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, 450 insertions, 0 deletions

diff --git a/drivers/usb/misc/usblcd.c b/drivers/usb/misc/usblcd.c
new file mode 100644
index 000000000..f794695de
--- /dev/null
+++ b/drivers/usb/misc/usblcd.c
@@ -0,0 +1,450 @@
+// SPDX-License-Identifier: GPL-2.0
+/*****************************************************************************
+ *                          USBLCD Kernel Driver                             *
+ *                            Version 1.05                                   *
+ *             (C) 2005 Georges Toth <g.toth@e-biz.lu>                       *
+ *                                                                           *
+ *     This file is licensed under the GPL. See COPYING in the package.      *
+ * Based on usb-skeleton.c 2.0 by Greg Kroah-Hartman (greg@kroah.com)        *
+ *                                                                           *
+ *                                                                           *
+ * 28.02.05 Complete rewrite of the original usblcd.c driver,                *
+ *          based on usb_skeleton.c.                                         *
+ *          This new driver allows more than one USB-LCD to be connected     *
+ *          and controlled, at once                                          *
+ *****************************************************************************/
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
+#include <linux/uaccess.h>
+#include <linux/usb.h>
+
+#define DRIVER_VERSION "USBLCD Driver Version 1.05"
+
+#define USBLCD_MINOR		144
+
+#define IOCTL_GET_HARD_VERSION	1
+#define IOCTL_GET_DRV_VERSION	2
+
+
+static const struct usb_device_id id_table[] = {
+	{ .idVendor = 0x10D2, .match_flags = USB_DEVICE_ID_MATCH_VENDOR, },
+	{ },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+struct usb_lcd {
+	struct usb_device	*udev;			/* init: probe_lcd */
+	struct usb_interface	*interface;		/* the interface for
+							   this device */
+	unsigned char		*bulk_in_buffer;	/* the buffer to receive
+							   data */
+	size_t			bulk_in_size;		/* the size of the
+							   receive buffer */
+	__u8			bulk_in_endpointAddr;	/* the address of the
+							   bulk in endpoint */
+	__u8			bulk_out_endpointAddr;	/* the address of the
+							   bulk out endpoint */
+	struct kref		kref;
+	struct semaphore	limit_sem;		/* to stop writes at
+							   full throttle from
+							   using up all RAM */
+	struct usb_anchor	submitted;		/* URBs to wait for
+							   before suspend */
+	struct rw_semaphore	io_rwsem;
+	unsigned long		disconnected:1;
+};
+#define to_lcd_dev(d) container_of(d, struct usb_lcd, kref)
+
+#define USB_LCD_CONCURRENT_WRITES	5
+
+static struct usb_driver lcd_driver;
+
+
+static void lcd_delete(struct kref *kref)
+{
+	struct usb_lcd *dev = to_lcd_dev(kref);
+
+	usb_put_dev(dev->udev);
+	kfree(dev->bulk_in_buffer);
+	kfree(dev);
+}
+
+
+static int lcd_open(struct inode *inode, struct file *file)
+{
+	struct usb_lcd *dev;
+	struct usb_interface *interface;
+	int subminor, r;
+
+	subminor = iminor(inode);
+
+	interface = usb_find_interface(&lcd_driver, subminor);
+	if (!interface) {
+		pr_err("USBLCD: %s - error, can't find device for minor %d\n",
+		       __func__, subminor);
+		return -ENODEV;
+	}
+
+	dev = usb_get_intfdata(interface);
+
+	/* increment our usage count for the device */
+	kref_get(&dev->kref);
+
+	/* grab a power reference */
+	r = usb_autopm_get_interface(interface);
+	if (r < 0) {
+		kref_put(&dev->kref, lcd_delete);
+		return r;
+	}
+
+	/* save our object in the file's private structure */
+	file->private_data = dev;
+
+	return 0;
+}
+
+static int lcd_release(struct inode *inode, struct file *file)
+{
+	struct usb_lcd *dev;
+
+	dev = file->private_data;
+	if (dev == NULL)
+		return -ENODEV;
+
+	/* decrement the count on our device */
+	usb_autopm_put_interface(dev->interface);
+	kref_put(&dev->kref, lcd_delete);
+	return 0;
+}
+
+static ssize_t lcd_read(struct file *file, char __user * buffer,
