Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 819 insertions, 0 deletions

diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
new file mode 100644
index 000000000..37b60c3aa
--- /dev/null
+++ b/drivers/hid/uhid.c
@@ -0,0 +1,819 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * User-space I/O driver support for HID subsystem
+ * Copyright (c) 2012 David Herrmann
+ */
+
+/*
+ */
+
+#include <linux/atomic.h>
+#include <linux/compat.h>
+#include <linux/cred.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/hid.h>
+#include <linux/input.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/uhid.h>
+#include <linux/wait.h>
+
+#define UHID_NAME	"uhid"
+#define UHID_BUFSIZE	32
+
+struct uhid_device {
+	struct mutex devlock;
+
+	/* This flag tracks whether the HID device is usable for commands from
+	 * userspace. The flag is already set before hid_add_device(), which
+	 * runs in workqueue context, to allow hid_add_device() to communicate
+	 * with userspace.
+	 * However, if hid_add_device() fails, the flag is cleared without
+	 * holding devlock.
+	 * We guarantee that if @running changes from true to false while you're
+	 * holding @devlock, it's still fine to access @hid.
+	 */
+	bool running;
+
+	__u8 *rd_data;
+	uint rd_size;
+
+	/* When this is NULL, userspace may use UHID_CREATE/UHID_CREATE2. */
+	struct hid_device *hid;
+	struct uhid_event input_buf;
+
+	wait_queue_head_t waitq;
+	spinlock_t qlock;
+	__u8 head;
+	__u8 tail;
+	struct uhid_event *outq[UHID_BUFSIZE];
+
+	/* blocking GET_REPORT support; state changes protected by qlock */
+	struct mutex report_lock;
+	wait_queue_head_t report_wait;
+	bool report_running;
+	u32 report_id;
+	u32 report_type;
+	struct uhid_event report_buf;
+	struct work_struct worker;
+};
+
+static struct miscdevice uhid_misc;
+
+static void uhid_device_add_worker(struct work_struct *work)
+{
+	struct uhid_device *uhid = container_of(work, struct uhid_device, worker);
+	int ret;
+
+	ret = hid_add_device(uhid->hid);
+	if (ret) {
+		hid_err(uhid->hid, "Cannot register HID device: error %d\n", ret);
+
+		/* We used to call hid_destroy_device() here, but that's really
+		 * messy to get right because we have to coordinate with
+		 * concurrent writes from userspace that might be in the middle
+		 * of using uhid->hid.
+		 * Just leave uhid->hid as-is for now, and clean it up when
+		 * userspace tries to close or reinitialize the uhid instance.
+		 *
+		 * However, we do have to clear the ->running flag and do a
+		 * wakeup to make sure userspace knows that the device is gone.
+		 */
+		WRITE_ONCE(uhid->running, false);
+		wake_up_interruptible(&uhid->report_wait);
+	}
+}
+
+static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
+{
+	__u8 newhead;
+
+	newhead = (uhid->head + 1) % UHID_BUFSIZE;
+
+	if (newhead != uhid->tail) {
+		uhid->outq[uhid->head] = ev;
+		uhid->head = newhead;
+		wake_up_interruptible(&uhid->waitq);
+	} else {
+		hid_warn(uhid->hid, "Output queue is full\n");
+		kfree(ev);
+	}
+}
+
+static int uhid_queue_event(struct uhid_device *uhid, __u32 event)
+{
+	unsigned long flags;
+	struct uhid_event *ev;
+
+	ev = kzalloc_obj(*ev);
+	if (!ev)
+		return -ENOMEM;
+
+	ev->type = event;
+
+	spin_lock_irqsave(&uhid->qlock, flags);
+	uhid_queue(uhid, ev);
+	spin_unlock_irqrestore(&uhid->qlock, flags);
+
+	return 0;
+}
+
+static int uhid_hid_start(struct hid_device *hid)
+{
+	struct uhid_device *uhid = hid->driver_data;
+	struct uhid_event *ev;
