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, 262 insertions, 0 deletions

diff --git a/drivers/macintosh/mac_hid.c b/drivers/macintosh/mac_hid.c
new file mode 100644
index 000000000..1fdf3855f
--- /dev/null
+++ b/drivers/macintosh/mac_hid.c
@@ -0,0 +1,262 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * drivers/macintosh/mac_hid.c
+ *
+ * HID support stuff for Macintosh computers.
+ *
+ * Copyright (C) 2000 Franz Sirl.
+ *
+ * This file will soon be removed in favor of an uinput userspace tool.
+ */
+
+#include <linux/init.h>
+#include <linux/proc_fs.h>
+#include <linux/sysctl.h>
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+MODULE_DESCRIPTION("Mouse button 2+3 emulation");
+MODULE_LICENSE("GPL");
+
+static int mouse_emulate_buttons;
+static int mouse_button2_keycode = KEY_RIGHTCTRL;	/* right control key */
+static int mouse_button3_keycode = KEY_RIGHTALT;	/* right option key */
+
+static struct input_dev *mac_hid_emumouse_dev;
+
+static DEFINE_MUTEX(mac_hid_emumouse_mutex);
+
+static int mac_hid_create_emumouse(void)
+{
+	static struct lock_class_key mac_hid_emumouse_dev_event_class;
+	static struct lock_class_key mac_hid_emumouse_dev_mutex_class;
+	int err;
+
+	mac_hid_emumouse_dev = input_allocate_device();
+	if (!mac_hid_emumouse_dev)
+		return -ENOMEM;
+
+	lockdep_set_class(&mac_hid_emumouse_dev->event_lock,
+			  &mac_hid_emumouse_dev_event_class);
+	lockdep_set_class(&mac_hid_emumouse_dev->mutex,
+			  &mac_hid_emumouse_dev_mutex_class);
+
+	mac_hid_emumouse_dev->name = "Macintosh mouse button emulation";
+	mac_hid_emumouse_dev->id.bustype = BUS_ADB;
+	mac_hid_emumouse_dev->id.vendor = 0x0001;
+	mac_hid_emumouse_dev->id.product = 0x0001;
+	mac_hid_emumouse_dev->id.version = 0x0100;
+
+	mac_hid_emumouse_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REL);
+	mac_hid_emumouse_dev->keybit[BIT_WORD(BTN_MOUSE)] =
+		BIT_MASK(BTN_LEFT) | BIT_MASK(BTN_MIDDLE) | BIT_MASK(BTN_RIGHT);
+	mac_hid_emumouse_dev->relbit[0] = BIT_MASK(REL_X) | BIT_MASK(REL_Y);
+
+	err = input_register_device(mac_hid_emumouse_dev);
+	if (err) {
+		input_free_device(mac_hid_emumouse_dev);
+		mac_hid_emumouse_dev = NULL;
+		return err;
+	}
+
+	return 0;
+}
+
+static void mac_hid_destroy_emumouse(void)
+{
+	input_unregister_device(mac_hid_emumouse_dev);
+	mac_hid_emumouse_dev = NULL;
+}
+
+static bool mac_hid_emumouse_filter(struct input_handle *handle,
+				    unsigned int type, unsigned int code,
+				    int value)
+{
+	unsigned int btn;
+
+	if (type != EV_KEY)
+		return false;
+
+	if (code == mouse_button2_keycode)
+		btn = BTN_MIDDLE;
+	else if (code == mouse_button3_keycode)
+		btn = BTN_RIGHT;
+	else
+		return false;
+
+	input_report_key(mac_hid_emumouse_dev, btn, value);
+	input_sync(mac_hid_emumouse_dev);
+
+	return true;
+}
+
+static int mac_hid_emumouse_connect(struct input_handler *handler,
+				    struct input_dev *dev,
+				    const struct input_device_id *id)
+{
+	struct input_handle *handle;
+	int error;
+
+	/* Don't bind to ourselves */
+	if (dev == mac_hid_emumouse_dev)
+		return -ENODEV;
+
+	handle = kzalloc_obj(struct input_handle);
+	if (!handle)
+		return -ENOMEM;
+
+	handle->dev = dev;