+			size_t count, loff_t *ppos)
+{
+	struct usb_lcd *dev;
+	int retval = 0;
+	int bytes_read;
+
+	dev = file->private_data;
+
+	down_read(&dev->io_rwsem);
+
+	if (dev->disconnected) {
+		retval = -ENODEV;
+		goto out_up_io;
+	}
+
+	/* do a blocking bulk read to get data from the device */
+	retval = usb_bulk_msg(dev->udev,
+			      usb_rcvbulkpipe(dev->udev,
+					      dev->bulk_in_endpointAddr),
+			      dev->bulk_in_buffer,
+			      min(dev->bulk_in_size, count),
+			      &bytes_read, 10000);
+
+	/* if the read was successful, copy the data to userspace */
+	if (!retval) {
+		if (copy_to_user(buffer, dev->bulk_in_buffer, bytes_read))
+			retval = -EFAULT;
+		else
+			retval = bytes_read;
+	}
+
+out_up_io:
+	up_read(&dev->io_rwsem);
+
+	return retval;
+}
+
+static long lcd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct usb_lcd *dev;
+	u16 bcdDevice;
+	char buf[30];
+
+	dev = file->private_data;
+	if (dev == NULL)
+		return -ENODEV;
+
+	switch (cmd) {
+	case IOCTL_GET_HARD_VERSION:
+		bcdDevice = le16_to_cpu((dev->udev)->descriptor.bcdDevice);
+		sprintf(buf, "%1d%1d.%1d%1d",
+			(bcdDevice & 0xF000)>>12,
+			(bcdDevice & 0xF00)>>8,
+			(bcdDevice & 0xF0)>>4,
+			(bcdDevice & 0xF));
+		if (copy_to_user((void __user *)arg, buf, strlen(buf)) != 0)
+			return -EFAULT;
+		break;
+	case IOCTL_GET_DRV_VERSION:
+		sprintf(buf, DRIVER_VERSION);
+		if (copy_to_user((void __user *)arg, buf, strlen(buf)) != 0)
+			return -EFAULT;
+		break;
+	default:
+		return -ENOTTY;
+	}
+
+	return 0;
+}
+
+static void lcd_write_bulk_callback(struct urb *urb)
+{
+	struct usb_lcd *dev;
+	int status = urb->status;
+
+	dev = urb->context;
+
+	/* sync/async unlink faults aren't errors */
+	if (status &&
+	    !(status == -ENOENT ||
+	      status == -ECONNRESET ||
+	      status == -ESHUTDOWN)) {
+		dev_dbg(&dev->interface->dev,
+			"nonzero write bulk status received: %d\n", status);
+	}
+
+	/* free up our allocated buffer */
+	usb_free_coherent(urb->dev, urb->transfer_buffer_length,
+			  urb->transfer_buffer, urb->transfer_dma);
+	up(&dev->limit_sem);
+}
+
+static ssize_t lcd_write(struct file *file, const char __user * user_buffer,
+			 size_t count, loff_t *ppos)
+{
+	struct usb_lcd *dev;
+	int retval = 0, r;
+	struct urb *urb = NULL;
+	char *buf = NULL;
+
+	dev = file->private_data;
+
+	/* verify that we actually have some data to write */
+	if (count == 0)
+		goto exit;
+
+	r = down_interruptible(&dev->limit_sem);
+	if (r < 0)
+		return -EINTR;
+
+	down_read(&dev->io_rwsem);
+
+	if (dev->disconnected) {
+		retval = -ENODEV;
+		goto err_up_io;
+	}
+
+	/* create a urb, and a buffer for it, and copy the data to the urb */
+	urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!urb) {
+		retval = -ENOMEM;
+		goto err_up_io;
+	}
+
+	buf = usb_alloc_coherent(dev->udev, count, GFP_KERNEL,
+				 &urb->transfer_dma);
+	if (!buf) {
+		retval = -ENOMEM;
+		goto error;
+	}
+
+	if (copy_from_user(buf, user_buffer, count)) {
+		retval = -EFAULT;
+		goto error;
+	}
+
+	/* initialize the urb properly */
+	usb_fill_bulk_urb(urb, dev->udev,
+			  usb_sndbulkpipe(dev->udev,
+			  dev->bulk_out_endpointAddr),
+			  buf, count, lcd_write_bulk_callback, dev);
+	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+
+	usb_anchor_urb(urb, &dev->submitted);
+
+	/* send the data out the bulk port */
+	retval = usb_submit_urb(urb, GFP_KERNEL);
+	if (retval) {
+		dev_err(&dev->udev->dev,
+			"%s - failed submitting write urb, error %d\n",
+			__func__, retval);
+		goto error_unanchor;
+	}
+
+	/* release our reference to this urb,
+	   the USB core will eventually free it entirely */
+	usb_free_urb(urb);
+
+	up_read(&dev->io_rwsem);
+exit:
+	return count;
+error_unanchor:
+	usb_unanchor_urb(urb);
+error:
+	usb_free_coherent(dev->udev, count, buf, urb->transfer_dma);
+	usb_free_urb(urb);
+err_up_io:
+	up_read(&dev->io_rwsem);
+	up(&dev->limit_sem);
+	return retval;
+}
+
+static const struct file_operations lcd_fops = {
+	.owner =        THIS_MODULE,
