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
  35         /* This flag tracks whether the HID device is usable for commands from
  36          * userspace. The flag is already set before hid_add_device(), which
  37          * runs in workqueue context, to allow hid_add_device() to communicate
  38          * with userspace.
  39          * However, if hid_add_device() fails, the flag is cleared without
  40          * holding devlock.
  41          * We guarantee that if @running changes from true to false while you're
  42          * holding @devlock, it's still fine to access @hid.
  43          */
  44         bool running;
  45
  46         __u8 *rd_data;
  47         uint rd_size;
  48
  49         /* When this is NULL, userspace may use UHID_CREATE/UHID_CREATE2. */
  50         struct hid_device *hid;
  51         struct uhid_event input_buf;
  52
  53         wait_queue_head_t waitq;
  54         spinlock_t qlock;
  55         __u8 head;
  56         __u8 tail;
  57         struct uhid_event *outq[UHID_BUFSIZE];
  58
  59         /* blocking GET_REPORT support; state changes protected by qlock */
  60         struct mutex report_lock;
  61         wait_queue_head_t report_wait;
  62         bool report_running;
  63         u32 report_id;
  64         u32 report_type;
  65         struct uhid_event report_buf;
  66         struct work_struct worker;
  67 };
  68
  69 static struct miscdevice uhid_misc;
  70
  71 static void uhid_device_add_worker(struct work_struct *work)
  72 {
  73         struct uhid_device *uhid = container_of(work, struct uhid_device, worker);
  74         int ret;
  75
  76         ret = hid_add_device(uhid->hid);
  77         if (ret) {
  78                 hid_err(uhid->hid, "Cannot register HID device: error %d\n", ret);
  79
  80                 /* We used to call hid_destroy_device() here, but that's really
  81                  * messy to get right because we have to coordinate with
  82                  * concurrent writes from userspace that might be in the middle
  83                  * of using uhid->hid.
  84                  * Just leave uhid->hid as-is for now, and clean it up when
  85                  * userspace tries to close or reinitialize the uhid instance.
  86                  *
  87                  * However, we do have to clear the ->running flag and do a
  88                  * wakeup to make sure userspace knows that the device is gone.
  89                  */
  90                 uhid->running = false;
  91                 wake_up_interruptible(&uhid->report_wait);
  92         }
  93 }
  94
  95 static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
  96 {
  97         __u8 newhead;
  98
  99         newhead = (uhid->head + 1) % UHID_BUFSIZE;
 100
 101         if (newhead != uhid->tail) {
 102                 uhid->outq[uhid->head] = ev;
 103                 uhid->head = newhead;
 104                 wake_up_interruptible(&uhid->waitq);
 105         } else {
 106                 hid_warn(uhid->hid, "Output queue is full\n");
 107                 kfree(ev);
 108         }
 109 }
 110
 111 static int uhid_queue_event(struct uhid_device *uhid, __u32 event)
 112 {
 113         unsigned long flags;
 114         struct uhid_event *ev;
 115
 116         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 117         if (!ev)
 118                 return -ENOMEM;
 119
 120         ev->type = event;
 121
 122         spin_lock_irqsave(&uhid->qlock, flags);
 123         uhid_queue(uhid, ev);
 124         spin_unlock_irqrestore(&uhid->qlock, flags);
 125
 126         return 0;
 127 }
 128
 129 static int uhid_hid_start(struct hid_device *hid)
 130 {
 131         struct uhid_device *uhid = hid->driver_data;
 132         struct uhid_event *ev;
 133         unsigned long flags;
 134
 135         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 136         if (!ev)
 137                 return -ENOMEM;
 138
 139         ev->type = UHID_START;
 140
 141         if (hid->report_enum[HID_FEATURE_REPORT].numbered)
 142                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_FEATURE_REPORTS;
 143         if (hid->report_enum[HID_OUTPUT_REPORT].numbered)
 144                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_OUTPUT_REPORTS;
