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 #include <linux/eventpoll.h>
  29
  30 #define UHID_NAME       "uhid"
  31 #define UHID_BUFSIZE    32
  32
  33 struct uhid_device {
  34         struct mutex devlock;
  35         bool running;
  36
  37         __u8 *rd_data;
  38         uint rd_size;
  39
  40         struct hid_device *hid;
  41         struct uhid_event input_buf;
  42
  43         wait_queue_head_t waitq;
  44         spinlock_t qlock;
  45         __u8 head;
  46         __u8 tail;
  47         struct uhid_event *outq[UHID_BUFSIZE];
  48
  49         /* blocking GET_REPORT support; state changes protected by qlock */
  50         struct mutex report_lock;
  51         wait_queue_head_t report_wait;
  52         bool report_running;
  53         u32 report_id;
  54         u32 report_type;
  55         struct uhid_event report_buf;
  56         struct work_struct worker;
  57 };
  58
  59 static struct miscdevice uhid_misc;
  60
  61 static void uhid_device_add_worker(struct work_struct *work)
  62 {
  63         struct uhid_device *uhid = container_of(work, struct uhid_device, worker);
  64         int ret;
  65
  66         ret = hid_add_device(uhid->hid);
  67         if (ret) {
  68                 hid_err(uhid->hid, "Cannot register HID device: error %d\n", ret);
  69
  70                 hid_destroy_device(uhid->hid);
  71                 uhid->hid = NULL;
  72                 uhid->running = false;
  73         }
  74 }
  75
  76 static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
  77 {
  78         __u8 newhead;
  79
  80         newhead = (uhid->head + 1) % UHID_BUFSIZE;
  81
  82         if (newhead != uhid->tail) {
  83                 uhid->outq[uhid->head] = ev;
  84                 uhid->head = newhead;
  85                 wake_up_interruptible(&uhid->waitq);
  86         } else {
  87                 hid_warn(uhid->hid, "Output queue is full\n");
  88                 kfree(ev);
  89         }
  90 }
  91
  92 static int uhid_queue_event(struct uhid_device *uhid, __u32 event)
  93 {
  94         unsigned long flags;
  95         struct uhid_event *ev;
  96
  97         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
  98         if (!ev)
  99                 return -ENOMEM;
 100
 101         ev->type = event;
 102
 103         spin_lock_irqsave(&uhid->qlock, flags);
 104         uhid_queue(uhid, ev);
 105         spin_unlock_irqrestore(&uhid->qlock, flags);
 106
 107         return 0;
 108 }
 109
 110 static int uhid_hid_start(struct hid_device *hid)
 111 {
 112         struct uhid_device *uhid = hid->driver_data;
 113         struct uhid_event *ev;
 114         unsigned long flags;
 115
 116         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 117         if (!ev)
 118                 return -ENOMEM;
 119
 120         ev->type = UHID_START;
 121
 122         if (hid->report_enum[HID_FEATURE_REPORT].numbered)
 123                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_FEATURE_REPORTS;
 124         if (hid->report_enum[HID_OUTPUT_REPORT].numbered)
 125                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_OUTPUT_REPORTS;
 126         if (hid->report_enum[HID_INPUT_REPORT].numbered)
 127                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_INPUT_REPORTS;
 128
 129         spin_lock_irqsave(&uhid->qlock, flags);
 130         uhid_queue(uhid, ev);
 131         spin_unlock_irqrestore(&uhid->qlock, flags);
 132
 133         return 0;
 134 }
 135
 136 static void uhid_hid_stop(struct hid_device *hid)
 137 {
 138         struct uhid_device *uhid = hid->driver_data;
 139
 140         hid->claimed = 0;
 141         uhid_queue_event(uhid, UHID_STOP);
 142 }
 143
 144 static int uhid_hid_open(struct hid_device *hid)
 145 {
 146         struct uhid_device *uhid = hid->driver_data;
 147
 148         return uhid_queue_event(uhid, UHID_OPEN);
 149 }
 150
 151 static void uhid_hid_close(struct hid_device *hid)
 152 {
 153         struct uhid_device *uhid = hid->driver_data;
 154
 155         uhid_queue_event(uhid, UHID_CLOSE);
 156 }
 157
 158 static int uhid_hid_parse(struct hid_device *hid)
 159 {
 160         struct uhid_device *uhid = hid->driver_data;
 161
 162         return hid_parse_report(hid, uhid->rd_data, uhid->rd_size);