+	.read =         lcd_read,
+	.write =        lcd_write,
+	.open =         lcd_open,
+	.unlocked_ioctl = lcd_ioctl,
+	.release =      lcd_release,
+	.llseek =	 noop_llseek,
+};
+
+/*
+ * usb class driver info in order to get a minor number from the usb core,
+ * and to have the device registered with the driver core
+ */
+static struct usb_class_driver lcd_class = {
+	.name =         "lcd%d",
+	.fops =         &lcd_fops,
+	.minor_base =   USBLCD_MINOR,
+};
+
+static int lcd_probe(struct usb_interface *interface,
+		     const struct usb_device_id *id)
+{
+	struct usb_lcd *dev = NULL;
+	struct usb_endpoint_descriptor *bulk_in, *bulk_out;
+	int i;
+	int retval;
+
+	/* allocate memory for our device state and initialize it */
+	dev = kzalloc_obj(*dev);
+	if (!dev)
+		return -ENOMEM;
+
+	kref_init(&dev->kref);
+	sema_init(&dev->limit_sem, USB_LCD_CONCURRENT_WRITES);
+	init_rwsem(&dev->io_rwsem);
+	init_usb_anchor(&dev->submitted);
+
+	dev->udev = usb_get_dev(interface_to_usbdev(interface));
+	dev->interface = interface;
+
+	if (le16_to_cpu(dev->udev->descriptor.idProduct) != 0x0001) {
+		dev_warn(&interface->dev, "USBLCD model not supported.\n");
+		retval = -ENODEV;
+		goto error;
+	}
+
+	/* set up the endpoint information */
+	/* use only the first bulk-in and bulk-out endpoints */
+	retval = usb_find_common_endpoints(interface->cur_altsetting,
+			&bulk_in, &bulk_out, NULL, NULL);
+	if (retval) {
+		dev_err(&interface->dev,
+			"Could not find both bulk-in and bulk-out endpoints\n");
+		goto error;
+	}
+
+	dev->bulk_in_size = usb_endpoint_maxp(bulk_in);
+	dev->bulk_in_endpointAddr = bulk_in->bEndpointAddress;
+	dev->bulk_in_buffer = kmalloc(dev->bulk_in_size, GFP_KERNEL);
+	if (!dev->bulk_in_buffer) {
+		retval = -ENOMEM;
+		goto error;
+	}
+
+	dev->bulk_out_endpointAddr = bulk_out->bEndpointAddress;
+
+	/* save our data pointer in this interface device */
+	usb_set_intfdata(interface, dev);
+
+	/* we can register the device now, as it is ready */
+	retval = usb_register_dev(interface, &lcd_class);
+	if (retval) {
+		/* something prevented us from registering this driver */
+		dev_err(&interface->dev,
+			"Not able to get a minor for this device.\n");
+		goto error;
+	}
+
+	i = le16_to_cpu(dev->udev->descriptor.bcdDevice);
+
+	dev_info(&interface->dev, "USBLCD Version %1d%1d.%1d%1d found "
+		 "at address %d\n", (i & 0xF000)>>12, (i & 0xF00)>>8,
+		 (i & 0xF0)>>4, (i & 0xF), dev->udev->devnum);
+
+	/* let the user know what node this device is now attached to */
+	dev_info(&interface->dev, "USB LCD device now attached to USBLCD-%d\n",
+		 interface->minor);
+	return 0;
+
+error:
+	kref_put(&dev->kref, lcd_delete);
+	return retval;
+}
+
+static void lcd_draw_down(struct usb_lcd *dev)
+{
+	int time;
+
+	time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
+	if (!time)
+		usb_kill_anchored_urbs(&dev->submitted);
+}
+
+static int lcd_suspend(struct usb_interface *intf, pm_message_t message)
+{
+	struct usb_lcd *dev = usb_get_intfdata(intf);
+
+	if (!dev)
+		return 0;
+	lcd_draw_down(dev);
+	return 0;
+}
+
+static int lcd_resume(struct usb_interface *intf)
+{
+	return 0;
+}
+
+static void lcd_disconnect(struct usb_interface *interface)
+{
+	struct usb_lcd *dev = usb_get_intfdata(interface);
+	int minor = interface->minor;
+
+	/* give back our minor */
+	usb_deregister_dev(interface, &lcd_class);
+
+	down_write(&dev->io_rwsem);
+	dev->disconnected = 1;
+	up_write(&dev->io_rwsem);
+
+	usb_kill_anchored_urbs(&dev->submitted);
+
+	/* decrement our usage count */
+	kref_put(&dev->kref, lcd_delete);
+
+	dev_info(&interface->dev, "USB LCD #%d now disconnected\n", minor);
+}
+
+static struct usb_driver lcd_driver = {
+	.name =		"usblcd",
+	.probe =	lcd_probe,
+	.disconnect =	lcd_disconnect,
+	.suspend =	lcd_suspend,
+	.resume =	lcd_resume,
+	.id_table =	id_table,
+	.supports_autosuspend = 1,
+};
+
+module_usb_driver(lcd_driver);
+
+MODULE_AUTHOR("Georges Toth <g.toth@e-biz.lu>");
+MODULE_DESCRIPTION(DRIVER_VERSION);
+MODULE_LICENSE("GPL");