drivers/hid/uhid.c

   1 /*
   2  * User-space I/O driver support for HID subsystem
   3  * Copyright (c) 2012 David Herrmann
   4  */
   5
   6 /*
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License as published by the Free
   9  * Software Foundation; either version 2 of the License, or (at your option)
  10  * any later version.
  11  */
  12
  13 #include <linux/atomic.h>
  14 #include <linux/compat.h>
  15 #include <linux/cred.h>
  16 #include <linux/device.h>
  17 #include <linux/fs.h>
  18 #include <linux/hid.h>
  19 #include <linux/input.h>
  20 #include <linux/miscdevice.h>
  21 #include <linux/module.h>
  22 #include <linux/mutex.h>
  23 #include <linux/poll.h>
  24 #include <linux/sched.h>
  25 #include <linux/spinlock.h>
  26 #include <linux/uhid.h>
  27 #include <linux/wait.h>
  28
  29 #define UHID_NAME       "uhid"
  30 #define UHID_BUFSIZE    32
  31
  32 struct uhid_device {
  33         struct mutex devlock;
  34         bool running;
  35
  36         __u8 *rd_data;
  37         uint rd_size;
  38
  39         struct hid_device *hid;
  40         struct uhid_event input_buf;
  41
  42         wait_queue_head_t waitq;
  43         spinlock_t qlock;
  44         __u8 head;
  45         __u8 tail;
  46         struct uhid_event *outq[UHID_BUFSIZE];
  47
  48         /* blocking GET_REPORT support; state changes protected by qlock */
  49         struct mutex report_lock;
  50         wait_queue_head_t report_wait;
  51         bool report_running;
  52         u32 report_id;
  53         u32 report_type;
  54         struct uhid_event report_buf;
  55         struct work_struct worker;
  56 };
  57
  58 static struct miscdevice uhid_misc;
  59
  60 static void uhid_device_add_worker(struct work_struct *work)
  61 {
  62         struct uhid_device *uhid = container_of(work, struct uhid_device, worker);
  63         int ret;
  64
  65         ret = hid_add_device(uhid->hid);
  66         if (ret) {
  67                 hid_err(uhid->hid, "Cannot register HID device: error %d\n", ret);
  68
  69                 hid_destroy_device(uhid->hid);
  70                 uhid->hid = NULL;
  71                 uhid->running = false;
  72         }
  73 }
  74
  75 static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
  76 {
  77         __u8 newhead;
  78
  79         newhead = (uhid->head + 1) % UHID_BUFSIZE;
  80
  81         if (newhead != uhid->tail) {
  82                 uhid->outq[uhid->head] = ev;
  83                 uhid->head = newhead;
  84                 wake_up_interruptible(&uhid->waitq);
  85         } else {
  86                 hid_warn(uhid->hid, "Output queue is full\n");
  87                 kfree(ev);
  88         }
  89 }
  90
  91 static int uhid_queue_event(struct uhid_device *uhid, __u32 event)
  92 {
  93         unsigned long flags;
  94         struct uhid_event *ev;
  95
  96         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
  97         if (!ev)
  98                 return -ENOMEM;
  99
 100         ev->type = event;
 101
 102         spin_lock_irqsave(&uhid->qlock, flags);
 103         uhid_queue(uhid, ev);
 104         spin_unlock_irqrestore(&uhid->qlock, flags);
 105
 106         return 0;
 107 }
 108
 109 static int uhid_hid_start(struct hid_device *hid)
 110 {
 111         struct uhid_device *uhid = hid->driver_data;
 112         struct uhid_event *ev;
 113         unsigned long flags;
 114
 115         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 116         if (!ev)
 117                 return -ENOMEM;
 118
 119         ev->type = UHID_START;
 120
 121         if (hid->report_enum[HID_FEATURE_REPORT].numbered)
 122                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_FEATURE_REPORTS;
 123         if (hid->report_enum[HID_OUTPUT_REPORT].numbered)
 124                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_OUTPUT_REPORTS;
 125         if (hid->report_enum[HID_INPUT_REPORT].numbered)
 126                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_INPUT_REPORTS;
 127
 128         spin_lock_irqsave(&uhid->qlock, flags);
 129         uhid_queue(uhid, ev);
 130         spin_unlock_irqrestore(&uhid->qlock, flags);