 163 }
 164
 165 /* must be called with report_lock held */
 166 static int __uhid_report_queue_and_wait(struct uhid_device *uhid,
 167                                         struct uhid_event *ev,
 168                                         __u32 *report_id)
 169 {
 170         unsigned long flags;
 171         int ret;
 172
 173         spin_lock_irqsave(&uhid->qlock, flags);
 174         *report_id = ++uhid->report_id;
 175         uhid->report_type = ev->type + 1;
 176         uhid->report_running = true;
 177         uhid_queue(uhid, ev);
 178         spin_unlock_irqrestore(&uhid->qlock, flags);
 179
 180         ret = wait_event_interruptible_timeout(uhid->report_wait,
 181                                 !uhid->report_running || !uhid->running,
 182                                 5 * HZ);
 183         if (!ret || !uhid->running || uhid->report_running)
 184                 ret = -EIO;
 185         else if (ret < 0)
 186                 ret = -ERESTARTSYS;
 187         else
 188                 ret = 0;
 189
 190         uhid->report_running = false;
 191
 192         return ret;
 193 }
 194
 195 static void uhid_report_wake_up(struct uhid_device *uhid, u32 id,
 196                                 const struct uhid_event *ev)
 197 {
 198         unsigned long flags;
 199
 200         spin_lock_irqsave(&uhid->qlock, flags);
 201
 202         /* id for old report; drop it silently */
 203         if (uhid->report_type != ev->type || uhid->report_id != id)
 204                 goto unlock;
 205         if (!uhid->report_running)
 206                 goto unlock;
 207
 208         memcpy(&uhid->report_buf, ev, sizeof(*ev));
 209         uhid->report_running = false;
 210         wake_up_interruptible(&uhid->report_wait);
 211
 212 unlock:
 213         spin_unlock_irqrestore(&uhid->qlock, flags);
 214 }
 215
 216 static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
 217                                u8 *buf, size_t count, u8 rtype)
 218 {
 219         struct uhid_device *uhid = hid->driver_data;
 220         struct uhid_get_report_reply_req *req;
 221         struct uhid_event *ev;
 222         int ret;
 223
 224         if (!uhid->running)
 225                 return -EIO;
 226
 227         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 228         if (!ev)
 229                 return -ENOMEM;
 230
 231         ev->type = UHID_GET_REPORT;
 232         ev->u.get_report.rnum = rnum;
 233         ev->u.get_report.rtype = rtype;
 234
 235         ret = mutex_lock_interruptible(&uhid->report_lock);
 236         if (ret) {
 237                 kfree(ev);
 238                 return ret;
 239         }
 240
 241         /* this _always_ takes ownership of @ev */
 242         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.get_report.id);
 243         if (ret)
 244                 goto unlock;
 245
 246         req = &uhid->report_buf.u.get_report_reply;
 247         if (req->err) {
 248                 ret = -EIO;
 249         } else {
 250                 ret = min3(count, (size_t)req->size, (size_t)UHID_DATA_MAX);
 251                 memcpy(buf, req->data, ret);
 252         }
 253
 254 unlock:
 255         mutex_unlock(&uhid->report_lock);
 256         return ret;
 257 }
 258
 259 static int uhid_hid_set_report(struct hid_device *hid, unsigned char rnum,
 260                                const u8 *buf, size_t count, u8 rtype)
 261 {
 262         struct uhid_device *uhid = hid->driver_data;
 263         struct uhid_event *ev;
 264         int ret;
 265
 266         if (!uhid->running || count > UHID_DATA_MAX)
 267                 return -EIO;
 268
 269         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 270         if (!ev)
 271                 return -ENOMEM;
 272
 273         ev->type = UHID_SET_REPORT;
 274         ev->u.set_report.rnum = rnum;
 275         ev->u.set_report.rtype = rtype;
 276         ev->u.set_report.size = count;
 277         memcpy(ev->u.set_report.data, buf, count);
 278
 279         ret = mutex_lock_interruptible(&uhid->report_lock);
 280         if (ret) {
 281                 kfree(ev);
 282                 return ret;
 283         }
 284
 285         /* this _always_ takes ownership of @ev */
