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* [PATCH v4 0/1] usb: gadget: add raw-gadget interface
@ 2019-12-18 19:26 Andrey Konovalov
  2019-12-18 19:26 ` [PATCH v4 1/1] " Andrey Konovalov
  2020-01-08 20:15 ` [PATCH v4 0/1] " Andrey Konovalov
  0 siblings, 2 replies; 9+ messages in thread
From: Andrey Konovalov @ 2019-12-18 19:26 UTC (permalink / raw)
  To: linux-usb, linux-kernel, Greg Kroah-Hartman, Alan Stern
  Cc: Jonathan Corbet, Felipe Balbi, Dmitry Vyukov,
	Alexander Potapenko, Marco Elver, Andrey Konovalov

This patchset (currently a single patch) adds a new userspace interface
for the USB Gadget subsystem called USB Raw Gadget (I don't mind changing
the name to something else if there are better ideas). This is what
currently being used to enable coverage-buided USB fuzzing with syzkaller:

https://github.com/google/syzkaller/blob/master/docs/linux/external_fuzzing_usb.md

Initially I was using GadgetFS (together with the Dummy HCD/UDC module)
to perform emulation of USB devices for fuzzing, but later switched to a
custom written interface. The incentive to implement a different interface
was to provide a somewhat raw and direct access to the USB Gadget layer
for the userspace, where every USB request is passed to the userspace to
get a response. See documentation for the list of differences between
Raw Gadget and GadgetFS.

This patchset has been pushed to the public Linux kernel Gerrit instance:

https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/2144

Changes v3 -> v4:
- Print debug message when maxpacket check fails.
- Use module_misc_device() instead of module_init/exit().
- Reuse DRIVER_NAME macro in raw_device struct definition.
- Don't print WARNING in raw_release().
- Add comment that explains locking into raw_event_queue_fetch().
- Print a WARNING when event queue size is exceeded.
- Rename raw.c to raw_gadget.c.
- Mention module name in Kconfig.
- Reworked logging to use dev_err/dbg() instead of pr_err/debug().

Changes v2 -> v3:
- Updated device path in documentation.
- Changed usb_raw_init struct layout to make it the same for 32 bit compat
  mode.
- Added compat_ioctl to raw_fops.
- Changed raw_ioctl_init() to return EINVAL for invalid USB speeds, except
  for USB_SPEED_UNKNOWN, which defaults to USB_SPEED_HIGH.
- Reject endpoints with maxpacket = 0 in raw_ioctl_ep_enable().

Changes v1 -> v2:
- Moved raw.c to legacy/.
- Changed uapi header to use __u* types.
- Switched from debugfs entry to a misc device.
- Changed raw_dev from refcount to kref.
- Moved UDC_NAME_LENGTH_MAX to uapi headers.
- Used usb_endpoint_type() and usb_endpoint_dir_in/out() functions instead
  of open coding them.
- Added "WITH Linux-syscall-note" to SPDX id in the uapi header.
- Removed pr_err() if case dev_new() fails.
- Reduced the number of debugging messages.

Andrey Konovalov (1):
  usb: gadget: add raw-gadget interface

 Documentation/usb/index.rst            |    1 +
 Documentation/usb/raw-gadget.rst       |   59 ++
 drivers/usb/gadget/legacy/Kconfig      |   11 +
 drivers/usb/gadget/legacy/Makefile     |    1 +
 drivers/usb/gadget/legacy/raw_gadget.c | 1071 ++++++++++++++++++++++++
 include/uapi/linux/usb/raw_gadget.h    |  167 ++++
 6 files changed, 1310 insertions(+)
 create mode 100644 Documentation/usb/raw-gadget.rst
 create mode 100644 drivers/usb/gadget/legacy/raw_gadget.c
 create mode 100644 include/uapi/linux/usb/raw_gadget.h

-- 
2.24.1.735.g03f4e72817-goog


^ permalink raw reply	[flat|nested] 9+ messages in thread

* [PATCH v4 1/1] usb: gadget: add raw-gadget interface
  2019-12-18 19:26 [PATCH v4 0/1] usb: gadget: add raw-gadget interface Andrey Konovalov
@ 2019-12-18 19:26 ` " Andrey Konovalov
  2020-01-11 19:31   ` Greg Kroah-Hartman
  2020-01-08 20:15 ` [PATCH v4 0/1] " Andrey Konovalov
  1 sibling, 1 reply; 9+ messages in thread
From: Andrey Konovalov @ 2019-12-18 19:26 UTC (permalink / raw)
  To: linux-usb, linux-kernel, Greg Kroah-Hartman, Alan Stern
  Cc: Jonathan Corbet, Felipe Balbi, Dmitry Vyukov,
	Alexander Potapenko, Marco Elver, Andrey Konovalov

USB Raw Gadget is a kernel module that provides a userspace interface for
the USB Gadget subsystem. Essentially it allows to emulate USB devices
from userspace. Enabled with CONFIG_USB_RAW_GADGET. Raw Gadget is
currently a strictly debugging feature and shouldn't be used in
production.

Raw Gadget is similar to GadgetFS, but provides a more low-level and
direct access to the USB Gadget layer for the userspace. The key
differences are:

1. Every USB request is passed to the userspace to get a response, while
   GadgetFS responds to some USB requests internally based on the provided
   descriptors. However note, that the UDC driver might respond to some
   requests on its own and never forward them to the Gadget layer.

2. GadgetFS performs some sanity checks on the provided USB descriptors,
   while Raw Gadget allows you to provide arbitrary data as responses to
   USB requests.

3. Raw Gadget provides a way to select a UDC device/driver to bind to,
   while GadgetFS currently binds to the first available UDC.

4. Raw Gadget uses predictable endpoint names (handles) across different
   UDCs (as long as UDCs have enough endpoints of each required transfer
   type).

5. Raw Gadget has ioctl-based interface instead of a filesystem-based one.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 Documentation/usb/index.rst            |    1 +
 Documentation/usb/raw-gadget.rst       |   59 ++
 drivers/usb/gadget/legacy/Kconfig      |   11 +
 drivers/usb/gadget/legacy/Makefile     |    1 +
 drivers/usb/gadget/legacy/raw_gadget.c | 1071 ++++++++++++++++++++++++
 include/uapi/linux/usb/raw_gadget.h    |  167 ++++
 6 files changed, 1310 insertions(+)
 create mode 100644 Documentation/usb/raw-gadget.rst
 create mode 100644 drivers/usb/gadget/legacy/raw_gadget.c
 create mode 100644 include/uapi/linux/usb/raw_gadget.h

diff --git a/Documentation/usb/index.rst b/Documentation/usb/index.rst
index e55386a4abfb..90310e2a0c1f 100644
--- a/Documentation/usb/index.rst
+++ b/Documentation/usb/index.rst
@@ -22,6 +22,7 @@ USB support
     misc_usbsevseg
     mtouchusb
     ohci
+    raw-gadget
     rio
     usbip_protocol
     usbmon
diff --git a/Documentation/usb/raw-gadget.rst b/Documentation/usb/raw-gadget.rst
new file mode 100644
index 000000000000..cbedf5451ed3
--- /dev/null
+++ b/Documentation/usb/raw-gadget.rst
@@ -0,0 +1,59 @@
+==============
+USB Raw Gadget
+==============
+
+USB Raw Gadget is a kernel module that provides a userspace interface for
+the USB Gadget subsystem. Essentially it allows to emulate USB devices
+from userspace. Enabled with CONFIG_USB_RAW_GADGET. Raw Gadget is
+currently a strictly debugging feature and shouldn't be used in
+production, use GadgetFS instead.
+
+Comparison to GadgetFS
+~~~~~~~~~~~~~~~~~~~~~~
+
+Raw Gadget is similar to GadgetFS, but provides a more low-level and
+direct access to the USB Gadget layer for the userspace. The key
+differences are:
+
+1. Every USB request is passed to the userspace to get a response, while
+   GadgetFS responds to some USB requests internally based on the provided
+   descriptors. However note, that the UDC driver might respond to some
+   requests on its own and never forward them to the Gadget layer.
+
+2. GadgetFS performs some sanity checks on the provided USB descriptors,
+   while Raw Gadget allows you to provide arbitrary data as responses to
+   USB requests.
+
+3. Raw Gadget provides a way to select a UDC device/driver to bind to,
+   while GadgetFS currently binds to the first available UDC.
+
+4. Raw Gadget uses predictable endpoint names (handles) across different
+   UDCs (as long as UDCs have enough endpoints of each required transfer
+   type).
+
+5. Raw Gadget has ioctl-based interface instead of a filesystem-based one.
+
+Userspace interface
+~~~~~~~~~~~~~~~~~~~
+
+To create a Raw Gadget instance open /dev/raw-gadget. Multiple raw-gadget
+instances (bound to different UDCs) can be used at the same time. The
+interaction with the opened file happens through the ioctl() calls, see
+comments in include/uapi/linux/usb/raw_gadget.h for details.
+
+The typical usage of Raw Gadget looks like:
+
+1. Open Raw Gadget instance via /dev/raw-gadget.
+2. Initialize the instance via USB_RAW_IOCTL_INIT.
+3. Launch the instance with USB_RAW_IOCTL_RUN.
+4. In a loop issue USB_RAW_IOCTL_EVENT_FETCH calls to receive events from
+   Raw Gadget and react to those depending on what kind of USB device
+   needs to be emulated.
+
+Potential future improvements
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+- Implement ioctl's for setting/clearing halt status on endpoints.
+
+- Reporting more events (suspend, resume, etc.) through
+  USB_RAW_IOCTL_EVENT_FETCH.
diff --git a/drivers/usb/gadget/legacy/Kconfig b/drivers/usb/gadget/legacy/Kconfig
index 119a4e47681f..55e495f5d103 100644
--- a/drivers/usb/gadget/legacy/Kconfig
+++ b/drivers/usb/gadget/legacy/Kconfig
@@ -489,3 +489,14 @@ config USB_G_WEBCAM
 
