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, 354 insertions, 0 deletions

diff --git a/drivers/usb/misc/appledisplay.c b/drivers/usb/misc/appledisplay.c
new file mode 100644
index 000000000..16883592f
--- /dev/null
+++ b/drivers/usb/misc/appledisplay.c
@@ -0,0 +1,354 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Apple Cinema Display driver
+ *
+ * Copyright (C) 2006  Michael Hanselmann (linux-kernel@hansmi.ch)
+ *
+ * Thanks to Caskey L. Dickson for his work with acdctl.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/hid.h>
+#include <linux/usb.h>
+#include <linux/backlight.h>
+#include <linux/timer.h>
+#include <linux/workqueue.h>
+#include <linux/atomic.h>
+
+#define APPLE_VENDOR_ID		0x05AC
+
+#define ACD_USB_TIMEOUT		250
+
+#define ACD_USB_EDID		0x0302
+#define ACD_USB_BRIGHTNESS	0x0310
+
+#define ACD_BTN_NONE		0
+#define ACD_BTN_BRIGHT_UP	3
+#define ACD_BTN_BRIGHT_DOWN	4
+
+#define ACD_URB_BUFFER_LEN	2
+#define ACD_MSG_BUFFER_LEN	2
+
+#define APPLEDISPLAY_DEVICE(prod)				\
+	.match_flags = USB_DEVICE_ID_MATCH_DEVICE |		\
+		       USB_DEVICE_ID_MATCH_INT_CLASS |		\
+		       USB_DEVICE_ID_MATCH_INT_PROTOCOL,	\
+	.idVendor = APPLE_VENDOR_ID,				\
+	.idProduct = (prod),					\
+	.bInterfaceClass = USB_CLASS_HID,			\
+	.bInterfaceProtocol = 0x00
+
+/* table of devices that work with this driver */
+static const struct usb_device_id appledisplay_table[] = {
+	{ APPLEDISPLAY_DEVICE(0x9218) },
+	{ APPLEDISPLAY_DEVICE(0x9219) },
+	{ APPLEDISPLAY_DEVICE(0x921c) },
+	{ APPLEDISPLAY_DEVICE(0x921d) },
+	{ APPLEDISPLAY_DEVICE(0x9222) },
+	{ APPLEDISPLAY_DEVICE(0x9226) },
+	{ APPLEDISPLAY_DEVICE(0x9236) },
+
+	/* Terminating entry */
+	{ }
+};
+MODULE_DEVICE_TABLE(usb, appledisplay_table);
+
+/* Structure to hold all of our device specific stuff */
+struct appledisplay {
+	struct usb_device *udev;	/* usb device */
+	struct urb *urb;		/* usb request block */
+	struct backlight_device *bd;	/* backlight device */
+	u8 *urbdata;			/* interrupt URB data buffer */
+	u8 *msgdata;			/* control message data buffer */
+
+	struct delayed_work work;
+	int button_pressed;
+	struct mutex sysfslock;		/* concurrent read and write */
+};
+
+static atomic_t count_displays = ATOMIC_INIT(0);
+
+static void appledisplay_complete(struct urb *urb)
+{
+	struct appledisplay *pdata = urb->context;
+	struct device *dev = &pdata->udev->dev;
+	int status = urb->status;
+	int retval;
+
+	switch (status) {
+	case 0:
+		/* success */
+		break;
+	case -EOVERFLOW:
+		dev_err(dev,
+			"OVERFLOW with data length %d, actual length is %d\n",
+			ACD_URB_BUFFER_LEN, pdata->urb->actual_length);
+		fallthrough;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+		/* This urb is terminated, clean up */
+		dev_dbg(dev, "%s - urb shuttingdown with status: %d\n",
+			__func__, status);
+		return;
+	default:
+		dev_dbg(dev, "%s - nonzero urb status received: %d\n",
+			__func__, status);
+		goto exit;
+	}
+
+	switch(pdata->urbdata[1]) {
+	case ACD_BTN_BRIGHT_UP:
+	case ACD_BTN_BRIGHT_DOWN:
+		pdata->button_pressed = 1;
+		/*
+		 * there is a window during which no device
+		 * is registered
+		 */
+		if (pdata->bd )
+			schedule_delayed_work(&pdata->work, 0);