 131
 132         return 0;
 133 }
 134
 135 static void uhid_hid_stop(struct hid_device *hid)
 136 {
 137         struct uhid_device *uhid = hid->driver_data;
 138
 139         hid->claimed = 0;
 140         uhid_queue_event(uhid, UHID_STOP);
 141 }
 142
 143 static int uhid_hid_open(struct hid_device *hid)
 144 {
 145         struct uhid_device *uhid = hid->driver_data;
 146
 147         return uhid_queue_event(uhid, UHID_OPEN);
 148 }
 149
 150 static void uhid_hid_close(struct hid_device *hid)
 151 {
 152         struct uhid_device *uhid = hid->driver_data;
 153
 154         uhid_queue_event(uhid, UHID_CLOSE);
 155 }
 156
 157 static int uhid_hid_parse(struct hid_device *hid)
 158 {
 159         struct uhid_device *uhid = hid->driver_data;
 160
 161         return hid_parse_report(hid, uhid->rd_data, uhid->rd_size);
 162 }
 163
 164 /* must be called with report_lock held */
 165 static int __uhid_report_queue_and_wait(struct uhid_device *uhid,
 166                                         struct uhid_event *ev,
 167                                         __u32 *report_id)
 168 {
 169         unsigned long flags;
 170         int ret;
 171
 172         spin_lock_irqsave(&uhid->qlock, flags);
 173         *report_id = ++uhid->report_id;
 174         uhid->report_type = ev->type + 1;
 175         uhid->report_running = true;
 176         uhid_queue(uhid, ev);
 177         spin_unlock_irqrestore(&uhid->qlock, flags);
 178
 179         ret = wait_event_interruptible_timeout(uhid->report_wait,
 180                                 !uhid->report_running || !uhid->running,
 181                                 5 * HZ);
 182         if (!ret || !uhid->running || uhid->report_running)
 183                 ret = -EIO;
 184         else if (ret < 0)
 185                 ret = -ERESTARTSYS;
 186         else
 187                 ret = 0;
 188
 189         uhid->report_running = false;
 190
 191         return ret;
 192 }
 193
 194 static void uhid_report_wake_up(struct uhid_device *uhid, u32 id,
 195                                 const struct uhid_event *ev)
 196 {
 197         unsigned long flags;
 198
 199         spin_lock_irqsave(&uhid->qlock, flags);
 200
 201         /* id for old report; drop it silently */
 202         if (uhid->report_type != ev->type || uhid->report_id != id)
 203                 goto unlock;
 204         if (!uhid->report_running)
 205                 goto unlock;
 206
 207         memcpy(&uhid->report_buf, ev, sizeof(*ev));
 208         uhid->report_running = false;
 209         wake_up_interruptible(&uhid->report_wait);
 210
 211 unlock:
 212         spin_unlock_irqrestore(&uhid->qlock, flags);
 213 }
 214
 215 static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
 216                                u8 *buf, size_t count, u8 rtype)
 217 {
 218         struct uhid_device *uhid = hid->driver_data;
 219         struct uhid_get_report_reply_req *req;
 220         struct uhid_event *ev;
 221         int ret;
 222
 223         if (!uhid->running)
 224                 return -EIO;
 225
 226         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 227         if (!ev)
 228                 return -ENOMEM;
 229
 230         ev->type = UHID_GET_REPORT;
 231         ev->u.get_report.rnum = rnum;
 232         ev->u.get_report.rtype = rtype;
 233
 234         ret = mutex_lock_interruptible(&uhid->report_lock);
 235         if (ret) {
 236                 kfree(ev);
 237                 return ret;
 238         }
 239
 240         /* this _always_ takes ownership of @ev */
 241         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.get_report.id);
 242         if (ret)
 243                 goto unlock;
 244
 245         req = &uhid->report_buf.u.get_report_reply;
 246         if (req->err) {
 247                 ret = -EIO;
 248         } else {
 249                 ret = min3(count, (size_t)req->size, (size_t)UHID_DATA_MAX);
 250                 memcpy(buf, req->data, ret);
 251         }
 252
 253 unlock:
 254         mutex_unlock(&uhid->report_lock);
 255         return ret;
 256 }
 257
 258 static int uhid_hid_set_report(struct hid_device *hid, unsigned char rnum,