+	unsigned long flags;
+
+	ev = kzalloc_obj(*ev);
+	if (!ev)
+		return -ENOMEM;
+
+	ev->type = UHID_START;
+
+	if (hid->report_enum[HID_FEATURE_REPORT].numbered)
+		ev->u.start.dev_flags |= UHID_DEV_NUMBERED_FEATURE_REPORTS;
+	if (hid->report_enum[HID_OUTPUT_REPORT].numbered)
+		ev->u.start.dev_flags |= UHID_DEV_NUMBERED_OUTPUT_REPORTS;
+	if (hid->report_enum[HID_INPUT_REPORT].numbered)
+		ev->u.start.dev_flags |= UHID_DEV_NUMBERED_INPUT_REPORTS;
+
+	spin_lock_irqsave(&uhid->qlock, flags);
+	uhid_queue(uhid, ev);
+	spin_unlock_irqrestore(&uhid->qlock, flags);
+
+	return 0;
+}
+
+static void uhid_hid_stop(struct hid_device *hid)
+{
+	struct uhid_device *uhid = hid->driver_data;
+
+	hid->claimed = 0;
+	uhid_queue_event(uhid, UHID_STOP);
+}
+
+static int uhid_hid_open(struct hid_device *hid)
+{
+	struct uhid_device *uhid = hid->driver_data;
+
+	return uhid_queue_event(uhid, UHID_OPEN);
+}
+
+static void uhid_hid_close(struct hid_device *hid)
+{
+	struct uhid_device *uhid = hid->driver_data;
+
+	uhid_queue_event(uhid, UHID_CLOSE);
+}
+
+static int uhid_hid_parse(struct hid_device *hid)
+{
+	struct uhid_device *uhid = hid->driver_data;
+
+	return hid_parse_report(hid, uhid->rd_data, uhid->rd_size);
+}
+
+/* must be called with report_lock held */
+static int __uhid_report_queue_and_wait(struct uhid_device *uhid,
+					struct uhid_event *ev,
+					__u32 *report_id)
+{
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&uhid->qlock, flags);
+	*report_id = ++uhid->report_id;
+	uhid->report_type = ev->type + 1;
+	uhid->report_running = true;
+	uhid_queue(uhid, ev);
+	spin_unlock_irqrestore(&uhid->qlock, flags);
+
+	ret = wait_event_interruptible_timeout(uhid->report_wait,
+				!uhid->report_running || !READ_ONCE(uhid->running),
+				5 * HZ);
+	if (!ret || !READ_ONCE(uhid->running) || uhid->report_running)
+		ret = -EIO;
+	else if (ret < 0)
+		ret = -ERESTARTSYS;
+	else
+		ret = 0;
+
+	uhid->report_running = false;
+
+	return ret;
+}
+
+static void uhid_report_wake_up(struct uhid_device *uhid, u32 id,
+				const struct uhid_event *ev)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&uhid->qlock, flags);
+
+	/* id for old report; drop it silently */
+	if (uhid->report_type != ev->type || uhid->report_id != id)
+		goto unlock;
+	if (!uhid->report_running)
+		goto unlock;
+
+	memcpy(&uhid->report_buf, ev, sizeof(*ev));
+	uhid->report_running = false;
+	wake_up_interruptible(&uhid->report_wait);
+
+unlock:
+	spin_unlock_irqrestore(&uhid->qlock, flags);
+}
+
+static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
+			       u8 *buf, size_t count, u8 rtype)
+{
+	struct uhid_device *uhid = hid->driver_data;
+	struct uhid_get_report_reply_req *req;
+	struct uhid_event *ev;
+	int ret;
+
+	if (!READ_ONCE(uhid->running))
+		return -EIO;
+
+	ev = kzalloc_obj(*ev);
+	if (!ev)
+		return -ENOMEM;
+
+	ev->type = UHID_GET_REPORT;
+	ev->u.get_report.rnum = rnum;
+	ev->u.get_report.rtype = rtype;
+
+	ret = mutex_lock_interruptible(&uhid->report_lock);
+	if (ret) {
+		kfree(ev);
+		return ret;
+	}
+
+	/* this _always_ takes ownership of @ev */
+	ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.get_report.id);
+	if (ret)
+		goto unlock;
+
+	req = &uhid->report_buf.u.get_report_reply;
+	if (req->err) {
+		ret = -EIO;
+	} else {
+		ret = min3(count, (size_t)req->size, (size_t)UHID_DATA_MAX);
+		memcpy(buf, req->data, ret);
+	}
+
+unlock:
+	mutex_unlock(&uhid->report_lock);
+	return ret;
+}
+
+static int uhid_hid_set_report(struct hid_device *hid, unsigned char rnum,
