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, 342 insertions, 0 deletions

diff --git a/drivers/input/joystick/n64joy.c b/drivers/input/joystick/n64joy.c
new file mode 100644
index 000000000..43a02bb99
--- /dev/null
+++ b/drivers/input/joystick/n64joy.c
@@ -0,0 +1,342 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for the four N64 controllers.
+ *
+ * Copyright (c) 2021 Lauri Kasanen
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/limits.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+
+MODULE_AUTHOR("Lauri Kasanen <cand@gmx.com>");
+MODULE_DESCRIPTION("Driver for N64 controllers");
+MODULE_LICENSE("GPL");
+
+#define PIF_RAM 0x1fc007c0
+
+#define SI_DRAM_REG 0
+#define SI_READ_REG 1
+#define SI_WRITE_REG 4
+#define SI_STATUS_REG 6
+
+#define SI_STATUS_DMA_BUSY  BIT(0)
+#define SI_STATUS_IO_BUSY   BIT(1)
+
+#define N64_CONTROLLER_ID 0x0500
+
+#define MAX_CONTROLLERS 4
+
+static const char *n64joy_phys[MAX_CONTROLLERS] = {
+	"n64joy/port0",
+	"n64joy/port1",
+	"n64joy/port2",
+	"n64joy/port3",
+};
+
+struct n64joy_priv {
+	u64 si_buf[8] ____cacheline_aligned;
+	struct timer_list timer;
+	struct mutex n64joy_mutex;
+	struct input_dev *n64joy_dev[MAX_CONTROLLERS];
+	u32 __iomem *reg_base;
+	u8 n64joy_opened;
+};
+
+struct joydata {
+	unsigned int: 16; /* unused */
+	unsigned int err: 2;
+	unsigned int: 14; /* unused */
+
+	union {
+		u32 data;
+
+		struct {
+			unsigned int a: 1;
+			unsigned int b: 1;
+			unsigned int z: 1;
+			unsigned int start: 1;
+			unsigned int up: 1;
+			unsigned int down: 1;
+			unsigned int left: 1;
+			unsigned int right: 1;
+			unsigned int: 2; /* unused */
+			unsigned int l: 1;
+			unsigned int r: 1;
+			unsigned int c_up: 1;
+			unsigned int c_down: 1;
+			unsigned int c_left: 1;
+			unsigned int c_right: 1;
+			signed int x: 8;
+			signed int y: 8;
+		};
+	};
+};
+
+static void n64joy_write_reg(u32 __iomem *reg_base, const u8 reg, const u32 value)
+{
+	writel(value, reg_base + reg);
+}
+
+static u32 n64joy_read_reg(u32 __iomem *reg_base, const u8 reg)
+{
+	return readl(reg_base + reg);
+}
+
+static void n64joy_wait_si_dma(u32 __iomem *reg_base)
+{
+	while (n64joy_read_reg(reg_base, SI_STATUS_REG) &
+	       (SI_STATUS_DMA_BUSY | SI_STATUS_IO_BUSY))
+		cpu_relax();
+}
+
+static void n64joy_exec_pif(struct n64joy_priv *priv, const u64 in[8])
+{
+	unsigned long flags;
+
+	dma_cache_wback_inv((unsigned long) in, 8 * 8);
+	dma_cache_inv((unsigned long) priv->si_buf, 8 * 8);
+
+	local_irq_save(flags);
+
+	n64joy_wait_si_dma(priv->reg_base);
+
+	barrier();
+	n64joy_write_reg(priv->reg_base, SI_DRAM_REG, virt_to_phys(in));
+	barrier();
+	n64joy_write_reg(priv->reg_base, SI_WRITE_REG, PIF_RAM);
+	barrier();
+
+	n64joy_wait_si_dma(priv->reg_base);
+
+	barrier();
+	n64joy_write_reg(priv->reg_base, SI_DRAM_REG, virt_to_phys(priv->si_buf));
+	barrier();
+	n64joy_write_reg(priv->reg_base, SI_READ_REG, PIF_RAM);
+	barrier();
+
+	n64joy_wait_si_dma(priv->reg_base);
+
+	local_irq_restore(flags);
+}
+
+static const u64 polldata[] ____cacheline_aligned = {
+	0xff010401ffffffff,
+	0xff010401ffffffff,
+	0xff010401ffffffff,
+	0xff010401ffffffff,
+	0xfe00000000000000,
+	0,
+	0,
+	1
+};
+
+static void n64joy_poll(struct timer_list *t)
+{
+	const struct joydata *data;
+	struct n64joy_priv *priv = container_of(t, struct n64joy_priv, timer);
+	struct input_dev *dev;
+	u32 i;
+
+	n64joy_exec_pif(priv, polldata);
+
+	data = (struct joydata *) priv->si_buf;
+
+	for (i = 0; i < MAX_CONTROLLERS; i++) {
+		if (!priv->n64joy_dev[i])
+			continue;
+
+		dev = priv->n64joy_dev[i];
+
+		/* d-pad */
+		input_report_key(dev, BTN_DPAD_UP, data[i].up);
+		input_report_key(dev, BTN_DPAD_DOWN, data[i].down);
+		input_report_key(dev, BTN_DPAD_LEFT, data[i].left);
+		input_report_key(dev, BTN_DPAD_RIGHT, data[i].right);
+
+		/* c buttons */
+		input_report_key(dev, BTN_FORWARD, data[i].c_up);
+		input_report_key(dev, BTN_BACK, data[i].c_down);
+		input_report_key(dev, BTN_LEFT, data[i].c_left);
+		input_report_key(dev, BTN_RIGHT, data[i].c_right);
+
+		/* matching buttons */
+		input_report_key(dev, BTN_START, data[i].start);
+		input_report_key(dev, BTN_Z, data[i].z);
+
+		/* remaining ones: a, b, l, r */
+		input_report_key(dev, BTN_0, data[i].a);
+		input_report_key(dev, BTN_1, data[i].b);
+		input_report_key(dev, BTN_2, data[i].l);
+		input_report_key(dev, BTN_3, data[i].r);
+
+		input_report_abs(dev, ABS_X, data[i].x);
+		input_report_abs(dev, ABS_Y, data[i].y);
+
+		input_sync(dev);
+	}
+
+	mod_timer(&priv->timer, jiffies + msecs_to_jiffies(16));
+}
+
+static int n64joy_open(struct input_dev *dev)
+{
+	struct n64joy_priv *priv = input_get_drvdata(dev);
+
+	scoped_guard(mutex_intr, &priv->n64joy_mutex) {
+		if (!priv->n64joy_opened) {
+			/*
+			 * We could use the vblank irq, but it's not important
+			 * if the poll point slightly changes.