 259                                const u8 *buf, size_t count, u8 rtype)
 260 {
 261         struct uhid_device *uhid = hid->driver_data;
 262         struct uhid_event *ev;
 263         int ret;
 264
 265         if (!uhid->running || count > UHID_DATA_MAX)
 266                 return -EIO;
 267
 268         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 269         if (!ev)
 270                 return -ENOMEM;
 271
 272         ev->type = UHID_SET_REPORT;
 273         ev->u.set_report.rnum = rnum;
 274         ev->u.set_report.rtype = rtype;
 275         ev->u.set_report.size = count;
 276         memcpy(ev->u.set_report.data, buf, count);
 277
 278         ret = mutex_lock_interruptible(&uhid->report_lock);
 279         if (ret) {
 280                 kfree(ev);
 281                 return ret;
 282         }
 283
 284         /* this _always_ takes ownership of @ev */
 285         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.set_report.id);
 286         if (ret)
 287                 goto unlock;
 288
 289         if (uhid->report_buf.u.set_report_reply.err)
 290                 ret = -EIO;
 291         else
 292                 ret = count;
 293
 294 unlock:
 295         mutex_unlock(&uhid->report_lock);
 296         return ret;
 297 }
 298
 299 static int uhid_hid_raw_request(struct hid_device *hid, unsigned char reportnum,
 300                                 __u8 *buf, size_t len, unsigned char rtype,
 301                                 int reqtype)
 302 {
 303         u8 u_rtype;
 304
 305         switch (rtype) {
 306         case HID_FEATURE_REPORT:
 307                 u_rtype = UHID_FEATURE_REPORT;
 308                 break;
 309         case HID_OUTPUT_REPORT:
 310                 u_rtype = UHID_OUTPUT_REPORT;
 311                 break;
 312         case HID_INPUT_REPORT:
 313                 u_rtype = UHID_INPUT_REPORT;
 314                 break;
 315         default:
 316                 return -EINVAL;
 317         }
 318
 319         switch (reqtype) {
 320         case HID_REQ_GET_REPORT:
 321                 return uhid_hid_get_report(hid, reportnum, buf, len, u_rtype);
 322         case HID_REQ_SET_REPORT:
 323                 return uhid_hid_set_report(hid, reportnum, buf, len, u_rtype);
 324         default:
 325                 return -EIO;
 326         }
 327 }
 328
 329 static int uhid_hid_output_raw(struct hid_device *hid, __u8 *buf, size_t count,
 330                                unsigned char report_type)
 331 {
 332         struct uhid_device *uhid = hid->driver_data;
 333         __u8 rtype;
 334         unsigned long flags;
 335         struct uhid_event *ev;
 336
 337         switch (report_type) {
 338         case HID_FEATURE_REPORT:
 339                 rtype = UHID_FEATURE_REPORT;
 340                 break;
 341         case HID_OUTPUT_REPORT:
 342                 rtype = UHID_OUTPUT_REPORT;
 343                 break;
 344         default:
 345                 return -EINVAL;
 346         }
 347
 348         if (count < 1 || count > UHID_DATA_MAX)
 349                 return -EINVAL;
 350
 351         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 352         if (!ev)
 353                 return -ENOMEM;
 354
 355         ev->type = UHID_OUTPUT;
 356         ev->u.output.size = count;
 357         ev->u.output.rtype = rtype;
 358         memcpy(ev->u.output.data, buf, count);
 359
 360         spin_lock_irqsave(&uhid->qlock, flags);
 361         uhid_queue(uhid, ev);
 362         spin_unlock_irqrestore(&uhid->qlock, flags);
 363
 364         return count;
 365 }
 366
 367 static int uhid_hid_output_report(struct hid_device *hid, __u8 *buf,
 368                                   size_t count)
 369 {
 370         return uhid_hid_output_raw(hid, buf, count, HID_OUTPUT_REPORT);
 371 }
 372
 373 struct hid_ll_driver uhid_hid_driver = {
 374         .start = uhid_hid_start,
 375         .stop = uhid_hid_stop,
 376         .open = uhid_hid_open,
 377         .close = uhid_hid_close,
 378         .parse = uhid_hid_parse,
 379         .raw_request = uhid_hid_raw_request,
 380         .output_report = uhid_hid_output_report,
 381 };
 382 EXPORT_SYMBOL_GPL(uhid_hid_driver);
 383
 384 #ifdef CONFIG_COMPAT