+			       const u8 *buf, size_t count, u8 rtype)
+{
+	struct uhid_device *uhid = hid->driver_data;
+	struct uhid_event *ev;
+	int ret;
+
+	if (!READ_ONCE(uhid->running) || count > UHID_DATA_MAX)
+		return -EIO;
+
+	ev = kzalloc_obj(*ev);
+	if (!ev)
+		return -ENOMEM;
+
+	ev->type = UHID_SET_REPORT;
+	ev->u.set_report.rnum = rnum;
+	ev->u.set_report.rtype = rtype;
+	ev->u.set_report.size = count;
+	memcpy(ev->u.set_report.data, buf, count);
+
+	ret = mutex_lock_interruptible(&uhid->report_lock);
+	if (ret) {
+		kfree(ev);
+		return ret;
+	}
+
+	/* this _always_ takes ownership of @ev */
+	ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.set_report.id);
+	if (ret)
+		goto unlock;
+
+	if (uhid->report_buf.u.set_report_reply.err)
+		ret = -EIO;
+	else
+		ret = count;
+
+unlock:
+	mutex_unlock(&uhid->report_lock);
+	return ret;
+}
+
+static int uhid_hid_raw_request(struct hid_device *hid, unsigned char reportnum,
+				__u8 *buf, size_t len, unsigned char rtype,
+				int reqtype)
+{
+	u8 u_rtype;
+
+	switch (rtype) {
+	case HID_FEATURE_REPORT:
+		u_rtype = UHID_FEATURE_REPORT;
+		break;
+	case HID_OUTPUT_REPORT:
+		u_rtype = UHID_OUTPUT_REPORT;
+		break;
+	case HID_INPUT_REPORT:
+		u_rtype = UHID_INPUT_REPORT;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	switch (reqtype) {
+	case HID_REQ_GET_REPORT:
+		return uhid_hid_get_report(hid, reportnum, buf, len, u_rtype);
+	case HID_REQ_SET_REPORT:
+		return uhid_hid_set_report(hid, reportnum, buf, len, u_rtype);
+	default:
+		return -EIO;
+	}
+}
+
+static int uhid_hid_output_raw(struct hid_device *hid, __u8 *buf, size_t count,
+			       unsigned char report_type)
+{
+	struct uhid_device *uhid = hid->driver_data;
+	__u8 rtype;
+	unsigned long flags;
+	struct uhid_event *ev;
+
+	switch (report_type) {
+	case HID_FEATURE_REPORT:
+		rtype = UHID_FEATURE_REPORT;
+		break;
+	case HID_OUTPUT_REPORT:
+		rtype = UHID_OUTPUT_REPORT;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (count < 1 || count > UHID_DATA_MAX)
+		return -EINVAL;
+
+	ev = kzalloc_obj(*ev);
+	if (!ev)
+		return -ENOMEM;
+
+	ev->type = UHID_OUTPUT;
+	ev->u.output.size = count;
+	ev->u.output.rtype = rtype;
+	memcpy(ev->u.output.data, buf, count);
+
+	spin_lock_irqsave(&uhid->qlock, flags);
+	uhid_queue(uhid, ev);
+	spin_unlock_irqrestore(&uhid->qlock, flags);
+
+	return count;
+}
+
+static int uhid_hid_output_report(struct hid_device *hid, __u8 *buf,
+				  size_t count)
+{
+	return uhid_hid_output_raw(hid, buf, count, HID_OUTPUT_REPORT);
+}
+
+static const struct hid_ll_driver uhid_hid_driver = {
+	.start = uhid_hid_start,
+	.stop = uhid_hid_stop,
+	.open = uhid_hid_open,
+	.close = uhid_hid_close,
+	.parse = uhid_hid_parse,
+	.raw_request = uhid_hid_raw_request,
+	.output_report = uhid_hid_output_report,
+	.max_buffer_size = UHID_DATA_MAX,
+};
+
+#ifdef CONFIG_COMPAT
+
+/* Apparently we haven't stepped on these rakes enough times yet. */
+struct uhid_create_req_compat {
+	__u8 name[128];
+	__u8 phys[64];
+	__u8 uniq[64];
+
+	compat_uptr_t rd_data;
+	__u16 rd_size;
+
+	__u16 bus;
+	__u32 vendor;
+	__u32 product;
+	__u32 version;
+	__u32 country;
+} __attribute__((__packed__));
+
+static int uhid_event_from_user(const char __user *buffer, size_t len,
+				struct uhid_event *event)
+{
+	if (in_compat_syscall()) {
+		u32 type;
+
+		if (get_user(type, buffer))
+			return -EFAULT;
+
+		if (type == UHID_CREATE) {
+			/*
+			 * This is our messed up request with compat pointer.
