       THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	if (priv->irq > 0) {
+		ret = devm_request_irq(&dev->dev, priv->irq,
+				       rtc7301_irq_handler, IRQF_SHARED,
+				       dev_name(&dev->dev), rtc);
+		if (ret) {
+			priv->irq = 0;
+			dev_err(&dev->dev, "unable to request IRQ\n");
+		} else {
+			device_set_wakeup_capable(&dev->dev, true);
+		}
+	}
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+
+static int rtc7301_suspend(struct device *dev)
+{
+	struct rtc7301_priv *priv = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(priv->irq);
+
+	return 0;
+}
+
+static int rtc7301_resume(struct device *dev)
+{
+	struct rtc7301_priv *priv = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(priv->irq);
+
+	return 0;
+}
+
+#endif
+
+static SIMPLE_DEV_PM_OPS(rtc7301_pm_ops, rtc7301_suspend, rtc7301_resume);
+
+static const struct of_device_id rtc7301_dt_match[] = {
+	{ .compatible = "epson,rtc7301sf" },
+	{ .compatible = "epson,rtc7301dg" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, rtc7301_dt_match);
+
+static struct platform_driver rtc7301_rtc_driver = {
+	.driver	= {
+		.name = DRV_NAME,
+		.of_match_table = rtc7301_dt_match,
+		.pm = &rtc7301_pm_ops,
+	},
+};
+
+module_platform_driver_probe(rtc7301_rtc_driver, rtc7301_rtc_probe);
+
+MODULE_AUTHOR("Akinobu Mita <akinobu.mita@gmail.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("EPSON TOYOCOM RTC-7301SF/DG Driver");
+MODULE_ALIAS("platform:rtc-r7301");