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/uaccess.h>
  29 #include <linux/eventpoll.h>
  30
  31 #define UHID_NAME       "uhid"
  32 #define UHID_BUFSIZE    32
  33
  34 struct uhid_device {
  35         struct mutex devlock;
  36         bool running;
  37
  38         __u8 *rd_data;
  39         uint rd_size;
  40
  41         struct hid_device *hid;
  42         struct uhid_event input_buf;
  43
  44         wait_queue_head_t waitq;
  45         spinlock_t qlock;
  46         __u8 head;
  47         __u8 tail;
  48         struct uhid_event *outq[UHID_BUFSIZE];
  49
  50         /* blocking GET_REPORT support; state changes protected by qlock */
  51         struct mutex report_lock;
  52         wait_queue_head_t report_wait;
  53         bool report_running;
  54         u32 report_id;
  55         u32 report_type;
  56         struct uhid_event report_buf;
  57         struct work_struct worker;
  58 };
  59
  60 static struct miscdevice uhid_misc;
  61
  62 static void uhid_device_add_worker(struct work_struct *work)
  63 {
  64         struct uhid_device *uhid = container_of(work, struct uhid_device, worker);
  65         int ret;
  66
  67         ret = hid_add_device(uhid->hid);
  68         if (ret) {
  69                 hid_err(uhid->hid, "Cannot register HID device: error %d\n", ret);
  70
  71                 hid_destroy_device(uhid->hid);
  72                 uhid->hid = NULL;
  73                 uhid->running = false;
  74         }
  75 }
  76
  77 static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
  78 {
  79         __u8 newhead;
  80
  81         newhead = (uhid->head + 1) % UHID_BUFSIZE;
  82
  83         if (newhead != uhid->tail) {
  84                 uhid->outq[uhid->head] = ev;
  85                 uhid->head = newhead;
  86                 wake_up_interruptible(&uhid->waitq);
  87         } else {
  88                 hid_warn(uhid->hid, "Output queue is full\n");
  89                 kfree(ev);
  90         }
  91 }
  92
  93 static int uhid_queue_event(struct uhid_device *uhid, __u32 event)
  94 {
  95         unsigned long flags;
  96         struct uhid_event *ev;
  97
  98         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
  99         if (!ev)
 100                 return -ENOMEM;
 101
 102         ev->type = event;
 103
 104         spin_lock_irqsave(&uhid->qlock, flags);
 105         uhid_queue(uhid, ev);
 106         spin_unlock_irqrestore(&uhid->qlock, flags);
 107
 108         return 0;
 109 }
 110
 111 static int uhid_hid_start(struct hid_device *hid)
 112 {
 113         struct uhid_device *uhid = hid->driver_data;
 114         struct uhid_event *ev;
 115         unsigned long flags;
 116
 117         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 118         if (!ev)
 119                 return -ENOMEM;
 120
 121         ev->type = UHID_START;
 122
 123         if (hid->report_enum[HID_FEATURE_REPORT].numbered)
 124                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_FEATURE_REPORTS;
 125         if (hid->report_enum[HID_OUTPUT_REPORT].numbered)
 126                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_OUTPUT_REPORTS;
 127         if (hid->report_enum[HID_INPUT_REPORT].numbered)
 128                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_INPUT_REPORTS;
 129
 130         spin_lock_irqsave(&uhid->qlock, flags);
 131         uhid_queue(uhid, ev);
 132         spin_unlock_irqrestore(&uhid->qlock, flags);
 133
 134         return 0;
 135 }
 136
 137 static void uhid_hid_stop(struct hid_device *hid)
 138 {
 139         struct uhid_device *uhid = hid->driver_data;
 140
 141         hid->claimed = 0;
 142         uhid_queue_event(uhid, UHID_STOP);
 143 }
 144
 145 static int uhid_hid_open(struct hid_device *hid)
 146 {
 147         struct uhid_device *uhid = hid->driver_data;
 148
 149         return uhid_queue_event(uhid, UHID_OPEN);
 150 }
 151
