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, 408 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-mpc5121.c b/drivers/rtc/rtc-mpc5121.c
new file mode 100644
index 000000000..b90f8337a
--- /dev/null
+++ b/drivers/rtc/rtc-mpc5121.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Real-time clock driver for MPC5121
+ *
+ * Copyright 2007, Domen Puncer <domen.puncer@telargo.com>
+ * Copyright 2008, Freescale Semiconductor, Inc. All rights reserved.
+ * Copyright 2011, Dmitry Eremin-Solenikov
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+
+struct mpc5121_rtc_regs {
+	u8 set_time;		/* RTC + 0x00 */
+	u8 hour_set;		/* RTC + 0x01 */
+	u8 minute_set;		/* RTC + 0x02 */
+	u8 second_set;		/* RTC + 0x03 */
+
+	u8 set_date;		/* RTC + 0x04 */
+	u8 month_set;		/* RTC + 0x05 */
+	u8 weekday_set;		/* RTC + 0x06 */
+	u8 date_set;		/* RTC + 0x07 */
+
+	u8 write_sw;		/* RTC + 0x08 */
+	u8 sw_set;		/* RTC + 0x09 */
+	u16 year_set;		/* RTC + 0x0a */
+
+	u8 alm_enable;		/* RTC + 0x0c */
+	u8 alm_hour_set;	/* RTC + 0x0d */
+	u8 alm_min_set;		/* RTC + 0x0e */
+	u8 int_enable;		/* RTC + 0x0f */
+
+	u8 reserved1;
+	u8 hour;		/* RTC + 0x11 */
+	u8 minute;		/* RTC + 0x12 */
+	u8 second;		/* RTC + 0x13 */
+
+	u8 month;		/* RTC + 0x14 */
+	u8 wday_mday;		/* RTC + 0x15 */
+	u16 year;		/* RTC + 0x16 */
+
+	u8 int_alm;		/* RTC + 0x18 */
+	u8 int_sw;		/* RTC + 0x19 */
+	u8 alm_status;		/* RTC + 0x1a */
+	u8 sw_minute;		/* RTC + 0x1b */
+
+	u8 bus_error_1;		/* RTC + 0x1c */
+	u8 int_day;		/* RTC + 0x1d */
+	u8 int_min;		/* RTC + 0x1e */
+	u8 int_sec;		/* RTC + 0x1f */
+
+	/*
+	 * target_time:
+	 *	intended to be used for hibernation but hibernation
+	 *	does not work on silicon rev 1.5 so use it for non-volatile
+	 *	storage of offset between the actual_time register and linux
+	 *	time
+	 */
+	u32 target_time;	/* RTC + 0x20 */
+	/*
+	 * actual_time:
+	 *	readonly time since VBAT_RTC was last connected
+	 */
+	u32 actual_time;	/* RTC + 0x24 */
+	u32 keep_alive;		/* RTC + 0x28 */
+};
+
+struct mpc5121_rtc_data {
+	unsigned irq;
+	unsigned irq_periodic;
+	struct mpc5121_rtc_regs __iomem *regs;
+	struct rtc_device *rtc;
+	struct rtc_wkalrm wkalarm;
+};
+
+/*
+ * Update second/minute/hour registers.
+ *
+ * This is just so alarm will work.
+ */
+static void mpc5121_rtc_update_smh(struct mpc5121_rtc_regs __iomem *regs,
+				   struct rtc_time *tm)
+{
+	out_8(&regs->second_set, tm->tm_sec);
+	out_8(&regs->minute_set, tm->tm_min);
+	out_8(&regs->hour_set, tm->tm_hour);
+
+	/* set time sequence */
+	out_8(&regs->set_time, 0x1);
+	out_8(&regs->set_time, 0x3);
+	out_8(&regs->set_time, 0x1);
+	out_8(&regs->set_time, 0x0);
+}
+
+static int mpc5121_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct mpc5121_rtc_data *rtc = dev_get_drvdata(dev);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+	unsigned long now;
+
+	/*
+	 * linux time is actual_time plus the offset saved in target_time
+	 */
+	now = in_be32(&regs->actual_time) + in_be32(&regs->target_time);
+
+	rtc_time64_to_tm(now, tm);
+
+	/*
+	 * update second minute hour registers
+	 * so alarms will work
+	 */
+	mpc5121_rtc_update_smh(regs, tm);
+
+	return 0;
+}
+
+static int mpc5121_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct mpc5121_rtc_data *rtc = dev_get_drvdata(dev);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+	unsigned long now;
+
+	/*
+	 * The actual_time register is read only so we write the offset
+	 * between it and linux time to the target_time register.
