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, 157 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-mlxbf.c b/drivers/gpio/gpio-mlxbf.c
new file mode 100644
index 000000000..a18fedbc4
--- /dev/null
+++ b/drivers/gpio/gpio-mlxbf.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/acpi.h>
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/gpio/driver.h>
+#include <linux/gpio/generic.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/resource.h>
+#include <linux/types.h>
+
+/* Number of pins on BlueField */
+#define MLXBF_GPIO_NR 54
+
+/* Pad Electrical Controls. */
+#define MLXBF_GPIO_PAD_CONTROL_FIRST_WORD 0x0700
+#define MLXBF_GPIO_PAD_CONTROL_1_FIRST_WORD 0x0708
+#define MLXBF_GPIO_PAD_CONTROL_2_FIRST_WORD 0x0710
+#define MLXBF_GPIO_PAD_CONTROL_3_FIRST_WORD 0x0718
+
+#define MLXBF_GPIO_PIN_DIR_I 0x1040
+#define MLXBF_GPIO_PIN_DIR_O 0x1048
+#define MLXBF_GPIO_PIN_STATE 0x1000
+#define MLXBF_GPIO_SCRATCHPAD 0x20
+
+#ifdef CONFIG_PM
+struct mlxbf_gpio_context_save_regs {
+	u64 scratchpad;
+	u64 pad_control[MLXBF_GPIO_NR];
+	u64 pin_dir_i;
+	u64 pin_dir_o;
+};
+#endif
+
+/* Device state structure. */
+struct mlxbf_gpio_state {
+	struct gpio_generic_chip chip;
+
+	/* Memory Address */
+	void __iomem *base;
+
+#ifdef CONFIG_PM
+	struct mlxbf_gpio_context_save_regs csave_regs;
+#endif
+};
+
+static int mlxbf_gpio_probe(struct platform_device *pdev)
+{
+	struct gpio_generic_chip_config config;
+	struct mlxbf_gpio_state *gs;
+	struct device *dev = &pdev->dev;
+	struct gpio_chip *gc;
+	int ret;
+
+	gs = devm_kzalloc(&pdev->dev, sizeof(*gs), GFP_KERNEL);
+	if (!gs)
+		return -ENOMEM;
+
+	gs->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(gs->base))
+		return PTR_ERR(gs->base);
+
+	gc = &gs->chip.gc;
+
+	config = (struct gpio_generic_chip_config) {
+		.dev = dev,
+		.sz = 8,
+		.dat = gs->base + MLXBF_GPIO_PIN_STATE,
+		.dirout = gs->base + MLXBF_GPIO_PIN_DIR_O,
+		.dirin =  gs->base + MLXBF_GPIO_PIN_DIR_I,
+	};
+
+	ret = gpio_generic_chip_init(&gs->chip, &config);
+	if (ret)
+		return -ENODEV;
+
+	gc->owner = THIS_MODULE;
+	gc->ngpio = MLXBF_GPIO_NR;
+
+	ret = devm_gpiochip_add_data(dev, &gs->chip.gc, gs);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed adding memory mapped gpiochip\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, gs);
+	dev_info(&pdev->dev, "registered Mellanox BlueField GPIO");
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int mlxbf_gpio_suspend(struct platform_device *pdev, pm_message_t state)
+{
+	struct mlxbf_gpio_state *gs = platform_get_drvdata(pdev);
+
+	gs->csave_regs.scratchpad = readq(gs->base + MLXBF_GPIO_SCRATCHPAD);
+	gs->csave_regs.pad_control[0] =
+		readq(gs->base + MLXBF_GPIO_PAD_CONTROL_FIRST_WORD);
+	gs->csave_regs.pad_control[1] =
+		readq(gs->base + MLXBF_GPIO_PAD_CONTROL_1_FIRST_WORD);
+	gs->csave_regs.pad_control[2] =
+		readq(gs->base + MLXBF_GPIO_PAD_CONTROL_2_FIRST_WORD);
+	gs->csave_regs.pad_control[3] =
+		readq(gs->base + MLXBF_GPIO_PAD_CONTROL_3_FIRST_WORD);
+	gs->csave_regs.pin_dir_i = readq(gs->base + MLXBF_GPIO_PIN_DIR_I);
+	gs->csave_regs.pin_dir_o = readq(gs->base + MLXBF_GPIO_PIN_DIR_O);
+
+	return 0;
+}
+
+static int mlxbf_gpio_resume(struct platform_device *pdev)
+{
+	struct mlxbf_gpio_state *gs = platform_get_drvdata(pdev);
+
+	writeq(gs->csave_regs.scratchpad, gs->base + MLXBF_GPIO_SCRATCHPAD);
+	writeq(gs->csave_regs.pad_control[0],
+	       gs->base + MLXBF_GPIO_PAD_CONTROL_FIRST_WORD);
+	writeq(gs->csave_regs.pad_control[1],
+	       gs->base + MLXBF_GPIO_PAD_CONTROL_1_FIRST_WORD);
+	writeq(gs->csave_regs.pad_control[2],
+	       gs->base + MLXBF_GPIO_PAD_CONTROL_2_FIRST_WORD);
+	writeq(gs->csave_regs.pad_control[3],
+	       gs->base + MLXBF_GPIO_PAD_CONTROL_3_FIRST_WORD);
+	writeq(gs->csave_regs.pin_dir_i, gs->base + MLXBF_GPIO_PIN_DIR_I);
+	writeq(gs->csave_regs.pin_dir_o, gs->base + MLXBF_GPIO_PIN_DIR_O);
+
+	return 0;
+}
+#endif
+
+static const struct acpi_device_id __maybe_unused mlxbf_gpio_acpi_match[] = {
+	{ "MLNXBF02", 0 },
+	{}
+};
+MODULE_DEVICE_TABLE(acpi, mlxbf_gpio_acpi_match);
+
+static struct platform_driver mlxbf_gpio_driver = {
+	.driver = {
+		.name = "mlxbf_gpio",
+		.acpi_match_table = ACPI_PTR(mlxbf_gpio_acpi_match),
+	},
+	.probe    = mlxbf_gpio_probe,
+#ifdef CONFIG_PM
+	.suspend  = mlxbf_gpio_suspend,
+	.resume   = mlxbf_gpio_resume,
+#endif
+};
+
+module_platform_driver(mlxbf_gpio_driver);
+
+MODULE_DESCRIPTION("Mellanox BlueField GPIO Driver");
+MODULE_AUTHOR("Mellanox Technologies");
+MODULE_LICENSE("GPL");