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, 228 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-msm6242.c b/drivers/rtc/rtc-msm6242.c
new file mode 100644
index 000000000..80e364baa
--- /dev/null
+++ b/drivers/rtc/rtc-msm6242.c
@@ -0,0 +1,228 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Oki MSM6242 RTC Driver
+ *
+ *  Copyright 2009 Geert Uytterhoeven
+ *
+ *  Based on the A2000 TOD code in arch/m68k/amiga/config.c
+ *  Copyright (C) 1993 Hamish Macdonald
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+
+enum {
+	MSM6242_SECOND1		= 0x0,	/* 1-second digit register */
+	MSM6242_SECOND10	= 0x1,	/* 10-second digit register */
+	MSM6242_MINUTE1		= 0x2,	/* 1-minute digit register */
+	MSM6242_MINUTE10	= 0x3,	/* 10-minute digit register */
+	MSM6242_HOUR1		= 0x4,	/* 1-hour digit register */
+	MSM6242_HOUR10		= 0x5,	/* PM/AM, 10-hour digit register */
+	MSM6242_DAY1		= 0x6,	/* 1-day digit register */
+	MSM6242_DAY10		= 0x7,	/* 10-day digit register */
+	MSM6242_MONTH1		= 0x8,	/* 1-month digit register */
+	MSM6242_MONTH10		= 0x9,	/* 10-month digit register */
+	MSM6242_YEAR1		= 0xa,	/* 1-year digit register */
+	MSM6242_YEAR10		= 0xb,	/* 10-year digit register */
+	MSM6242_WEEK		= 0xc,	/* Week register */
+	MSM6242_CD		= 0xd,	/* Control Register D */
+	MSM6242_CE		= 0xe,	/* Control Register E */
+	MSM6242_CF		= 0xf,	/* Control Register F */
+};
+
+#define MSM6242_HOUR10_AM	(0 << 2)
+#define MSM6242_HOUR10_PM	(1 << 2)
+#define MSM6242_HOUR10_HR_MASK	(3 << 0)
+
+#define MSM6242_WEEK_SUNDAY	0
+#define MSM6242_WEEK_MONDAY	1
+#define MSM6242_WEEK_TUESDAY	2
+#define MSM6242_WEEK_WEDNESDAY	3
+#define MSM6242_WEEK_THURSDAY	4
+#define MSM6242_WEEK_FRIDAY	5
+#define MSM6242_WEEK_SATURDAY	6
+
+#define MSM6242_CD_30_S_ADJ	(1 << 3)	/* 30-second adjustment */
+#define MSM6242_CD_IRQ_FLAG	(1 << 2)
+#define MSM6242_CD_BUSY		(1 << 1)
+#define MSM6242_CD_HOLD		(1 << 0)
+
+#define MSM6242_CE_T_MASK	(3 << 2)
+#define MSM6242_CE_T_64HZ	(0 << 2)	/* period 1/64 second */
+#define MSM6242_CE_T_1HZ	(1 << 2)	/* period 1 second */
+#define MSM6242_CE_T_1MINUTE	(2 << 2)	/* period 1 minute */
+#define MSM6242_CE_T_1HOUR	(3 << 2)	/* period 1 hour */
+
+#define MSM6242_CE_ITRPT_STND	(1 << 1)
+#define MSM6242_CE_MASK		(1 << 0)	/* STD.P output control */
+
+#define MSM6242_CF_TEST		(1 << 3)
+#define MSM6242_CF_12H		(0 << 2)
+#define MSM6242_CF_24H		(1 << 2)
+#define MSM6242_CF_STOP		(1 << 1)
+#define MSM6242_CF_REST		(1 << 0)	/* reset */
+
+
+struct msm6242_priv {
+	u32 __iomem *regs;
+	struct rtc_device *rtc;
+};
+
+static inline unsigned int msm6242_read(struct msm6242_priv *priv,
+				       unsigned int reg)
+{
+	return __raw_readl(&priv->regs[reg]) & 0xf;
+}
+
+static inline void msm6242_write(struct msm6242_priv *priv, unsigned int val,
+				unsigned int reg)
+{
+	__raw_writel(val, &priv->regs[reg]);
+}
+
+static void msm6242_lock(struct msm6242_priv *priv)
+{
+	int cnt = 5;
+
+	msm6242_write(priv, MSM6242_CD_HOLD|MSM6242_CD_IRQ_FLAG, MSM6242_CD);
+
+	while ((msm6242_read(priv, MSM6242_CD) & MSM6242_CD_BUSY) && cnt) {
+		msm6242_write(priv, MSM6242_CD_IRQ_FLAG, MSM6242_CD);
+		udelay(70);
+		msm6242_write(priv, MSM6242_CD_HOLD|MSM6242_CD_IRQ_FLAG, MSM6242_CD);
+		cnt--;
+	}
+
+	if (!cnt)
+		pr_warn("timed out waiting for RTC (0x%x)\n",
+			msm6242_read(priv, MSM6242_CD));
+}
+
+static void msm6242_unlock(struct msm6242_priv *priv)
+{
+	msm6242_write(priv, MSM6242_CD_IRQ_FLAG, MSM6242_CD);