 145         if (hid->report_enum[HID_INPUT_REPORT].numbered)
 146                 ev->u.start.dev_flags |= UHID_DEV_NUMBERED_INPUT_REPORTS;
 147
 148         spin_lock_irqsave(&uhid->qlock, flags);
 149         uhid_queue(uhid, ev);
 150         spin_unlock_irqrestore(&uhid->qlock, flags);
 151
 152         return 0;
 153 }
 154
 155 static void uhid_hid_stop(struct hid_device *hid)
 156 {
 157         struct uhid_device *uhid = hid->driver_data;
 158
 159         hid->claimed = 0;
 160         uhid_queue_event(uhid, UHID_STOP);
 161 }
 162
 163 static int uhid_hid_open(struct hid_device *hid)
 164 {
 165         struct uhid_device *uhid = hid->driver_data;
 166
 167         return uhid_queue_event(uhid, UHID_OPEN);
 168 }
 169
 170 static void uhid_hid_close(struct hid_device *hid)
 171 {
 172         struct uhid_device *uhid = hid->driver_data;
 173
 174         uhid_queue_event(uhid, UHID_CLOSE);
 175 }
 176
 177 static int uhid_hid_parse(struct hid_device *hid)
 178 {
 179         struct uhid_device *uhid = hid->driver_data;
 180
 181         return hid_parse_report(hid, uhid->rd_data, uhid->rd_size);
 182 }
 183
 184 /* must be called with report_lock held */
 185 static int __uhid_report_queue_and_wait(struct uhid_device *uhid,
 186                                         struct uhid_event *ev,
 187                                         __u32 *report_id)
 188 {
 189         unsigned long flags;
 190         int ret;
 191
 192         spin_lock_irqsave(&uhid->qlock, flags);
 193         *report_id = ++uhid->report_id;
 194         uhid->report_type = ev->type + 1;
 195         uhid->report_running = true;
 196         uhid_queue(uhid, ev);
 197         spin_unlock_irqrestore(&uhid->qlock, flags);
 198
 199         ret = wait_event_interruptible_timeout(uhid->report_wait,
 200                                 !uhid->report_running || !uhid->running,
 201                                 5 * HZ);
 202         if (!ret || !uhid->running || uhid->report_running)
 203                 ret = -EIO;
 204         else if (ret < 0)
 205                 ret = -ERESTARTSYS;
 206         else
 207                 ret = 0;
 208
 209         uhid->report_running = false;
 210
 211         return ret;
 212 }
 213
 214 static void uhid_report_wake_up(struct uhid_device *uhid, u32 id,
 215                                 const struct uhid_event *ev)
 216 {
 217         unsigned long flags;
 218
 219         spin_lock_irqsave(&uhid->qlock, flags);
 220
 221         /* id for old report; drop it silently */
 222         if (uhid->report_type != ev->type || uhid->report_id != id)
 223                 goto unlock;
 224         if (!uhid->report_running)
 225                 goto unlock;
 226
 227         memcpy(&uhid->report_buf, ev, sizeof(*ev));
 228         uhid->report_running = false;
 229         wake_up_interruptible(&uhid->report_wait);
 230
 231 unlock:
 232         spin_unlock_irqrestore(&uhid->qlock, flags);
 233 }
 234
 235 static int uhid_hid_get_report(struct hid_device *hid, unsigned char rnum,
 236                                u8 *buf, size_t count, u8 rtype)
 237 {
 238         struct uhid_device *uhid = hid->driver_data;
 239         struct uhid_get_report_reply_req *req;
 240         struct uhid_event *ev;
 241         int ret;
 242
 243         if (!uhid->running)
 244                 return -EIO;
 245
 246         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 247         if (!ev)
 248                 return -ENOMEM;
 249
 250         ev->type = UHID_GET_REPORT;
 251         ev->u.get_report.rnum = rnum;
 252         ev->u.get_report.rtype = rtype;
 253
 254         ret = mutex_lock_interruptible(&uhid->report_lock);
 255         if (ret) {
 256                 kfree(ev);
 257                 return ret;
 258         }
 259
 260         /* this _always_ takes ownership of @ev */
 261         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.get_report.id);
 262         if (ret)
 263                 goto unlock;
 264
 265         req = &uhid->report_buf.u.get_report_reply;
 266         if (req->err) {
 267                 ret = -EIO;
 268         } else {
 269                 ret = min3(count, (size_t)req->size, (size_t)UHID_DATA_MAX);
