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, 184 insertions, 0 deletions

diff --git a/drivers/hid/hid-holtek-kbd.c b/drivers/hid/hid-holtek-kbd.c
new file mode 100644
index 000000000..d13543517
--- /dev/null
+++ b/drivers/hid/hid-holtek-kbd.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HID driver for Holtek keyboard
+ * Copyright (c) 2012 Tom Harwood
+*/
+
+/*
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+
+#include "hid-ids.h"
+#include "usbhid/usbhid.h"
+
+/* Holtek based keyboards (USB ID 04d9:a055) have the following issues:
+ * - The report descriptor specifies an excessively large number of consumer
+ *   usages (2^15), which is more than HID_MAX_USAGES. This prevents proper
+ *   parsing of the report descriptor.
+ * - The report descriptor reports on caps/scroll/num lock key presses, but
+ *   doesn't have an LED output usage block.
+ *
+ * The replacement descriptor below fixes the number of consumer usages,
+ * and provides an LED output usage block. LED output events are redirected
+ * to the boot interface.
+ */
+
+static const __u8 holtek_kbd_rdesc_fixed[] = {
+	/* Original report descriptor, with reduced number of consumer usages */
+	0x05, 0x01,         /*  Usage Page (Desktop),                         */
+	0x09, 0x80,         /*  Usage (Sys Control),                          */
+	0xA1, 0x01,         /*  Collection (Application),                     */
+	0x85, 0x01,         /*      Report ID (1),                            */
+	0x19, 0x81,         /*      Usage Minimum (Sys Power Down),           */
+	0x29, 0x83,         /*      Usage Maximum (Sys Wake Up),              */
+	0x15, 0x00,         /*      Logical Minimum (0),                      */
+	0x25, 0x01,         /*      Logical Maximum (1),                      */
+	0x95, 0x03,         /*      Report Count (3),                         */
+	0x75, 0x01,         /*      Report Size (1),                          */
+	0x81, 0x02,         /*      Input (Variable),                         */
+	0x95, 0x01,         /*      Report Count (1),                         */
+	0x75, 0x05,         /*      Report Size (5),                          */
+	0x81, 0x01,         /*      Input (Constant),                         */
+	0xC0,               /*  End Collection,                               */
+	0x05, 0x0C,         /*  Usage Page (Consumer),                        */
+	0x09, 0x01,         /*  Usage (Consumer Control),                     */
+	0xA1, 0x01,         /*  Collection (Application),                     */
+	0x85, 0x02,         /*      Report ID (2),                            */
+	0x19, 0x00,         /*      Usage Minimum (00h),                      */
+	0x2A, 0xFF, 0x2F,   /*      Usage Maximum (0x2FFF), previously 0x7FFF */
+	0x15, 0x00,         /*      Logical Minimum (0),                      */
+	0x26, 0xFF, 0x2F,   /*      Logical Maximum (0x2FFF),previously 0x7FFF*/
+	0x95, 0x01,         /*      Report Count (1),                         */
+	0x75, 0x10,         /*      Report Size (16),                         */
+	0x81, 0x00,         /*      Input,                                    */
+	0xC0,               /*  End Collection,                               */
+	0x05, 0x01,         /*  Usage Page (Desktop),                         */
+	0x09, 0x06,         /*  Usage (Keyboard),                             */
+	0xA1, 0x01,         /*  Collection (Application),                     */
+	0x85, 0x03,         /*      Report ID (3),                            */
+	0x95, 0x38,         /*      Report Count (56),                        */
+	0x75, 0x01,         /*      Report Size (1),                          */
+	0x15, 0x00,         /*      Logical Minimum (0),                      */
+	0x25, 0x01,         /*      Logical Maximum (1),                      */
+	0x05, 0x07,         /*      Usage Page (Keyboard),                    */
+	0x19, 0xE0,         /*      Usage Minimum (KB Leftcontrol),           */
+	0x29, 0xE7,         /*      Usage Maximum (KB Right GUI),             */
+	0x19, 0x00,         /*      Usage Minimum (None),                     */
+	0x29, 0x2F,         /*      Usage Maximum (KB Lboxbracket And Lbrace),*/
+	0x81, 0x02,         /*      Input (Variable),                         */
+	0xC0,               /*  End Collection,                               */
