1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * User-space I/O driver support for HID subsystem
4 * Copyright (c) 2012 David Herrmann
10 #include <linux/atomic.h>
11 #include <linux/compat.h>
12 #include <linux/cred.h>
13 #include <linux/device.h>
15 #include <linux/hid.h>
16 #include <linux/input.h>
17 #include <linux/miscdevice.h>
18 #include <linux/module.h>
19 #include <linux/mutex.h>
20 #include <linux/poll.h>
21 #include <linux/sched.h>
22 #include <linux/spinlock.h>
23 #include <linux/uhid.h>
24 #include <linux/wait.h>
26 #define UHID_NAME "uhid"
27 #define UHID_BUFSIZE 32
36 struct hid_device *hid;
37 struct uhid_event input_buf;
39 wait_queue_head_t waitq;
43 struct uhid_event *outq[UHID_BUFSIZE];
45 /* blocking GET_REPORT support; state changes protected by qlock */
46 struct mutex report_lock;
47 wait_queue_head_t report_wait;
51 struct uhid_event report_buf;
52 struct work_struct worker;
55 static struct miscdevice uhid_misc;
57 static void uhid_device_add_worker(struct work_struct *work)
59 struct uhid_device *uhid = container_of(work, struct uhid_device, worker);
62 ret = hid_add_device(uhid->hid);
64 hid_err(uhid->hid, "Cannot register HID device: error %d\n", ret);
66 hid_destroy_device(uhid->hid);
68 uhid->running = false;
72 static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
76 newhead = (uhid->head + 1) % UHID_BUFSIZE;
78 if (newhead != uhid->tail) {
79 uhid->outq[uhid->head] = ev;
81 wake_up_interruptible(&uhid->waitq);
83 hid_warn(uhid->hid, "Output queue is full\n");
88 static int uhid_queue_event(struct uhid_device *uhid, __u32 event)
91 struct uhid_event *ev;
93 ev = kzalloc(sizeof(*ev), GFP_KERNEL);
99 spin_lock_irqsave(&uhid->qlock, flags);
100 uhid_queue(uhid, ev);
101 spin_unlock_irqrestore(&uhid->qlock, flags);
106 static int uhid_hid_start(struct hid_device *hid)
108 struct uhid_device *uhid = hid->driver_data;
109 struct uhid_event *ev;
112 ev = kzalloc(sizeof(*ev), GFP_KERNEL);
116 ev->type = UHID_START;
118 if (hid->report_enum[HID_FEATURE_REPORT].numbered)
119 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_FEATURE_REPORTS;
120 if (hid->report_enum[HID_OUTPUT_REPORT].numbered)
121 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_OUTPUT_REPORTS;
122 if (hid->report_enum[HID_INPUT_REPORT].numbered)
123 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_INPUT_REPORTS;
125 spin_lock_irqsave(&uhid->qlock, flags);
126 uhid_queue(uhid, ev);
127 spin_unlock_irqrestore(&uhid->qlock, flags);
132 static void uhid_hid_stop(struct hid_device *hid)
134 struct uhid_device *uhid = hid->driver_data;
137 uhid_queue_event(uhid, UHID_STOP);
140 static int uhid_hid_open(struct hid_device *hid)
142 struct uhid_device *uhid = hid->driver_data;
144 return uhid_queue_event(uhid, UHID_OPEN);
147 static void uhid_hid_close(struct hid_device *hid)
149 struct uhid_device *uhid = hid->driver_data;
151 uhid_queue_event(uhid, UHID_CLOSE);
154 static int uhid_hid_parse(struct hid_device *hid)
156 struct uhid_device *uhid = hid->driver_data;
158 return hid_parse_report(hid, uhid->rd_data, uhid->rd_size);
161 /* must be called with report_lock held */
162 static int __uhid_report_queue_and_wait(struct uhid_device *uhid,
163 struct uhid_event *ev,
169 spin_lock_irqsave(&uhid->qlock, flags);
170 *report_id = ++uhid->report_id;
171 uhid->report_type = ev->type + 1;
172 uhid->report_running = true;