 270                 memcpy(buf, req->data, ret);
 271         }
 272
 273 unlock:
 274         mutex_unlock(&uhid->report_lock);
 275         return ret;
 276 }
 277
 278 static int uhid_hid_set_report(struct hid_device *hid, unsigned char rnum,
 279                                const u8 *buf, size_t count, u8 rtype)
 280 {
 281         struct uhid_device *uhid = hid->driver_data;
 282         struct uhid_event *ev;
 283         int ret;
 284
 285         if (!uhid->running || count > UHID_DATA_MAX)
 286                 return -EIO;
 287
 288         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 289         if (!ev)
 290                 return -ENOMEM;
 291
 292         ev->type = UHID_SET_REPORT;
 293         ev->u.set_report.rnum = rnum;
 294         ev->u.set_report.rtype = rtype;
 295         ev->u.set_report.size = count;
 296         memcpy(ev->u.set_report.data, buf, count);
 297
 298         ret = mutex_lock_interruptible(&uhid->report_lock);
 299         if (ret) {
 300                 kfree(ev);
 301                 return ret;
 302         }
 303
 304         /* this _always_ takes ownership of @ev */
 305         ret = __uhid_report_queue_and_wait(uhid, ev, &ev->u.set_report.id);
 306         if (ret)
 307                 goto unlock;
 308
 309         if (uhid->report_buf.u.set_report_reply.err)
 310                 ret = -EIO;
 311         else
 312                 ret = count;
 313
 314 unlock:
 315         mutex_unlock(&uhid->report_lock);
 316         return ret;
 317 }
 318
 319 static int uhid_hid_raw_request(struct hid_device *hid, unsigned char reportnum,
 320                                 __u8 *buf, size_t len, unsigned char rtype,
 321                                 int reqtype)
 322 {
 323         u8 u_rtype;
 324
 325         switch (rtype) {
 326         case HID_FEATURE_REPORT:
 327                 u_rtype = UHID_FEATURE_REPORT;
 328                 break;
 329         case HID_OUTPUT_REPORT:
 330                 u_rtype = UHID_OUTPUT_REPORT;
 331                 break;
 332         case HID_INPUT_REPORT:
 333                 u_rtype = UHID_INPUT_REPORT;
 334                 break;
 335         default:
 336                 return -EINVAL;
 337         }
 338
 339         switch (reqtype) {
 340         case HID_REQ_GET_REPORT:
 341                 return uhid_hid_get_report(hid, reportnum, buf, len, u_rtype);
 342         case HID_REQ_SET_REPORT:
 343                 return uhid_hid_set_report(hid, reportnum, buf, len, u_rtype);
 344         default:
 345                 return -EIO;
 346         }
 347 }
 348
 349 static int uhid_hid_output_raw(struct hid_device *hid, __u8 *buf, size_t count,
 350                                unsigned char report_type)
 351 {
 352         struct uhid_device *uhid = hid->driver_data;
 353         __u8 rtype;
 354         unsigned long flags;
 355         struct uhid_event *ev;
 356
 357         switch (report_type) {
 358         case HID_FEATURE_REPORT:
 359                 rtype = UHID_FEATURE_REPORT;
 360                 break;
 361         case HID_OUTPUT_REPORT:
 362                 rtype = UHID_OUTPUT_REPORT;
 363                 break;
 364         default:
 365                 return -EINVAL;
 366         }
 367
 368         if (count < 1 || count > UHID_DATA_MAX)
 369                 return -EINVAL;
 370
 371         ev = kzalloc(sizeof(*ev), GFP_KERNEL);
 372         if (!ev)
 373                 return -ENOMEM;
 374
 375         ev->type = UHID_OUTPUT;
 376         ev->u.output.size = count;
 377         ev->u.output.rtype = rtype;
 378         memcpy(ev->u.output.data, buf, count);
 379
 380         spin_lock_irqsave(&uhid->qlock, flags);
 381         uhid_queue(uhid, ev);
 382         spin_unlock_irqrestore(&uhid->qlock, flags);
 383
 384         return count;
 385 }
 386
 387 static int uhid_hid_output_report(struct hid_device *hid, __u8 *buf,
 388                                   size_t count)
 389 {
 390         return uhid_hid_output_raw(hid, buf, count, HID_OUTPUT_REPORT);
 391 }
 392
 393 struct hid_ll_driver uhid_hid_driver = {
 394         .start = uhid_hid_start,
 395         .stop = uhid_hid_stop,
 396         .open = uhid_hid_open,
 397         .close = uhid_hid_close,
 398         .parse = uhid_hid_parse,