 152 static void uhid_hid_close(struct hid_device *hid)
 153 {
 154         struct uhid_device *uhid = hid->driver_data;
 155
 156         uhid_queue_event(uhid, UHID_CLOSE);
 157 }
 158
 159 static int uhid_hid_parse(struct hid_device *hid)
 160 {
 161         struct uhid_device *uhid = hid->driver_data;
 162
 163         return hid_parse_report(hid, uhid->rd_data, uhid->rd_size);
 164 }
 165
 166 /* must be called with report_lock held */
 167 static int __uhid_report_queue_and_wait(struct uhid_device *uhid,
 168                                         struct uhid_event *ev,
 169                                         __u32 *report_id)
 170 {
 171         unsigned long flags;
 172         int ret;
 173
 174         spin_lock_irqsave(&uhid->qlock, flags);
 175         *report_id = ++uhid->report_id;
 176         uhid->report_type = ev->type + 1;
 177         uhid->report_running = true;
 178         uhid_queue(uhid, ev);
 179         spin_unlock_irqrestore(&uhid->qlock, flags);
 180
 181         ret = wait_event_interruptible_timeout(uhid->report_wait,
 182                                 !uhid->report_running || !uhid->running,
 183                                 5 * HZ);
 184         if (!ret || !uhid->running || uhid->report_running)
 185                 ret = -EIO;
 186         else if (ret < 0)
 187                 ret = -ERESTARTSYS;
 188         else
 189                 ret = 0;
 190
 191         uhid->report_running = false;
 192
 193         return ret;
 194 }
 195
 196 static void uhid_report_wake_up(struct uhid_device *uhid, u32 id,
 197                                 const struct uhid_event *ev)
 198 {
 199         unsigned long flags;
 200
 201         spin_lock_irqsave(&uhid->qlock, flags);
 202
 203         /* id for old report; drop it silently */
 204         if (uhid->report_type != ev->type || uhid->report_id != id)
 205                 goto unlock;
 206         if (!uhid->report_running)
 207                 goto unlock;
 208
 209         memcpy(&uhid->report_buf, ev, sizeof(*ev));
 210         uhid->report_running = false;
 211         wake_up_interruptible(&uhid->report_wait);
 212
 213 unlock:
 214         spin_unlock_irqrestore(&uhid->qlock, flags);
 215 }
 216
 217 static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
 218                                u8 *buf, size_t count, u8 rtype)
 219 {
 220         struct uhid_device *uhid = hid->driver_data;
 221         struct uhid_get_report_reply_req *req;
 222         struct uhid_event *ev;
 223         int ret;
 224
 225         if (!uhid->running)
 226                 return -EIO;
 227
 228         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 229         if (!ev)
 230                 return -ENOMEM;
 231
 232         ev->type = UHID_GET_REPORT;
 233         ev->u.get_report.rnum = rnum;
 234         ev->u.get_report.rtype = rtype;
 235
 236         ret = mutex_lock_interruptible(&uhid->report_lock);
 237         if (ret) {
 238                 kfree(ev);
 239                 return ret;
 240         }
 241
 242         /* this _always_ takes ownership of @ev */
 243         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.get_report.id);
 244         if (ret)
 245                 goto unlock;
 246
 247         req = &uhid->report_buf.u.get_report_reply;
 248         if (req->err) {
 249                 ret = -EIO;
 250         } else {
 251                 ret = min3(count, (size_t)req->size, (size_t)UHID_DATA_MAX);
 252                 memcpy(buf, req->data, ret);
 253         }
 254
 255 unlock:
 256         mutex_unlock(&uhid->report_lock);
 257         return ret;
 258 }
 259
 260 static int uhid_hid_set_report(struct hid_device *hid, unsigned char rnum,
 261                                const u8 *buf, size_t count, u8 rtype)
 262 {
 263         struct uhid_device *uhid = hid->driver_data;
 264         struct uhid_event *ev;
 265         int ret;
 266
 267         if (!uhid->running || count > UHID_DATA_MAX)
