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, 231 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-nxp-bbnsm.c b/drivers/rtc/rtc-nxp-bbnsm.c
new file mode 100644
index 000000000..d4fc9dc58
--- /dev/null
+++ b/drivers/rtc/rtc-nxp-bbnsm.c
@@ -0,0 +1,231 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Copyright 2022 NXP.
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm_wakeirq.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+
+#define BBNSM_CTRL	0x8
+#define BBNSM_INT_EN	0x10
+#define BBNSM_EVENTS	0x14
+#define BBNSM_RTC_LS	0x40
+#define BBNSM_RTC_MS	0x44
+#define BBNSM_TA	0x50
+
+#define RTC_EN		0x2
+#define RTC_EN_MSK	0x3
+#define TA_EN		(0x2 << 2)
+#define TA_DIS		(0x1 << 2)
+#define TA_EN_MSK	(0x3 << 2)
+#define RTC_INT_EN	0x2
+#define TA_INT_EN	(0x2 << 2)
+
+#define BBNSM_EVENT_TA	(0x2 << 2)
+
+#define CNTR_TO_SECS_SH	15
+
+struct bbnsm_rtc {
+	struct rtc_device *rtc;
+	struct regmap *regmap;
+	int irq;
+	struct clk *clk;
+};
+
+static u32 bbnsm_read_counter(struct bbnsm_rtc *bbnsm)
+{
+	u32 rtc_msb, rtc_lsb;
+	unsigned int timeout = 100;
+	u32 time;
+	u32 tmp = 0;
+
+	do {
+		time = tmp;
+		/* read the msb */
+		regmap_read(bbnsm->regmap, BBNSM_RTC_MS, &rtc_msb);
+		/* read the lsb */
+		regmap_read(bbnsm->regmap, BBNSM_RTC_LS, &rtc_lsb);
+		/* convert to seconds */
+		tmp = (rtc_msb << 17) | (rtc_lsb >> 15);
+	} while (tmp != time && --timeout);
+
+	return time;
+}
+
+static int bbnsm_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+	unsigned long time;
+	u32 val;
+
+	regmap_read(bbnsm->regmap, BBNSM_CTRL, &val);
+	if ((val & RTC_EN_MSK) != RTC_EN)
+		return -EINVAL;
+
+	time = bbnsm_read_counter(bbnsm);
+	rtc_time64_to_tm(time, tm);
+
+	return 0;
+}
+
+static int bbnsm_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+	unsigned long time = rtc_tm_to_time64(tm);
+
+	/* disable the RTC first */
+	regmap_update_bits(bbnsm->regmap, BBNSM_CTRL, RTC_EN_MSK, 0);
+
+	/* write the 32bit sec time to 47 bit timer counter, leaving 15 LSBs blank */
+	regmap_write(bbnsm->regmap, BBNSM_RTC_LS, time << CNTR_TO_SECS_SH);
+	regmap_write(bbnsm->regmap, BBNSM_RTC_MS, time >> (32 - CNTR_TO_SECS_SH));
+
+	/* Enable the RTC again */
+	regmap_update_bits(bbnsm->regmap, BBNSM_CTRL, RTC_EN_MSK, RTC_EN);
+
+	return 0;
+}
+
+static int bbnsm_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+	u32 bbnsm_events, bbnsm_ta;
+
+	regmap_read(bbnsm->regmap, BBNSM_TA, &bbnsm_ta);
+	rtc_time64_to_tm(bbnsm_ta, &alrm->time);
+
+	regmap_read(bbnsm->regmap, BBNSM_EVENTS, &bbnsm_events);
+	alrm->pending = (bbnsm_events & BBNSM_EVENT_TA) ? 1 : 0;
+
+	return 0;
+}
+
+static int bbnsm_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+
+	/* enable the alarm event */
+	regmap_update_bits(bbnsm->regmap, BBNSM_CTRL, TA_EN_MSK, enable ? TA_EN : TA_DIS);
+	/* enable the alarm interrupt */
+	regmap_update_bits(bbnsm->regmap, BBNSM_INT_EN, TA_EN_MSK, enable ? TA_EN : TA_DIS);
+
+	return 0;