+		break;
+	case ACD_BTN_NONE:
+	default:
+		pdata->button_pressed = 0;
+		break;
+	}
+
+exit:
+	retval = usb_submit_urb(pdata->urb, GFP_ATOMIC);
+	if (retval) {
+		dev_err(dev, "%s - usb_submit_urb failed with result %d\n",
+			__func__, retval);
+	}
+}
+
+static int appledisplay_bl_update_status(struct backlight_device *bd)
+{
+	struct appledisplay *pdata = bl_get_data(bd);
+	int retval;
+
+	mutex_lock(&pdata->sysfslock);
+	pdata->msgdata[0] = 0x10;
+	pdata->msgdata[1] = bd->props.brightness;
+
+	retval = usb_control_msg(
+		pdata->udev,
+		usb_sndctrlpipe(pdata->udev, 0),
+		HID_REQ_SET_REPORT,
+		USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+		ACD_USB_BRIGHTNESS,
+		0,
+		pdata->msgdata, 2,
+		ACD_USB_TIMEOUT);
+	mutex_unlock(&pdata->sysfslock);
+
+	if (retval < 0)
+		return retval;
+	else
+		return 0;
+}
+
+static int appledisplay_bl_get_brightness(struct backlight_device *bd)
+{
+	struct appledisplay *pdata = bl_get_data(bd);
+	int retval, brightness;
+
+	mutex_lock(&pdata->sysfslock);
+	retval = usb_control_msg(
+		pdata->udev,
+		usb_rcvctrlpipe(pdata->udev, 0),
+		HID_REQ_GET_REPORT,
+		USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE,
+		ACD_USB_BRIGHTNESS,
+		0,
+		pdata->msgdata, 2,
+		ACD_USB_TIMEOUT);
+	if (retval < 2) {
+		if (retval >= 0)
+			retval = -EMSGSIZE;
+	} else {
+		brightness = pdata->msgdata[1];
+	}
+	mutex_unlock(&pdata->sysfslock);
+
+	if (retval < 0)
+		return retval;
+	else
+		return brightness;
+}
+
+static const struct backlight_ops appledisplay_bl_data = {
+	.get_brightness	= appledisplay_bl_get_brightness,
+	.update_status	= appledisplay_bl_update_status,
+};
+
+static void appledisplay_work(struct work_struct *work)
+{
+	struct appledisplay *pdata =
+		container_of(work, struct appledisplay, work.work);
+	int retval;
+
+	retval = appledisplay_bl_get_brightness(pdata->bd);
+	if (retval >= 0)
+		pdata->bd->props.brightness = retval;
+
+	/* Poll again in about 125ms if there's still a button pressed */
+	if (pdata->button_pressed)
+		schedule_delayed_work(&pdata->work, HZ / 8);
+}
+
+static int appledisplay_probe(struct usb_interface *iface,
+	const struct usb_device_id *id)
+{
+	struct backlight_properties props;
+	struct backlight_device *backlight;
+	struct appledisplay *pdata;
+	struct usb_device *udev = interface_to_usbdev(iface);
+	struct usb_endpoint_descriptor *endpoint;
+	int int_in_endpointAddr = 0;
+	int retval, brightness;
+	char bl_name[20];
+
+	/* set up the endpoint information */
+	/* use only the first interrupt-in endpoint */
+	retval = usb_find_int_in_endpoint(iface->cur_altsetting, &endpoint);
+	if (retval) {
+		dev_err(&iface->dev, "Could not find int-in endpoint\n");
+		return retval;
+	}
+
+	int_in_endpointAddr = endpoint->bEndpointAddress;
+
+	/* allocate memory for our device state and initialize it */
+	pdata = kzalloc_obj(struct appledisplay);
+	if (!pdata) {
+		retval = -ENOMEM;
+		goto error;
+	}
+
+	pdata->udev = udev;
+
+	INIT_DELAYED_WORK(&pdata->work, appledisplay_work);
+	mutex_init(&pdata->sysfslock);
+
+	/* Allocate buffer for control messages */
+	pdata->msgdata = kmalloc(ACD_MSG_BUFFER_LEN, GFP_KERNEL);
+	if (!pdata->msgdata) {