 268                 return -EIO;
 269
 270         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 271         if (!ev)
 272                 return -ENOMEM;
 273
 274         ev->type = UHID_SET_REPORT;
 275         ev->u.set_report.rnum = rnum;
 276         ev->u.set_report.rtype = rtype;
 277         ev->u.set_report.size = count;
 278         memcpy(ev->u.set_report.data, buf, count);
 279
 280         ret = mutex_lock_interruptible(&uhid->report_lock);
 281         if (ret) {
 282                 kfree(ev);
 283                 return ret;
 284         }
 285
 286         /* this _always_ takes ownership of @ev */
 287         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.set_report.id);
 288         if (ret)
 289                 goto unlock;
 290
 291         if (uhid->report_buf.u.set_report_reply.err)
 292                 ret = -EIO;
 293         else
 294                 ret = count;
 295
 296 unlock:
 297         mutex_unlock(&uhid->report_lock);
 298         return ret;
 299 }
 300
 301 static int uhid_hid_raw_request(struct hid_device *hid, unsigned char reportnum,
 302                                 __u8 *buf, size_t len, unsigned char rtype,
 303                                 int reqtype)
 304 {
 305         u8 u_rtype;
 306
 307         switch (rtype) {
 308         case HID_FEATURE_REPORT:
 309                 u_rtype = UHID_FEATURE_REPORT;
 310                 break;
 311         case HID_OUTPUT_REPORT:
 312                 u_rtype = UHID_OUTPUT_REPORT;
 313                 break;
 314         case HID_INPUT_REPORT:
 315                 u_rtype = UHID_INPUT_REPORT;
 316                 break;
 317         default:
 318                 return -EINVAL;
 319         }
 320
 321         switch (reqtype) {
 322         case HID_REQ_GET_REPORT:
 323                 return uhid_hid_get_report(hid, reportnum, buf, len, u_rtype);
 324         case HID_REQ_SET_REPORT:
 325                 return uhid_hid_set_report(hid, reportnum, buf, len, u_rtype);
 326         default:
 327                 return -EIO;
 328         }
 329 }
 330
 331 static int uhid_hid_output_raw(struct hid_device *hid, __u8 *buf, size_t count,
 332                                unsigned char report_type)
 333 {
 334         struct uhid_device *uhid = hid->driver_data;
 335         __u8 rtype;
 336         unsigned long flags;
 337         struct uhid_event *ev;
 338
 339         switch (report_type) {
 340         case HID_FEATURE_REPORT:
 341                 rtype = UHID_FEATURE_REPORT;
 342                 break;
 343         case HID_OUTPUT_REPORT:
 344                 rtype = UHID_OUTPUT_REPORT;
 345                 break;
 346         default:
 347                 return -EINVAL;
 348         }
 349
 350         if (count < 1 || count > UHID_DATA_MAX)
 351                 return -EINVAL;
 352
 353         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 354         if (!ev)
 355                 return -ENOMEM;
 356
 357         ev->type = UHID_OUTPUT;
 358         ev->u.output.size = count;
 359         ev->u.output.rtype = rtype;
 360         memcpy(ev->u.output.data, buf, count);
 361
 362         spin_lock_irqsave(&uhid->qlock, flags);
 363         uhid_queue(uhid, ev);
 364         spin_unlock_irqrestore(&uhid->qlock, flags);
 365
 366         return count;
 367 }
 368
 369 static int uhid_hid_output_report(struct hid_device *hid, __u8 *buf,
 370                                   size_t count)
 371 {
 372         return uhid_hid_output_raw(hid, buf, count, HID_OUTPUT_REPORT);
 373 }
 374
 375 static struct hid_ll_driver uhid_hid_driver = {
 376         .start = uhid_hid_start,
 377         .stop = uhid_hid_stop,
 378         .open = uhid_hid_open,
 379         .close = uhid_hid_close,
 380         .parse = uhid_hid_parse,
 381         .raw_request = uhid_hid_raw_request,
 382         .output_report = uhid_hid_output_report,
 383 };
 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);