 	  Say "y" to link the driver statically, or "m" to build a
 	  dynamically linked module called "g_webcam".
+
+config USB_RAW_GADGET
+	tristate "USB Raw Gadget"
+	help
+	  USB Raw Gadget is a kernel module that provides a userspace interface
+	  for the USB Gadget subsystem. Essentially it allows to emulate USB
+	  devices from userspace. See Documentation/usb/raw-gadget.rst for
+	  details.
+
+	  Say "y" to link the driver statically, or "m" to build a
+	  dynamically linked module called "raw_gadget".
diff --git a/drivers/usb/gadget/legacy/Makefile b/drivers/usb/gadget/legacy/Makefile
index abd0c3e66a05..4d864bf82799 100644
--- a/drivers/usb/gadget/legacy/Makefile
+++ b/drivers/usb/gadget/legacy/Makefile
@@ -43,3 +43,4 @@ obj-$(CONFIG_USB_G_WEBCAM)	+= g_webcam.o
 obj-$(CONFIG_USB_G_NCM)		+= g_ncm.o
 obj-$(CONFIG_USB_G_ACM_MS)	+= g_acm_ms.o
 obj-$(CONFIG_USB_GADGET_TARGET)	+= tcm_usb_gadget.o
+obj-$(CONFIG_USB_RAW_GADGET)	+= raw_gadget.o
diff --git a/drivers/usb/gadget/legacy/raw_gadget.c b/drivers/usb/gadget/legacy/raw_gadget.c
new file mode 100644
index 000000000000..1c921fe26ef1
--- /dev/null
+++ b/drivers/usb/gadget/legacy/raw_gadget.c
@@ -0,0 +1,1071 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB Raw Gadget driver.
+ * See Documentation/usb/raw-gadget.rst for more details.
+ *
+ * Andrey Konovalov <andreyknvl@gmail.com>
+ */
+
+#include <linux/compiler.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
+#include <linux/kref.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/semaphore.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/wait.h>
+
+#include <linux/usb.h>
+#include <linux/usb/ch9.h>
+#include <linux/usb/ch11.h>
+#include <linux/usb/gadget.h>
+
+#include <uapi/linux/usb/raw_gadget.h>
+
+#define	DRIVER_DESC "USB Raw Gadget"
+#define DRIVER_NAME "raw-gadget"
+
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_AUTHOR("Andrey Konovalov");
+MODULE_LICENSE("GPL");
+
+/*----------------------------------------------------------------------*/
+
+#define RAW_EVENT_QUEUE_SIZE	128
+
+struct raw_event_queue {
+	/* See the comment in raw_event_queue_fetch() for locking details. */
+	spinlock_t		lock;
+	struct semaphore	sema;
+	struct usb_raw_event	*events[RAW_EVENT_QUEUE_SIZE];
+	int			size;
+};
+
+static void raw_event_queue_init(struct raw_event_queue *queue)
+{
+	spin_lock_init(&queue->lock);
+	sema_init(&queue->sema, 0);
+	queue->size = 0;
+}
+
+static int raw_event_queue_add(struct raw_event_queue *queue,
+	enum usb_raw_event_type type, size_t length, const void *data)
+{
+	unsigned long flags;
+	struct usb_raw_event *event;
+
+	spin_lock_irqsave(&queue->lock, flags);
+	if (WARN_ON(queue->size >= RAW_EVENT_QUEUE_SIZE)) {
+		spin_unlock_irqrestore(&queue->lock, flags);
+		return -ENOMEM;
+	}
+	event = kmalloc(sizeof(*event) + length, GFP_ATOMIC);
+	if (!event) {
+		spin_unlock_irqrestore(&queue->lock, flags);
+		return -ENOMEM;
+	}
+	event->type = type;
+	event->length = length;
+	if (event->length)
+		memcpy(&event->data[0], data, length);
+	queue->events[queue->size] = event;
+	queue->size++;
+	up(&queue->sema);
+	spin_unlock_irqrestore(&queue->lock, flags);
+	return 0;
+}
+
+static struct usb_raw_event *raw_event_queue_fetch(
+				struct raw_event_queue *queue)
+{
+	unsigned long flags;
+	struct usb_raw_event *event;
+
+	/*
+	 * This function can be called concurrently. We first check that
+	 * there's at least one event queued by decrementing the semaphore,
+	 * and then take the lock to protect queue struct fields.
+	 */
+	if (down_interruptible(&queue->sema))
+		return NULL;
+	spin_lock_irqsave(&queue->lock, flags);
+	if (WARN_ON(!queue->size))
+		return NULL;
+	event = queue->events[0];
+	queue->size--;
+	memmove(&queue->events[0], &queue->events[1],
+			queue->size * sizeof(queue->events[0]));
+	spin_unlock_irqrestore(&queue->lock, flags);
+	return event;
+}
+
+static void raw_event_queue_destroy(struct raw_event_queue *queue)
+{
+	int i;
+
+	for (i = 0; i < queue->size; i++)
+		kfree(queue->events[i]);
+	queue->size = 0;
+}
+
+/*----------------------------------------------------------------------*/
+
+struct raw_dev;
+
+#define USB_RAW_MAX_ENDPOINTS 32
+
+enum ep_state {
+	STATE_EP_DISABLED,
+	STATE_EP_ENABLED,
+};
+
+struct raw_ep {
+	struct raw_dev		*dev;
+	enum ep_state		state;
+	struct usb_ep		*ep;
+	struct usb_request	*req;
+	bool			urb_queued;
+	bool			disabling;
+	ssize_t			status;
+};
+
+enum dev_state {
+	STATE_DEV_INVALID = 0,
+	STATE_DEV_OPENED,
+	STATE_DEV_INITIALIZED,
+	STATE_DEV_RUNNING,
+	STATE_DEV_CLOSED,
+	STATE_DEV_FAILED
+};
+
+struct raw_dev {
+	struct kref			count;
+	spinlock_t			lock;
+
+	const char			*udc_name;
+	struct usb_gadget_driver	driver;
+
+	/* Reference to misc device: */
+	struct device			*dev;
+
+	/* Protected by lock: */
+	enum dev_state			state;
+	bool				gadget_registered;
+	struct usb_gadget		*gadget;
+	struct usb_request		*req;
+	bool				ep0_in_pending;
+	bool				ep0_out_pending;
+	bool				ep0_urb_queued;
+	ssize_t				ep0_status;
+	struct raw_ep			eps[USB_RAW_MAX_ENDPOINTS];
+
+	struct completion		ep0_done;
+	struct raw_event_queue		queue;
+};
+
+static struct raw_dev *dev_new(void)
+{
+	struct raw_dev *dev;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return NULL;
+	/* Matches kref_put() in raw_release(). */
+	kref_init(&dev->count);
+	spin_lock_init(&dev->lock);
+	init_completion(&dev->ep0_done);
+	raw_event_queue_init(&dev->queue);
+	return dev;
+}
+
+static void dev_free(struct kref *kref)
+{
+	struct raw_dev *dev = container_of(kref, struct raw_dev, count);
+	int i;
+
+	kfree(dev->udc_name);
+	kfree(dev->driver.udc_name);
+	if (dev->req) {
+		if (dev->ep0_urb_queued)
+			usb_ep_dequeue(dev->gadget->ep0, dev->req);
+		usb_ep_free_request(dev->gadget->ep0, dev->req);
+	}
+	raw_event_queue_destroy(&dev->queue);
+	for (i = 0; i < USB_RAW_MAX_ENDPOINTS; i++) {
+		if (dev->eps[i].state != STATE_EP_ENABLED)
+			continue;
+		usb_ep_disable(dev->eps[i].ep);
+		usb_ep_free_request(dev->eps[i].ep, dev->eps[i].req);
+		kfree(dev->eps[i].ep->desc);
+		dev->eps[i].state = STATE_EP_DISABLED;
+	}
+	kfree(dev);
+}
+
+/*----------------------------------------------------------------------*/
+
+static int raw_queue_event(struct raw_dev *dev,
+	enum usb_raw_event_type type, size_t length, const void *data)
+{
+	int ret = 0;
+	unsigned long flags;
+
+	ret = raw_event_queue_add(&dev->queue, type, length, data);
+	if (ret < 0) {
+		spin_lock_irqsave(&dev->lock, flags);
+		dev->state = STATE_DEV_FAILED;
+		spin_unlock_irqrestore(&dev->lock, flags);
+	}
+	return ret;
+}
+
+static void gadget_ep0_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct raw_dev *dev = req->context;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (req->status)
+		dev->ep0_status = req->status;
+	else
+		dev->ep0_status = req->actual;
+	if (dev->ep0_in_pending)
+		dev->ep0_in_pending = false;
+	else
+		dev->ep0_out_pending = false;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	complete(&dev->ep0_done);
+}
+
+static int gadget_bind(struct usb_gadget *gadget,
+			struct usb_gadget_driver *driver)
+{
+	int ret = 0;
+	struct raw_dev *dev = container_of(driver, struct raw_dev, driver);
+	struct usb_request *req;
+	unsigned long flags;
+
+	if (strcmp(gadget->name, dev->udc_name) != 0)
+		return -ENODEV;
+
+	set_gadget_data(gadget, dev);
+	req = usb_ep_alloc_request(gadget->ep0, GFP_KERNEL);
+	if (!req) {
+		dev_err(&gadget->dev, "usb_ep_alloc_request failed\n");
+		set_gadget_data(gadget, NULL);
+		return -ENOMEM;
+	}
+
+	spin_lock_irqsave(&dev->lock, flags);
+	dev->req = req;
+	dev->req->context = dev;
+	dev->req->complete = gadget_ep0_complete;
+	dev->gadget = gadget;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	/* Matches kref_put() in gadget_unbind(). */
+	kref_get(&dev->count);
+
+	ret = raw_queue_event(dev, USB_RAW_EVENT_CONNECT, 0, NULL);
+	if (ret < 0)
+		dev_err(&gadget->dev, "failed to queue event\n");
+
+	return ret;
+}
+
+static void gadget_unbind(struct usb_gadget *gadget)
+{
+	struct raw_dev *dev = get_gadget_data(gadget);
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	set_gadget_data(gadget, NULL);
+	spin_unlock_irqrestore(&dev->lock, flags);
+	/* Matches kref_get() in gadget_bind(). */
+	kref_put(&dev->count, dev_free);
+}
+
+static int gadget_setup(struct usb_gadget *gadget,
+			const struct usb_ctrlrequest *ctrl)
+{
+	int ret = 0;
+	struct raw_dev *dev = get_gadget_data(gadget);
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_RUNNING) {
+		dev_err(&gadget->dev, "ignoring, device is not running\n");
+		ret = -ENODEV;
+		goto out_unlock;
+	}
+	if (dev->ep0_in_pending || dev->ep0_out_pending) {
+		dev_dbg(&gadget->dev, "stalling, request already pending\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	if ((ctrl->bRequestType & USB_DIR_IN) && ctrl->wLength)
+		dev->ep0_in_pending = true;
+	else
+		dev->ep0_out_pending = true;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	ret = raw_queue_event(dev, USB_RAW_EVENT_CONTROL, sizeof(*ctrl), ctrl);
+	if (ret < 0)
+		dev_err(&gadget->dev, "failed to queue event\n");
+	goto out;
+
+out_unlock:
+	spin_unlock_irqrestore(&dev->lock, flags);
+out:
+	return ret;
+}
+
+/* These are currently unused but present in case UDC driver requires them. */
+static void gadget_disconnect(struct usb_gadget *gadget) { }
+static void gadget_suspend(struct usb_gadget *gadget) { }
+static void gadget_resume(struct usb_gadget *gadget) { }
+static void gadget_reset(struct usb_gadget *gadget) { }
+
+/*----------------------------------------------------------------------*/
+
+static struct miscdevice raw_misc_device;
+
+static int raw_open(struct inode *inode, struct file *fd)
+{
+	struct raw_dev *dev;
+
+	dev = dev_new();
+	if (!dev)
+		return -ENOMEM;
+	fd->private_data = dev;
+	dev->state = STATE_DEV_OPENED;
+	dev->dev = raw_misc_device.this_device;
+	return 0;
+}
+
+static int raw_release(struct inode *inode, struct file *fd)
+{
+	int ret = 0;
+	struct raw_dev *dev = fd->private_data;
+	unsigned long flags;
+	bool unregister = false;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	dev->state = STATE_DEV_CLOSED;
+	if (!dev->gadget) {
+		spin_unlock_irqrestore(&dev->lock, flags);
+		goto out_put;
+	}
+	if (dev->gadget_registered)
+		unregister = true;
+	dev->gadget_registered = false;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	if (unregister) {
+		ret = usb_gadget_unregister_driver(&dev->driver);
+		if (ret != 0)
+			dev_err(dev->dev,
+				"usb_gadget_unregister_driver() failed with %d\n",
+				ret);
+		/* Matches kref_get() in raw_ioctl_run(). */
+		kref_put(&dev->count, dev_free);
+	}
+
+out_put:
+	/* Matches dev_new() in raw_open(). */
+	kref_put(&dev->count, dev_free);
+	return ret;
+}
+
+/*----------------------------------------------------------------------*/
+
+static int raw_ioctl_init(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0;
+	struct usb_raw_init arg;
+	char *udc_driver_name;
+	char *udc_device_name;
+	unsigned long flags;
+
+	ret = copy_from_user(&arg, (void __user *)value, sizeof(arg));
+	if (ret)
+		return ret;
+
+	switch (arg.speed) {
+	case USB_SPEED_UNKNOWN:
+		arg.speed = USB_SPEED_HIGH;
+		break;
+	case USB_SPEED_LOW:
+	case USB_SPEED_FULL:
