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, 160 insertions, 0 deletions

diff --git a/drivers/mfd/vexpress-sysreg.c b/drivers/mfd/vexpress-sysreg.c
new file mode 100644
index 000000000..f49cee91f
--- /dev/null
+++ b/drivers/mfd/vexpress-sysreg.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Copyright (C) 2012 ARM Limited
+ */
+
+#include <linux/gpio/driver.h>
+#include <linux/gpio/generic.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+#include <linux/stat.h>
+
+#define SYS_ID			0x000
+#define SYS_SW			0x004
+#define SYS_LED			0x008
+#define SYS_100HZ		0x024
+#define SYS_FLAGSSET		0x030
+#define SYS_FLAGSCLR		0x034
+#define SYS_NVFLAGS		0x038
+#define SYS_NVFLAGSSET		0x038
+#define SYS_NVFLAGSCLR		0x03c
+#define SYS_MCI			0x048
+#define SYS_FLASH		0x04c
+#define SYS_CFGSW		0x058
+#define SYS_24MHZ		0x05c
+#define SYS_MISC		0x060
+#define SYS_DMA			0x064
+#define SYS_PROCID0		0x084
+#define SYS_PROCID1		0x088
+#define SYS_CFGDATA		0x0a0
+#define SYS_CFGCTRL		0x0a4
+#define SYS_CFGSTAT		0x0a8
+
+/* The sysreg block is just a random collection of various functions... */
+
+static const struct property_entry vexpress_sysreg_sys_led_props[] = {
+	PROPERTY_ENTRY_STRING("label", "sys_led"),
+	PROPERTY_ENTRY_U32("ngpios", 8),
+	{ }
+};
+
+static const struct software_node vexpress_sysreg_sys_led_swnode = {
+	.properties = vexpress_sysreg_sys_led_props,
+};
+
+static const struct property_entry vexpress_sysreg_sys_mci_props[] = {
+	PROPERTY_ENTRY_STRING("label", "sys_mci"),
+	PROPERTY_ENTRY_U32("ngpios", 2),
+	{ }
+};
+
+static const struct software_node vexpress_sysreg_sys_mci_swnode = {
+	.properties = vexpress_sysreg_sys_mci_props,
+};
+
+static const struct property_entry vexpress_sysreg_sys_flash_props[] = {
+	PROPERTY_ENTRY_STRING("label", "sys_flash"),
+	PROPERTY_ENTRY_U32("ngpios", 1),
+	{ }
+};
+
+static const struct software_node vexpress_sysreg_sys_flash_swnode = {
+	.properties = vexpress_sysreg_sys_flash_props,
+};
+
+static struct mfd_cell vexpress_sysreg_cells[] = {
+	{
+		.name = "basic-mmio-gpio",
+		.of_compatible = "arm,vexpress-sysreg,sys_led",
+		.num_resources = 1,
+		.resources = &DEFINE_RES_MEM_NAMED(SYS_LED, 0x4, "dat"),
+		.swnode = &vexpress_sysreg_sys_led_swnode,
+	}, {
+		.name = "basic-mmio-gpio",
+		.of_compatible = "arm,vexpress-sysreg,sys_mci",
+		.num_resources = 1,
+		.resources = &DEFINE_RES_MEM_NAMED(SYS_MCI, 0x4, "dat"),
+		.swnode = &vexpress_sysreg_sys_mci_swnode,
+	}, {
+		.name = "basic-mmio-gpio",
+		.of_compatible = "arm,vexpress-sysreg,sys_flash",
+		.num_resources = 1,
+		.resources = &DEFINE_RES_MEM_NAMED(SYS_FLASH, 0x4, "dat"),
+		.swnode = &vexpress_sysreg_sys_flash_swnode,
+	}, {
+		.name = "vexpress-syscfg",
+		.num_resources = 1,
+		.resources = &DEFINE_RES_MEM(SYS_MISC, 0x4c),
+	}
+};
+
+static int vexpress_sysreg_probe(struct platform_device *pdev)
+{
+	struct gpio_generic_chip *mmc_gpio_chip;
+	struct gpio_generic_chip_config config;
+	struct resource *mem;
+	void __iomem *base;
+	int ret;
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!mem)
+		return -EINVAL;
+
+	base = devm_ioremap(&pdev->dev, mem->start, resource_size(mem));
+	if (!base)
+		return -ENOMEM;
+
+	/*
+	 * Duplicated SYS_MCI pseudo-GPIO controller for compatibility with
+	 * older trees using sysreg node for MMC control lines.
+	 */
+	mmc_gpio_chip = devm_kzalloc(&pdev->dev, sizeof(*mmc_gpio_chip),
+			GFP_KERNEL);
+	if (!mmc_gpio_chip)
+		return -ENOMEM;
+
+	config = (struct gpio_generic_chip_config) {
+		.dev = &pdev->dev,
+		.sz = 4,
+		.dat = base + SYS_MCI,
+	};
+
+	ret = gpio_generic_chip_init(mmc_gpio_chip, &config);
+	if (ret)
+		return ret;
+
+	mmc_gpio_chip->gc.ngpio = 2;
+
+	ret = devm_gpiochip_add_data(&pdev->dev, &mmc_gpio_chip->gc, NULL);
+	if (ret)
+		return ret;
+
+	return devm_mfd_add_devices(&pdev->dev, PLATFORM_DEVID_AUTO,
+			vexpress_sysreg_cells,
+			ARRAY_SIZE(vexpress_sysreg_cells), mem, 0, NULL);
+}
+
+static const struct of_device_id vexpress_sysreg_match[] = {
+	{ .compatible = "arm,vexpress-sysreg", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, vexpress_sysreg_match);
+
+static struct platform_driver vexpress_sysreg_driver = {
+	.driver = {
+		.name = "vexpress-sysreg",
+		.of_match_table = vexpress_sysreg_match,
+	},
+	.probe = vexpress_sysreg_probe,
+};
+
+module_platform_driver(vexpress_sysreg_driver);
+MODULE_DESCRIPTION("Versatile Express system registers driver");
+MODULE_LICENSE("GPL v2");