+	0x05, 0x01,         /*  Usage Page (Desktop),                         */
+	0x09, 0x06,         /*  Usage (Keyboard),                             */
+	0xA1, 0x01,         /*  Collection (Application),                     */
+	0x85, 0x04,         /*      Report ID (4),                            */
+	0x95, 0x38,         /*      Report Count (56),                        */
+	0x75, 0x01,         /*      Report Size (1),                          */
+	0x15, 0x00,         /*      Logical Minimum (0),                      */
+	0x25, 0x01,         /*      Logical Maximum (1),                      */
+	0x05, 0x07,         /*      Usage Page (Keyboard),                    */
+	0x19, 0x30,         /*      Usage Minimum (KB Rboxbracket And Rbrace),*/
+	0x29, 0x67,         /*      Usage Maximum (KP Equals),                */
+	0x81, 0x02,         /*      Input (Variable),                         */
+	0xC0,               /*  End Collection                                */
+
+	/* LED usage for the boot protocol interface */
+	0x05, 0x01,         /*  Usage Page (Desktop),                         */
+	0x09, 0x06,         /*  Usage (Keyboard),                             */
+	0xA1, 0x01,         /*  Collection (Application),                     */
+	0x05, 0x08,         /*      Usage Page (LED),                         */
+	0x19, 0x01,         /*      Usage Minimum (01h),                      */
+	0x29, 0x03,         /*      Usage Maximum (03h),                      */
+	0x15, 0x00,         /*      Logical Minimum (0),                      */
+	0x25, 0x01,         /*      Logical Maximum (1),                      */
+	0x75, 0x01,         /*      Report Size (1),                          */
+	0x95, 0x03,         /*      Report Count (3),                         */
+	0x91, 0x02,         /*      Output (Variable),                        */
+	0x95, 0x05,         /*      Report Count (5),                         */
+	0x91, 0x01,         /*      Output (Constant),                        */
+	0xC0,               /*  End Collection                                */
+};
+
+static const __u8 *holtek_kbd_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	struct usb_interface *intf = to_usb_interface(hdev->dev.parent);
+
+	if (intf->cur_altsetting->desc.bInterfaceNumber == 1) {
+		*rsize = sizeof(holtek_kbd_rdesc_fixed);
+		return holtek_kbd_rdesc_fixed;
+	}
+	return rdesc;
+}
+
+static int holtek_kbd_input_event(struct input_dev *dev, unsigned int type,
+		unsigned int code,
+		int value)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct usb_device *usb_dev = hid_to_usb_dev(hid);
+
+	/* Locate the boot interface, to receive the LED change events */
+	struct usb_interface *boot_interface = usb_ifnum_to_if(usb_dev, 0);
+	struct hid_device *boot_hid;
+	struct hid_input *boot_hid_input;
+
+	if (unlikely(boot_interface == NULL))
+		return -ENODEV;
+
+	boot_hid = usb_get_intfdata(boot_interface);
+	if (list_empty(&boot_hid->inputs)) {
+		hid_err(hid, "no inputs found\n");
+		return -ENODEV;
+	}
+	boot_hid_input = list_first_entry(&boot_hid->inputs,
+		struct hid_input, list);
+
+	return boot_hid_input->input->event(boot_hid_input->input, type, code,
+			value);
+}
+
+static int holtek_kbd_probe(struct hid_device *hdev,
+		const struct hid_device_id *id)
+{
+	struct usb_interface *intf;
+	int ret;
+
+	if (!hid_is_usb(hdev))
+		return -EINVAL;
+
+	ret = hid_parse(hdev);
+	if (!ret)
+		ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+
+	intf = to_usb_interface(hdev->dev.parent);
+	if (!ret && intf->cur_altsetting->desc.bInterfaceNumber == 1) {
+		struct hid_input *hidinput;
+		list_for_each_entry(hidinput, &hdev->inputs, list) {
+			hidinput->input->event = holtek_kbd_input_event;
+		}
+	}
+
+	return ret;
+}
+
+static const struct hid_device_id holtek_kbd_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_HOLTEK_ALT,
+			USB_DEVICE_ID_HOLTEK_ALT_KEYBOARD) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, holtek_kbd_devices);
+
+static struct hid_driver holtek_kbd_driver = {
+	.name = "holtek_kbd",
+	.id_table = holtek_kbd_devices,
+	.report_fixup = holtek_kbd_report_fixup,
+	.probe = holtek_kbd_probe
+};
+module_hid_driver(holtek_kbd_driver);
+
+MODULE_DESCRIPTION("HID driver for Holtek keyboard");
+MODULE_LICENSE("GPL");