173 uhid_queue(uhid, ev);
174 spin_unlock_irqrestore(&uhid->qlock, flags);
176 ret = wait_event_interruptible_timeout(uhid->report_wait,
177 !uhid->report_running || !uhid->running,
179 if (!ret || !uhid->running || uhid->report_running)
186 uhid->report_running = false;
191 static void uhid_report_wake_up(struct uhid_device *uhid, u32 id,
192 const struct uhid_event *ev)
196 spin_lock_irqsave(&uhid->qlock, flags);
198 /* id for old report; drop it silently */
199 if (uhid->report_type != ev->type || uhid->report_id != id)
201 if (!uhid->report_running)
204 memcpy(&uhid->report_buf, ev, sizeof(*ev));
205 uhid->report_running = false;
206 wake_up_interruptible(&uhid->report_wait);
209 spin_unlock_irqrestore(&uhid->qlock, flags);
212 static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
213 u8 *buf, size_t count, u8 rtype)
215 struct uhid_device *uhid = hid->driver_data;
216 struct uhid_get_report_reply_req *req;
217 struct uhid_event *ev;
223 ev = kzalloc(sizeof(*ev), GFP_KERNEL);
227 ev->type = UHID_GET_REPORT;
228 ev->u.get_report.rnum = rnum;
229 ev->u.get_report.rtype = rtype;
231 ret = mutex_lock_interruptible(&uhid->report_lock);
237 /* this _always_ takes ownership of @ev */
238 ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.get_report.id);
242 req = &uhid->report_buf.u.get_report_reply;
246 ret = min3(count, (size_t)req->size, (size_t)UHID_DATA_MAX);
247 memcpy(buf, req->data, ret);
251 mutex_unlock(&uhid->report_lock);
255 static int uhid_hid_set_report(struct hid_device *hid, unsigned char rnum,
256 const u8 *buf, size_t count, u8 rtype)
258 struct uhid_device *uhid = hid->driver_data;
259 struct uhid_event *ev;
262 if (!uhid->running || count > UHID_DATA_MAX)
265 ev = kzalloc(sizeof(*ev), GFP_KERNEL);
269 ev->type = UHID_SET_REPORT;
270 ev->u.set_report.rnum = rnum;
271 ev->u.set_report.rtype = rtype;
272 ev->u.set_report.size = count;
273 memcpy(ev->u.set_report.data, buf, count);
275 ret = mutex_lock_interruptible(&uhid->report_lock);
281 /* this _always_ takes ownership of @ev */
282 ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.set_report.id);
286 if (uhid->report_buf.u.set_report_reply.err)
292 mutex_unlock(&uhid->report_lock);
296 static int uhid_hid_raw_request(struct hid_device *hid, unsigned char reportnum,
297 __u8 *buf, size_t len, unsigned char rtype,
303 case HID_FEATURE_REPORT:
304 u_rtype = UHID_FEATURE_REPORT;
306 case HID_OUTPUT_REPORT:
307 u_rtype = UHID_OUTPUT_REPORT;
309 case HID_INPUT_REPORT:
310 u_rtype = UHID_INPUT_REPORT;
317 case HID_REQ_GET_REPORT:
318 return uhid_hid_get_report(hid, reportnum, buf, len, u_rtype);
319 case HID_REQ_SET_REPORT:
320 return uhid_hid_set_report(hid, reportnum, buf, len, u_rtype);
326 static int uhid_hid_output_raw(struct hid_device *hid, __u8 *buf, size_t count,
327 unsigned char report_type)
329 struct uhid_device *uhid = hid->driver_data;
332 struct uhid_event *ev;
334 switch (report_type) {
335 case HID_FEATURE_REPORT:
336 rtype = UHID_FEATURE_REPORT;
338 case HID_OUTPUT_REPORT:
339 rtype = UHID_OUTPUT_REPORT;
345 if (count < 1 || count > UHID_DATA_MAX)
348 ev = kzalloc(sizeof(*ev), GFP_KERNEL);
352 ev->type = UHID_OUTPUT;
353 ev->u.output.size = count;
354 ev->u.output.rtype = rtype;
355 memcpy(ev->u.output.data, buf, count);
357 spin_lock_irqsave(&uhid->qlock, flags);
358 uhid_queue(uhid, ev);
359 spin_unlock_irqrestore(&uhid->qlock, flags);
