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, 279 insertions, 0 deletions

diff --git a/drivers/misc/atmel-ssc.c b/drivers/misc/atmel-ssc.c
new file mode 100644
index 000000000..35a196341
--- /dev/null
+++ b/drivers/misc/atmel-ssc.c
@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Atmel SSC driver
+ *
+ * Copyright (C) 2007 Atmel Corporation
+ */
+
+#include <linux/platform_device.h>
+#include <linux/list.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mutex.h>
+#include <linux/atmel-ssc.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include <linux/of.h>
+
+#include "../../sound/soc/atmel/atmel_ssc_dai.h"
+
+/* Serialize access to ssc_list and user count */
+static DEFINE_MUTEX(user_lock);
+static LIST_HEAD(ssc_list);
+
+struct ssc_device *ssc_request(unsigned int ssc_num)
+{
+	int ssc_valid = 0;
+	struct ssc_device *ssc;
+
+	mutex_lock(&user_lock);
+	list_for_each_entry(ssc, &ssc_list, list) {
+		if (ssc->pdev->dev.of_node) {
+			if (of_alias_get_id(ssc->pdev->dev.of_node, "ssc")
+				== ssc_num) {
+				ssc->pdev->id = ssc_num;
+				ssc_valid = 1;
+				break;
+			}
+		} else if (ssc->pdev->id == ssc_num) {
+			ssc_valid = 1;
+			break;
+		}
+	}
+
+	if (!ssc_valid) {
+		mutex_unlock(&user_lock);
+		pr_err("ssc: ssc%d platform device is missing\n", ssc_num);
+		return ERR_PTR(-ENODEV);
+	}
+
+	if (ssc->user) {
+		mutex_unlock(&user_lock);
+		dev_dbg(&ssc->pdev->dev, "module busy\n");
+		return ERR_PTR(-EBUSY);
+	}
+	ssc->user++;
+	mutex_unlock(&user_lock);
+
+	clk_prepare(ssc->clk);
+
+	return ssc;
+}
+EXPORT_SYMBOL(ssc_request);
+
+void ssc_free(struct ssc_device *ssc)
+{
+	bool disable_clk = true;
+
+	mutex_lock(&user_lock);
+	if (ssc->user)
+		ssc->user--;
+	else {
+		disable_clk = false;
+		dev_dbg(&ssc->pdev->dev, "device already free\n");
+	}
+	mutex_unlock(&user_lock);
+
+	if (disable_clk)
+		clk_unprepare(ssc->clk);
+}
+EXPORT_SYMBOL(ssc_free);
+
+static struct atmel_ssc_platform_data at91rm9200_config = {
+	.use_dma = 0,
+	.has_fslen_ext = 0,
+};
+
+static struct atmel_ssc_platform_data at91sam9rl_config = {
+	.use_dma = 0,
+	.has_fslen_ext = 1,
+};
+
+static struct atmel_ssc_platform_data at91sam9g45_config = {
+	.use_dma = 1,
+	.has_fslen_ext = 1,
+};
+
+static const struct platform_device_id atmel_ssc_devtypes[] = {
+	{
+		.name = "at91rm9200_ssc",
+		.driver_data = (unsigned long) &at91rm9200_config,
+	}, {
+		.name = "at91sam9rl_ssc",
+		.driver_data = (unsigned long) &at91sam9rl_config,
+	}, {
+		.name = "at91sam9g45_ssc",
+		.driver_data = (unsigned long) &at91sam9g45_config,
+	}, {
+		/* sentinel */
+	}
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id atmel_ssc_dt_ids[] = {
+	{
+		.compatible = "atmel,at91rm9200-ssc",
+		.data = &at91rm9200_config,
+	}, {
+		.compatible = "atmel,at91sam9rl-ssc",
+		.data = &at91sam9rl_config,
+	}, {
+		.compatible = "atmel,at91sam9g45-ssc",
+		.data = &at91sam9g45_config,
+	}, {
+		/* sentinel */
+	}
+};
+MODULE_DEVICE_TABLE(of, atmel_ssc_dt_ids);
+#endif
+
+static inline const struct atmel_ssc_platform_data *
+	atmel_ssc_get_driver_data(struct platform_device *pdev)
+{
+	if (pdev->dev.of_node) {
+		const struct of_device_id *match;
+		match = of_match_node(atmel_ssc_dt_ids, pdev->dev.of_node);
+		if (match == NULL)