 286         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.set_report.id);
 287         if (ret)
 288                 goto unlock;
 289
 290         if (uhid->report_buf.u.set_report_reply.err)
 291                 ret = -EIO;
 292         else
 293                 ret = count;
 294
 295 unlock:
 296         mutex_unlock(&uhid->report_lock);
 297         return ret;
 298 }
 299
 300 static int uhid_hid_raw_request(struct hid_device *hid, unsigned char reportnum,
 301                                 __u8 *buf, size_t len, unsigned char rtype,
 302                                 int reqtype)
 303 {
 304         u8 u_rtype;
 305
 306         switch (rtype) {
 307         case HID_FEATURE_REPORT:
 308                 u_rtype = UHID_FEATURE_REPORT;
 309                 break;
 310         case HID_OUTPUT_REPORT:
 311                 u_rtype = UHID_OUTPUT_REPORT;
 312                 break;
 313         case HID_INPUT_REPORT:
 314                 u_rtype = UHID_INPUT_REPORT;
 315                 break;
 316         default:
 317                 return -EINVAL;
 318         }
 319
 320         switch (reqtype) {
 321         case HID_REQ_GET_REPORT:
 322                 return uhid_hid_get_report(hid, reportnum, buf, len, u_rtype);
 323         case HID_REQ_SET_REPORT:
 324                 return uhid_hid_set_report(hid, reportnum, buf, len, u_rtype);
 325         default:
 326                 return -EIO;
 327         }
 328 }
 329
 330 static int uhid_hid_output_raw(struct hid_device *hid, __u8 *buf, size_t count,
 331                                unsigned char report_type)
 332 {
 333         struct uhid_device *uhid = hid->driver_data;
 334         __u8 rtype;
 335         unsigned long flags;
 336         struct uhid_event *ev;
 337
 338         switch (report_type) {
 339         case HID_FEATURE_REPORT:
 340                 rtype = UHID_FEATURE_REPORT;
 341                 break;
 342         case HID_OUTPUT_REPORT:
 343                 rtype = UHID_OUTPUT_REPORT;
 344                 break;
 345         default:
 346                 return -EINVAL;
 347         }
 348
 349         if (count < 1 || count > UHID_DATA_MAX)
 350                 return -EINVAL;
 351
 352         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 353         if (!ev)
 354                 return -ENOMEM;
 355
 356         ev->type = UHID_OUTPUT;
 357         ev->u.output.size = count;
 358         ev->u.output.rtype = rtype;
 359         memcpy(ev->u.output.data, buf, count);
 360
 361         spin_lock_irqsave(&uhid->qlock, flags);
 362         uhid_queue(uhid, ev);
 363         spin_unlock_irqrestore(&uhid->qlock, flags);
 364
 365         return count;
 366 }
 367
 368 static int uhid_hid_output_report(struct hid_device *hid, __u8 *buf,
 369                                   size_t count)
 370 {
 371         return uhid_hid_output_raw(hid, buf, count, HID_OUTPUT_REPORT);
 372 }
 373
 374 struct hid_ll_driver uhid_hid_driver = {
 375         .start = uhid_hid_start,
 376         .stop = uhid_hid_stop,
 377         .open = uhid_hid_open,
 378         .close = uhid_hid_close,
 379         .parse = uhid_hid_parse,
 380         .raw_request = uhid_hid_raw_request,
 381         .output_report = uhid_hid_output_report,
 382 };
 383 EXPORT_SYMBOL_GPL(uhid_hid_driver);
 384
 385 #ifdef CONFIG_COMPAT
 386
 387 /* Apparently we haven't stepped on these rakes enough times yet. */
 388 struct uhid_create_req_compat {
 389         __u8 name[128];
 390         __u8 phys[64];
 391         __u8 uniq[64];
 392
 393         compat_uptr_t rd_data;
 394         __u16 rd_size;
 395
 396         __u16 bus;
 397         __u32 vendor;
 398         __u32 product;
 399         __u32 version;
 400         __u32 country;
 401 } __attribute__((__packed__));
 402
 403 static int uhid_event_from_user(const char __user *buffer, size_t len,
 404                                 struct uhid_event *event)
 405 {
 406         if (in_compat_syscall()) {
 407                 u32 type;
 408
 409                 if (get_user(type, buffer))
 410                         return -EFAULT;
 411
 412                 if (type == UHID_CREATE) {
 413                         /*
 414                          * This is our messed up request with compat pointer.