364 static int uhid_hid_output_report(struct hid_device *hid, __u8 *buf,
367 return uhid_hid_output_raw(hid, buf, count, HID_OUTPUT_REPORT);
370 struct hid_ll_driver uhid_hid_driver = {
371 .start = uhid_hid_start,
372 .stop = uhid_hid_stop,
373 .open = uhid_hid_open,
374 .close = uhid_hid_close,
375 .parse = uhid_hid_parse,
376 .raw_request = uhid_hid_raw_request,
377 .output_report = uhid_hid_output_report,
379 EXPORT_SYMBOL_GPL(uhid_hid_driver);
383 /* Apparently we haven't stepped on these rakes enough times yet. */
384 struct uhid_create_req_compat {
389 compat_uptr_t rd_data;
397 } __attribute__((__packed__));
399 static int uhid_event_from_user(const char __user *buffer, size_t len,
400 struct uhid_event *event)
402 if (in_compat_syscall()) {
405 if (get_user(type, buffer))
408 if (type == UHID_CREATE) {
410 * This is our messed up request with compat pointer.
411 * It is largish (more than 256 bytes) so we better
412 * allocate it from the heap.
414 struct uhid_create_req_compat *compat;
416 compat = kzalloc(sizeof(*compat), GFP_KERNEL);
420 buffer += sizeof(type);
422 if (copy_from_user(compat, buffer,
423 min(len, sizeof(*compat)))) {
428 /* Shuffle the data over to proper structure */
431 memcpy(event->u.create.name, compat->name,
432 sizeof(compat->name));
433 memcpy(event->u.create.phys, compat->phys,
434 sizeof(compat->phys));
435 memcpy(event->u.create.uniq, compat->uniq,
436 sizeof(compat->uniq));
438 event->u.create.rd_data = compat_ptr(compat->rd_data);
439 event->u.create.rd_size = compat->rd_size;
441 event->u.create.bus = compat->bus;
442 event->u.create.vendor = compat->vendor;
443 event->u.create.product = compat->product;
444 event->u.create.version = compat->version;
445 event->u.create.country = compat->country;
450 /* All others can be copied directly */
453 if (copy_from_user(event, buffer, min(len, sizeof(*event))))
459 static int uhid_event_from_user(const char __user *buffer, size_t len,
460 struct uhid_event *event)
462 if (copy_from_user(event, buffer, min(len, sizeof(*event))))
469 static int uhid_dev_create2(struct uhid_device *uhid,
470 const struct uhid_event *ev)
472 struct hid_device *hid;
480 rd_size = ev->u.create2.rd_size;
481 if (rd_size <= 0 || rd_size > HID_MAX_DESCRIPTOR_SIZE)
484 rd_data = kmemdup(ev->u.create2.rd_data, rd_size, GFP_KERNEL);
488 uhid->rd_size = rd_size;
489 uhid->rd_data = rd_data;
491 hid = hid_allocate_device();
497 /* @hid is zero-initialized, strncpy() is correct, strlcpy() not */
498 len = min(sizeof(hid->name), sizeof(ev->u.create2.name)) - 1;
499 strncpy(hid->name, ev->u.create2.name, len);
500 len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys)) - 1;
501 strncpy(hid->phys, ev->u.create2.phys, len);
502 len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq)) - 1;
503 strncpy(hid->uniq, ev->u.create2.uniq, len);
505 hid->ll_driver = &uhid_hid_driver;
506 hid->bus = ev->u.create2.bus;
507 hid->vendor = ev->u.create2.vendor;
508 hid->product = ev->u.create2.product;
509 hid->version = ev->u.create2.version;
510 hid->country = ev->u.create2.country;
511 hid->driver_data = uhid;
512 hid->dev.parent = uhid_misc.this_device;
515 uhid->running = true;
517 /* Adding of a HID device is done through a worker, to allow HID drivers
518 * which use feature requests during .probe to work, without they would
519 * be blocked on devlock, which is held by uhid_char_write.