+			 * It is largish (more than 256 bytes) so we better
+			 * allocate it from the heap.
+			 */
+			struct uhid_create_req_compat *compat;
+
+			compat = kzalloc_obj(*compat);
+			if (!compat)
+				return -ENOMEM;
+
+			buffer += sizeof(type);
+			len -= sizeof(type);
+			if (copy_from_user(compat, buffer,
+					   min(len, sizeof(*compat)))) {
+				kfree(compat);
+				return -EFAULT;
+			}
+
+			/* Shuffle the data over to proper structure */
+			event->type = type;
+
+			memcpy(event->u.create.name, compat->name,
+				sizeof(compat->name));
+			memcpy(event->u.create.phys, compat->phys,
+				sizeof(compat->phys));
+			memcpy(event->u.create.uniq, compat->uniq,
+				sizeof(compat->uniq));
+
+			event->u.create.rd_data = compat_ptr(compat->rd_data);
+			event->u.create.rd_size = compat->rd_size;
+
+			event->u.create.bus = compat->bus;
+			event->u.create.vendor = compat->vendor;
+			event->u.create.product = compat->product;
+			event->u.create.version = compat->version;
+			event->u.create.country = compat->country;
+
+			kfree(compat);
+			return 0;
+		}
+		/* All others can be copied directly */
+	}
+
+	if (copy_from_user(event, buffer, min(len, sizeof(*event))))
+		return -EFAULT;
+
+	return 0;
+}
+#else
+static int uhid_event_from_user(const char __user *buffer, size_t len,
+				struct uhid_event *event)
+{
+	if (copy_from_user(event, buffer, min(len, sizeof(*event))))
+		return -EFAULT;
+
+	return 0;
+}
+#endif
+
+static int uhid_dev_create2(struct uhid_device *uhid,
+			    const struct uhid_event *ev)
+{
+	struct hid_device *hid;
+	size_t rd_size;
+	void *rd_data;
+	int ret;
+
+	if (uhid->hid)
+		return -EALREADY;
+
+	rd_size = ev->u.create2.rd_size;
+	if (rd_size <= 0 || rd_size > HID_MAX_DESCRIPTOR_SIZE)
+		return -EINVAL;
+
+	rd_data = kmemdup(ev->u.create2.rd_data, rd_size, GFP_KERNEL);
+	if (!rd_data)
+		return -ENOMEM;
+
+	uhid->rd_size = rd_size;
+	uhid->rd_data = rd_data;
+
+	hid = hid_allocate_device();
+	if (IS_ERR(hid)) {
+		ret = PTR_ERR(hid);
+		goto err_free;
+	}
+
+	BUILD_BUG_ON(sizeof(hid->name) != sizeof(ev->u.create2.name));
+	strscpy(hid->name, ev->u.create2.name, sizeof(hid->name));
+	BUILD_BUG_ON(sizeof(hid->phys) != sizeof(ev->u.create2.phys));
+	strscpy(hid->phys, ev->u.create2.phys, sizeof(hid->phys));
+	BUILD_BUG_ON(sizeof(hid->uniq) != sizeof(ev->u.create2.uniq));
+	strscpy(hid->uniq, ev->u.create2.uniq, sizeof(hid->uniq));
+
+	hid->ll_driver = &uhid_hid_driver;
+	hid->bus = ev->u.create2.bus;
+	hid->vendor = ev->u.create2.vendor;
+	hid->product = ev->u.create2.product;
+	hid->version = ev->u.create2.version;
+	hid->country = ev->u.create2.country;
+	hid->driver_data = uhid;
+	hid->dev.parent = uhid_misc.this_device;
+
+	uhid->hid = hid;
+	uhid->running = true;
+
+	/* Adding of a HID device is done through a worker, to allow HID drivers
+	 * which use feature requests during .probe to work, without they would
+	 * be blocked on devlock, which is held by uhid_char_write.