 385
 386 /* Apparently we haven't stepped on these rakes enough times yet. */
 387 struct uhid_create_req_compat {
 388         __u8 name[128];
 389         __u8 phys[64];
 390         __u8 uniq[64];
 391
 392         compat_uptr_t rd_data;
 393         __u16 rd_size;
 394
 395         __u16 bus;
 396         __u32 vendor;
 397         __u32 product;
 398         __u32 version;
 399         __u32 country;
 400 } __attribute__((__packed__));
 401
 402 static int uhid_event_from_user(const char __user *buffer, size_t len,
 403                                 struct uhid_event *event)
 404 {
 405         if (in_compat_syscall()) {
 406                 u32 type;
 407
 408                 if (get_user(type, buffer))
 409                         return -EFAULT;
 410
 411                 if (type == UHID_CREATE) {
 412                         /*
 413                          * This is our messed up request with compat pointer.
 414                          * It is largish (more than 256 bytes) so we better
 415                          * allocate it from the heap.
 416                          */
 417                         struct uhid_create_req_compat *compat;
 418
 419                         compat = kzalloc(sizeof(*compat), GFP_KERNEL);
 420                         if (!compat)
 421                                 return -ENOMEM;
 422
 423                         buffer += sizeof(type);
 424                         len -= sizeof(type);
 425                         if (copy_from_user(compat, buffer,
 426                                            min(len, sizeof(*compat)))) {
 427                                 kfree(compat);
 428                                 return -EFAULT;
 429                         }
 430
 431                         /* Shuffle the data over to proper structure */
 432                         event->type = type;
 433
 434                         memcpy(event->u.create.name, compat->name,
 435                                 sizeof(compat->name));
 436                         memcpy(event->u.create.phys, compat->phys,
 437                                 sizeof(compat->phys));
 438                         memcpy(event->u.create.uniq, compat->uniq,
 439                                 sizeof(compat->uniq));
 440
 441                         event->u.create.rd_data = compat_ptr(compat->rd_data);
 442                         event->u.create.rd_size = compat->rd_size;
 443
 444                         event->u.create.bus = compat->bus;
 445                         event->u.create.vendor = compat->vendor;
 446                         event->u.create.product = compat->product;
 447                         event->u.create.version = compat->version;
 448                         event->u.create.country = compat->country;
 449
 450                         kfree(compat);
 451                         return 0;
 452                 }
 453                 /* All others can be copied directly */
 454         }
 455
 456         if (copy_from_user(event, buffer, min(len, sizeof(*event))))
 457                 return -EFAULT;
 458
 459         return 0;
 460 }
 461 #else
 462 static int uhid_event_from_user(const char __user *buffer, size_t len,
 463                                 struct uhid_event *event)
 464 {
 465         if (copy_from_user(event, buffer, min(len, sizeof(*event))))
 466                 return -EFAULT;
 467
 468         return 0;
 469 }
 470 #endif
 471
 472 static int uhid_dev_create2(struct uhid_device *uhid,
 473                             const struct uhid_event *ev)
 474 {
 475         struct hid_device *hid;
 476         size_t rd_size, len;
 477         void *rd_data;
 478         int ret;
 479
 480         if (uhid->running)
 481                 return -EALREADY;
 482
 483         rd_size = ev->u.create2.rd_size;
 484         if (rd_size <= 0 || rd_size > HID_MAX_DESCRIPTOR_SIZE)
 485                 return -EINVAL;
 486
 487         rd_data = kmemdup(ev->u.create2.rd_data, rd_size, GFP_KERNEL);
 488         if (!rd_data)
 489                 return -ENOMEM;
 490
 491         uhid->rd_size = rd_size;
 492         uhid->rd_data = rd_data;
 493
 494         hid = hid_allocate_device();