521 schedule_work(&uhid->worker);
526 kfree(uhid->rd_data);
527 uhid->rd_data = NULL;
532 static int uhid_dev_create(struct uhid_device *uhid,
533 struct uhid_event *ev)
535 struct uhid_create_req orig;
539 if (orig.rd_size <= 0 || orig.rd_size > HID_MAX_DESCRIPTOR_SIZE)
541 if (copy_from_user(&ev->u.create2.rd_data, orig.rd_data, orig.rd_size))
544 memcpy(ev->u.create2.name, orig.name, sizeof(orig.name));
545 memcpy(ev->u.create2.phys, orig.phys, sizeof(orig.phys));
546 memcpy(ev->u.create2.uniq, orig.uniq, sizeof(orig.uniq));
547 ev->u.create2.rd_size = orig.rd_size;
548 ev->u.create2.bus = orig.bus;
549 ev->u.create2.vendor = orig.vendor;
550 ev->u.create2.product = orig.product;
551 ev->u.create2.version = orig.version;
552 ev->u.create2.country = orig.country;
554 return uhid_dev_create2(uhid, ev);
557 static int uhid_dev_destroy(struct uhid_device *uhid)
562 uhid->running = false;
563 wake_up_interruptible(&uhid->report_wait);
565 cancel_work_sync(&uhid->worker);
567 hid_destroy_device(uhid->hid);
568 kfree(uhid->rd_data);
573 static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
578 hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data,
579 min_t(size_t, ev->u.input.size, UHID_DATA_MAX), 0);
584 static int uhid_dev_input2(struct uhid_device *uhid, struct uhid_event *ev)
589 hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input2.data,
590 min_t(size_t, ev->u.input2.size, UHID_DATA_MAX), 0);
595 static int uhid_dev_get_report_reply(struct uhid_device *uhid,
596 struct uhid_event *ev)
601 uhid_report_wake_up(uhid, ev->u.get_report_reply.id, ev);
605 static int uhid_dev_set_report_reply(struct uhid_device *uhid,
606 struct uhid_event *ev)
611 uhid_report_wake_up(uhid, ev->u.set_report_reply.id, ev);
615 static int uhid_char_open(struct inode *inode, struct file *file)
617 struct uhid_device *uhid;
619 uhid = kzalloc(sizeof(*uhid), GFP_KERNEL);
623 mutex_init(&uhid->devlock);
624 mutex_init(&uhid->report_lock);
625 spin_lock_init(&uhid->qlock);
626 init_waitqueue_head(&uhid->waitq);
627 init_waitqueue_head(&uhid->report_wait);
628 uhid->running = false;
629 INIT_WORK(&uhid->worker, uhid_device_add_worker);
631 file->private_data = uhid;
632 stream_open(inode, file);
637 static int uhid_char_release(struct inode *inode, struct file *file)
639 struct uhid_device *uhid = file->private_data;
642 uhid_dev_destroy(uhid);
644 for (i = 0; i < UHID_BUFSIZE; ++i)
645 kfree(uhid->outq[i]);
652 static ssize_t uhid_char_read(struct file *file, char __user *buffer,
653 size_t count, loff_t *ppos)
655 struct uhid_device *uhid = file->private_data;
660 /* they need at least the "type" member of uhid_event */
661 if (count < sizeof(__u32))
665 if (file->f_flags & O_NONBLOCK) {
666 if (uhid->head == uhid->tail)
669 ret = wait_event_interruptible(uhid->waitq,