+	 */
+	now = rtc_tm_to_time64(tm);
+	out_be32(&regs->target_time, now - in_be32(&regs->actual_time));
+
+	/*
+	 * update second minute hour registers
+	 * so alarms will work
+	 */
+	mpc5121_rtc_update_smh(regs, tm);
+
+	return 0;
+}
+
+static int mpc5200_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct mpc5121_rtc_data *rtc = dev_get_drvdata(dev);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+	int tmp;
+
+	tm->tm_sec = in_8(&regs->second);
+	tm->tm_min = in_8(&regs->minute);
+
+	/* 12 hour format? */
+	if (in_8(&regs->hour) & 0x20)
+		tm->tm_hour = (in_8(&regs->hour) >> 1) +
+			(in_8(&regs->hour) & 1 ? 12 : 0);
+	else
+		tm->tm_hour = in_8(&regs->hour);
+
+	tmp = in_8(&regs->wday_mday);
+	tm->tm_mday = tmp & 0x1f;
+	tm->tm_mon = in_8(&regs->month) - 1;
+	tm->tm_year = in_be16(&regs->year) - 1900;
+	tm->tm_wday = (tmp >> 5) % 7;
+	tm->tm_yday = rtc_year_days(tm->tm_mday, tm->tm_mon, tm->tm_year);
+	tm->tm_isdst = 0;
+
+	return 0;
+}
+
+static int mpc5200_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct mpc5121_rtc_data *rtc = dev_get_drvdata(dev);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+
+	mpc5121_rtc_update_smh(regs, tm);
+
+	/* date */
+	out_8(&regs->month_set, tm->tm_mon + 1);
+	out_8(&regs->weekday_set, tm->tm_wday ? tm->tm_wday : 7);
+	out_8(&regs->date_set, tm->tm_mday);
+	out_be16(&regs->year_set, tm->tm_year + 1900);
+
+	/* set date sequence */
+	out_8(&regs->set_date, 0x1);
+	out_8(&regs->set_date, 0x3);
+	out_8(&regs->set_date, 0x1);
+	out_8(&regs->set_date, 0x0);
+
+	return 0;
+}
+
+static int mpc5121_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct mpc5121_rtc_data *rtc = dev_get_drvdata(dev);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+
+	*alarm = rtc->wkalarm;
+
+	alarm->pending = in_8(&regs->alm_status);
+
+	return 0;
+}
+
+static int mpc5121_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct mpc5121_rtc_data *rtc = dev_get_drvdata(dev);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+
+	alarm->time.tm_mday = -1;
+	alarm->time.tm_mon = -1;
+	alarm->time.tm_year = -1;
+
+	out_8(&regs->alm_min_set, alarm->time.tm_min);
+	out_8(&regs->alm_hour_set, alarm->time.tm_hour);
+
+	out_8(&regs->alm_enable, alarm->enabled);
+
+	rtc->wkalarm = *alarm;
+	return 0;
+}
+
+static irqreturn_t mpc5121_rtc_handler(int irq, void *dev)
+{
+	struct mpc5121_rtc_data *rtc = dev_get_drvdata((struct device *)dev);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+
+	if (in_8(&regs->int_alm)) {
+		/* acknowledge and clear status */
+		out_8(&regs->int_alm, 1);
+		out_8(&regs->alm_status, 1);
+
+		rtc_update_irq(rtc->rtc, 1, RTC_IRQF | RTC_AF);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static irqreturn_t mpc5121_rtc_handler_upd(int irq, void *dev)
+{
+	struct mpc5121_rtc_data *rtc = dev_get_drvdata((struct device *)dev);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+
+	if (in_8(&regs->int_sec) && (in_8(&regs->int_enable) & 0x1)) {
+		/* acknowledge */
+		out_8(&regs->int_sec, 1);
+
+		rtc_update_irq(rtc->rtc, 1, RTC_IRQF | RTC_UF);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int mpc5121_rtc_alarm_irq_enable(struct device *dev,
+					unsigned int enabled)
+{
+	struct mpc5121_rtc_data *rtc = dev_get_drvdata(dev);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+	int val;
+
+	if (enabled)
+		val = 1;
+	else
+		val = 0;
+
+	out_8(&regs->alm_enable, val);
+	rtc->wkalarm.enabled = val;
+
+	return 0;
+}
+
+static const struct rtc_class_ops mpc5121_rtc_ops = {
+	.read_time = mpc5121_rtc_read_time,
+	.set_time = mpc5121_rtc_set_time,
+	.read_alarm = mpc5121_rtc_read_alarm,
+	.set_alarm = mpc5121_rtc_set_alarm,