 399         .raw_request = uhid_hid_raw_request,
 400         .output_report = uhid_hid_output_report,
 401 };
 402 EXPORT_SYMBOL_GPL(uhid_hid_driver);
 403
 404 #ifdef CONFIG_COMPAT
 405
 406 /* Apparently we haven't stepped on these rakes enough times yet. */
 407 struct uhid_create_req_compat {
 408         __u8 name[128];
 409         __u8 phys[64];
 410         __u8 uniq[64];
 411
 412         compat_uptr_t rd_data;
 413         __u16 rd_size;
 414
 415         __u16 bus;
 416         __u32 vendor;
 417         __u32 product;
 418         __u32 version;
 419         __u32 country;
 420 } __attribute__((__packed__));
 421
 422 static int uhid_event_from_user(const char __user *buffer, size_t len,
 423                                 struct uhid_event *event)
 424 {
 425         if (in_compat_syscall()) {
 426                 u32 type;
 427
 428                 if (get_user(type, buffer))
 429                         return -EFAULT;
 430
 431                 if (type == UHID_CREATE) {
 432                         /*
 433                          * This is our messed up request with compat pointer.
 434                          * It is largish (more than 256 bytes) so we better
 435                          * allocate it from the heap.
 436                          */
 437                         struct uhid_create_req_compat *compat;
 438
 439                         compat = kzalloc(sizeof(*compat), GFP_KERNEL);
 440                         if (!compat)
 441                                 return -ENOMEM;
 442
 443                         buffer += sizeof(type);
 444                         len -= sizeof(type);
 445                         if (copy_from_user(compat, buffer,
 446                                            min(len, sizeof(*compat)))) {
 447                                 kfree(compat);
 448                                 return -EFAULT;
 449                         }
 450
 451                         /* Shuffle the data over to proper structure */
 452                         event->type = type;
 453
 454                         memcpy(event->u.create.name, compat->name,
 455                                 sizeof(compat->name));
 456                         memcpy(event->u.create.phys, compat->phys,
 457                                 sizeof(compat->phys));
 458                         memcpy(event->u.create.uniq, compat->uniq,
 459                                 sizeof(compat->uniq));
 460
 461                         event->u.create.rd_data = compat_ptr(compat->rd_data);
 462                         event->u.create.rd_size = compat->rd_size;
 463
 464                         event->u.create.bus = compat->bus;
 465                         event->u.create.vendor = compat->vendor;
 466                         event->u.create.product = compat->product;
 467                         event->u.create.version = compat->version;
 468                         event->u.create.country = compat->country;
 469
 470                         kfree(compat);
 471                         return 0;
 472                 }
 473                 /* All others can be copied directly */
 474         }
 475
 476         if (copy_from_user(event, buffer, min(len, sizeof(*event))))
 477                 return -EFAULT;
 478
 479         return 0;
 480 }
 481 #else
 482 static int uhid_event_from_user(const char __user *buffer, size_t len,
 483                                 struct uhid_event *event)
 484 {
 485         if (copy_from_user(event, buffer, min(len, sizeof(*event))))
 486                 return -EFAULT;
 487
 488         return 0;
 489 }
 490 #endif
 491
 492 static int uhid_dev_create2(struct uhid_device *uhid,
 493                             const struct uhid_event *ev)
 494 {
 495         struct hid_device *hid;
 496         size_t rd_size, len;
 497         void *rd_data;
 498         int ret;
 499
 500         if (uhid->hid)
 501                 return -EALREADY;
 502
 503         rd_size = ev->u.create2.rd_size;
 504         if (rd_size <= 0 || rd_size > HID_MAX_DESCRIPTOR_SIZE)
 505                 return -EINVAL;
 506
 507         rd_data = kmemdup(ev->u.create2.rd_data, rd_size, GFP_KERNEL);
 508         if (!rd_data)
 509                 return -ENOMEM;
 510