 495         if (IS_ERR(hid)) {
 496                 ret = PTR_ERR(hid);
 497                 goto err_free;
 498         }
 499
 500         /* @hid is zero-initialized, strncpy() is correct, strlcpy() not */
 501         len = min(sizeof(hid->name), sizeof(ev->u.create2.name)) - 1;
 502         strncpy(hid->name, ev->u.create2.name, len);
 503         len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys)) - 1;
 504         strncpy(hid->phys, ev->u.create2.phys, len);
 505         len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq)) - 1;
 506         strncpy(hid->uniq, ev->u.create2.uniq, len);
 507
 508         hid->ll_driver = &uhid_hid_driver;
 509         hid->bus = ev->u.create2.bus;
 510         hid->vendor = ev->u.create2.vendor;
 511         hid->product = ev->u.create2.product;
 512         hid->version = ev->u.create2.version;
 513         hid->country = ev->u.create2.country;
 514         hid->driver_data = uhid;
 515         hid->dev.parent = uhid_misc.this_device;
 516
 517         uhid->hid = hid;
 518         uhid->running = true;
 519
 520         /* Adding of a HID device is done through a worker, to allow HID drivers
 521          * which use feature requests during .probe to work, without they would
 522          * be blocked on devlock, which is held by uhid_char_write.
 523          */
 524         schedule_work(&uhid->worker);
 525
 526         return 0;
 527
 528 err_free:
 529         kfree(uhid->rd_data);
 530         uhid->rd_data = NULL;
 531         uhid->rd_size = 0;
 532         return ret;
 533 }
 534
 535 static int uhid_dev_create(struct uhid_device *uhid,
 536                            struct uhid_event *ev)
 537 {
 538         struct uhid_create_req orig;
 539
 540         orig = ev->u.create;
 541
 542         if (orig.rd_size <= 0 || orig.rd_size > HID_MAX_DESCRIPTOR_SIZE)
 543                 return -EINVAL;
 544         if (copy_from_user(&ev->u.create2.rd_data, orig.rd_data, orig.rd_size))
 545                 return -EFAULT;
 546
 547         memcpy(ev->u.create2.name, orig.name, sizeof(orig.name));
 548         memcpy(ev->u.create2.phys, orig.phys, sizeof(orig.phys));
 549         memcpy(ev->u.create2.uniq, orig.uniq, sizeof(orig.uniq));
 550         ev->u.create2.rd_size = orig.rd_size;
 551         ev->u.create2.bus = orig.bus;
 552         ev->u.create2.vendor = orig.vendor;
 553         ev->u.create2.product = orig.product;
 554         ev->u.create2.version = orig.version;
 555         ev->u.create2.country = orig.country;
 556
 557         return uhid_dev_create2(uhid, ev);
 558 }
 559
 560 static int uhid_dev_destroy(struct uhid_device *uhid)
 561 {
 562         if (!uhid->running)
 563                 return -EINVAL;
 564
 565         uhid->running = false;
 566         wake_up_interruptible(&uhid->report_wait);
 567
 568         cancel_work_sync(&uhid->worker);
 569
 570         hid_destroy_device(uhid->hid);
 571         kfree(uhid->rd_data);
 572
 573         return 0;
 574 }
 575
 576 static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
 577 {
 578         if (!uhid->running)
 579                 return -EINVAL;
 580
 581         hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data,
 582                          min_t(size_t, ev->u.input.size, UHID_DATA_MAX), 0);
 583
 584         return 0;
 585 }
 586
 587 static int uhid_dev_input2(struct uhid_device *uhid, struct uhid_event *ev)
 588 {
 589         if (!uhid->running)
 590                 return -EINVAL;
 591
 592         hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input2.data,
 593                          min_t(size_t, ev->u.input2.size, UHID_DATA_MAX), 0);
 594
 595         return 0;
 596 }
 597
 598 static int uhid_dev_get_report_reply(struct uhid_device *uhid,
 599                                      struct uhid_event *ev)
 600 {
 601         if (!uhid->running)
 602                 return -EINVAL;
 603
 604         uhid_report_wake_up(uhid, ev->u.get_report_reply.id, ev);
 605         return 0;
 606 }
 607
 608 static int uhid_dev_set_report_reply(struct uhid_device *uhid,
 609                                      struct uhid_event *ev)
 610 {
 611         if (!uhid->running)