+	case USB_SPEED_HIGH:
+	case USB_SPEED_SUPER:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	udc_driver_name = kmalloc(UDC_NAME_LENGTH_MAX, GFP_KERNEL);
+	if (!udc_driver_name)
+		return -ENOMEM;
+	ret = strscpy(udc_driver_name, &arg.driver_name[0],
+				UDC_NAME_LENGTH_MAX);
+	if (ret < 0) {
+		kfree(udc_driver_name);
+		return ret;
+	}
+	ret = 0;
+
+	udc_device_name = kmalloc(UDC_NAME_LENGTH_MAX, GFP_KERNEL);
+	if (!udc_device_name) {
+		kfree(udc_driver_name);
+		return -ENOMEM;
+	}
+	ret = strscpy(udc_device_name, &arg.device_name[0],
+				UDC_NAME_LENGTH_MAX);
+	if (ret < 0) {
+		kfree(udc_driver_name);
+		kfree(udc_device_name);
+		return ret;
+	}
+	ret = 0;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_OPENED) {
+		dev_dbg(dev->dev, "fail, device is not opened\n");
+		kfree(udc_driver_name);
+		kfree(udc_device_name);
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	dev->udc_name = udc_driver_name;
+
+	dev->driver.function = DRIVER_DESC;
+	dev->driver.max_speed = arg.speed;
+	dev->driver.setup = gadget_setup;
+	dev->driver.disconnect = gadget_disconnect;
+	dev->driver.bind = gadget_bind;
+	dev->driver.unbind = gadget_unbind;
+	dev->driver.suspend = gadget_suspend;
+	dev->driver.resume = gadget_resume;
+	dev->driver.reset = gadget_reset;
+	dev->driver.driver.name = DRIVER_NAME;
+	dev->driver.udc_name = udc_device_name;
+	dev->driver.match_existing_only = 1;
+
+	dev->state = STATE_DEV_INITIALIZED;
+
+out_unlock:
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return ret;
+}
+
+static int raw_ioctl_run(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0;
+	unsigned long flags;
+
+	if (value)
+		return -EINVAL;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_INITIALIZED) {
+		dev_dbg(dev->dev, "fail, device is not initialized\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	ret = usb_gadget_probe_driver(&dev->driver);
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (ret) {
+		dev_err(dev->dev,
+			"fail, usb_gadget_probe_driver returned %d\n", ret);
+		dev->state = STATE_DEV_FAILED;
+		goto out_unlock;
+	}
+	dev->gadget_registered = true;
+	dev->state = STATE_DEV_RUNNING;
+	/* Matches kref_put() in raw_release(). */
+	kref_get(&dev->count);
+
+out_unlock:
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return ret;
+}
+
+static int raw_ioctl_event_fetch(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0;
+	struct usb_raw_event arg;
+	unsigned long flags;
+	struct usb_raw_event *event;
+	uint32_t length;
+
+	ret = copy_from_user(&arg, (void __user *)value, sizeof(arg));
+	if (ret)
+		return ret;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_RUNNING) {
+		dev_dbg(dev->dev, "fail, device is not running\n");
+		spin_unlock_irqrestore(&dev->lock, flags);
+		return -EINVAL;
+	}
+	if (!dev->gadget) {
+		dev_dbg(dev->dev, "fail, gadget is not bound\n");
+		spin_unlock_irqrestore(&dev->lock, flags);
+		return -EBUSY;
+	}
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	event = raw_event_queue_fetch(&dev->queue);
+	if (!event) {
+		dev_dbg(&dev->gadget->dev, "event fetching interrupted\n");
+		return -EINTR;
+	}
+	length = min(arg.length, event->length);
+	ret = copy_to_user((void __user *)value, event,
+				sizeof(*event) + length);
+	return ret;
+}
+
+static void *raw_alloc_io_data(struct usb_raw_ep_io *io, void __user *ptr,
+				bool get_from_user)
+{
+	int ret;
+	void *data;
+
+	ret = copy_from_user(io, ptr, sizeof(*io));
+	if (ret)
+		return ERR_PTR(ret);
+	if (io->ep >= USB_RAW_MAX_ENDPOINTS)
+		return ERR_PTR(-EINVAL);
+	if (!usb_raw_io_flags_valid(io->flags))
+		return ERR_PTR(-EINVAL);
+	if (io->length > PAGE_SIZE)
+		return ERR_PTR(-EINVAL);
+	if (get_from_user)
+		data = memdup_user(ptr + sizeof(*io), io->length);
+	else {
+		data = kmalloc(io->length, GFP_KERNEL);
+		if (!data)
+			data = ERR_PTR(-ENOMEM);
+	}
+	return data;
+}
+
+static int raw_process_ep0_io(struct raw_dev *dev, struct usb_raw_ep_io *io,
+				void *data, bool in)
+{
+	int ret = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_RUNNING) {
+		dev_dbg(dev->dev, "fail, device is not running\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	if (!dev->gadget) {
+		dev_dbg(dev->dev, "fail, gadget is not bound\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	if (dev->ep0_urb_queued) {
+		dev_dbg(&dev->gadget->dev, "fail, urb already queued\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	if ((in && !dev->ep0_in_pending) ||
+			(!in && !dev->ep0_out_pending)) {
+		dev_dbg(&dev->gadget->dev, "fail, wrong direction\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	if (WARN_ON(in && dev->ep0_out_pending)) {
+		ret = -ENODEV;
+		dev->state = STATE_DEV_FAILED;
+		goto out_done;
+	}
+	if (WARN_ON(!in && dev->ep0_in_pending)) {
+		ret = -ENODEV;
+		dev->state = STATE_DEV_FAILED;
+		goto out_done;
+	}
+
+	dev->req->buf = data;
+	dev->req->length = io->length;
+	dev->req->zero = usb_raw_io_flags_zero(io->flags);
+	dev->ep0_urb_queued = true;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	ret = usb_ep_queue(dev->gadget->ep0, dev->req, GFP_ATOMIC);
+	if (ret) {
+		dev_err(&dev->gadget->dev,
+				"fail, usb_ep_queue returned %d\n", ret);
+		spin_lock_irqsave(&dev->lock, flags);
+		dev->state = STATE_DEV_FAILED;
+		goto out_done;
+	}
+
+	ret = wait_for_completion_interruptible(&dev->ep0_done);
+	if (ret) {
+		dev_dbg(&dev->gadget->dev, "wait interrupted\n");
+		usb_ep_dequeue(dev->gadget->ep0, dev->req);
+		wait_for_completion(&dev->ep0_done);
+		spin_lock_irqsave(&dev->lock, flags);
+		goto out_done;
+	}
+
+	spin_lock_irqsave(&dev->lock, flags);
+	ret = dev->ep0_status;
+
+out_done:
+	dev->ep0_urb_queued = false;
+out_unlock:
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return ret;
+}
+
+static int raw_ioctl_ep0_write(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0;
+	void *data;
+	struct usb_raw_ep_io io;
+
+	data = raw_alloc_io_data(&io, (void __user *)value, true);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+	ret = raw_process_ep0_io(dev, &io, data, true);
+	kfree(data);
+	return ret;
+}
+
+static int raw_ioctl_ep0_read(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0;
+	void *data;
+	struct usb_raw_ep_io io;
+	unsigned int length;
+
+	data = raw_alloc_io_data(&io, (void __user *)value, false);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+	ret = raw_process_ep0_io(dev, &io, data, false);
+	if (ret < 0) {
+		kfree(data);
+		return ret;
+	}
+	length = min(io.length, (unsigned int)ret);
+	ret = copy_to_user((void __user *)(value + sizeof(io)), data, length);
+	kfree(data);
+	return ret;
+}
+
+static bool check_ep_caps(struct usb_ep *ep,
+				struct usb_endpoint_descriptor *desc)
+{
+	switch (usb_endpoint_type(desc)) {
+	case USB_ENDPOINT_XFER_ISOC:
+		if (!ep->caps.type_iso)
+			return false;
+		break;
+	case USB_ENDPOINT_XFER_BULK:
+		if (!ep->caps.type_bulk)
+			return false;
+		break;
+	case USB_ENDPOINT_XFER_INT:
+		if (!ep->caps.type_int)
+			return false;
+		break;
+	default:
+		return false;
+	}
+
+	if (usb_endpoint_dir_in(desc) && !ep->caps.dir_in)
+		return false;
+	if (usb_endpoint_dir_out(desc) && !ep->caps.dir_out)
+		return false;
+
+	return true;
+}
+
+static int raw_ioctl_ep_enable(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0, i;
+	unsigned long flags;
+	struct usb_endpoint_descriptor *desc;
+	struct usb_ep *ep = NULL;
+
+	desc = memdup_user((void __user *)value, sizeof(*desc));
+	if (IS_ERR(desc))
+		return PTR_ERR(desc);
+
+	/*
+	 * Endpoints with a maxpacket length of 0 can cause crashes in UDC
+	 * drivers.
+	 */
+	if (usb_endpoint_maxp(desc) == 0) {
+		dev_dbg(dev->dev, "fail, bad endpoint maxpacket\n");
+		kfree(desc);
+		return -EINVAL;
+	}
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_RUNNING) {
+		dev_dbg(dev->dev, "fail, device is not running\n");
+		ret = -EINVAL;
+		goto out_free;
+	}
+	if (!dev->gadget) {
+		dev_dbg(dev->dev, "fail, gadget is not bound\n");
+		ret = -EBUSY;
+		goto out_free;
+	}
+
+	for (i = 0; i < USB_RAW_MAX_ENDPOINTS; i++) {
+		if (dev->eps[i].state == STATE_EP_ENABLED)
+			continue;
+		break;
+	}
+	if (i == USB_RAW_MAX_ENDPOINTS) {
+		dev_dbg(&dev->gadget->dev,
+				"fail, no device endpoints available\n");
+		ret = -EBUSY;
+		goto out_free;
+	}
+
+	gadget_for_each_ep(ep, dev->gadget) {
+		if (ep->enabled)
+			continue;
+		if (!check_ep_caps(ep, desc))
+			continue;
+		ep->desc = desc;
+		ret = usb_ep_enable(ep);
+		if (ret < 0) {
+			dev_err(&dev->gadget->dev,
+				"fail, usb_ep_enable returned %d\n", ret);
+			goto out_free;
+		}
+		dev->eps[i].req = usb_ep_alloc_request(ep, GFP_ATOMIC);
+		if (!dev->eps[i].req) {
+			dev_err(&dev->gadget->dev,
+				"fail, usb_ep_alloc_request failed\n");
+			usb_ep_disable(ep);
+			ret = -ENOMEM;
+			goto out_free;
+		}
+		dev->eps[i].ep = ep;
+		dev->eps[i].state = STATE_EP_ENABLED;
+		ep->driver_data = &dev->eps[i];
+		ret = i;
+		goto out_unlock;
+	}
+
+	dev_dbg(&dev->gadget->dev, "fail, no gadget endpoints available\n");
+	ret = -EBUSY;
+
+out_free:
+	kfree(desc);
+out_unlock:
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return ret;
+}
+
+static int raw_ioctl_ep_disable(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0, i = value;
+	unsigned long flags;
+	const void *desc;
+
+	if (i < 0 || i >= USB_RAW_MAX_ENDPOINTS)
+		return -EINVAL;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_RUNNING) {
+		dev_dbg(dev->dev, "fail, device is not running\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	if (!dev->gadget) {
+		dev_dbg(dev->dev, "fail, gadget is not bound\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	if (dev->eps[i].state != STATE_EP_ENABLED) {
+		dev_dbg(&dev->gadget->dev, "fail, endpoint is not enabled\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	if (dev->eps[i].disabling) {
+		dev_dbg(&dev->gadget->dev,
+				"fail, disable already in progress\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	dev->eps[i].disabling = true;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	usb_ep_disable(dev->eps[i].ep);
+
+	spin_lock_irqsave(&dev->lock, flags);
+	usb_ep_free_request(dev->eps[i].ep, dev->eps[i].req);
+	desc = dev->eps[i].ep->desc;
+	dev->eps[i].ep = NULL;
+	dev->eps[i].state = STATE_EP_DISABLED;
+	kfree(desc);
+	dev->eps[i].disabling = false;
+
+out_unlock:
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return ret;
+}
+
+static void gadget_ep_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct raw_ep *r_ep = (struct raw_ep *)ep->driver_data;
+	struct raw_dev *dev = r_ep->dev;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (req->status)
+		r_ep->status = req->status;
+	else
+		r_ep->status = req->actual;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	complete((struct completion *)req->context);
+}
+
+static int raw_process_ep_io(struct raw_dev *dev, struct usb_raw_ep_io *io,
+				void *data, bool in)
+{
+	int ret = 0;
+	unsigned long flags;
+	struct raw_ep *ep = &dev->eps[io->ep];
+	DECLARE_COMPLETION_ONSTACK(done);
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_RUNNING) {
+		dev_dbg(dev->dev, "fail, device is not running\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	if (!dev->gadget) {
