drivers/hid/uhid.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * User-space I/O driver support for HID subsystem
   4  * Copyright (c) 2012 David Herrmann
   5  */
   6
   7 /*
   8  */
   9
  10 #include <linux/atomic.h>
  11 #include <linux/compat.h>
  12 #include <linux/cred.h>
  13 #include <linux/device.h>
  14 #include <linux/fs.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>
  25
  26 #define UHID_NAME       "uhid"
  27 #define UHID_BUFSIZE    32
  28
  29 struct uhid_device {
  30         struct mutex devlock;
  31         bool running;
  32
  33         __u8 *rd_data;
  34         uint rd_size;
  35
  36         struct hid_device *hid;
  37         struct uhid_event input_buf;
  38
  39         wait_queue_head_t waitq;
  40         spinlock_t qlock;
  41         __u8 head;
  42         __u8 tail;
  43         struct uhid_event *outq[UHID_BUFSIZE];
  44
  45         /* blocking GET_REPORT support; state changes protected by qlock */
  46         struct mutex report_lock;
  47         wait_queue_head_t report_wait;
  48         bool report_running;
  49         u32 report_id;
  50         u32 report_type;
  51         struct uhid_event report_buf;
  52         struct work_struct worker;
  53 };
  54
  55 static struct miscdevice uhid_misc;
  56
  57 static void uhid_device_add_worker(struct work_struct *work)
  58 {
  59         struct uhid_device *uhid = container_of(work, struct uhid_device, worker);
  60         int ret;
  61
  62         ret = hid_add_device(uhid->hid);
  63         if (ret) {
  64                 hid_err(uhid->hid, "Cannot register HID device: error %d\n", ret);
  65
  66                 hid_destroy_device(uhid->hid);
  67                 uhid->hid = NULL;
  68                 uhid->running = false;
  69         }
  70 }
  71
  72 static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
  73 {
  74         __u8 newhead;
  75
  76         newhead = (uhid->head + 1) % UHID_BUFSIZE;
  77
  78         if (newhead != uhid->tail) {
  79                 uhid->outq[uhid->head] = ev;
  80                 uhid->head = newhead;
  81                 wake_up_interruptible(&uhid->waitq);
  82         } else {
  83                 hid_warn(uhid->hid, "Output queue is full\n");
  84                 kfree(ev);
  85         }
  86 }
  87
  88 static int uhid_queue_event(struct uhid_device *uhid, __u32 event)
  89 {
  90         unsigned long flags;
  91         struct uhid_event *ev;
  92
  93         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
  94         if (!ev)
  95                 return -ENOMEM;
  96
  97         ev->type = event;
  98
  99         spin_lock_irqsave(&uhid->qlock, flags);
 100         uhid_queue(uhid, ev);
 101         spin_unlock_irqrestore(&uhid->qlock, flags);
 102
 103         return 0;
 104 }
 105
 106 static int uhid_hid_start(struct hid_device *hid)
 107 {
 108         struct uhid_device *uhid = hid->driver_data;
 109         struct uhid_event *ev;
 110         unsigned long flags;
 111
 112         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 113         if (!ev)
 114                 return -ENOMEM;
 115
 116         ev->type = UHID_START;
 117
 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;
 124
 125         spin_lock_irqsave(&uhid->qlock, flags);
 126         uhid_queue(uhid, ev);
 127         spin_unlock_irqrestore(&uhid->qlock, flags);
 128
 129         return 0;
 130 }
 131
 132 static void uhid_hid_stop(struct hid_device *hid)
 133 {
 134         struct uhid_device *uhid = hid->driver_data;
 135
 136         hid->claimed = 0;
 137         uhid_queue_event(uhid, UHID_STOP);
 138 }
 139
 140 static int uhid_hid_open(struct hid_device *hid)
 141 {
 142         struct uhid_device *uhid = hid->driver_data;
 143
 144         return uhid_queue_event(uhid, UHID_OPEN);
 145 }
 146
 147 static void uhid_hid_close(struct hid_device *hid)
 148 {
 149         struct uhid_device *uhid = hid->driver_data;
 150
 151         uhid_queue_event(uhid, UHID_CLOSE);
 152 }
 153
 154 static int uhid_hid_parse(struct hid_device *hid)
 155 {
 156         struct uhid_device *uhid = hid->driver_data;
 157
 158         return hid_parse_report(hid, uhid->rd_data, uhid->rd_size);
 159 }
 160
 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,
 164                                         __u32 *report_id)
 165 {
 166         unsigned long flags;
 167         int ret;
 168
 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);
 175
 176         ret = wait_event_interruptible_timeout(uhid->report_wait,
 177                                 !uhid->report_running || !uhid->running,
 178                                 5 * HZ);
 179         if (!ret || !uhid->running || uhid->report_running)
 180                 ret = -EIO;
 181         else if (ret < 0)