 511         uhid->rd_size = rd_size;
 512         uhid->rd_data = rd_data;
 513
 514         hid = hid_allocate_device();
 515         if (IS_ERR(hid)) {
 516                 ret = PTR_ERR(hid);
 517                 goto err_free;
 518         }
 519
 520         /* @hid is zero-initialized, strncpy() is correct, strlcpy() not */
 521         len = min(sizeof(hid->name), sizeof(ev->u.create2.name)) - 1;
 522         strncpy(hid->name, ev->u.create2.name, len);
 523         len = min(sizeof(hid->phys), sizeof(ev->u.create2.phys)) - 1;
 524         strncpy(hid->phys, ev->u.create2.phys, len);
 525         len = min(sizeof(hid->uniq), sizeof(ev->u.create2.uniq)) - 1;
 526         strncpy(hid->uniq, ev->u.create2.uniq, len);
 527
 528         hid->ll_driver = &uhid_hid_driver;
 529         hid->bus = ev->u.create2.bus;
 530         hid->vendor = ev->u.create2.vendor;
 531         hid->product = ev->u.create2.product;
 532         hid->version = ev->u.create2.version;
 533         hid->country = ev->u.create2.country;
 534         hid->driver_data = uhid;
 535         hid->dev.parent = uhid_misc.this_device;
 536
 537         uhid->hid = hid;
 538         uhid->running = true;
 539
 540         /* Adding of a HID device is done through a worker, to allow HID drivers
 541          * which use feature requests during .probe to work, without they would
 542          * be blocked on devlock, which is held by uhid_char_write.
 543          */
 544         schedule_work(&uhid->worker);
 545
 546         return 0;
 547
 548 err_free:
 549         kfree(uhid->rd_data);
 550         uhid->rd_data = NULL;
 551         uhid->rd_size = 0;
 552         return ret;
 553 }
 554
 555 static int uhid_dev_create(struct uhid_device *uhid,
 556                            struct uhid_event *ev)
 557 {
 558         struct uhid_create_req orig;
 559
 560         orig = ev->u.create;
 561
 562         if (orig.rd_size <= 0 || orig.rd_size > HID_MAX_DESCRIPTOR_SIZE)
 563                 return -EINVAL;
 564         if (copy_from_user(&ev->u.create2.rd_data, orig.rd_data, orig.rd_size))
 565                 return -EFAULT;
 566
 567         memcpy(ev->u.create2.name, orig.name, sizeof(orig.name));
 568         memcpy(ev->u.create2.phys, orig.phys, sizeof(orig.phys));
 569         memcpy(ev->u.create2.uniq, orig.uniq, sizeof(orig.uniq));
 570         ev->u.create2.rd_size = orig.rd_size;
 571         ev->u.create2.bus = orig.bus;
 572         ev->u.create2.vendor = orig.vendor;
 573         ev->u.create2.product = orig.product;
 574         ev->u.create2.version = orig.version;
 575         ev->u.create2.country = orig.country;
 576
 577         return uhid_dev_create2(uhid, ev);
 578 }
 579
 580 static int uhid_dev_destroy(struct uhid_device *uhid)
 581 {
 582         if (!uhid->hid)
 583                 return -EINVAL;
 584
 585         uhid->running = false;
 586         wake_up_interruptible(&uhid->report_wait);
 587
 588         cancel_work_sync(&uhid->worker);
 589
 590         hid_destroy_device(uhid->hid);
 591         uhid->hid = NULL;
 592         kfree(uhid->rd_data);
 593
 594         return 0;
 595 }
 596
 597 static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
 598 {
 599         if (!uhid->running)
 600                 return -EINVAL;
 601
 602         hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data,
 603                          min_t(size_t, ev->u.input.size, UHID_DATA_MAX), 0);
 604
 605         return 0;
 606 }
 607
 608 static int uhid_dev_input2(struct uhid_device *uhid, struct uhid_event *ev)
 609 {
 610         if (!uhid->running)
 611                 return -EINVAL;
 612
 613         hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input2.data,
 614                          min_t(size_t, ev->u.input2.size, UHID_DATA_MAX), 0);
 615
 616         return 0;
 617 }
 618
 619 static int uhid_dev_get_report_reply(struct uhid_device *uhid,
 620                                      struct uhid_event *ev)
 621 {
 622         if (!uhid->running)
 623                 return -EINVAL;
 624
 625         uhid_report_wake_up(uhid, ev->u.get_report_reply.id, ev);
 626         return 0;
 627 }
 628
 629 static int uhid_dev_set_report_reply(struct uhid_device *uhid,