+		dev_dbg(dev->dev, "fail, gadget is not bound\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	if (ep->state != STATE_EP_ENABLED) {
+		dev_dbg(&dev->gadget->dev, "fail, endpoint is not enabled\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	if (ep->disabling) {
+		dev_dbg(&dev->gadget->dev,
+				"fail, endpoint is already being disabled\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	if (ep->urb_queued) {
+		dev_dbg(&dev->gadget->dev, "fail, urb already queued\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	if ((in && !ep->ep->caps.dir_in) || (!in && ep->ep->caps.dir_in)) {
+		dev_dbg(&dev->gadget->dev, "fail, wrong direction\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	ep->dev = dev;
+	ep->req->context = &done;
+	ep->req->complete = gadget_ep_complete;
+	ep->req->buf = data;
+	ep->req->length = io->length;
+	ep->req->zero = usb_raw_io_flags_zero(io->flags);
+	ep->urb_queued = true;
+	spin_unlock_irqrestore(&dev->lock, flags);
+
+	ret = usb_ep_queue(ep->ep, ep->req, GFP_ATOMIC);
+	if (ret) {
+		dev_err(&dev->gadget->dev,
+				"fail, usb_ep_queue returned %d\n", ret);
+		spin_lock_irqsave(&dev->lock, flags);
+		dev->state = STATE_DEV_FAILED;
+		goto out_done;
+	}
+
+	ret = wait_for_completion_interruptible(&done);
+	if (ret) {
+		dev_dbg(&dev->gadget->dev, "wait interrupted\n");
+		usb_ep_dequeue(ep->ep, ep->req);
+		wait_for_completion(&done);
+		spin_lock_irqsave(&dev->lock, flags);
+		goto out_done;
+	}
+
+	spin_lock_irqsave(&dev->lock, flags);
+	ret = ep->status;
+
+out_done:
+	ep->urb_queued = false;
+out_unlock:
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return ret;
+}
+
+static int raw_ioctl_ep_write(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0;
+	char *data;
+	struct usb_raw_ep_io io;
+
+	data = raw_alloc_io_data(&io, (void __user *)value, true);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+	ret = raw_process_ep_io(dev, &io, data, true);
+	kfree(data);
+	return ret;
+}
+
+static int raw_ioctl_ep_read(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0;
+	char *data;
+	struct usb_raw_ep_io io;
+	unsigned int length;
+
+	data = raw_alloc_io_data(&io, (void __user *)value, false);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
+	ret = raw_process_ep_io(dev, &io, data, false);
+	if (ret < 0) {
+		kfree(data);
+		return ret;
+	}
+	length = min(io.length, (unsigned int)ret);
+	ret = copy_to_user((void __user *)(value + sizeof(io)), data, length);
+	kfree(data);
+	return ret;
+}
+
+static int raw_ioctl_configure(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0;
+	unsigned long flags;
+
+	if (value)
+		return -EINVAL;
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_RUNNING) {
+		dev_dbg(dev->dev, "fail, device is not running\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	if (!dev->gadget) {
+		dev_dbg(dev->dev, "fail, gadget is not bound\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	usb_gadget_set_state(dev->gadget, USB_STATE_CONFIGURED);
+
+out_unlock:
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return ret;
+}
+
+static int raw_ioctl_vbus_draw(struct raw_dev *dev, unsigned long value)
+{
+	int ret = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	if (dev->state != STATE_DEV_RUNNING) {
+		dev_dbg(dev->dev, "fail, device is not running\n");
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+	if (!dev->gadget) {
+		dev_dbg(dev->dev, "fail, gadget is not bound\n");
+		ret = -EBUSY;
+		goto out_unlock;
+	}
+	usb_gadget_vbus_draw(dev->gadget, 2 * value);
+
+out_unlock:
+	spin_unlock_irqrestore(&dev->lock, flags);
+	return ret;
+}
+
+static long raw_ioctl(struct file *fd, unsigned int cmd, unsigned long value)
+{
+	struct raw_dev *dev = fd->private_data;
+	int ret = 0;
+
+	if (!dev)
+		return -EBUSY;
+
+	switch (cmd) {
+	case USB_RAW_IOCTL_INIT:
+		ret = raw_ioctl_init(dev, value);
+		break;
+	case USB_RAW_IOCTL_RUN:
+		ret = raw_ioctl_run(dev, value);
+		break;
+	case USB_RAW_IOCTL_EVENT_FETCH:
+		ret = raw_ioctl_event_fetch(dev, value);
+		break;
+	case USB_RAW_IOCTL_EP0_WRITE:
+		ret = raw_ioctl_ep0_write(dev, value);
+		break;
+	case USB_RAW_IOCTL_EP0_READ:
+		ret = raw_ioctl_ep0_read(dev, value);
+		break;
+	case USB_RAW_IOCTL_EP_ENABLE:
+		ret = raw_ioctl_ep_enable(dev, value);
+		break;
+	case USB_RAW_IOCTL_EP_DISABLE:
+		ret = raw_ioctl_ep_disable(dev, value);
+		break;
+	case USB_RAW_IOCTL_EP_WRITE:
+		ret = raw_ioctl_ep_write(dev, value);
+		break;
+	case USB_RAW_IOCTL_EP_READ:
+		ret = raw_ioctl_ep_read(dev, value);
+		break;
+	case USB_RAW_IOCTL_CONFIGURE:
+		ret = raw_ioctl_configure(dev, value);
+		break;
+	case USB_RAW_IOCTL_VBUS_DRAW:
+		ret = raw_ioctl_vbus_draw(dev, value);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+/*----------------------------------------------------------------------*/
+
+static const struct file_operations raw_fops = {
+	.open =			raw_open,
+	.unlocked_ioctl =	raw_ioctl,
+	.compat_ioctl =		raw_ioctl,
+	.release =		raw_release,
+	.llseek =		no_llseek,
+};
+
+static struct miscdevice raw_misc_device = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = DRIVER_NAME,
+	.fops = &raw_fops,
+};
+
+module_misc_device(raw_misc_device);
diff --git a/include/uapi/linux/usb/raw_gadget.h b/include/uapi/linux/usb/raw_gadget.h
new file mode 100644
index 000000000000..c84ad6d9e81c
--- /dev/null
+++ b/include/uapi/linux/usb/raw_gadget.h
@@ -0,0 +1,167 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * USB Raw Gadget driver.
+ *
+ * See Documentation/usb/raw-gadget.rst for more details.
+ */
+
+#ifndef _UAPI__LINUX_USB_RAW_GADGET_H
+#define _UAPI__LINUX_USB_RAW_GADGET_H
+
+#include <asm/ioctl.h>
+#include <linux/types.h>
+#include <linux/usb/ch9.h>
+
+/* Maximum length of driver_name/device_name in the usb_raw_init struct. */
+#define UDC_NAME_LENGTH_MAX 128
+
+/*
+ * struct usb_raw_init - argument for USB_RAW_IOCTL_INIT ioctl.
+ * @speed: The speed of the emulated USB device, takes the same values as
+ *     the usb_device_speed enum: USB_SPEED_FULL, USB_SPEED_HIGH, etc.
+ * @driver_name: The name of the UDC driver.
+ * @device_name: The name of a UDC instance.
+ *
+ * The last two fields identify a UDC the gadget driver should bind to.
+ * For example, Dummy UDC has "dummy_udc" as its driver_name and "dummy_udc.N"
+ * as its device_name, where N in the index of the Dummy UDC instance.
+ * At the same time the dwc2 driver that is used on Raspberry Pi Zero, has
+ * "20980000.usb" as both driver_name and device_name.
+ */
+struct usb_raw_init {
+	__u8	driver_name[UDC_NAME_LENGTH_MAX];
+	__u8	device_name[UDC_NAME_LENGTH_MAX];
+	__u8	speed;
+};
+
+/* The type of event fetched with the USB_RAW_IOCTL_EVENT_FETCH ioctl. */
+enum usb_raw_event_type {
+	USB_RAW_EVENT_INVALID,
+
+	/* This event is queued when the driver has bound to a UDC. */
+	USB_RAW_EVENT_CONNECT,
+
+	/* This event is queued when a new control request arrived to ep0. */
+	USB_RAW_EVENT_CONTROL,
+
+	/* The list might grow in the future. */
+};
+
+/*
+ * struct usb_raw_event - argument for USB_RAW_IOCTL_EVENT_FETCH ioctl.
+ * @type: The type of the fetched event.
+ * @length: Length of the data buffer. Updated by the driver and set to the
+ *     actual length of the fetched event data.
+ * @data: A buffer to store the fetched event data.
+ *
+ * Currently the fetched data buffer is empty for USB_RAW_EVENT_CONNECT,
+ * and contains struct usb_ctrlrequest for USB_RAW_EVENT_CONTROL.
+ */
+struct usb_raw_event {
+	__u32		type;
+	__u32		length;
+	__u8		data[0];
+};
+
+#define USB_RAW_IO_FLAGS_ZERO	0x0001
+#define USB_RAW_IO_FLAGS_MASK	0x0001
+
+static int usb_raw_io_flags_valid(__u16 flags)
+{
+	return (flags & ~USB_RAW_IO_FLAGS_MASK) == 0;
+}
+
+static int usb_raw_io_flags_zero(__u16 flags)
+{
+	return (flags & USB_RAW_IO_FLAGS_ZERO);
+}
+
+/*
+ * struct usb_raw_ep_io - argument for USB_RAW_IOCTL_EP0/EP_WRITE/READ ioctls.
+ * @ep: Endpoint handle as returned by USB_RAW_IOCTL_EP_ENABLE for
+ *     USB_RAW_IOCTL_EP_WRITE/READ. Ignored for USB_RAW_IOCTL_EP0_WRITE/READ.
+ * @flags: When USB_RAW_IO_FLAGS_ZERO is specified, the zero flag is set on
+ *     the submitted USB request, see include/linux/usb/gadget.h for details.
+ * @length: Length of data.
+ * @data: Data to send for USB_RAW_IOCTL_EP0/EP_WRITE. Buffer to store received
+ *     data for USB_RAW_IOCTL_EP0/EP_READ.
+ */
+struct usb_raw_ep_io {
+	__u16		ep;
+	__u16		flags;
+	__u32		length;
+	__u8		data[0];
+};
+
+/*
+ * Initializes a Raw Gadget instance.
+ * Accepts a pointer to the usb_raw_init struct as an argument.
+ * Returns 0 on success or negative error code on failure.
+ */
+#define USB_RAW_IOCTL_INIT		_IOW('U', 0, struct usb_raw_init)
+
+/*
+ * Instructs Raw Gadget to bind to a UDC and start emulating a USB device.
+ * Returns 0 on success or negative error code on failure.
+ */
+#define USB_RAW_IOCTL_RUN		_IO('U', 1)
+
+/*
+ * A blocking ioctl that waits for an event and returns fetched event data to
+ * the user.
+ * Accepts a pointer to the usb_raw_event struct.
+ * Returns 0 on success or negative error code on failure.
+ */
+#define USB_RAW_IOCTL_EVENT_FETCH	_IOR('U', 2, struct usb_raw_event)
+
+/*
+ * Queues an IN (OUT for READ) urb as a response to the last control request
+ * received on endpoint 0, provided that was an IN (OUT for READ) request and
+ * waits until the urb is completed. Copies received data to user for READ.
+ * Accepts a pointer to the usb_raw_ep_io struct as an argument.
+ * Returns length of trasferred data on success or negative error code on
+ * failure.
+ */
+#define USB_RAW_IOCTL_EP0_WRITE		_IOW('U', 3, struct usb_raw_ep_io)
+#define USB_RAW_IOCTL_EP0_READ		_IOWR('U', 4, struct usb_raw_ep_io)
+
+/*
+ * Finds an endpoint that supports the transfer type specified in the
+ * descriptor and enables it.
+ * Accepts a pointer to the usb_endpoint_descriptor struct as an argument.
+ * Returns enabled endpoint handle on success or negative error code on failure.
+ */
+#define USB_RAW_IOCTL_EP_ENABLE		_IOW('U', 5, struct usb_endpoint_descriptor)
+
+/* Disables specified endpoint.
+ * Accepts endpoint handle as an argument.
+ * Returns 0 on success or negative error code on failure.
+ */
+#define USB_RAW_IOCTL_EP_DISABLE	_IOW('U', 6, __u32)
+
+/*
+ * Queues an IN (OUT for READ) urb as a response to the last control request
+ * received on endpoint usb_raw_ep_io.ep, provided that was an IN (OUT for READ)
+ * request and waits until the urb is completed. Copies received data to user
+ * for READ.
+ * Accepts a pointer to the usb_raw_ep_io struct as an argument.
+ * Returns length of trasferred data on success or negative error code on
+ * failure.
+ */
+#define USB_RAW_IOCTL_EP_WRITE		_IOW('U', 7, struct usb_raw_ep_io)
+#define USB_RAW_IOCTL_EP_READ		_IOWR('U', 8, struct usb_raw_ep_io)
+
+/*
+ * Switches the gadget into the configured state.
+ * Returns 0 on success or negative error code on failure.
+ */
+#define USB_RAW_IOCTL_CONFIGURE		_IO('U', 9)
+
+/*
+ * Constrains UDC VBUS power usage.
+ * Accepts current limit in 2 mA units as an argument.
+ * Returns 0 on success or negative error code on failure.
+ */
+#define USB_RAW_IOCTL_VBUS_DRAW		_IOW('U', 10, __u32)
+
+#endif /* _UAPI__LINUX_USB_RAW_GADGET_H */
-- 
2.24.1.735.g03f4e72817-goog