 415                          * It is largish (more than 256 bytes) so we better
 416                          * allocate it from the heap.
 417                          */
 418                         struct uhid_create_req_compat *compat;
 419
 420                         compat = kzalloc(sizeof(*compat), GFP_KERNEL);
 421                         if (!compat)
 422                                 return -ENOMEM;
 423
 424                         buffer += sizeof(type);
 425                         len -= sizeof(type);
 426                         if (copy_from_user(compat, buffer,
 427                                            min(len, sizeof(*compat)))) {
 428                                 kfree(compat);
 429                                 return -EFAULT;
 430                         }
 431
 432                         /* Shuffle the data over to proper structure */
 433                         event->type = type;
 434
 435                         memcpy(event->u.create.name, compat->name,
 436                                 sizeof(compat->name));
 437                         memcpy(event->u.create.phys, compat->phys,
 438                                 sizeof(compat->phys));
 439                         memcpy(event->u.create.uniq, compat->uniq,
 440                                 sizeof(compat->uniq));
 441
 442                         event->u.create.rd_data = compat_ptr(compat->rd_data);
 443                         event->u.create.rd_size = compat->rd_size;
 444
 445                         event->u.create.bus = compat->bus;
 446                         event->u.create.vendor = compat->vendor;
 447                         event->u.create.product = compat->product;
 448                         event->u.create.version = compat->version;
 449                         event->u.create.country = compat->country;
 450
 451                         kfree(compat);
 452                         return 0;
 453                 }
 454                 /* All others can be copied directly */
 455         }
 456
 457         if (copy_from_user(event, buffer, min(len, sizeof(*event))))
 458                 return -EFAULT;
 459
 460         return 0;
 461 }
 462 #else
 463 static int uhid_event_from_user(const char __user *buffer, size_t len,
 464                                 struct uhid_event *event)
 465 {
 466         if (copy_from_user(event, buffer, min(len, sizeof(*event))))
 467                 return -EFAULT;
 468
 469         return 0;
 470 }
 471 #endif
 472
 473 static int uhid_dev_create2(struct uhid_device *uhid,
 474                             const struct uhid_event *ev)
 475 {
 476         struct hid_device *hid;
 477         size_t rd_size, len;
 478         void *rd_data;
 479         int ret;
 480
 481         if (uhid->running)
 482                 return -EALREADY;
 483
 484         rd_size = ev->u.create2.rd_size;
 485         if (rd_size <= 0 || rd_size > HID_MAX_DESCRIPTOR_SIZE)
 486                 return -EINVAL;
 487
 488         rd_data = kmemdup(ev->u.create2.rd_data, rd_size, GFP_KERNEL);
 489         if (!rd_data)
 490                 return -ENOMEM;
 491
 492         uhid->rd_size = rd_size;
 493         uhid->rd_data = rd_data;
 494
 495         hid = hid_allocate_device();
 496         if (IS_ERR(hid)) {
 497                 ret = PTR_ERR(hid);
 498                 goto err_free;
 499         }
 500
 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 unsigned int uhid_char_poll(struct file *file, poll_table *wait)
 770 {
 771         struct uhid_device *uhid = file->private_data;
 772         unsigned int mask = POLLOUT | POLLWRNORM; /* uhid is always writable */
 773
 774         poll_wait(file, &uhid->waitq, wait);
 775
 776         if (uhid->head != uhid->tail)
 777                 mask |= POLLIN | POLLRDNORM;
 778
 779         return mask;
 780 }
 781
 782 static const struct file_operations uhid_fops = {
 783         .owner          = THIS_MODULE,
 784         .open           = uhid_char_open,
 785         .release        = uhid_char_release,
 786         .read           = uhid_char_read,
 787         .write          = uhid_char_write,
 788         .poll           = uhid_char_poll,
 789         .llseek         = no_llseek,
 790 };
 791
 792 static struct miscdevice uhid_misc = {
 793         .fops           = &uhid_fops,
 794         .minor          = UHID_MINOR,
 795         .name           = UHID_NAME,
 796 };
 797 module_misc_device(uhid_misc);
 798
 799 MODULE_LICENSE("GPL");
 800 MODULE_AUTHOR("David Herrmann <dh.herrmann@gmail.com>");
 801 MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");
 802 MODULE_ALIAS_MISCDEV(UHID_MINOR);
 803 MODULE_ALIAS("devname:" UHID_NAME);