 630                                      struct uhid_event *ev)
 631 {
 632         if (!uhid->running)
 633                 return -EINVAL;
 634
 635         uhid_report_wake_up(uhid, ev->u.set_report_reply.id, ev);
 636         return 0;
 637 }
 638
 639 static int uhid_char_open(struct inode *inode, struct file *file)
 640 {
 641         struct uhid_device *uhid;
 642
 643         uhid = kzalloc(sizeof(*uhid), GFP_KERNEL);
 644         if (!uhid)
 645                 return -ENOMEM;
 646
 647         mutex_init(&uhid->devlock);
 648         mutex_init(&uhid->report_lock);
 649         spin_lock_init(&uhid->qlock);
 650         init_waitqueue_head(&uhid->waitq);
 651         init_waitqueue_head(&uhid->report_wait);
 652         uhid->running = false;
 653         INIT_WORK(&uhid->worker, uhid_device_add_worker);
 654
 655         file->private_data = uhid;
 656         nonseekable_open(inode, file);
 657
 658         return 0;
 659 }
 660
 661 static int uhid_char_release(struct inode *inode, struct file *file)
 662 {
 663         struct uhid_device *uhid = file->private_data;
 664         unsigned int i;
 665
 666         uhid_dev_destroy(uhid);
 667
 668         for (i = 0; i < UHID_BUFSIZE; ++i)
 669                 kfree(uhid->outq[i]);
 670
 671         kfree(uhid);
 672
 673         return 0;
 674 }
 675
 676 static ssize_t uhid_char_read(struct file *file, char __user *buffer,
 677                                 size_t count, loff_t *ppos)
 678 {
 679         struct uhid_device *uhid = file->private_data;
 680         int ret;
 681         unsigned long flags;
 682         size_t len;
 683
 684         /* they need at least the "type" member of uhid_event */
 685         if (count < sizeof(__u32))
 686                 return -EINVAL;
 687
 688 try_again:
 689         if (file->f_flags & O_NONBLOCK) {
 690                 if (uhid->head == uhid->tail)
 691                         return -EAGAIN;
 692         } else {
 693                 ret = wait_event_interruptible(uhid->waitq,
 694                                                 uhid->head != uhid->tail);
 695                 if (ret)
 696                         return ret;
 697         }
 698
 699         ret = mutex_lock_interruptible(&uhid->devlock);
 700         if (ret)
 701                 return ret;
 702
 703         if (uhid->head == uhid->tail) {
 704                 mutex_unlock(&uhid->devlock);
 705                 goto try_again;
 706         } else {
 707                 len = min(count, sizeof(**uhid->outq));
 708                 if (copy_to_user(buffer, uhid->outq[uhid->tail], len)) {
 709                         ret = -EFAULT;
 710                 } else {
 711                         kfree(uhid->outq[uhid->tail]);
 712                         uhid->outq[uhid->tail] = NULL;
 713
 714                         spin_lock_irqsave(&uhid->qlock, flags);
 715                         uhid->tail = (uhid->tail + 1) % UHID_BUFSIZE;
 716                         spin_unlock_irqrestore(&uhid->qlock, flags);
 717                 }
 718         }
 719
 720         mutex_unlock(&uhid->devlock);
 721         return ret ? ret : len;
 722 }
 723
 724 static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
 725                                 size_t count, loff_t *ppos)
 726 {
 727         struct uhid_device *uhid = file->private_data;
 728         int ret;
 729         size_t len;
 730
 731         /* we need at least the "type" member of uhid_event */
 732         if (count < sizeof(__u32))
 733                 return -EINVAL;
 734
 735         ret = mutex_lock_interruptible(&uhid->devlock);
 736         if (ret)
 737                 return ret;
 738
 739         memset(&uhid->input_buf, 0, sizeof(uhid->input_buf));
 740         len = min(count, sizeof(uhid->input_buf));
 741
 742         ret = uhid_event_from_user(buffer, len, &uhid->input_buf);
 743         if (ret)
 744                 goto unlock;
 745
 746         switch (uhid->input_buf.type) {
 747         case UHID_CREATE:
 748                 /*
 749                  * 'struct uhid_create_req' contains a __user pointer which is
 750                  * copied from, so it's unsafe to allow this with elevated
 751                  * privileges (e.g. from a setuid binary) or via kernel_write().