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 0/1] usb: gadget: add raw-gadget interface
  2019-12-18 19:26 [PATCH v4 0/1] usb: gadget: add raw-gadget interface Andrey Konovalov
  2019-12-18 19:26 ` [PATCH v4 1/1] " Andrey Konovalov
@ 2020-01-08 20:15 ` " Andrey Konovalov
  1 sibling, 0 replies; 9+ messages in thread
From: Andrey Konovalov @ 2020-01-08 20:15 UTC (permalink / raw)
  To: USB list, LKML, Greg Kroah-Hartman, Alan Stern
  Cc: Jonathan Corbet, Felipe Balbi, Dmitry Vyukov,
	Alexander Potapenko, Marco Elver

On Wed, Dec 18, 2019 at 8:27 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> This patchset (currently a single patch) adds a new userspace interface
> for the USB Gadget subsystem called USB Raw Gadget (I don't mind changing
> the name to something else if there are better ideas). This is what
> currently being used to enable coverage-buided USB fuzzing with syzkaller:
>
> https://github.com/google/syzkaller/blob/master/docs/linux/external_fuzzing_usb.md
>
> Initially I was using GadgetFS (together with the Dummy HCD/UDC module)
> to perform emulation of USB devices for fuzzing, but later switched to a
> custom written interface. The incentive to implement a different interface
> was to provide a somewhat raw and direct access to the USB Gadget layer
> for the userspace, where every USB request is passed to the userspace to
> get a response. See documentation for the list of differences between
> Raw Gadget and GadgetFS.
>
> This patchset has been pushed to the public Linux kernel Gerrit instance:
>
> https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/2144

