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, 147 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-amdpt.c b/drivers/gpio/gpio-amdpt.c
new file mode 100644
index 000000000..8458a6949
--- /dev/null
+++ b/drivers/gpio/gpio-amdpt.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD Promontory GPIO driver
+ *
+ * Copyright (C) 2015 ASMedia Technology Inc.
+ * Author: YD Tseng <yd_tseng@asmedia.com.tw>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/generic.h>
+#include <linux/spinlock.h>
+#include <linux/acpi.h>
+#include <linux/platform_device.h>
+
+#define PT_TOTAL_GPIO 8
+#define PT_TOTAL_GPIO_EX 24
+
+/* PCI-E MMIO register offsets */
+#define PT_DIRECTION_REG   0x00
+#define PT_INPUTDATA_REG   0x04
+#define PT_OUTPUTDATA_REG  0x08
+#define PT_CLOCKRATE_REG   0x0C
+#define PT_SYNC_REG        0x28
+
+struct pt_gpio_chip {
+	struct gpio_generic_chip chip;
+	void __iomem             *reg_base;
+};
+
+static int pt_gpio_request(struct gpio_chip *gc, unsigned offset)
+{
+	struct gpio_generic_chip *gen_gc = to_gpio_generic_chip(gc);
+	struct pt_gpio_chip *pt_gpio = gpiochip_get_data(gc);
+	u32 using_pins;
+
+	dev_dbg(gc->parent, "pt_gpio_request offset=%x\n", offset);
+
+	guard(gpio_generic_lock_irqsave)(gen_gc);
+
+	using_pins = readl(pt_gpio->reg_base + PT_SYNC_REG);
+	if (using_pins & BIT(offset)) {
+		dev_warn(gc->parent, "PT GPIO pin %x reconfigured\n",
+			 offset);
+		return -EINVAL;
+	}
+
+	writel(using_pins | BIT(offset), pt_gpio->reg_base + PT_SYNC_REG);
+
+	return 0;
+}
+
+static void pt_gpio_free(struct gpio_chip *gc, unsigned offset)
+{
+	struct gpio_generic_chip *gen_gc = to_gpio_generic_chip(gc);
+	struct pt_gpio_chip *pt_gpio = gpiochip_get_data(gc);
+	u32 using_pins;
+
+	guard(gpio_generic_lock_irqsave)(gen_gc);
+
+	using_pins = readl(pt_gpio->reg_base + PT_SYNC_REG);
+	using_pins &= ~BIT(offset);
+	writel(using_pins, pt_gpio->reg_base + PT_SYNC_REG);
+
+	dev_dbg(gc->parent, "pt_gpio_free offset=%x\n", offset);
+}
+
+static int pt_gpio_probe(struct platform_device *pdev)
+{
+	struct gpio_generic_chip_config config;
+	struct device *dev = &pdev->dev;
+	struct pt_gpio_chip *pt_gpio;
+	int ret = 0;
+
+	if (!ACPI_COMPANION(dev)) {
+		dev_err(dev, "PT GPIO device node not found\n");
+		return -ENODEV;
+	}
+
+	pt_gpio = devm_kzalloc(dev, sizeof(struct pt_gpio_chip), GFP_KERNEL);
+	if (!pt_gpio)
+		return -ENOMEM;
+
+	pt_gpio->reg_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(pt_gpio->reg_base)) {
+		dev_err(dev, "Failed to map MMIO resource for PT GPIO.\n");
+		return PTR_ERR(pt_gpio->reg_base);
+	}
+
+	config = (struct gpio_generic_chip_config) {
+		.dev = dev,
+		.sz = 4,
+		.dat = pt_gpio->reg_base + PT_INPUTDATA_REG,
+		.set = pt_gpio->reg_base + PT_OUTPUTDATA_REG,
+		.dirout = pt_gpio->reg_base + PT_DIRECTION_REG,
+		.flags = GPIO_GENERIC_READ_OUTPUT_REG_SET,
+	};
+
+	ret = gpio_generic_chip_init(&pt_gpio->chip, &config);
+	if (ret) {
+		dev_err(dev, "failed to initialize the generic GPIO chip\n");
+		return ret;
+	}
+
+	pt_gpio->chip.gc.owner = THIS_MODULE;
+	pt_gpio->chip.gc.request = pt_gpio_request;
+	pt_gpio->chip.gc.free = pt_gpio_free;
+	pt_gpio->chip.gc.ngpio = (uintptr_t)device_get_match_data(dev);
+
+	ret = devm_gpiochip_add_data(dev, &pt_gpio->chip.gc, pt_gpio);
+	if (ret) {
+		dev_err(dev, "Failed to register GPIO lib\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, pt_gpio);
+
+	/* initialize register setting */
+	writel(0, pt_gpio->reg_base + PT_SYNC_REG);
+	writel(0, pt_gpio->reg_base + PT_CLOCKRATE_REG);
+
+	dev_dbg(dev, "PT GPIO driver loaded\n");
+	return ret;
+}
+
+static const struct acpi_device_id pt_gpio_acpi_match[] = {
+	{ "AMDF030", PT_TOTAL_GPIO },
+	{ "AMDIF030", PT_TOTAL_GPIO },
+	{ "AMDIF031", PT_TOTAL_GPIO_EX },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, pt_gpio_acpi_match);
+
+static struct platform_driver pt_gpio_driver = {
+	.driver = {
+		.name = "pt-gpio",
+		.acpi_match_table = ACPI_PTR(pt_gpio_acpi_match),
+	},
+	.probe = pt_gpio_probe,
+};
+
+module_platform_driver(pt_gpio_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("YD Tseng <yd_tseng@asmedia.com.tw>");
+MODULE_DESCRIPTION("AMD Promontory GPIO Driver");