+	 */
+	schedule_work(&uhid->worker);
+
+	return 0;
+
+err_free:
+	kfree(uhid->rd_data);
+	uhid->rd_data = NULL;
+	uhid->rd_size = 0;
+	return ret;
+}
+
+static int uhid_dev_create(struct uhid_device *uhid,
+			   struct uhid_event *ev)
+{
+	struct uhid_create_req orig;
+
+	orig = ev->u.create;
+
+	if (orig.rd_size <= 0 || orig.rd_size > HID_MAX_DESCRIPTOR_SIZE)
+		return -EINVAL;
+	if (copy_from_user(&ev->u.create2.rd_data, orig.rd_data, orig.rd_size))
+		return -EFAULT;
+
+	memcpy(ev->u.create2.name, orig.name, sizeof(orig.name));
+	memcpy(ev->u.create2.phys, orig.phys, sizeof(orig.phys));
+	memcpy(ev->u.create2.uniq, orig.uniq, sizeof(orig.uniq));
+	ev->u.create2.rd_size = orig.rd_size;
+	ev->u.create2.bus = orig.bus;
+	ev->u.create2.vendor = orig.vendor;
+	ev->u.create2.product = orig.product;
+	ev->u.create2.version = orig.version;
+	ev->u.create2.country = orig.country;
+
+	return uhid_dev_create2(uhid, ev);
+}
+
+static int uhid_dev_destroy(struct uhid_device *uhid)
+{
+	if (!uhid->hid)
+		return -EINVAL;
+
+	WRITE_ONCE(uhid->running, false);
+	wake_up_interruptible(&uhid->report_wait);
+
+	cancel_work_sync(&uhid->worker);
+
+	hid_destroy_device(uhid->hid);
+	uhid->hid = NULL;
+	kfree(uhid->rd_data);
+
+	return 0;
+}
+
+static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
+{
+	if (!READ_ONCE(uhid->running))
+		return -EINVAL;
+
+	hid_safe_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data, UHID_DATA_MAX,
+			      min_t(size_t, ev->u.input.size, UHID_DATA_MAX), 0);
+
+	return 0;
+}
+
+static int uhid_dev_input2(struct uhid_device *uhid, struct uhid_event *ev)
+{
+	if (!READ_ONCE(uhid->running))
+		return -EINVAL;
+
+	hid_safe_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input2.data, UHID_DATA_MAX,
+			      min_t(size_t, ev->u.input2.size, UHID_DATA_MAX), 0);
+
+	return 0;
+}
+
+static int uhid_dev_get_report_reply(struct uhid_device *uhid,
+				     struct uhid_event *ev)
+{
+	if (!READ_ONCE(uhid->running))
+		return -EINVAL;
+
+	uhid_report_wake_up(uhid, ev->u.get_report_reply.id, ev);
+	return 0;
+}
+
+static int uhid_dev_set_report_reply(struct uhid_device *uhid,
+				     struct uhid_event *ev)
+{
+	if (!READ_ONCE(uhid->running))
+		return -EINVAL;
+
+	uhid_report_wake_up(uhid, ev->u.set_report_reply.id, ev);
+	return 0;
+}
+
+static int uhid_char_open(struct inode *inode, struct file *file)
+{
+	struct uhid_device *uhid;
+
+	uhid = kzalloc_obj(*uhid);
+	if (!uhid)
+		return -ENOMEM;
+
+	mutex_init(&uhid->devlock);
+	mutex_init(&uhid->report_lock);
+	spin_lock_init(&uhid->qlock);
+	init_waitqueue_head(&uhid->waitq);
+	init_waitqueue_head(&uhid->report_wait);
+	uhid->running = false;
+	INIT_WORK(&uhid->worker, uhid_device_add_worker);
+
+	file->private_data = uhid;
+	stream_open(inode, file);
+
+	return 0;
+}
+
+static int uhid_char_release(struct inode *inode, struct file *file)
+{
+	struct uhid_device *uhid = file->private_data;
+	unsigned int i;
+
+	uhid_dev_destroy(uhid);
+
+	for (i = 0; i < UHID_BUFSIZE; ++i)
+		kfree(uhid->outq[i]);
+
+	kfree(uhid);
+
+	return 0;
+}
+
+static ssize_t uhid_char_read(struct file *file, char __user *buffer,
+				size_t count, loff_t *ppos)
+{
+	struct uhid_device *uhid = file->private_data;
+	int ret;
+	unsigned long flags;
+	size_t len;
+
+	/* they need at least the "type" member of uhid_event */
+	if (count < sizeof(__u32))
+		return -EINVAL;
+
+try_again:
+	if (file->f_flags & O_NONBLOCK) {
+		if (uhid->head == uhid->tail)
