Commit message: usb: yurex: Fix use-after-free in yurex_delete

syzbot reported the following crash [0]:

BUG: KASAN: use-after-free in usb_free_coherent+0x79/0x80
drivers/usb/core/usb.c:928
Read of size 8 at addr ffff8881b18599c8 by task syz-executor.4/16007

CPU: 0 PID: 16007 Comm: syz-executor.4 Not tainted 5.3.0-rc2+ #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0xca/0x13e lib/dump_stack.c:113
  print_address_description+0x6a/0x32c mm/kasan/report.c:351
  __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:482
  kasan_report+0xe/0x12 mm/kasan/common.c:612
  usb_free_coherent+0x79/0x80 drivers/usb/core/usb.c:928
  yurex_delete+0x138/0x330 drivers/usb/misc/yurex.c:100
  kref_put include/linux/kref.h:65 [inline]
  yurex_release+0x66/0x90 drivers/usb/misc/yurex.c:392
  __fput+0x2d7/0x840 fs/file_table.c:280
  task_work_run+0x13f/0x1c0 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
  exit_to_usermode_loop+0x1d2/0x200 arch/x86/entry/common.c:163
  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
  do_syscall_64+0x45f/0x580 arch/x86/entry/common.c:299
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x413511
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48
83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48
89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffc424ea2e0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000007 RCX: 0000000000413511
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 0000000000000001 R08: 0000000029a2fc22 R09: 0000000029a2fc26
R10: 00007ffc424ea3c0 R11: 0000000000000293 R12: 000000000075c9a0
R13: 000000000075c9a0 R14: 0000000000761938 R15: ffffffffffffffff

Allocated by task 2776:
  save_stack+0x1b/0x80 mm/kasan/common.c:69
  set_track mm/kasan/common.c:77 [inline]
  __kasan_kmalloc mm/kasan/common.c:487 [inline]
  __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:460
  kmalloc include/linux/slab.h:552 [inline]
  kzalloc include/linux/slab.h:748 [inline]
  usb_alloc_dev+0x51/0xf95 drivers/usb/core/usb.c:583
  hub_port_connect drivers/usb/core/hub.c:5004 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
  port_event drivers/usb/core/hub.c:5359 [inline]
  hub_event+0x15c0/0x3640 drivers/usb/core/hub.c:5441
  process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
  worker_thread+0x96/0xe20 kernel/workqueue.c:2415
  kthread+0x318/0x420 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Freed by task 16007:
  save_stack+0x1b/0x80 mm/kasan/common.c:69
  set_track mm/kasan/common.c:77 [inline]
  __kasan_slab_free+0x130/0x180 mm/kasan/common.c:449
  slab_free_hook mm/slub.c:1423 [inline]
  slab_free_freelist_hook mm/slub.c:1470 [inline]
  slab_free mm/slub.c:3012 [inline]
  kfree+0xe4/0x2f0 mm/slub.c:3953
  device_release+0x71/0x200 drivers/base/core.c:1064
  kobject_cleanup lib/kobject.c:693 [inline]
  kobject_release lib/kobject.c:722 [inline]
  kref_put include/linux/kref.h:65 [inline]
  kobject_put+0x171/0x280 lib/kobject.c:739
  put_device+0x1b/0x30 drivers/base/core.c:2213
  usb_put_dev+0x1f/0x30 drivers/usb/core/usb.c:725
  yurex_delete+0x40/0x330 drivers/usb/misc/yurex.c:95
  kref_put include/linux/kref.h:65 [inline]
  yurex_release+0x66/0x90 drivers/usb/misc/yurex.c:392
  __fput+0x2d7/0x840 fs/file_table.c:280
  task_work_run+0x13f/0x1c0 kernel/task_work.c:113
  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
  exit_to_usermode_loop+0x1d2/0x200 arch/x86/entry/common.c:163
  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
  do_syscall_64+0x45f/0x580 arch/x86/entry/common.c:299
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881b1859980
  which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 72 bytes inside of
  2048-byte region [ffff8881b1859980, ffff8881b185a180)
The buggy address belongs to the page:
page:ffffea0006c61600 refcount:1 mapcount:0 mapping:ffff8881da00c000
index:0x0 compound_mapcount: 0
flags: 0x200000000010200(slab|head)
raw: 0200000000010200 0000000000000000 0000000100000001 ffff8881da00c000
raw: 0000000000000000 00000000000f000f 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8881b1859880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8881b1859900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8881b1859980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                               ^
  ffff8881b1859a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8881b1859a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

A quick look at the yurex_delete() shows that we drop the reference
to the usb_device before releasing any buffers associated with the
device. Delay the reference drop until we have finished the cleanup.

