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, 327 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-tps6586x.c b/drivers/rtc/rtc-tps6586x.c
new file mode 100644
index 000000000..54c8429b1
--- /dev/null
+++ b/drivers/rtc/rtc-tps6586x.c
@@ -0,0 +1,327 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * rtc-tps6586x.c: RTC driver for TI PMIC TPS6586X
+ *
+ * Copyright (c) 2012, NVIDIA Corporation.
+ *
+ * Author: Laxman Dewangan <ldewangan@nvidia.com>
+ */
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/mfd/tps6586x.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+#define RTC_CTRL			0xc0
+#define POR_RESET_N			BIT(7)
+#define OSC_SRC_SEL			BIT(6)
+#define RTC_ENABLE			BIT(5)	/* enables alarm */
+#define RTC_BUF_ENABLE			BIT(4)	/* 32 KHz buffer enable */
+#define PRE_BYPASS			BIT(3)	/* 0=1KHz or 1=32KHz updates */
+#define CL_SEL_MASK			(BIT(2)|BIT(1))
+#define CL_SEL_POS			1
+#define RTC_ALARM1_HI			0xc1
+#define RTC_COUNT4			0xc6
+
+/* start a PMU RTC access by reading the register prior to the RTC_COUNT4 */
+#define RTC_COUNT4_DUMMYREAD		0xc5
+
+/*only 14-bits width in second*/
+#define ALM1_VALID_RANGE_IN_SEC		0x3FFF
+
+#define TPS6586X_RTC_CL_SEL_1_5PF	0x0
+#define TPS6586X_RTC_CL_SEL_6_5PF	0x1
+#define TPS6586X_RTC_CL_SEL_7_5PF	0x2
+#define TPS6586X_RTC_CL_SEL_12_5PF	0x3
+
+struct tps6586x_rtc {
+	struct device		*dev;
+	struct rtc_device	*rtc;
+	int			irq;
+	bool			irq_en;
+};
+
+static inline struct device *to_tps6586x_dev(struct device *dev)
+{
+	return dev->parent;
+}
+
+static int tps6586x_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct device *tps_dev = to_tps6586x_dev(dev);
+	unsigned long long ticks = 0;
+	time64_t seconds;
+	u8 buff[6];
+	int ret;
+	int i;
+
+	ret = tps6586x_reads(tps_dev, RTC_COUNT4_DUMMYREAD, sizeof(buff), buff);
+	if (ret < 0) {
+		dev_err(dev, "read counter failed with err %d\n", ret);
+		return ret;
+	}
+
+	for (i = 1; i < sizeof(buff); i++) {
+		ticks <<= 8;
+		ticks |= buff[i];
+	}
+
+	seconds = ticks >> 10;
+	rtc_time64_to_tm(seconds, tm);
+
+	return 0;
+}
+
+static int tps6586x_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct device *tps_dev = to_tps6586x_dev(dev);
+	unsigned long long ticks;
+	time64_t seconds;
+	u8 buff[5];
+	int ret;
+
+	seconds = rtc_tm_to_time64(tm);
+
+	ticks = (unsigned long long)seconds << 10;
+	buff[0] = (ticks >> 32) & 0xff;
+	buff[1] = (ticks >> 24) & 0xff;
+	buff[2] = (ticks >> 16) & 0xff;
+	buff[3] = (ticks >> 8) & 0xff;
+	buff[4] = ticks & 0xff;
+
+	/* Disable RTC before changing time */
+	ret = tps6586x_clr_bits(tps_dev, RTC_CTRL, RTC_ENABLE);
+	if (ret < 0) {
+		dev_err(dev, "failed to clear RTC_ENABLE\n");
+		return ret;
+	}
+
+	ret = tps6586x_writes(tps_dev, RTC_COUNT4, sizeof(buff), buff);