Hi Greg,

Just an after holidays reminder that I've sent v4 of this patchset and
looking forward to a review.

Thanks!

>
> Changes v3 -> v4:
> - Print debug message when maxpacket check fails.
> - Use module_misc_device() instead of module_init/exit().
> - Reuse DRIVER_NAME macro in raw_device struct definition.
> - Don't print WARNING in raw_release().
> - Add comment that explains locking into raw_event_queue_fetch().
> - Print a WARNING when event queue size is exceeded.
> - Rename raw.c to raw_gadget.c.
> - Mention module name in Kconfig.
> - Reworked logging to use dev_err/dbg() instead of pr_err/debug().
>
> Changes v2 -> v3:
> - Updated device path in documentation.
> - Changed usb_raw_init struct layout to make it the same for 32 bit compat
>   mode.
> - Added compat_ioctl to raw_fops.
> - Changed raw_ioctl_init() to return EINVAL for invalid USB speeds, except
>   for USB_SPEED_UNKNOWN, which defaults to USB_SPEED_HIGH.
> - Reject endpoints with maxpacket = 0 in raw_ioctl_ep_enable().
>
> Changes v1 -> v2:
> - Moved raw.c to legacy/.
> - Changed uapi header to use __u* types.
> - Switched from debugfs entry to a misc device.
> - Changed raw_dev from refcount to kref.
> - Moved UDC_NAME_LENGTH_MAX to uapi headers.
> - Used usb_endpoint_type() and usb_endpoint_dir_in/out() functions instead
>   of open coding them.
> - Added "WITH Linux-syscall-note" to SPDX id in the uapi header.
> - Removed pr_err() if case dev_new() fails.
> - Reduced the number of debugging messages.
>
> Andrey Konovalov (1):
>   usb: gadget: add raw-gadget interface
>
>  Documentation/usb/index.rst            |    1 +
>  Documentation/usb/raw-gadget.rst       |   59 ++
>  drivers/usb/gadget/legacy/Kconfig      |   11 +
>  drivers/usb/gadget/legacy/Makefile     |    1 +
>  drivers/usb/gadget/legacy/raw_gadget.c | 1071 ++++++++++++++++++++++++
>  include/uapi/linux/usb/raw_gadget.h    |  167 ++++
>  6 files changed, 1310 insertions(+)
>  create mode 100644 Documentation/usb/raw-gadget.rst
>  create mode 100644 drivers/usb/gadget/legacy/raw_gadget.c
>  create mode 100644 include/uapi/linux/usb/raw_gadget.h
>
> --
> 2.24.1.735.g03f4e72817-goog
>

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 1/1] usb: gadget: add raw-gadget interface
  2019-12-18 19:26 ` [PATCH v4 1/1] " Andrey Konovalov
@ 2020-01-11 19:31   ` Greg Kroah-Hartman
  2020-01-13 13:40     ` Andrey Konovalov
  0 siblings, 1 reply; 9+ messages in thread
From: Greg Kroah-Hartman @ 2020-01-11 19:31 UTC (permalink / raw)
  To: Andrey Konovalov
  Cc: linux-usb, linux-kernel, Alan Stern, Jonathan Corbet,
	Felipe Balbi, Dmitry Vyukov, Alexander Potapenko, Marco Elver