 182                 ret = -ERESTARTSYS;
 183         else
 184                 ret = 0;
 185
 186         uhid->report_running = false;
 187
 188         return ret;
 189 }
 190
 191 static void uhid_report_wake_up(struct uhid_device *uhid, u32 id,
 192                                 const struct uhid_event *ev)
 193 {
 194         unsigned long flags;
 195
 196         spin_lock_irqsave(&uhid->qlock, flags);
 197
 198         /* id for old report; drop it silently */
 199         if (uhid->report_type != ev->type || uhid->report_id != id)
 200                 goto unlock;
 201         if (!uhid->report_running)
 202                 goto unlock;
 203
 204         memcpy(&uhid->report_buf, ev, sizeof(*ev));
 205         uhid->report_running = false;
 206         wake_up_interruptible(&uhid->report_wait);
 207
 208 unlock:
 209         spin_unlock_irqrestore(&uhid->qlock, flags);
 210 }
 211
 212 static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
 213                                u8 *buf, size_t count, u8 rtype)
 214 {
 215         struct uhid_device *uhid = hid->driver_data;
 216         struct uhid_get_report_reply_req *req;
 217         struct uhid_event *ev;
 218         int ret;
 219
 220         if (!uhid->running)
 221                 return -EIO;
 222
 223         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 224         if (!ev)
 225                 return -ENOMEM;
 226
 227         ev->type = UHID_GET_REPORT;
 228         ev->u.get_report.rnum = rnum;
 229         ev->u.get_report.rtype = rtype;
 230
 231         ret = mutex_lock_interruptible(&uhid->report_lock);
 232         if (ret) {
 233                 kfree(ev);
 234                 return ret;
 235         }
 236
 237         /* this _always_ takes ownership of @ev */
 238         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.get_report.id);
 239         if (ret)
 240                 goto unlock;
 241
 242         req = &uhid->report_buf.u.get_report_reply;
 243         if (req->err) {
 244                 ret = -EIO;
 245         } else {
 246                 ret = min3(count, (size_t)req->size, (size_t)UHID_DATA_MAX);
 247                 memcpy(buf, req->data, ret);
 248         }
 249
 250 unlock:
 251         mutex_unlock(&uhid->report_lock);
 252         return ret;
 253 }
 254
 255 static int uhid_hid_set_report(struct hid_device *hid, unsigned char rnum,
 256                                const u8 *buf, size_t count, u8 rtype)
 257 {
 258         struct uhid_device *uhid = hid->driver_data;
 259         struct uhid_event *ev;
 260         int ret;
 261
 262         if (!uhid->running || count > UHID_DATA_MAX)
 263                 return -EIO;
 264
 265         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 266         if (!ev)
 267                 return -ENOMEM;
 268
 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);
 274
 275         ret = mutex_lock_interruptible(&uhid->report_lock);
 276         if (ret) {
 277                 kfree(ev);
 278                 return ret;
 279         }
 280
 281         /* this _always_ takes ownership of @ev */
 282         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.set_report.id);
 283         if (ret)
 284                 goto unlock;
 285
 286         if (uhid->report_buf.u.set_report_reply.err)
 287                 ret = -EIO;
 288         else
 289                 ret = count;
 290
 291 unlock:
 292         mutex_unlock(&uhid->report_lock);
 293         return ret;
 294 }
 295
 296 static int uhid_hid_raw_request(struct hid_device *hid, unsigned char reportnum,
 297                                 __u8 *buf, size_t len, unsigned char rtype,
 298                                 int reqtype)
 299 {
 300         u8 u_rtype;
 301
 302         switch (rtype) {
 303         case HID_FEATURE_REPORT:
 304                 u_rtype = UHID_FEATURE_REPORT;
 305                 break;
 306         case HID_OUTPUT_REPORT:
 307                 u_rtype = UHID_OUTPUT_REPORT;
 308                 break;
 309         case HID_INPUT_REPORT:
 310                 u_rtype = UHID_INPUT_REPORT;
 311                 break;
 312         default:
 313                 return -EINVAL;
 314         }
 315
 316         switch (reqtype) {
 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);
 321         default:
 322                 return -EIO;
 323         }
 324 }
 325
 326 static int uhid_hid_output_raw(struct hid_device *hid, __u8 *buf, size_t count,
 327                                unsigned char report_type)
 328 {
 329         struct uhid_device *uhid = hid->driver_data;
 330         __u8 rtype;
 331         unsigned long flags;
 332         struct uhid_event *ev;
 333
 334         switch (report_type) {
 335         case HID_FEATURE_REPORT:
 336                 rtype = UHID_FEATURE_REPORT;