+	if (ret < 0) {
+		dev_err(dev, "failed to program new time\n");
+		return ret;
+	}
+
+	/* Enable RTC */
+	ret = tps6586x_set_bits(tps_dev, RTC_CTRL, RTC_ENABLE);
+	if (ret < 0) {
+		dev_err(dev, "failed to set RTC_ENABLE\n");
+		return ret;
+	}
+	return 0;
+}
+
+static int tps6586x_rtc_alarm_irq_enable(struct device *dev,
+			 unsigned int enabled)
+{
+	struct tps6586x_rtc *rtc = dev_get_drvdata(dev);
+
+	if (enabled && !rtc->irq_en) {
+		enable_irq(rtc->irq);
+		rtc->irq_en = true;
+	} else if (!enabled && rtc->irq_en)  {
+		disable_irq(rtc->irq);
+		rtc->irq_en = false;
+	}
+	return 0;
+}
+
+static int tps6586x_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct device *tps_dev = to_tps6586x_dev(dev);
+	time64_t seconds;
+	unsigned long ticks;
+	unsigned long rtc_current_time;
+	unsigned long long rticks = 0;
+	u8 buff[3];
+	u8 rbuff[6];
+	int ret;
+	int i;
+
+	seconds = rtc_tm_to_time64(&alrm->time);
+
+	ret = tps6586x_rtc_alarm_irq_enable(dev, alrm->enabled);
+	if (ret < 0) {
+		dev_err(dev, "can't set alarm irq, err %d\n", ret);
+		return ret;
+	}
+
+	ret = tps6586x_reads(tps_dev, RTC_COUNT4_DUMMYREAD,
+			sizeof(rbuff), rbuff);
+	if (ret < 0) {
+		dev_err(dev, "read counter failed with err %d\n", ret);
+		return ret;
+	}
+
+	for (i = 1; i < sizeof(rbuff); i++) {
+		rticks <<= 8;
+		rticks |= rbuff[i];
+	}
+
+	rtc_current_time = rticks >> 10;
+	if ((seconds - rtc_current_time) > ALM1_VALID_RANGE_IN_SEC)
+		seconds = rtc_current_time - 1;
+
+	ticks = (unsigned long long)seconds << 10;
+	buff[0] = (ticks >> 16) & 0xff;
+	buff[1] = (ticks >> 8) & 0xff;
+	buff[2] = ticks & 0xff;
+
+	ret = tps6586x_writes(tps_dev, RTC_ALARM1_HI, sizeof(buff), buff);
+	if (ret)
+		dev_err(dev, "programming alarm failed with err %d\n", ret);
+
+	return ret;
+}
+
+static int tps6586x_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct device *tps_dev = to_tps6586x_dev(dev);
+	unsigned long ticks;
+	time64_t seconds;
+	u8 buff[3];
+	int ret;
+
+	ret = tps6586x_reads(tps_dev, RTC_ALARM1_HI, sizeof(buff), buff);
+	if (ret) {
+		dev_err(dev, "read RTC_ALARM1_HI failed with err %d\n", ret);
+		return ret;
+	}
+
+	ticks = (buff[0] << 16) | (buff[1] << 8) | buff[2];
+	seconds = ticks >> 10;
+
+	rtc_time64_to_tm(seconds, &alrm->time);
+	return 0;
+}
+
+static const struct rtc_class_ops tps6586x_rtc_ops = {
+	.read_time	= tps6586x_rtc_read_time,
+	.set_time	= tps6586x_rtc_set_time,
+	.set_alarm	= tps6586x_rtc_set_alarm,
+	.read_alarm	= tps6586x_rtc_read_alarm,
+	.alarm_irq_enable = tps6586x_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t tps6586x_rtc_irq(int irq, void *data)
+{
+	struct tps6586x_rtc *rtc = data;
+
+	rtc_update_irq(rtc->rtc, 1, RTC_IRQF | RTC_AF);
+	return IRQ_HANDLED;
+}
+
+static int tps6586x_rtc_probe(struct platform_device *pdev)