On Wed, Dec 18, 2019 at 08:26:57PM +0100, Andrey Konovalov wrote:
> USB Raw Gadget is a kernel module that provides a userspace interface for
> the USB Gadget subsystem. Essentially it allows to emulate USB devices
> from userspace. Enabled with CONFIG_USB_RAW_GADGET. Raw Gadget is
> currently a strictly debugging feature and shouldn't be used in
> production.
> 
> Raw Gadget is similar to GadgetFS, but provides a more low-level and
> direct access to the USB Gadget layer for the userspace. The key
> differences are:
> 
> 1. Every USB request is passed to the userspace to get a response, while
>    GadgetFS responds to some USB requests internally based on the provided
>    descriptors. However note, that the UDC driver might respond to some
>    requests on its own and never forward them to the Gadget layer.
> 
> 2. GadgetFS performs some sanity checks on the provided USB descriptors,
>    while Raw Gadget allows you to provide arbitrary data as responses to
>    USB requests.
> 
> 3. Raw Gadget provides a way to select a UDC device/driver to bind to,
>    while GadgetFS currently binds to the first available UDC.
> 
> 4. Raw Gadget uses predictable endpoint names (handles) across different
>    UDCs (as long as UDCs have enough endpoints of each required transfer
>    type).
> 
> 5. Raw Gadget has ioctl-based interface instead of a filesystem-based one.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

This looks good to me, with the one minor problem below that you can fix
with a follow-on patch.  This should probably go through Felipe's tree
though, so I'll wait for him to review the gadget side and then queue it
up in his tree:


> +/* The type of event fetched with the USB_RAW_IOCTL_EVENT_FETCH ioctl. */
> +enum usb_raw_event_type {
> +	USB_RAW_EVENT_INVALID,
> +
> +	/* This event is queued when the driver has bound to a UDC. */
> +	USB_RAW_EVENT_CONNECT,
> +
> +	/* This event is queued when a new control request arrived to ep0. */
> +	USB_RAW_EVENT_CONTROL,
> +
> +	/* The list might grow in the future. */
> +};

You have to manually specify the enum values in the .h file for all
entries in order to assure that both userspace and the kernel will be in
sync with the same values.  I think that's documented in the "how to
write an ioctl interface" document that is somewhere in
Documentation/...

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 1/1] usb: gadget: add raw-gadget interface
  2020-01-11 19:31   ` Greg Kroah-Hartman
@ 2020-01-13 13:40     ` Andrey Konovalov
  2020-01-13 16:50       ` Alan Stern
  0 siblings, 1 reply; 9+ messages in thread
From: Andrey Konovalov @ 2020-01-13 13:40 UTC (permalink / raw)
  To: Greg Kroah-Hartman, Felipe Balbi, Alan Stern
  Cc: USB list, LKML, Jonathan Corbet, Dmitry Vyukov,
	Alexander Potapenko, Marco Elver

On Sat, Jan 11, 2020 at 9:02 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Wed, Dec 18, 2019 at 08:26:57PM +0100, Andrey Konovalov wrote:
> > USB Raw Gadget is a kernel module that provides a userspace interface for
> > the USB Gadget subsystem. Essentially it allows to emulate USB devices
> > from userspace. Enabled with CONFIG_USB_RAW_GADGET. Raw Gadget is
> > currently a strictly debugging feature and shouldn't be used in
> > production.
> >
> > Raw Gadget is similar to GadgetFS, but provides a more low-level and
> > direct access to the USB Gadget layer for the userspace. The key
> > differences are:
> >
> > 1. Every USB request is passed to the userspace to get a response, while
> >    GadgetFS responds to some USB requests internally based on the provided
> >    descriptors. However note, that the UDC driver might respond to some
> >    requests on its own and never forward them to the Gadget layer.
> >
> > 2. GadgetFS performs some sanity checks on the provided USB descriptors,
> >    while Raw Gadget allows you to provide arbitrary data as responses to
> >    USB requests.
> >
> > 3. Raw Gadget provides a way to select a UDC device/driver to bind to,
> >    while GadgetFS currently binds to the first available UDC.
> >
> > 4. Raw Gadget uses predictable endpoint names (handles) across different
> >    UDCs (as long as UDCs have enough endpoints of each required transfer
> >    type).
> >
> > 5. Raw Gadget has ioctl-based interface instead of a filesystem-based one.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
>
> This looks good to me, with the one minor problem below that you can fix
> with a follow-on patch.

Great, thanks! I'd prefer to send out v5 to keep this a single patch
if that's OK.

I've also found an issue, but I'm not sure if that is the bug in Raw
Gadget, or in the gadget layer (in the former case I'll add this fix
to v5 as well). What I believe I'm seeing is
__fput()->usb_gadget_unregister_driver()->usb_gadget_remove_driver()->gadget_unbind()
racing with dummy_timer()->gadget_setup(). In my case it results in
gadget_unbind() doing set_gadget_data(gadget, NULL), and then
gadget_setup() dereferencing get_gadget_data(gadget).

Alan, does it look possible for those two functions to race? Should
this be prevented by the gadget layer, or should I use some kind of
locking in my gadget driver to prevent this?

> This should probably go through Felipe's tree
> though, so I'll wait for him to review the gadget side and then queue it
> up in his tree:

OK, looking forward to Felipe's review.

> > +/* The type of event fetched with the USB_RAW_IOCTL_EVENT_FETCH ioctl. */
> > +enum usb_raw_event_type {
> > +     USB_RAW_EVENT_INVALID,
> > +
> > +     /* This event is queued when the driver has bound to a UDC. */
> > +     USB_RAW_EVENT_CONNECT,
> > +
> > +     /* This event is queued when a new control request arrived to ep0. */
> > +     USB_RAW_EVENT_CONTROL,
> > +
> > +     /* The list might grow in the future. */
> > +};
>
> You have to manually specify the enum values in the .h file for all
> entries in order to assure that both userspace and the kernel will be in
> sync with the same values.  I think that's documented in the "how to
> write an ioctl interface" document that is somewhere in
> Documentation/...

Will fix in v5, thanks!

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 1/1] usb: gadget: add raw-gadget interface
  2020-01-13 13:40     ` Andrey Konovalov
@ 2020-01-13 16:50       ` Alan Stern
  2020-01-13 17:34         ` Andrey Konovalov
  0 siblings, 1 reply; 9+ messages in thread
From: Alan Stern @ 2020-01-13 16:50 UTC (permalink / raw)
  To: Andrey Konovalov
  Cc: Greg Kroah-Hartman, Felipe Balbi, USB list, LKML,
	Jonathan Corbet, Dmitry Vyukov, Alexander Potapenko, Marco Elver

On Mon, 13 Jan 2020, Andrey Konovalov wrote:

> I've also found an issue, but I'm not sure if that is the bug in Raw
> Gadget, or in the gadget layer (in the former case I'll add this fix
> to v5 as well). What I believe I'm seeing is
> __fput()->usb_gadget_unregister_driver()->usb_gadget_remove_driver()->gadget_unbind()
> racing with dummy_timer()->gadget_setup(). In my case it results in
> gadget_unbind() doing set_gadget_data(gadget, NULL), and then
> gadget_setup() dereferencing get_gadget_data(gadget).
> 
> Alan, does it look possible for those two functions to race? Should
> this be prevented by the gadget layer, or should I use some kind of
> locking in my gadget driver to prevent this?

In your situation this race shouldn't happen, because before
udc->driver->unbind() is invoked we call usb_gadget_disconnect().  If
that routine succeeds -- which it always does under dummy-hcd -- then
there can't be any more setup callbacks, because find_endpoint() will
always return NULL (the is_active() test fails; see the various
set_link_state* routines).  So I don't see how you could have ended up
with the race you describe.

However, a real UDC might not be able to perform a disconnect under
software control.  In that case usb_gadget_disconnect() would not
change the pullup state, and there would be a real possibility of a
setup callback racing with an unbind callback.  This seems like a 
genuine problem and I can't think of a solution offhand.

What we would need is a way to tell the UDC driver to stop invoking
gadget callbacks, _before_ the UDC driver's stop callback gets called.
Maybe this should be merged into the pullup callback somehow.

Alan Stern


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 1/1] usb: gadget: add raw-gadget interface
  2020-01-13 16:50       ` Alan Stern
@ 2020-01-13 17:34         ` Andrey Konovalov
  2020-01-13 17:40           ` Andrey Konovalov
  0 siblings, 1 reply; 9+ messages in thread
From: Andrey Konovalov @ 2020-01-13 17:34 UTC (permalink / raw)
  To: Alan Stern
  Cc: Greg Kroah-Hartman, Felipe Balbi, USB list, LKML,
	Jonathan Corbet, Dmitry Vyukov, Alexander Potapenko, Marco Elver

On Mon, Jan 13, 2020 at 5:50 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Mon, 13 Jan 2020, Andrey Konovalov wrote:
>
> > I've also found an issue, but I'm not sure if that is the bug in Raw
> > Gadget, or in the gadget layer (in the former case I'll add this fix
> > to v5 as well). What I believe I'm seeing is
> > __fput()->usb_gadget_unregister_driver()->usb_gadget_remove_driver()->gadget_unbind()
> > racing with dummy_timer()->gadget_setup(). In my case it results in
> > gadget_unbind() doing set_gadget_data(gadget, NULL), and then
> > gadget_setup() dereferencing get_gadget_data(gadget).
> >
> > Alan, does it look possible for those two functions to race? Should
> > this be prevented by the gadget layer, or should I use some kind of
> > locking in my gadget driver to prevent this?
>
> In your situation this race shouldn't happen, because before
> udc->driver->unbind() is invoked we call usb_gadget_disconnect().  If
> that routine succeeds -- which it always does under dummy-hcd -- then
> there can't be any more setup callbacks, because find_endpoint() will
> always return NULL (the is_active() test fails; see the various
> set_link_state* routines).  So I don't see how you could have ended up
> with the race you describe.