 337                 break;
 338         case HID_OUTPUT_REPORT:
 339                 rtype = UHID_OUTPUT_REPORT;
 340                 break;
 341         default:
 342                 return -EINVAL;
 343         }
 344
 345         if (count < 1 || count > UHID_DATA_MAX)
 346                 return -EINVAL;
 347
 348         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 349         if (!ev)
 350                 return -ENOMEM;
 351
 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);
 356
 357         spin_lock_irqsave(&uhid->qlock, flags);
 358         uhid_queue(uhid, ev);
 359         spin_unlock_irqrestore(&uhid->qlock, flags);
 360
 361         return count;
 362 }
 363
 364 static int uhid_hid_output_report(struct hid_device *hid, __u8 *buf,
 365                                   size_t count)
 366 {
 367         return uhid_hid_output_raw(hid, buf, count, HID_OUTPUT_REPORT);
 368 }
 369
 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,
 378 };
 379 EXPORT_SYMBOL_GPL(uhid_hid_driver);
 380
 381 #ifdef CONFIG_COMPAT
 382
 383 /* Apparently we haven't stepped on these rakes enough times yet. */
 384 struct uhid_create_req_compat {
 385         __u8 name[128];
 386         __u8 phys[64];
 387         __u8 uniq[64];
 388
 389         compat_uptr_t rd_data;
 390         __u16 rd_size;
 391
 392         __u16 bus;
 393         __u32 vendor;
 394         __u32 product;
 395         __u32 version;
 396         __u32 country;
 397 } __attribute__((__packed__));
 398
 399 static int uhid_event_from_user(const char __user *buffer, size_t len,
 400                                 struct uhid_event *event)
 401 {
 402         if (in_compat_syscall()) {
 403                 u32 type;
 404
 405                 if (get_user(type, buffer))
 406                         return -EFAULT;
 407
 408                 if (type == UHID_CREATE) {
 409                         /*
 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.
 413                          */
 414                         struct uhid_create_req_compat *compat;
 415
 416                         compat = kzalloc(sizeof(*compat), GFP_KERNEL);
 417                         if (!compat)
 418                                 return -ENOMEM;
 419
 420                         buffer += sizeof(type);
 421                         len -= sizeof(type);
 422                         if (copy_from_user(compat, buffer,
 423                                            min(len, sizeof(*compat)))) {
 424                                 kfree(compat);
 425                                 return -EFAULT;
 426                         }
 427
 428                         /* Shuffle the data over to proper structure */
 429                         event->type = type;
 430
 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));
 437
 438                         event->u.create.rd_data = compat_ptr(compat->rd_data);
 439                         event->u.create.rd_size = compat->rd_size;
 440
 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;
 446
 447                         kfree(compat);
 448                         return 0;
 449                 }
 450                 /* All others can be copied directly */
 451         }
 452
 453         if (copy_from_user(event, buffer, min(len, sizeof(*event))))
 454                 return -EFAULT;
 455
 456         return 0;
 457 }
 458 #else
 459 static int uhid_event_from_user(const char __user *buffer, size_t len,
 460                                 struct uhid_event *event)
 461 {
 462         if (copy_from_user(event, buffer, min(len, sizeof(*event))))
 463                 return -EFAULT;
 464
 465         return 0;
 466 }
 467 #endif
 468
 469 static int uhid_dev_create2(struct uhid_device *uhid,
 470                             const struct uhid_event *ev)
 471 {
 472         struct hid_device *hid;
 473         size_t rd_size, len;
 474         void *rd_data;
 475         int ret;
 476
 477         if (uhid->running)
 478                 return -EALREADY;
 479
 480         rd_size = ev->u.create2.rd_size;
 481         if (rd_size <= 0 || rd_size > HID_MAX_DESCRIPTOR_SIZE)
 482                 return -EINVAL;
 483
 484         rd_data = kmemdup(ev->u.create2.rd_data, rd_size, GFP_KERNEL);
 485         if (!rd_data)
 486                 return -ENOMEM;
 487
 488         uhid->rd_size = rd_size;
 489         uhid->rd_data = rd_data;
 490
 491         hid = hid_allocate_device();
 492         if (IS_ERR(hid)) {
 493                 ret = PTR_ERR(hid);
 494                 goto err_free;
 495         }
 496
 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);
 504
 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;
 513
 514         uhid->hid = hid;
 515         uhid->running = true;
 516
 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.