 612                 return -EINVAL;
 613
 614         uhid_report_wake_up(uhid, ev->u.set_report_reply.id, ev);
 615         return 0;
 616 }
 617
 618 static int uhid_char_open(struct inode *inode, struct file *file)
 619 {
 620         struct uhid_device *uhid;
 621
 622         uhid = kzalloc(sizeof(*uhid), GFP_KERNEL);
 623         if (!uhid)
 624                 return -ENOMEM;
 625
 626         mutex_init(&uhid->devlock);
 627         mutex_init(&uhid->report_lock);
 628         spin_lock_init(&uhid->qlock);
 629         init_waitqueue_head(&uhid->waitq);
 630         init_waitqueue_head(&uhid->report_wait);
 631         uhid->running = false;
 632         INIT_WORK(&uhid->worker, uhid_device_add_worker);
 633
 634         file->private_data = uhid;
 635         nonseekable_open(inode, file);
 636
 637         return 0;
 638 }
 639
 640 static int uhid_char_release(struct inode *inode, struct file *file)
 641 {
 642         struct uhid_device *uhid = file->private_data;
 643         unsigned int i;
 644
 645         uhid_dev_destroy(uhid);
 646
 647         for (i = 0; i < UHID_BUFSIZE; ++i)
 648                 kfree(uhid->outq[i]);
 649
 650         kfree(uhid);
 651
 652         return 0;
 653 }
 654
 655 static ssize_t uhid_char_read(struct file *file, char __user *buffer,
 656                                 size_t count, loff_t *ppos)
 657 {
 658         struct uhid_device *uhid = file->private_data;
 659         int ret;
 660         unsigned long flags;
 661         size_t len;
 662
 663         /* they need at least the "type" member of uhid_event */
 664         if (count < sizeof(__u32))
 665                 return -EINVAL;
 666
 667 try_again:
 668         if (file->f_flags & O_NONBLOCK) {
 669                 if (uhid->head == uhid->tail)
 670                         return -EAGAIN;
 671         } else {
 672                 ret = wait_event_interruptible(uhid->waitq,
 673                                                 uhid->head != uhid->tail);
 674                 if (ret)
 675                         return ret;
 676         }
 677
 678         ret = mutex_lock_interruptible(&uhid->devlock);
 679         if (ret)
 680                 return ret;
 681
 682         if (uhid->head == uhid->tail) {
 683                 mutex_unlock(&uhid->devlock);
 684                 goto try_again;
 685         } else {
 686                 len = min(count, sizeof(**uhid->outq));
 687                 if (copy_to_user(buffer, uhid->outq[uhid->tail], len)) {
 688                         ret = -EFAULT;
 689                 } else {
 690                         kfree(uhid->outq[uhid->tail]);
 691                         uhid->outq[uhid->tail] = NULL;
 692
 693                         spin_lock_irqsave(&uhid->qlock, flags);
 694                         uhid->tail = (uhid->tail + 1) % UHID_BUFSIZE;
 695                         spin_unlock_irqrestore(&uhid->qlock, flags);
 696                 }
 697         }
 698
 699         mutex_unlock(&uhid->devlock);
 700         return ret ? ret : len;
 701 }
 702
 703 static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
 704                                 size_t count, loff_t *ppos)
 705 {
 706         struct uhid_device *uhid = file->private_data;
 707         int ret;
 708         size_t len;
 709
 710         /* we need at least the "type" member of uhid_event */
 711         if (count < sizeof(__u32))
 712                 return -EINVAL;
 713
 714         ret = mutex_lock_interruptible(&uhid->devlock);
 715         if (ret)
 716                 return ret;
 717
 718         memset(&uhid->input_buf, 0, sizeof(uhid->input_buf));
 719         len = min(count, sizeof(uhid->input_buf));
 720
 721         ret = uhid_event_from_user(buffer, len, &uhid->input_buf);
 722         if (ret)
 723                 goto unlock;
 724
 725         switch (uhid->input_buf.type) {
 726         case UHID_CREATE:
 727                 /*
 728                  * 'struct uhid_create_req' contains a __user pointer which is
 729                  * copied from, so it's unsafe to allow this with elevated
 730                  * privileges (e.g. from a setuid binary) or via kernel_write().