 752                  */
 753                 if (file->f_cred != current_cred() || uaccess_kernel()) {
 754                         pr_err_once("UHID_CREATE from different security context by process %d (%s), this is not allowed.\n",
 755                                     task_tgid_vnr(current), current->comm);
 756                         ret = -EACCES;
 757                         goto unlock;
 758                 }
 759                 ret = uhid_dev_create(uhid, &uhid->input_buf);
 760                 break;
 761         case UHID_CREATE2:
 762                 ret = uhid_dev_create2(uhid, &uhid->input_buf);
 763                 break;
 764         case UHID_DESTROY:
 765                 ret = uhid_dev_destroy(uhid);
 766                 break;
 767         case UHID_INPUT:
 768                 ret = uhid_dev_input(uhid, &uhid->input_buf);
 769                 break;
 770         case UHID_INPUT2:
 771                 ret = uhid_dev_input2(uhid, &uhid->input_buf);
 772                 break;
 773         case UHID_GET_REPORT_REPLY:
 774                 ret = uhid_dev_get_report_reply(uhid, &uhid->input_buf);
 775                 break;
 776         case UHID_SET_REPORT_REPLY:
 777                 ret = uhid_dev_set_report_reply(uhid, &uhid->input_buf);
 778                 break;
 779         default:
 780                 ret = -EOPNOTSUPP;
 781         }
 782
 783 unlock:
 784         mutex_unlock(&uhid->devlock);
 785
 786         /* return "count" not "len" to not confuse the caller */
 787         return ret ? ret : count;
 788 }
 789
 790 static __poll_t uhid_char_poll(struct file *file, poll_table *wait)
 791 {
 792         struct uhid_device *uhid = file->private_data;
 793         __poll_t mask = EPOLLOUT | EPOLLWRNORM; /* uhid is always writable */
 794
 795         poll_wait(file, &uhid->waitq, wait);
 796
 797         if (uhid->head != uhid->tail)
 798                 mask |= EPOLLIN | EPOLLRDNORM;
 799
 800         return mask;
 801 }
 802
 803 static const struct file_operations uhid_fops = {
 804         .owner          = THIS_MODULE,
 805         .open           = uhid_char_open,
 806         .release        = uhid_char_release,
 807         .read           = uhid_char_read,
 808         .write          = uhid_char_write,
 809         .poll           = uhid_char_poll,
 810         .llseek         = no_llseek,
 811 };
 812
 813 static struct miscdevice uhid_misc = {
 814         .fops           = &uhid_fops,
 815         .minor          = UHID_MINOR,
 816         .name           = UHID_NAME,
 817 };
 818 module_misc_device(uhid_misc);
 819
 820 MODULE_LICENSE("GPL");
 821 MODULE_AUTHOR("David Herrmann <dh.herrmann@gmail.com>");
 822 MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");
 823 MODULE_ALIAS_MISCDEV(UHID_MINOR);
 824 MODULE_ALIAS("devname:" UHID_NAME);