I've managed to reproduce the race by adding an mdelay() into the
beginning of the setup() callback. AFAIU what happens is setup() gets
called (and waits on the mdelay()), then unbind() comes in and does
set_gadget_data(NULL), and then setup() proceeds, gets NULL through
get_gadget_data() and crashes on null-ptr-deref. I've got the same
crash a few times after many days of fuzzing, so I assume it can
happen without the mdelay() as well.

> However, a real UDC might not be able to perform a disconnect under
> software control.  In that case usb_gadget_disconnect() would not
> change the pullup state, and there would be a real possibility of a
> setup callback racing with an unbind callback.  This seems like a
> genuine problem and I can't think of a solution offhand.
>
> What we would need is a way to tell the UDC driver to stop invoking
> gadget callbacks, _before_ the UDC driver's stop callback gets called.
> Maybe this should be merged into the pullup callback somehow.
>
> Alan Stern
>

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 1/1] usb: gadget: add raw-gadget interface
  2020-01-13 17:34         ` Andrey Konovalov
@ 2020-01-13 17:40           ` Andrey Konovalov
  2020-01-13 18:45             ` Alan Stern
  0 siblings, 1 reply; 9+ messages in thread
From: Andrey Konovalov @ 2020-01-13 17:40 UTC (permalink / raw)
  To: Alan Stern
  Cc: Greg Kroah-Hartman, Felipe Balbi, USB list, LKML,
	Jonathan Corbet, Dmitry Vyukov, Alexander Potapenko, Marco Elver

On Mon, Jan 13, 2020 at 6:34 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> On Mon, Jan 13, 2020 at 5:50 PM Alan Stern <stern@rowland.harvard.edu> wrote:
> >
> > On Mon, 13 Jan 2020, Andrey Konovalov wrote:
> >
> > > I've also found an issue, but I'm not sure if that is the bug in Raw
> > > Gadget, or in the gadget layer (in the former case I'll add this fix
> > > to v5 as well). What I believe I'm seeing is
> > > __fput()->usb_gadget_unregister_driver()->usb_gadget_remove_driver()->gadget_unbind()
> > > racing with dummy_timer()->gadget_setup(). In my case it results in
> > > gadget_unbind() doing set_gadget_data(gadget, NULL), and then
> > > gadget_setup() dereferencing get_gadget_data(gadget).
> > >
> > > Alan, does it look possible for those two functions to race? Should
> > > this be prevented by the gadget layer, or should I use some kind of
> > > locking in my gadget driver to prevent this?
> >
> > In your situation this race shouldn't happen, because before
> > udc->driver->unbind() is invoked we call usb_gadget_disconnect().  If
> > that routine succeeds -- which it always does under dummy-hcd -- then
> > there can't be any more setup callbacks, because find_endpoint() will
> > always return NULL (the is_active() test fails; see the various
> > set_link_state* routines).  So I don't see how you could have ended up
> > with the race you describe.
>
> I've managed to reproduce the race by adding an mdelay() into the
> beginning of the setup() callback. AFAIU what happens is setup() gets
> called (and waits on the mdelay()), then unbind() comes in and does
> set_gadget_data(NULL), and then setup() proceeds, gets NULL through
> get_gadget_data() and crashes on null-ptr-deref. I've got the same
> crash a few times after many days of fuzzing, so I assume it can
> happen without the mdelay() as well.
>
> > However, a real UDC might not be able to perform a disconnect under
> > software control.  In that case usb_gadget_disconnect() would not
> > change the pullup state, and there would be a real possibility of a
> > setup callback racing with an unbind callback.  This seems like a
> > genuine problem and I can't think of a solution offhand.
> >
> > What we would need is a way to tell the UDC driver to stop invoking
> > gadget callbacks, _before_ the UDC driver's stop callback gets called.
> > Maybe this should be merged into the pullup callback somehow.

Perhaps for the dummy driver we need to wait for setup() to finish if
it's being executed and then stop the dummy timer in dummy_pullup()?

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v4 1/1] usb: gadget: add raw-gadget interface
  2020-01-13 17:40           ` Andrey Konovalov
@ 2020-01-13 18:45             ` Alan Stern
  0 siblings, 0 replies; 9+ messages in thread
From: Alan Stern @ 2020-01-13 18:45 UTC (permalink / raw)
  To: Andrey Konovalov, Felipe Balbi
  Cc: Greg Kroah-Hartman, USB list, LKML, Jonathan Corbet,
	Dmitry Vyukov, Alexander Potapenko, Marco Elver

On Mon, 13 Jan 2020, Andrey Konovalov wrote:

> On Mon, Jan 13, 2020 at 6:34 PM Andrey Konovalov <andreyknvl@google.com> wrote:
> >
> > On Mon, Jan 13, 2020 at 5:50 PM Alan Stern <stern@rowland.harvard.edu> wrote:
> > >
> > > On Mon, 13 Jan 2020, Andrey Konovalov wrote:
> > >
> > > > I've also found an issue, but I'm not sure if that is the bug in Raw
> > > > Gadget, or in the gadget layer (in the former case I'll add this fix
> > > > to v5 as well). What I believe I'm seeing is
> > > > __fput()->usb_gadget_unregister_driver()->usb_gadget_remove_driver()->gadget_unbind()
> > > > racing with dummy_timer()->gadget_setup(). In my case it results in
> > > > gadget_unbind() doing set_gadget_data(gadget, NULL), and then
> > > > gadget_setup() dereferencing get_gadget_data(gadget).
> > > >
> > > > Alan, does it look possible for those two functions to race? Should
> > > > this be prevented by the gadget layer, or should I use some kind of
> > > > locking in my gadget driver to prevent this?
> > >
> > > In your situation this race shouldn't happen, because before
> > > udc->driver->unbind() is invoked we call usb_gadget_disconnect().  If
> > > that routine succeeds -- which it always does under dummy-hcd -- then
> > > there can't be any more setup callbacks, because find_endpoint() will
> > > always return NULL (the is_active() test fails; see the various
> > > set_link_state* routines).  So I don't see how you could have ended up
> > > with the race you describe.
> >
> > I've managed to reproduce the race by adding an mdelay() into the
> > beginning of the setup() callback. AFAIU what happens is setup() gets
> > called (and waits on the mdelay()), then unbind() comes in and does
> > set_gadget_data(NULL), and then setup() proceeds, gets NULL through
> > get_gadget_data() and crashes on null-ptr-deref. I've got the same
> > crash a few times after many days of fuzzing, so I assume it can
> > happen without the mdelay() as well.
> >
> > > However, a real UDC might not be able to perform a disconnect under
> > > software control.  In that case usb_gadget_disconnect() would not
> > > change the pullup state, and there would be a real possibility of a
> > > setup callback racing with an unbind callback.  This seems like a
> > > genuine problem and I can't think of a solution offhand.
> > >
> > > What we would need is a way to tell the UDC driver to stop invoking
> > > gadget callbacks, _before_ the UDC driver's stop callback gets called.
> > > Maybe this should be merged into the pullup callback somehow.
> 
> Perhaps for the dummy driver we need to wait for setup() to finish if
> it's being executed and then stop the dummy timer in dummy_pullup()?

Yes, we need to wait for a setup callback to finish.  But dummy_timer 
should not be stopped; otherwise URBs that have already been submitted 
would never be given back.

The big problem is that usb_gadget_disconnect() can be called in
interrupt context.  In general, a UDC driver will need to call
synchronize_irq() to make sure there aren't any callbacks still
running, and that can be done only in process context.  dummy-hcd is
slightly different since it doesn't manage actual hardware; it calls
usleep_range() instead of synchronize_irq() -- but that also requires
process context.

We could change the gadget API to require that usb_gadget_disconnect()  
and related routines always be called in process context.  I don't know
if that's such a good idea though.  A gadget driver might want to
disconnect from within its setup handler or a completion routine, for
example.

A better approach would be to add a new synchronize_callbacks()  
pointer in the usb_gadget_ops structure.  But to work properly it 
would have to be mandatory for every UDC driver, and that's not so easy 
to accomplish.

Suggestions?

Alan Stern


^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, back to index

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-18 19:26 [PATCH v4 0/1] usb: gadget: add raw-gadget interface Andrey Konovalov
2019-12-18 19:26 ` [PATCH v4 1/1] " Andrey Konovalov
2020-01-11 19:31   ` Greg Kroah-Hartman
2020-01-13 13:40     ` Andrey Konovalov
2020-01-13 16:50       ` Alan Stern
2020-01-13 17:34         ` Andrey Konovalov
2020-01-13 17:40           ` Andrey Konovalov
2020-01-13 18:45             ` Alan Stern
2020-01-08 20:15 ` [PATCH v4 0/1] " Andrey Konovalov

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