+			 */
+			timer_setup(&priv->timer, n64joy_poll, 0);
+			mod_timer(&priv->timer, jiffies + msecs_to_jiffies(16));
+		}
+
+		priv->n64joy_opened++;
+		return 0;
+	}
+
+	return -EINTR;
+}
+
+static void n64joy_close(struct input_dev *dev)
+{
+	struct n64joy_priv *priv = input_get_drvdata(dev);
+
+	guard(mutex)(&priv->n64joy_mutex);
+
+	if (!--priv->n64joy_opened)
+		timer_delete_sync(&priv->timer);
+}
+
+static const u64 __initconst scandata[] ____cacheline_aligned = {
+	0xff010300ffffffff,
+	0xff010300ffffffff,
+	0xff010300ffffffff,
+	0xff010300ffffffff,
+	0xfe00000000000000,
+	0,
+	0,
+	1
+};
+
+/*
+ * The target device is embedded and RAM-constrained. We save RAM
+ * by initializing in __init code that gets dropped late in boot.
+ * For the same reason there is no module or unloading support.
+ */
+static int __init n64joy_probe(struct platform_device *pdev)
+{
+	const struct joydata *data;
+	struct n64joy_priv *priv;
+	struct input_dev *dev;
+	int err = 0;
+	u32 i, j, found = 0;
+
+	priv = kzalloc_obj(*priv);
+	if (!priv)
+		return -ENOMEM;
+	mutex_init(&priv->n64joy_mutex);
+
+	priv->reg_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(priv->reg_base)) {
+		err = PTR_ERR(priv->reg_base);
+		goto fail;
+	}
+
+	/* The controllers are not hotpluggable, so we can scan in init */
+	n64joy_exec_pif(priv, scandata);
+
+	data = (struct joydata *) priv->si_buf;
+
+	for (i = 0; i < MAX_CONTROLLERS; i++) {
+		if (!data[i].err && data[i].data >> 16 == N64_CONTROLLER_ID) {
+			found++;
+
+			dev = priv->n64joy_dev[i] = input_allocate_device();
+			if (!priv->n64joy_dev[i]) {
+				err = -ENOMEM;
+				goto fail;
+			}
+
+			input_set_drvdata(dev, priv);
+
+			dev->name = "N64 controller";
+			dev->phys = n64joy_phys[i];
+			dev->id.bustype = BUS_HOST;
+			dev->id.vendor = 0;
+			dev->id.product = data[i].data >> 16;
+			dev->id.version = 0;
+			dev->dev.parent = &pdev->dev;
+
+			dev->open = n64joy_open;
+			dev->close = n64joy_close;
+
+			/* d-pad */
+			input_set_capability(dev, EV_KEY, BTN_DPAD_UP);
+			input_set_capability(dev, EV_KEY, BTN_DPAD_DOWN);
+			input_set_capability(dev, EV_KEY, BTN_DPAD_LEFT);
+			input_set_capability(dev, EV_KEY, BTN_DPAD_RIGHT);
+			/* c buttons */
+			input_set_capability(dev, EV_KEY, BTN_LEFT);
+			input_set_capability(dev, EV_KEY, BTN_RIGHT);
+			input_set_capability(dev, EV_KEY, BTN_FORWARD);
+			input_set_capability(dev, EV_KEY, BTN_BACK);
+			/* matching buttons */
+			input_set_capability(dev, EV_KEY, BTN_START);
+			input_set_capability(dev, EV_KEY, BTN_Z);
+			/* remaining ones: a, b, l, r */
+			input_set_capability(dev, EV_KEY, BTN_0);
+			input_set_capability(dev, EV_KEY, BTN_1);
+			input_set_capability(dev, EV_KEY, BTN_2);
+			input_set_capability(dev, EV_KEY, BTN_3);
+
+			for (j = 0; j < 2; j++)
+				input_set_abs_params(dev, ABS_X + j,
+						     S8_MIN, S8_MAX, 0, 0);
+
+			err = input_register_device(dev);
+			if (err) {
+				input_free_device(dev);
+				goto fail;
+			}
+		}
+	}
+
+	pr_info("%u controller(s) connected\n", found);
+
+	if (!found)
+		return -ENODEV;
+
+	return 0;
+fail:
+	for (i = 0; i < MAX_CONTROLLERS; i++) {
+		if (!priv->n64joy_dev[i])
+			continue;
+		input_unregister_device(priv->n64joy_dev[i]);
+	}
+	return err;
+}
+
+static struct platform_driver n64joy_driver = {
+	.driver = {
+		.name = "n64joy",
+	},
+};
+
+static int __init n64joy_init(void)
+{
+	return platform_driver_probe(&n64joy_driver, n64joy_probe);
+}
+
+module_init(n64joy_init);