+			return -EAGAIN;
+	} else {
+		ret = wait_event_interruptible(uhid->waitq,
+						uhid->head != uhid->tail);
+		if (ret)
+			return ret;
+	}
+
+	ret = mutex_lock_interruptible(&uhid->devlock);
+	if (ret)
+		return ret;
+
+	if (uhid->head == uhid->tail) {
+		mutex_unlock(&uhid->devlock);
+		goto try_again;
+	} else {
+		len = min(count, sizeof(**uhid->outq));
+		if (copy_to_user(buffer, uhid->outq[uhid->tail], len)) {
+			ret = -EFAULT;
+		} else {
+			kfree(uhid->outq[uhid->tail]);
+			uhid->outq[uhid->tail] = NULL;
+
+			spin_lock_irqsave(&uhid->qlock, flags);
+			uhid->tail = (uhid->tail + 1) % UHID_BUFSIZE;
+			spin_unlock_irqrestore(&uhid->qlock, flags);
+		}
+	}
+
+	mutex_unlock(&uhid->devlock);
+	return ret ? ret : len;
+}
+
+static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
+				size_t count, loff_t *ppos)
+{
+	struct uhid_device *uhid = file->private_data;
+	int ret;
+	size_t len;
+
+	/* we need at least the "type" member of uhid_event */
+	if (count < sizeof(__u32))
+		return -EINVAL;
+
+	ret = mutex_lock_interruptible(&uhid->devlock);
+	if (ret)
+		return ret;
+
+	memset(&uhid->input_buf, 0, sizeof(uhid->input_buf));
+	len = min(count, sizeof(uhid->input_buf));
+
+	ret = uhid_event_from_user(buffer, len, &uhid->input_buf);
+	if (ret)
+		goto unlock;
+
+	switch (uhid->input_buf.type) {
+	case UHID_CREATE:
+		/*
+		 * 'struct uhid_create_req' contains a __user pointer which is
+		 * copied from, so it's unsafe to allow this with elevated
+		 * privileges (e.g. from a setuid binary) or via kernel_write().
+		 */
+		if (file->f_cred != current_cred()) {
+			pr_err_once("UHID_CREATE from different security context by process %d (%s), this is not allowed.\n",
+				    task_tgid_vnr(current), current->comm);
+			ret = -EACCES;
+			goto unlock;
+		}
+		ret = uhid_dev_create(uhid, &uhid->input_buf);
+		break;
+	case UHID_CREATE2:
+		ret = uhid_dev_create2(uhid, &uhid->input_buf);
+		break;
+	case UHID_DESTROY:
+		ret = uhid_dev_destroy(uhid);
+		break;
+	case UHID_INPUT:
+		ret = uhid_dev_input(uhid, &uhid->input_buf);
+		break;
+	case UHID_INPUT2:
+		ret = uhid_dev_input2(uhid, &uhid->input_buf);
+		break;
+	case UHID_GET_REPORT_REPLY:
+		ret = uhid_dev_get_report_reply(uhid, &uhid->input_buf);
+		break;
+	case UHID_SET_REPORT_REPLY:
+		ret = uhid_dev_set_report_reply(uhid, &uhid->input_buf);
+		break;
+	default:
+		ret = -EOPNOTSUPP;
+	}
+
+unlock:
+	mutex_unlock(&uhid->devlock);
+
+	/* return "count" not "len" to not confuse the caller */
+	return ret ? ret : count;
+}
+
+static __poll_t uhid_char_poll(struct file *file, poll_table *wait)
+{
+	struct uhid_device *uhid = file->private_data;
+	__poll_t mask = EPOLLOUT | EPOLLWRNORM; /* uhid is always writable */
+
+	poll_wait(file, &uhid->waitq, wait);
+
+	if (uhid->head != uhid->tail)
+		mask |= EPOLLIN | EPOLLRDNORM;
+
+	return mask;
+}
+
+static const struct file_operations uhid_fops = {
+	.owner		= THIS_MODULE,
+	.open		= uhid_char_open,
+	.release	= uhid_char_release,
+	.read		= uhid_char_read,
+	.write		= uhid_char_write,
+	.poll		= uhid_char_poll,
+};
+
+static struct miscdevice uhid_misc = {
+	.fops		= &uhid_fops,
+	.minor		= UHID_MINOR,
+	.name		= UHID_NAME,
+};
+module_misc_device(uhid_misc);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("David Herrmann <dh.herrmann@gmail.com>");
+MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");
+MODULE_ALIAS_MISCDEV(UHID_MINOR);
+MODULE_ALIAS("devname:" UHID_NAME);