 731                  */
 732                 if (file->f_cred != current_cred() || uaccess_kernel()) {
 733                         pr_err_once("UHID_CREATE from different security context by process %d (%s), this is not allowed.\n",
 734                                     task_tgid_vnr(current), current->comm);
 735                         ret = -EACCES;
 736                         goto unlock;
 737                 }
 738                 ret = uhid_dev_create(uhid, &uhid->input_buf);
 739                 break;
 740         case UHID_CREATE2:
 741                 ret = uhid_dev_create2(uhid, &uhid->input_buf);
 742                 break;
 743         case UHID_DESTROY:
 744                 ret = uhid_dev_destroy(uhid);
 745                 break;
 746         case UHID_INPUT:
 747                 ret = uhid_dev_input(uhid, &uhid->input_buf);
 748                 break;
 749         case UHID_INPUT2:
 750                 ret = uhid_dev_input2(uhid, &uhid->input_buf);
 751                 break;
 752         case UHID_GET_REPORT_REPLY:
 753                 ret = uhid_dev_get_report_reply(uhid, &uhid->input_buf);
 754                 break;
 755         case UHID_SET_REPORT_REPLY:
 756                 ret = uhid_dev_set_report_reply(uhid, &uhid->input_buf);
 757                 break;
 758         default:
 759                 ret = -EOPNOTSUPP;
 760         }
 761
 762 unlock:
 763         mutex_unlock(&uhid->devlock);
 764
 765         /* return "count" not "len" to not confuse the caller */
 766         return ret ? ret : count;
 767 }
 768
 769 static __poll_t uhid_char_poll(struct file *file, poll_table *wait)
 770 {
 771         struct uhid_device *uhid = file->private_data;
 772
 773         poll_wait(file, &uhid->waitq, wait);
 774
 775         if (uhid->head != uhid->tail)
 776                 return EPOLLIN | EPOLLRDNORM;
 777
 778         return 0;
 779 }
 780
 781 static const struct file_operations uhid_fops = {
 782         .owner          = THIS_MODULE,
 783         .open           = uhid_char_open,
 784         .release        = uhid_char_release,
 785         .read           = uhid_char_read,
 786         .write          = uhid_char_write,
 787         .poll           = uhid_char_poll,
 788         .llseek         = no_llseek,
 789 };
 790
 791 static struct miscdevice uhid_misc = {
 792         .fops           = &uhid_fops,
 793         .minor          = UHID_MINOR,
 794         .name           = UHID_NAME,
 795 };
 796 module_misc_device(uhid_misc);
 797
 798 MODULE_LICENSE("GPL");
 799 MODULE_AUTHOR("David Herrmann <dh.herrmann@gmail.com>");
 800 MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");
 801 MODULE_ALIAS_MISCDEV(UHID_MINOR);
 802 MODULE_ALIAS("devname:" UHID_NAME);