 520          */
 521         schedule_work(&uhid->worker);
 522
 523         return 0;
 524
 525 err_free:
 526         kfree(uhid->rd_data);
 527         uhid->rd_data = NULL;
 528         uhid->rd_size = 0;
 529         return ret;
 530 }
 531
 532 static int uhid_dev_create(struct uhid_device *uhid,
 533                            struct uhid_event *ev)
 534 {
 535         struct uhid_create_req orig;
 536
 537         orig = ev->u.create;
 538
 539         if (orig.rd_size <= 0 || orig.rd_size > HID_MAX_DESCRIPTOR_SIZE)
 540                 return -EINVAL;
 541         if (copy_from_user(&ev->u.create2.rd_data, orig.rd_data, orig.rd_size))
 542                 return -EFAULT;
 543
 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;
 553
 554         return uhid_dev_create2(uhid, ev);
 555 }
 556
 557 static int uhid_dev_destroy(struct uhid_device *uhid)
 558 {
 559         if (!uhid->running)
 560                 return -EINVAL;
 561
 562         uhid->running = false;
 563         wake_up_interruptible(&uhid->report_wait);
 564
 565         cancel_work_sync(&uhid->worker);
 566
 567         hid_destroy_device(uhid->hid);
 568         kfree(uhid->rd_data);
 569
 570         return 0;
 571 }
 572
 573 static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
 574 {
 575         if (!uhid->running)
 576                 return -EINVAL;
 577
 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);
 580
 581         return 0;
 582 }
 583
 584 static int uhid_dev_input2(struct uhid_device *uhid, struct uhid_event *ev)
 585 {
 586         if (!uhid->running)
 587                 return -EINVAL;
 588
 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);
 591
 592         return 0;
 593 }
 594
 595 static int uhid_dev_get_report_reply(struct uhid_device *uhid,
 596                                      struct uhid_event *ev)
 597 {
 598         if (!uhid->running)
 599                 return -EINVAL;
 600
 601         uhid_report_wake_up(uhid, ev->u.get_report_reply.id, ev);
 602         return 0;
 603 }
 604
 605 static int uhid_dev_set_report_reply(struct uhid_device *uhid,
 606                                      struct uhid_event *ev)
 607 {
 608         if (!uhid->running)
 609                 return -EINVAL;
 610
 611         uhid_report_wake_up(uhid, ev->u.set_report_reply.id, ev);
 612         return 0;
 613 }
 614
 615 static int uhid_char_open(struct inode *inode, struct file *file)
 616 {
 617         struct uhid_device *uhid;
 618
 619         uhid = kzalloc(sizeof(*uhid), GFP_KERNEL);
 620         if (!uhid)
 621                 return -ENOMEM;
 622
 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);
 630
 631         file->private_data = uhid;
 632         stream_open(inode, file);
 633
 634         return 0;
 635 }
 636
 637 static int uhid_char_release(struct inode *inode, struct file *file)
 638 {
 639         struct uhid_device *uhid = file->private_data;
 640         unsigned int i;
 641
 642         uhid_dev_destroy(uhid);
 643
 644         for (i = 0; i < UHID_BUFSIZE; ++i)
 645                 kfree(uhid->outq[i]);
 646
 647         kfree(uhid);
 648
 649         return 0;
 650 }
 651
 652 static ssize_t uhid_char_read(struct file *file, char __user *buffer,
 653                                 size_t count, loff_t *ppos)
 654 {
 655         struct uhid_device *uhid = file->private_data;
 656         int ret;
 657         unsigned long flags;
 658         size_t len;
 659
 660         /* they need at least the "type" member of uhid_event */
 661         if (count < sizeof(__u32))
 662                 return -EINVAL;
 663
 664 try_again:
 665         if (file->f_flags & O_NONBLOCK) {
 666                 if (uhid->head == uhid->tail)
 667                         return -EAGAIN;
 668         } else {
 669                 ret = wait_event_interruptible(uhid->waitq,
 670                                                 uhid->head != uhid->tail);
 671                 if (ret)
 672                         return ret;
 673         }
 674