+			return NULL;
+		return match->data;
+	}
+
+	return (struct atmel_ssc_platform_data *)
+		platform_get_device_id(pdev)->driver_data;
+}
+
+#ifdef CONFIG_SND_ATMEL_SOC_SSC
+static int ssc_sound_dai_probe(struct ssc_device *ssc)
+{
+	struct device_node *np = ssc->pdev->dev.of_node;
+	int ret;
+	int id;
+
+	ssc->sound_dai = false;
+
+	if (!of_property_present(np, "#sound-dai-cells"))
+		return 0;
+
+	id = of_alias_get_id(np, "ssc");
+	if (id < 0)
+		return id;
+
+	ret = atmel_ssc_set_audio(id);
+	ssc->sound_dai = !ret;
+
+	return ret;
+}
+
+static void ssc_sound_dai_remove(struct ssc_device *ssc)
+{
+	if (!ssc->sound_dai)
+		return;
+
+	atmel_ssc_put_audio(of_alias_get_id(ssc->pdev->dev.of_node, "ssc"));
+}
+#else
+static inline int ssc_sound_dai_probe(struct ssc_device *ssc)
+{
+	if (of_property_present(ssc->pdev->dev.of_node, "#sound-dai-cells"))
+		return -ENOTSUPP;
+
+	return 0;
+}
+
+static inline void ssc_sound_dai_remove(struct ssc_device *ssc)
+{
+}
+#endif
+
+static int ssc_probe(struct platform_device *pdev)
+{
+	struct resource *regs;
+	struct ssc_device *ssc;
+	const struct atmel_ssc_platform_data *plat_dat;
+
+	ssc = devm_kzalloc(&pdev->dev, sizeof(struct ssc_device), GFP_KERNEL);
+	if (!ssc) {
+		dev_dbg(&pdev->dev, "out of memory\n");
+		return -ENOMEM;
+	}
+
+	ssc->pdev = pdev;
+
+	plat_dat = atmel_ssc_get_driver_data(pdev);
+	if (!plat_dat)
+		return -ENODEV;
+	ssc->pdata = (struct atmel_ssc_platform_data *)plat_dat;
+
+	if (pdev->dev.of_node) {
+		struct device_node *np = pdev->dev.of_node;
+		ssc->clk_from_rk_pin =
+			of_property_read_bool(np, "atmel,clk-from-rk-pin");
+	}
+
+	ssc->regs = devm_platform_get_and_ioremap_resource(pdev, 0, &regs);
+	if (IS_ERR(ssc->regs))
+		return PTR_ERR(ssc->regs);
+
+	ssc->phybase = regs->start;
+
+	ssc->clk = devm_clk_get(&pdev->dev, "pclk");
+	if (IS_ERR(ssc->clk)) {
+		dev_dbg(&pdev->dev, "no pclk clock defined\n");
+		return -ENXIO;
+	}
+
+	/* disable all interrupts */
+	clk_prepare_enable(ssc->clk);
+	ssc_writel(ssc->regs, IDR, -1);
+	ssc_readl(ssc->regs, SR);
+	clk_disable_unprepare(ssc->clk);
+
+	ssc->irq = platform_get_irq(pdev, 0);
+	if (ssc->irq < 0) {
+		dev_dbg(&pdev->dev, "could not get irq\n");
+		return ssc->irq;
+	}
+
+	mutex_lock(&user_lock);
+	list_add_tail(&ssc->list, &ssc_list);
+	mutex_unlock(&user_lock);
+
+	platform_set_drvdata(pdev, ssc);
+
+	dev_info(&pdev->dev, "Atmel SSC device at 0x%p (irq %d)\n",
+			ssc->regs, ssc->irq);
+
+	if (ssc_sound_dai_probe(ssc))
+		dev_err(&pdev->dev, "failed to auto-setup ssc for audio\n");
+
+	return 0;
+}
+
+static void ssc_remove(struct platform_device *pdev)
+{
+	struct ssc_device *ssc = platform_get_drvdata(pdev);
+
+	ssc_sound_dai_remove(ssc);
+
+	mutex_lock(&user_lock);
+	list_del(&ssc->list);
+	mutex_unlock(&user_lock);
+}
+
+static struct platform_driver ssc_driver = {
+	.driver		= {
+		.name		= "ssc",
+		.of_match_table	= of_match_ptr(atmel_ssc_dt_ids),
+	},
+	.id_table	= atmel_ssc_devtypes,
+	.probe		= ssc_probe,
+	.remove		= ssc_remove,
+};
+module_platform_driver(ssc_driver);
+
+MODULE_AUTHOR("Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>");
+MODULE_DESCRIPTION("SSC driver for Atmel AT91");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ssc");