+{
+	struct device *tps_dev = to_tps6586x_dev(&pdev->dev);
+	struct tps6586x_rtc *rtc;
+	int ret;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+
+	rtc->dev = &pdev->dev;
+	rtc->irq = platform_get_irq(pdev, 0);
+
+	/* 1 kHz tick mode, enable tick counting */
+	ret = tps6586x_update(tps_dev, RTC_CTRL,
+		RTC_ENABLE | OSC_SRC_SEL |
+		((TPS6586X_RTC_CL_SEL_1_5PF << CL_SEL_POS) & CL_SEL_MASK),
+		RTC_ENABLE | OSC_SRC_SEL | PRE_BYPASS | CL_SEL_MASK);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "unable to start counter\n");
+		return ret;
+	}
+
+	device_init_wakeup(&pdev->dev, true);
+
+	platform_set_drvdata(pdev, rtc);
+	rtc->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc->rtc)) {
+		ret = PTR_ERR(rtc->rtc);
+		goto fail_rtc_register;
+	}
+
+	rtc->rtc->ops = &tps6586x_rtc_ops;
+	rtc->rtc->range_max = (1ULL << 30) - 1; /* 30-bit seconds */
+	rtc->rtc->alarm_offset_max = ALM1_VALID_RANGE_IN_SEC;
+	rtc->rtc->start_secs = mktime64(2009, 1, 1, 0, 0, 0);
+	rtc->rtc->set_start_time = true;
+
+	irq_set_status_flags(rtc->irq, IRQ_NOAUTOEN);
+
+	ret = devm_request_threaded_irq(&pdev->dev, rtc->irq, NULL,
+				tps6586x_rtc_irq,
+				IRQF_ONESHOT,
+				dev_name(&pdev->dev), rtc);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "request IRQ(%d) failed with ret %d\n",
+				rtc->irq, ret);
+		goto fail_rtc_register;
+	}
+
+	ret = devm_rtc_register_device(rtc->rtc);
+	if (ret)
+		goto fail_rtc_register;
+
+	return 0;
+
+fail_rtc_register:
+	tps6586x_update(tps_dev, RTC_CTRL, 0,
+		RTC_ENABLE | OSC_SRC_SEL | PRE_BYPASS | CL_SEL_MASK);
+	return ret;
+};
+
+static void tps6586x_rtc_remove(struct platform_device *pdev)
+{
+	struct device *tps_dev = to_tps6586x_dev(&pdev->dev);
+
+	tps6586x_update(tps_dev, RTC_CTRL, 0,
+		RTC_ENABLE | OSC_SRC_SEL | PRE_BYPASS | CL_SEL_MASK);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int tps6586x_rtc_suspend(struct device *dev)
+{
+	struct tps6586x_rtc *rtc = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		enable_irq_wake(rtc->irq);
+	return 0;
+}
+
+static int tps6586x_rtc_resume(struct device *dev)
+{
+	struct tps6586x_rtc *rtc = dev_get_drvdata(dev);
+
+	if (device_may_wakeup(dev))
+		disable_irq_wake(rtc->irq);
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(tps6586x_pm_ops, tps6586x_rtc_suspend,
+			tps6586x_rtc_resume);
+
+static struct platform_driver tps6586x_rtc_driver = {
+	.driver	= {
+		.name	= "tps6586x-rtc",
+		.pm	= &tps6586x_pm_ops,
+	},
+	.probe	= tps6586x_rtc_probe,
+	.remove = tps6586x_rtc_remove,
+};
+module_platform_driver(tps6586x_rtc_driver);
+
+MODULE_ALIAS("platform:tps6586x-rtc");
+MODULE_DESCRIPTION("TI TPS6586x RTC driver");
+MODULE_AUTHOR("Laxman dewangan <ldewangan@nvidia.com>");
+MODULE_LICENSE("GPL v2");