+}
+
+static int msm6242_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct msm6242_priv *priv = dev_get_drvdata(dev);
+
+	msm6242_lock(priv);
+
+	tm->tm_sec  = msm6242_read(priv, MSM6242_SECOND10) * 10 +
+		      msm6242_read(priv, MSM6242_SECOND1);
+	tm->tm_min  = msm6242_read(priv, MSM6242_MINUTE10) * 10 +
+		      msm6242_read(priv, MSM6242_MINUTE1);
+	tm->tm_hour = (msm6242_read(priv, MSM6242_HOUR10) &
+		       MSM6242_HOUR10_HR_MASK) * 10 +
+		      msm6242_read(priv, MSM6242_HOUR1);
+	tm->tm_mday = msm6242_read(priv, MSM6242_DAY10) * 10 +
+		      msm6242_read(priv, MSM6242_DAY1);
+	tm->tm_wday = msm6242_read(priv, MSM6242_WEEK);
+	tm->tm_mon  = msm6242_read(priv, MSM6242_MONTH10) * 10 +
+		      msm6242_read(priv, MSM6242_MONTH1) - 1;
+	tm->tm_year = msm6242_read(priv, MSM6242_YEAR10) * 10 +
+		      msm6242_read(priv, MSM6242_YEAR1);
+	if (tm->tm_year <= 69)
+		tm->tm_year += 100;
+
+	if (!(msm6242_read(priv, MSM6242_CF) & MSM6242_CF_24H)) {
+		unsigned int pm = msm6242_read(priv, MSM6242_HOUR10) &
+				  MSM6242_HOUR10_PM;
+		if (!pm && tm->tm_hour == 12)
+			tm->tm_hour = 0;
+		else if (pm && tm->tm_hour != 12)
+			tm->tm_hour += 12;
+	}
+
+	msm6242_unlock(priv);
+
+	return 0;
+}
+
+static int msm6242_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct msm6242_priv *priv = dev_get_drvdata(dev);
+
+	msm6242_lock(priv);
+
+	msm6242_write(priv, tm->tm_sec / 10, MSM6242_SECOND10);
+	msm6242_write(priv, tm->tm_sec % 10, MSM6242_SECOND1);
+	msm6242_write(priv, tm->tm_min / 10, MSM6242_MINUTE10);
+	msm6242_write(priv, tm->tm_min % 10, MSM6242_MINUTE1);
+	if (msm6242_read(priv, MSM6242_CF) & MSM6242_CF_24H)
+		msm6242_write(priv, tm->tm_hour / 10, MSM6242_HOUR10);
+	else if (tm->tm_hour >= 12)
+		msm6242_write(priv, MSM6242_HOUR10_PM + (tm->tm_hour - 12) / 10,
+			      MSM6242_HOUR10);
+	else
+		msm6242_write(priv, tm->tm_hour / 10, MSM6242_HOUR10);
+	msm6242_write(priv, tm->tm_hour % 10, MSM6242_HOUR1);
+	msm6242_write(priv, tm->tm_mday / 10, MSM6242_DAY10);
+	msm6242_write(priv, tm->tm_mday % 10, MSM6242_DAY1);
+	if (tm->tm_wday != -1)
+		msm6242_write(priv, tm->tm_wday, MSM6242_WEEK);
+	msm6242_write(priv, (tm->tm_mon + 1) / 10, MSM6242_MONTH10);
+	msm6242_write(priv, (tm->tm_mon + 1) % 10, MSM6242_MONTH1);
+	if (tm->tm_year >= 100)
+		tm->tm_year -= 100;
+	msm6242_write(priv, tm->tm_year / 10, MSM6242_YEAR10);
+	msm6242_write(priv, tm->tm_year % 10, MSM6242_YEAR1);
+
+	msm6242_unlock(priv);
+	return 0;
+}
+
+static const struct rtc_class_ops msm6242_rtc_ops = {
+	.read_time	= msm6242_read_time,
+	.set_time	= msm6242_set_time,
+};
+
+static int __init msm6242_rtc_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct msm6242_priv *priv;
+	struct rtc_device *rtc;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->regs = devm_ioremap(&pdev->dev, res->start, resource_size(res));
+	if (!priv->regs)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, priv);
+
+	rtc = devm_rtc_device_register(&pdev->dev, "rtc-msm6242",
+				&msm6242_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	priv->rtc = rtc;
+	return 0;
+}
+
+static struct platform_driver msm6242_rtc_driver = {
+	.driver	= {
+		.name	= "rtc-msm6242",
+	},
+};
+
+module_platform_driver_probe(msm6242_rtc_driver, msm6242_rtc_probe);
+
+MODULE_AUTHOR("Geert Uytterhoeven <geert@linux-m68k.org>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Oki MSM6242 RTC driver");
+MODULE_ALIAS("platform:rtc-msm6242");