+	.alarm_irq_enable = mpc5121_rtc_alarm_irq_enable,
+};
+
+static const struct rtc_class_ops mpc5200_rtc_ops = {
+	.read_time = mpc5200_rtc_read_time,
+	.set_time = mpc5200_rtc_set_time,
+	.read_alarm = mpc5121_rtc_read_alarm,
+	.set_alarm = mpc5121_rtc_set_alarm,
+	.alarm_irq_enable = mpc5121_rtc_alarm_irq_enable,
+};
+
+static int mpc5121_rtc_probe(struct platform_device *op)
+{
+	struct mpc5121_rtc_data *rtc;
+	int err = 0;
+
+	rtc = devm_kzalloc(&op->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+
+	rtc->regs = devm_platform_ioremap_resource(op, 0);
+	if (IS_ERR(rtc->regs)) {
+		dev_err(&op->dev, "%s: couldn't map io space\n", __func__);
+		return PTR_ERR(rtc->regs);
+	}
+
+	device_init_wakeup(&op->dev, true);
+
+	platform_set_drvdata(op, rtc);
+
+	rtc->irq = irq_of_parse_and_map(op->dev.of_node, 1);
+	err = devm_request_irq(&op->dev, rtc->irq, mpc5121_rtc_handler, 0,
+			       "mpc5121-rtc", &op->dev);
+	if (err) {
+		dev_err(&op->dev, "%s: could not request irq: %i\n",
+							__func__, rtc->irq);
+		goto out_dispose;
+	}
+
+	rtc->irq_periodic = irq_of_parse_and_map(op->dev.of_node, 0);
+	err = devm_request_irq(&op->dev, rtc->irq_periodic,
+			       mpc5121_rtc_handler_upd, 0, "mpc5121-rtc_upd",
+			       &op->dev);
+	if (err) {
+		dev_err(&op->dev, "%s: could not request irq: %i\n",
+						__func__, rtc->irq_periodic);
+		goto out_dispose2;
+	}
+
+	rtc->rtc = devm_rtc_allocate_device(&op->dev);
+	if (IS_ERR(rtc->rtc)) {
+		err = PTR_ERR(rtc->rtc);
+		goto out_dispose2;
+	}
+
+	rtc->rtc->ops = &mpc5200_rtc_ops;
+	set_bit(RTC_FEATURE_ALARM_RES_MINUTE, rtc->rtc->features);
+	clear_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->rtc->features);
+	rtc->rtc->range_min = RTC_TIMESTAMP_BEGIN_0000;
+	rtc->rtc->range_max = 65733206399ULL; /* 4052-12-31 23:59:59 */
+
+	if (of_device_is_compatible(op->dev.of_node, "fsl,mpc5121-rtc")) {
+		u32 ka;
+		ka = in_be32(&rtc->regs->keep_alive);
+		if (ka & 0x02) {
+			dev_warn(&op->dev,
+				"mpc5121-rtc: Battery or oscillator failure!\n");
+			out_be32(&rtc->regs->keep_alive, ka);
+		}
+		rtc->rtc->ops = &mpc5121_rtc_ops;
+		/*
+		 * This is a limitation of the driver that abuses the target
+		 * time register, the actual maximum year for the mpc5121 is
+		 * also 4052.
+		 */
+		rtc->rtc->range_min = 0;
+		rtc->rtc->range_max = U32_MAX;
+	}
+
+	err = devm_rtc_register_device(rtc->rtc);
+	if (err)
+		goto out_dispose2;
+
+	return 0;
+
+out_dispose2:
+	irq_dispose_mapping(rtc->irq_periodic);
+out_dispose:
+	irq_dispose_mapping(rtc->irq);
+
+	return err;
+}
+
+static void mpc5121_rtc_remove(struct platform_device *op)
+{
+	struct mpc5121_rtc_data *rtc = platform_get_drvdata(op);
+	struct mpc5121_rtc_regs __iomem *regs = rtc->regs;
+
+	/* disable interrupt, so there are no nasty surprises */
+	out_8(&regs->alm_enable, 0);
+	out_8(&regs->int_enable, in_8(&regs->int_enable) & ~0x1);
+
+	irq_dispose_mapping(rtc->irq);
+	irq_dispose_mapping(rtc->irq_periodic);
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id mpc5121_rtc_match[] = {
+	{ .compatible = "fsl,mpc5121-rtc", },
+	{ .compatible = "fsl,mpc5200-rtc", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mpc5121_rtc_match);
+#endif
+
+static struct platform_driver mpc5121_rtc_driver = {
+	.driver = {
+		.name = "mpc5121-rtc",
+		.of_match_table = of_match_ptr(mpc5121_rtc_match),
+	},
+	.probe = mpc5121_rtc_probe,
+	.remove = mpc5121_rtc_remove,
+};
+
+module_platform_driver(mpc5121_rtc_driver);
+
+MODULE_DESCRIPTION("Freescale MPC5121 built-in RTC driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("John Rigby <jcrigby@gmail.com>");