+	handle->handler = handler;
+	handle->name = "mac-button-emul";
+
+	error = input_register_handle(handle);
+	if (error) {
+		printk(KERN_ERR
+			"mac_hid: Failed to register button emulation handle, "
+			"error %d\n", error);
+		goto err_free;
+	}
+
+	error = input_open_device(handle);
+	if (error) {
+		printk(KERN_ERR
+			"mac_hid: Failed to open input device, error %d\n",
+			error);
+		goto err_unregister;
+	}
+
+	return 0;
+
+ err_unregister:
+	input_unregister_handle(handle);
+ err_free:
+	kfree(handle);
+	return error;
+}
+
+static void mac_hid_emumouse_disconnect(struct input_handle *handle)
+{
+	input_close_device(handle);
+	input_unregister_handle(handle);
+	kfree(handle);
+}
+
+static const struct input_device_id mac_hid_emumouse_ids[] = {
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+	},
+	{ },
+};
+
+MODULE_DEVICE_TABLE(input, mac_hid_emumouse_ids);
+
+static struct input_handler mac_hid_emumouse_handler = {
+	.filter		= mac_hid_emumouse_filter,
+	.connect	= mac_hid_emumouse_connect,
+	.disconnect	= mac_hid_emumouse_disconnect,
+	.name		= "mac-button-emul",
+	.id_table	= mac_hid_emumouse_ids,
+};
+
+static int mac_hid_start_emulation(void)
+{
+	int err;
+
+	err = mac_hid_create_emumouse();
+	if (err)
+		return err;
+
+	err = input_register_handler(&mac_hid_emumouse_handler);
+	if (err) {
+		mac_hid_destroy_emumouse();
+		return err;
+	}
+
+	return 0;
+}
+
+static void mac_hid_stop_emulation(void)
+{
+	input_unregister_handler(&mac_hid_emumouse_handler);
+	mac_hid_destroy_emumouse();
+}
+
+static int mac_hid_toggle_emumouse(const struct ctl_table *table, int write,
+				   void *buffer, size_t *lenp, loff_t *ppos)
+{
+	int *valp = table->data;
+	int old_val;
+	int rc;
+
+	rc = mutex_lock_killable(&mac_hid_emumouse_mutex);
+	if (rc)
+		return rc;
+
+	old_val = *valp;
+	rc = proc_dointvec(table, write, buffer, lenp, ppos);
+
+	if (rc == 0 && write && *valp != old_val) {
+		if (*valp == 1)
+			rc = mac_hid_start_emulation();
+		else if (*valp == 0)
+			mac_hid_stop_emulation();
+		else
+			rc = -EINVAL;
+	}
+
+	/* Restore the old value in case of error */
+	if (rc)
+		*valp = old_val;
+
+	mutex_unlock(&mac_hid_emumouse_mutex);
+
+	return rc;
+}
+
+/* file(s) in /proc/sys/dev/mac_hid */
+static const struct ctl_table mac_hid_files[] = {
+	{
+		.procname	= "mouse_button_emulation",
+		.data		= &mouse_emulate_buttons,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= mac_hid_toggle_emumouse,
+	},
+	{
+		.procname	= "mouse_button2_keycode",
+		.data		= &mouse_button2_keycode,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+	{
+		.procname	= "mouse_button3_keycode",
+		.data		= &mouse_button3_keycode,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+};
+
+static struct ctl_table_header *mac_hid_sysctl_header;
+
+static int __init mac_hid_init(void)
+{
+	mac_hid_sysctl_header = register_sysctl("dev/mac_hid", mac_hid_files);
+	if (!mac_hid_sysctl_header)
+		return -ENOMEM;
+
+	return 0;
+}
+module_init(mac_hid_init);
+
+static void __exit mac_hid_exit(void)
+{
+	unregister_sysctl_table(mac_hid_sysctl_header);
+
+	if (mouse_emulate_buttons)
+		mac_hid_stop_emulation();
+}
+module_exit(mac_hid_exit);