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