[0] https://lore.kernel.org/lkml/0000000000003f86d8058f0bd671@google.com/

Fixes: 6bc235a2e24a5e ("USB: add driver for Meywa-Denki & Kayac YUREX")
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Tomoki Sekiyama <tomoki.sekiyama@gmail.com>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: andreyknvl@google.com
Cc: gregkh@linuxfoundation.org
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: syzkaller-bugs@googlegroups.com
Cc: dtor@chromium.org
Reported-by: syzbot+d1fedb1c1fdb07fca507@syzkaller.appspotmail.com
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20190805111528.6758-1-suzuki.poulose@arm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CVE: CVE-2019-19531
CWE: CWE-416
Vulnerability description: In the Linux kernel before 5.2.9, there is a use-after-free bug that can be caused by a malicious USB device in the drivers/usb/misc/yurex.c driver, aka CID-fc05481b2fca.

Project: linux

static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
			   size_t count, loff_t *ppos)
{
	struct usb_yurex *dev;
	int i, set = 0, retval = 0;
	char buffer[16 + 1];
	char *data = buffer;
	unsigned long long c, c2 = 0;
	signed long timeout = 0;
	DEFINE_WAIT(wait);

	count = min(sizeof(buffer) - 1, count);
	dev = file->private_data;

	/* verify that we actually have some data to write */
	if (count == 0)
		goto error;

	mutex_lock(&dev->io_mutex);
	if (!dev->interface) {		/* already disconnected */
		mutex_unlock(&dev->io_mutex);
		retval = -ENODEV;
		goto error;
	}

	if (copy_from_user(buffer, user_buffer, count)) {
		mutex_unlock(&dev->io_mutex);
		retval = -EFAULT;
		goto error;
	}
	buffer[count] = 0;
	memset(dev->cntl_buffer, CMD_PADDING, YUREX_BUF_SIZE);

	switch (buffer[0]) {
	case CMD_ANIMATE:
	case CMD_LED:
		dev->cntl_buffer[0] = buffer[0];
		dev->cntl_buffer[1] = buffer[1];
		dev->cntl_buffer[2] = CMD_EOF;
		break;
	case CMD_READ:
	case CMD_VERSION:
		dev->cntl_buffer[0] = buffer[0];
		dev->cntl_buffer[1] = 0x00;
		dev->cntl_buffer[2] = CMD_EOF;
		break;
	case CMD_SET:
		data++;
		/* FALL THROUGH */
	case '0' ... '9':
		set = 1;
		c = c2 = simple_strtoull(data, NULL, 0);
		dev->cntl_buffer[0] = CMD_SET;
		for (i = 1; i < 6; i++) {
			dev->cntl_buffer[i] = (c>>32) & 0xff;
			c <<= 8;
		}
		buffer[6] = CMD_EOF;
		break;
	default:
		mutex_unlock(&dev->io_mutex);
		return -EINVAL;
	}

	/* send the data as the control msg */
	prepare_to_wait(&dev->waitq, &wait, TASK_INTERRUPTIBLE);
	dev_dbg(&dev->interface->dev, "%s - submit %c\n", __func__,
		dev->cntl_buffer[0]);
	retval = usb_submit_urb(dev->cntl_urb, GFP_KERNEL);
	if (retval >= 0)
		timeout = schedule_timeout(YUREX_WRITE_TIMEOUT);
	finish_wait(&dev->waitq, &wait);

	mutex_unlock(&dev->io_mutex);

	if (retval < 0) {
		dev_err(&dev->interface->dev,
			"%s - failed to send bulk msg, error %d\n",
			__func__, retval);
		goto error;
	}
	if (set && timeout)
		dev->bbu = c2;
	return timeout ? count : -EIO;

error:
	return retval;
}

Project: linux

static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
			  loff_t *ppos)
{
	struct usb_yurex *dev;
	int len = 0;
	char in_buffer[20];
	unsigned long flags;

	dev = file->private_data;