+}
+
+static int bbnsm_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+	unsigned long time = rtc_tm_to_time64(&alrm->time);
+
+	/* disable the alarm */
+	regmap_update_bits(bbnsm->regmap, BBNSM_CTRL, TA_EN, TA_EN);
+
+	/* write the seconds to TA */
+	regmap_write(bbnsm->regmap, BBNSM_TA, time);
+
+	return bbnsm_rtc_alarm_irq_enable(dev, alrm->enabled);
+}
+
+static const struct rtc_class_ops bbnsm_rtc_ops = {
+	.read_time = bbnsm_rtc_read_time,
+	.set_time = bbnsm_rtc_set_time,
+	.read_alarm = bbnsm_rtc_read_alarm,
+	.set_alarm = bbnsm_rtc_set_alarm,
+	.alarm_irq_enable = bbnsm_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t bbnsm_rtc_irq_handler(int irq, void *dev_id)
+{
+	struct device *dev = dev_id;
+	struct bbnsm_rtc  *bbnsm = dev_get_drvdata(dev);
+	u32 val;
+
+	regmap_read(bbnsm->regmap, BBNSM_EVENTS, &val);
+	if (val & BBNSM_EVENT_TA) {
+		bbnsm_rtc_alarm_irq_enable(dev, false);
+		/* clear the alarm event */
+		regmap_write_bits(bbnsm->regmap, BBNSM_EVENTS, TA_EN_MSK, BBNSM_EVENT_TA);
+		rtc_update_irq(bbnsm->rtc, 1, RTC_AF | RTC_IRQF);
+
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int bbnsm_rtc_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct bbnsm_rtc *bbnsm;
+	int ret;
+
+	bbnsm = devm_kzalloc(&pdev->dev, sizeof(*bbnsm), GFP_KERNEL);
+	if (!bbnsm)
+		return -ENOMEM;
+
+	bbnsm->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(bbnsm->rtc))
+		return PTR_ERR(bbnsm->rtc);
+
+	bbnsm->regmap = syscon_node_to_regmap(np->parent);
+	if (IS_ERR(bbnsm->regmap)) {
+		dev_dbg(&pdev->dev, "bbnsm get regmap failed\n");
+		return PTR_ERR(bbnsm->regmap);
+	}
+
+	bbnsm->irq = platform_get_irq(pdev, 0);
+	if (bbnsm->irq < 0)
+		return bbnsm->irq;
+
+	platform_set_drvdata(pdev, bbnsm);
+
+	/* clear all the pending events */
+	regmap_write(bbnsm->regmap, BBNSM_EVENTS, 0x7A);
+
+	ret = devm_device_init_wakeup(&pdev->dev);
+	if (ret)
+		dev_err(&pdev->dev, "failed to init wakeup, %d\n", ret);
+
+	ret = devm_pm_set_wake_irq(&pdev->dev, bbnsm->irq);
+	if (ret)
+		dev_err(&pdev->dev, "failed to set wake irq, %d\n", ret);
+
+	ret = devm_request_irq(&pdev->dev, bbnsm->irq, bbnsm_rtc_irq_handler,
+			       IRQF_SHARED, "rtc alarm", &pdev->dev);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to request irq %d: %d\n",
+			bbnsm->irq, ret);
+		return ret;
+	}
+
+	bbnsm->rtc->ops = &bbnsm_rtc_ops;
+	bbnsm->rtc->range_max = U32_MAX;
+
+	return devm_rtc_register_device(bbnsm->rtc);
+}
+
+static const struct of_device_id bbnsm_dt_ids[] = {
+	{ .compatible = "nxp,imx93-bbnsm-rtc" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, bbnsm_dt_ids);
+
+static struct platform_driver bbnsm_rtc_driver = {
+	.driver = {
+		.name = "bbnsm_rtc",
+		.of_match_table = bbnsm_dt_ids,
+	},
+	.probe = bbnsm_rtc_probe,
+};
+module_platform_driver(bbnsm_rtc_driver);
+
+MODULE_AUTHOR("Jacky Bai <ping.bai@nxp.com>");
+MODULE_DESCRIPTION("NXP BBNSM RTC Driver");
+MODULE_LICENSE("GPL");