670 uhid->head != uhid->tail);
675 ret = mutex_lock_interruptible(&uhid->devlock);
679 if (uhid->head == uhid->tail) {
680 mutex_unlock(&uhid->devlock);
683 len = min(count, sizeof(**uhid->outq));
684 if (copy_to_user(buffer, uhid->outq[uhid->tail], len)) {
687 kfree(uhid->outq[uhid->tail]);
688 uhid->outq[uhid->tail] = NULL;
690 spin_lock_irqsave(&uhid->qlock, flags);
691 uhid->tail = (uhid->tail + 1) % UHID_BUFSIZE;
692 spin_unlock_irqrestore(&uhid->qlock, flags);
696 mutex_unlock(&uhid->devlock);
697 return ret ? ret : len;
700 static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
701 size_t count, loff_t *ppos)
703 struct uhid_device *uhid = file->private_data;
707 /* we need at least the "type" member of uhid_event */
708 if (count < sizeof(__u32))
711 ret = mutex_lock_interruptible(&uhid->devlock);
715 memset(&uhid->input_buf, 0, sizeof(uhid->input_buf));
716 len = min(count, sizeof(uhid->input_buf));
718 ret = uhid_event_from_user(buffer, len, &uhid->input_buf);
722 switch (uhid->input_buf.type) {
725 * 'struct uhid_create_req' contains a __user pointer which is
726 * copied from, so it's unsafe to allow this with elevated
727 * privileges (e.g. from a setuid binary) or via kernel_write().
729 if (file->f_cred != current_cred() || uaccess_kernel()) {
730 pr_err_once("UHID_CREATE from different security context by process %d (%s), this is not allowed.\n",
731 task_tgid_vnr(current), current->comm);
735 ret = uhid_dev_create(uhid, &uhid->input_buf);
738 ret = uhid_dev_create2(uhid, &uhid->input_buf);
741 ret = uhid_dev_destroy(uhid);
744 ret = uhid_dev_input(uhid, &uhid->input_buf);
747 ret = uhid_dev_input2(uhid, &uhid->input_buf);
749 case UHID_GET_REPORT_REPLY:
750 ret = uhid_dev_get_report_reply(uhid, &uhid->input_buf);
752 case UHID_SET_REPORT_REPLY:
753 ret = uhid_dev_set_report_reply(uhid, &uhid->input_buf);
760 mutex_unlock(&uhid->devlock);
762 /* return "count" not "len" to not confuse the caller */
763 return ret ? ret : count;
766 static __poll_t uhid_char_poll(struct file *file, poll_table *wait)
768 struct uhid_device *uhid = file->private_data;
769 __poll_t mask = EPOLLOUT | EPOLLWRNORM; /* uhid is always writable */
771 poll_wait(file, &uhid->waitq, wait);
773 if (uhid->head != uhid->tail)
774 mask |= EPOLLIN | EPOLLRDNORM;
779 static const struct file_operations uhid_fops = {
780 .owner = THIS_MODULE,
781 .open = uhid_char_open,
782 .release = uhid_char_release,
783 .read = uhid_char_read,
784 .write = uhid_char_write,
785 .poll = uhid_char_poll,
789 static struct miscdevice uhid_misc = {
794 module_misc_device(uhid_misc);
796 MODULE_LICENSE("GPL");
797 MODULE_AUTHOR("David Herrmann <dh.herrmann@gmail.com>");
798 MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");
799 MODULE_ALIAS_MISCDEV(UHID_MINOR);
800 MODULE_ALIAS("devname:" UHID_NAME);