	mutex_lock(&dev->io_mutex);
	if (!dev->interface) {		/* already disconnected */
		mutex_unlock(&dev->io_mutex);
		return -ENODEV;
	}

	spin_lock_irqsave(&dev->lock, flags);
	len = snprintf(in_buffer, 20, "%lld\n", dev->bbu);
	spin_unlock_irqrestore(&dev->lock, flags);
	mutex_unlock(&dev->io_mutex);

	if (WARN_ON_ONCE(len >= sizeof(in_buffer)))
		return -EIO;

	return simple_read_from_buffer(buffer, count, ppos, in_buffer, len);
}

Project: linux

static void yurex_delete(struct kref *kref)
{
	struct usb_yurex *dev = to_yurex_dev(kref);

	dev_dbg(&dev->interface->dev, "%s\n", __func__);

	if (dev->cntl_urb) {
		usb_kill_urb(dev->cntl_urb);
		kfree(dev->cntl_req);
		if (dev->cntl_buffer)
			usb_free_coherent(dev->udev, YUREX_BUF_SIZE,
				dev->cntl_buffer, dev->cntl_urb->transfer_dma);
		usb_free_urb(dev->cntl_urb);
	}
	if (dev->urb) {
		usb_kill_urb(dev->urb);
		if (dev->int_buffer)
			usb_free_coherent(dev->udev, YUREX_BUF_SIZE,
				dev->int_buffer, dev->urb->transfer_dma);
		usb_free_urb(dev->urb);
	}
	usb_put_dev(dev->udev);
	kfree(dev);
}

Project: linux

static void yurex_disconnect(struct usb_interface *interface)
{
	struct usb_yurex *dev;
	int minor = interface->minor;

	dev = usb_get_intfdata(interface);
	usb_set_intfdata(interface, NULL);

	/* give back our minor */
	usb_deregister_dev(interface, &yurex_class);

	/* prevent more I/O from starting */
	usb_poison_urb(dev->urb);
	mutex_lock(&dev->io_mutex);
	dev->interface = NULL;
	mutex_unlock(&dev->io_mutex);

	/* wakeup waiters */
	kill_fasync(&dev->async_queue, SIGIO, POLL_IN);
	wake_up_interruptible(&dev->waitq);

	/* decrement our usage count */
	kref_put(&dev->kref, yurex_delete);

	dev_info(&interface->dev, "USB YUREX #%d now disconnected\n", minor);
}

Project: linux
File: yurex.c

static void yurex_interrupt(struct urb *urb)
{
	struct usb_yurex *dev = urb->context;
	unsigned char *buf = dev->int_buffer;
	int status = urb->status;
	unsigned long flags;
	int retval, i;

	switch (status) {
	case 0: /*success*/
		break;
	case -EOVERFLOW:
		dev_err(&dev->interface->dev,
			"%s - overflow with length %d, actual length is %d\n",
			__func__, YUREX_BUF_SIZE, dev->urb->actual_length);
	case -ECONNRESET:
	case -ENOENT:
	case -ESHUTDOWN:
	case -EILSEQ:
		/* The device is terminated, clean up */
		return;
	default:
		dev_err(&dev->interface->dev,
			"%s - unknown status received: %d\n", __func__, status);
		goto exit;
	}

	/* handle received message */
	switch (buf[0]) {
	case CMD_COUNT:
	case CMD_READ:
		if (buf[6] == CMD_EOF) {
			spin_lock_irqsave(&dev->lock, flags);
			dev->bbu = 0;
			for (i = 1; i < 6; i++) {
				dev->bbu += buf[i];
				if (i != 5)
					dev->bbu <<= 8;
			}
			dev_dbg(&dev->interface->dev, "%s count: %lld\n",
				__func__, dev->bbu);
			spin_unlock_irqrestore(&dev->lock, flags);

			kill_fasync(&dev->async_queue, SIGIO, POLL_IN);
		}
		else
			dev_dbg(&dev->interface->dev,
				"data format error - no EOF\n");
		break;
	case CMD_ACK:
		dev_dbg(&dev->interface->dev, "%s ack: %c\n",
			__func__, buf[1]);
		wake_up_interruptible(&dev->waitq);
		break;
	}

exit:
	retval = usb_submit_urb(dev->urb, GFP_ATOMIC);
	if (retval) {
		dev_err(&dev->interface->dev, "%s - usb_submit_urb failed: %d\n",
			__func__, retval);
	}
}