+		retval = -ENOMEM;
+		goto error;
+	}
+
+	/* Allocate interrupt URB */
+	pdata->urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!pdata->urb) {
+		retval = -ENOMEM;
+		goto error;
+	}
+
+	/* Allocate buffer for interrupt data */
+	pdata->urbdata = usb_alloc_coherent(pdata->udev, ACD_URB_BUFFER_LEN,
+		GFP_KERNEL, &pdata->urb->transfer_dma);
+	if (!pdata->urbdata) {
+		retval = -ENOMEM;
+		dev_err(&iface->dev, "Allocating URB buffer failed\n");
+		goto error;
+	}
+
+	/* Configure interrupt URB */
+	usb_fill_int_urb(pdata->urb, udev,
+		usb_rcvintpipe(udev, int_in_endpointAddr),
+		pdata->urbdata, ACD_URB_BUFFER_LEN, appledisplay_complete,
+		pdata, 1);
+	pdata->urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
+	if (usb_submit_urb(pdata->urb, GFP_KERNEL)) {
+		retval = -EIO;
+		dev_err(&iface->dev, "Submitting URB failed\n");
+		goto error;
+	}
+
+	/* Register backlight device */
+	snprintf(bl_name, sizeof(bl_name), "appledisplay%d",
+		atomic_inc_return(&count_displays) - 1);
+	memset(&props, 0, sizeof(struct backlight_properties));
+	props.type = BACKLIGHT_RAW;
+	props.max_brightness = 0xff;
+	backlight = backlight_device_register(bl_name, NULL, pdata,
+					      &appledisplay_bl_data, &props);
+	if (IS_ERR(backlight)) {
+		dev_err(&iface->dev, "Backlight registration failed\n");
+		retval = PTR_ERR(backlight);
+		goto error;
+	}
+	pdata->bd = backlight;
+
+	/* Try to get brightness */
+	brightness = appledisplay_bl_get_brightness(pdata->bd);
+
+	if (brightness < 0) {
+		retval = brightness;
+		dev_err(&iface->dev,
+			"Error while getting initial brightness: %d\n", retval);
+		goto error;
+	}
+
+	/* Set brightness in backlight device */
+	pdata->bd->props.brightness = brightness;
+
+	/* save our data pointer in the interface device */
+	usb_set_intfdata(iface, pdata);
+
+	printk(KERN_INFO "appledisplay: Apple Cinema Display connected\n");
+
+	return 0;
+
+error:
+	if (pdata) {
+		if (pdata->urb) {
+			usb_kill_urb(pdata->urb);
+			cancel_delayed_work_sync(&pdata->work);
+			usb_free_coherent(pdata->udev, ACD_URB_BUFFER_LEN,
+					pdata->urbdata, pdata->urb->transfer_dma);
+			usb_free_urb(pdata->urb);
+		}
+		if (!IS_ERR(pdata->bd))
+			backlight_device_unregister(pdata->bd);
+		kfree(pdata->msgdata);
+	}
+	usb_set_intfdata(iface, NULL);
+	kfree(pdata);
+	return retval;
+}
+
+static void appledisplay_disconnect(struct usb_interface *iface)
+{
+	struct appledisplay *pdata = usb_get_intfdata(iface);
+
+	if (pdata) {
+		usb_kill_urb(pdata->urb);
+		cancel_delayed_work_sync(&pdata->work);
+		backlight_device_unregister(pdata->bd);
+		usb_free_coherent(pdata->udev, ACD_URB_BUFFER_LEN,
+			pdata->urbdata, pdata->urb->transfer_dma);
+		usb_free_urb(pdata->urb);
+		kfree(pdata->msgdata);
+		kfree(pdata);
+	}
+
+	printk(KERN_INFO "appledisplay: Apple Cinema Display disconnected\n");
+}
+
+static struct usb_driver appledisplay_driver = {
+	.name		= "appledisplay",
+	.probe		= appledisplay_probe,
+	.disconnect	= appledisplay_disconnect,
+	.id_table	= appledisplay_table,
+};
+module_usb_driver(appledisplay_driver);
+
+MODULE_AUTHOR("Michael Hanselmann");
+MODULE_DESCRIPTION("Apple Cinema Display driver");
+MODULE_LICENSE("GPL");