 675         ret = mutex_lock_interruptible(&uhid->devlock);
 676         if (ret)
 677                 return ret;
 678
 679         if (uhid->head == uhid->tail) {
 680                 mutex_unlock(&uhid->devlock);
 681                 goto try_again;
 682         } else {
 683                 len = min(count, sizeof(**uhid->outq));
 684                 if (copy_to_user(buffer, uhid->outq[uhid->tail], len)) {
 685                         ret = -EFAULT;
 686                 } else {
 687                         kfree(uhid->outq[uhid->tail]);
 688                         uhid->outq[uhid->tail] = NULL;
 689
 690                         spin_lock_irqsave(&uhid->qlock, flags);
 691                         uhid->tail = (uhid->tail + 1) % UHID_BUFSIZE;
 692                         spin_unlock_irqrestore(&uhid->qlock, flags);
 693                 }
 694         }
 695
 696         mutex_unlock(&uhid->devlock);
 697         return ret ? ret : len;
 698 }
 699
 700 static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
 701                                 size_t count, loff_t *ppos)
 702 {
 703         struct uhid_device *uhid = file->private_data;
 704         int ret;
 705         size_t len;
 706
 707         /* we need at least the "type" member of uhid_event */
 708         if (count < sizeof(__u32))
 709                 return -EINVAL;
 710
 711         ret = mutex_lock_interruptible(&uhid->devlock);
 712         if (ret)
 713                 return ret;
 714
 715         memset(&uhid->input_buf, 0, sizeof(uhid->input_buf));
 716         len = min(count, sizeof(uhid->input_buf));
 717
 718         ret = uhid_event_from_user(buffer, len, &uhid->input_buf);
 719         if (ret)
 720                 goto unlock;
 721
 722         switch (uhid->input_buf.type) {
 723         case UHID_CREATE:
 724                 /*
 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().
 728                  */
 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);
 732                         ret = -EACCES;
 733                         goto unlock;
 734                 }
 735                 ret = uhid_dev_create(uhid, &uhid->input_buf);
 736                 break;
 737         case UHID_CREATE2:
 738                 ret = uhid_dev_create2(uhid, &uhid->input_buf);
 739                 break;
 740         case UHID_DESTROY:
 741                 ret = uhid_dev_destroy(uhid);
 742                 break;
 743         case UHID_INPUT:
 744                 ret = uhid_dev_input(uhid, &uhid->input_buf);
 745                 break;
 746         case UHID_INPUT2:
 747                 ret = uhid_dev_input2(uhid, &uhid->input_buf);
 748                 break;
 749         case UHID_GET_REPORT_REPLY:
 750                 ret = uhid_dev_get_report_reply(uhid, &uhid->input_buf);
 751                 break;
 752         case UHID_SET_REPORT_REPLY:
 753                 ret = uhid_dev_set_report_reply(uhid, &uhid->input_buf);
 754                 break;
 755         default:
 756                 ret = -EOPNOTSUPP;
 757         }
 758
 759 unlock:
 760         mutex_unlock(&uhid->devlock);
 761
 762         /* return "count" not "len" to not confuse the caller */
 763         return ret ? ret : count;
 764 }
 765
 766 static __poll_t uhid_char_poll(struct file *file, poll_table *wait)
 767 {
 768         struct uhid_device *uhid = file->private_data;
 769         __poll_t mask = EPOLLOUT | EPOLLWRNORM; /* uhid is always writable */
 770
 771         poll_wait(file, &uhid->waitq, wait);
 772
 773         if (uhid->head != uhid->tail)
 774                 mask |= EPOLLIN | EPOLLRDNORM;
 775
 776         return mask;
 777 }
 778
 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,
 786         .llseek         = no_llseek,
 787 };
 788
 789 static struct miscdevice uhid_misc = {
 790         .fops           = &uhid_fops,
 791         .minor          = UHID_MINOR,
 792         .name           = UHID_NAME,
 793 };
 794 module_misc_device(uhid_misc);
 795
 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);