drivers/usb/wusbcore/security.c

   1 /*
   2  * Wireless USB Host Controller
   3  * Security support: encryption enablement, etc
   4  *
   5  * Copyright (C) 2006 Intel Corporation
   6  * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License version
  10  * 2 as published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  20  * 02110-1301, USA.
  21  *
  22  *
  23  * FIXME: docs
  24  */
  25 #include <linux/types.h>
  26 #include <linux/slab.h>
  27 #include <linux/usb/ch9.h>
  28 #include <linux/random.h>
  29 #include <linux/export.h>
  30 #include "wusbhc.h"
  31
  32 static void wusbhc_gtk_rekey_work(struct work_struct *work);
  33
  34 int wusbhc_sec_create(struct wusbhc *wusbhc)
  35 {
  36         wusbhc->gtk.descr.bLength = sizeof(wusbhc->gtk.descr) + sizeof(wusbhc->gtk.data);
  37         wusbhc->gtk.descr.bDescriptorType = USB_DT_KEY;
  38         wusbhc->gtk.descr.bReserved = 0;
  39         wusbhc->gtk_index = 0;
  40
  41         INIT_WORK(&wusbhc->gtk_rekey_work, wusbhc_gtk_rekey_work);
  42
  43         return 0;
  44 }
  45
  46
  47 /* Called when the HC is destroyed */
  48 void wusbhc_sec_destroy(struct wusbhc *wusbhc)
  49 {
  50 }
  51
  52
  53 /**
  54  * wusbhc_next_tkid - generate a new, currently unused, TKID
  55  * @wusbhc:   the WUSB host controller
  56  * @wusb_dev: the device whose PTK the TKID is for
  57  *            (or NULL for a TKID for a GTK)
  58  *
  59  * The generated TKID consist of two parts: the device's authenicated
  60  * address (or 0 or a GTK); and an incrementing number.  This ensures
  61  * that TKIDs cannot be shared between devices and by the time the
  62  * incrementing number wraps around the older TKIDs will no longer be
  63  * in use (a maximum of two keys may be active at any one time).
  64  */
  65 static u32 wusbhc_next_tkid(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev)
  66 {
  67         u32 *tkid;
  68         u32 addr;
  69
  70         if (wusb_dev == NULL) {
  71                 tkid = &wusbhc->gtk_tkid;
  72                 addr = 0;
  73         } else {
  74                 tkid = &wusb_port_by_idx(wusbhc, wusb_dev->port_idx)->ptk_tkid;
  75                 addr = wusb_dev->addr & 0x7f;
  76         }
  77
  78         *tkid = (addr << 8) | ((*tkid + 1) & 0xff);
  79
  80         return *tkid;
  81 }
  82
  83 static void wusbhc_generate_gtk(struct wusbhc *wusbhc)
  84 {
  85         const size_t key_size = sizeof(wusbhc->gtk.data);
  86         u32 tkid;
  87
  88         tkid = wusbhc_next_tkid(wusbhc, NULL);
  89
  90         wusbhc->gtk.descr.tTKID[0] = (tkid >>  0) & 0xff;
  91         wusbhc->gtk.descr.tTKID[1] = (tkid >>  8) & 0xff;
  92         wusbhc->gtk.descr.tTKID[2] = (tkid >> 16) & 0xff;
  93
  94         get_random_bytes(wusbhc->gtk.descr.bKeyData, key_size);
  95 }
  96
  97 /**
  98  * wusbhc_sec_start - start the security management process
  99  * @wusbhc: the WUSB host controller
 100  *
 101  * Generate and set an initial GTK on the host controller.
 102  *
 103  * Called when the HC is started.
 104  */
 105 int wusbhc_sec_start(struct wusbhc *wusbhc)
 106 {
 107         const size_t key_size = sizeof(wusbhc->gtk.data);
 108         int result;
 109
 110         wusbhc_generate_gtk(wusbhc);
 111
 112         result = wusbhc->set_gtk(wusbhc, wusbhc->gtk_tkid,
 113                                 &wusbhc->gtk.descr.bKeyData, key_size);
 114         if (result < 0)
 115                 dev_err(wusbhc->dev, "cannot set GTK for the host: %d\n",
 116                         result);
 117
 118         return result;
 119 }
 120
 121 /**
 122  * wusbhc_sec_stop - stop the security management process
 123  * @wusbhc: the WUSB host controller
 124  *
 125  * Wait for any pending GTK rekeys to stop.
 126  */
 127 void wusbhc_sec_stop(struct wusbhc *wusbhc)
 128 {
 129         cancel_work_sync(&wusbhc->gtk_rekey_work);
 130 }
 131
 132
 133 /** @returns encryption type name */
 134 const char *wusb_et_name(u8 x)
 135 {
 136         switch (x) {
 137         case USB_ENC_TYPE_UNSECURE:     return "unsecure";
 138         case USB_ENC_TYPE_WIRED:        return "wired";
 139         case USB_ENC_TYPE_CCM_1:        return "CCM-1";
 140         case USB_ENC_TYPE_RSA_1:        return "RSA-1";
 141         default:                        return "unknown";
 142         }
 143 }
 144 EXPORT_SYMBOL_GPL(wusb_et_name);
 145
 146 /*
 147  * Set the device encryption method
 148  *
 149  * We tell the device which encryption method to use; we do this when
 150  * setting up the device's security.
 151  */
 152 static int wusb_dev_set_encryption(struct usb_device *usb_dev, int value)
 153 {
 154         int result;
 155         struct device *dev = &usb_dev->dev;
 156         struct wusb_dev *wusb_dev = usb_dev->wusb_dev;
 157
 158         if (value) {
 159                 value = wusb_dev->ccm1_etd.bEncryptionValue;
 160         } else {
 161                 /* FIXME: should be wusb_dev->etd[UNSECURE].bEncryptionValue */
 162                 value = 0;
 163         }
 164         /* Set device's */
 165         result = usb_control_msg(usb_dev, usb_sndctrlpipe(usb_dev, 0),
 166                         USB_REQ_SET_ENCRYPTION,
 167                         USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 168                         value, 0, NULL, 0, USB_CTRL_SET_TIMEOUT);
 169         if (result < 0)
 170                 dev_err(dev, "Can't set device's WUSB encryption to "
 171                         "%s (value %d): %d\n",
 172                         wusb_et_name(wusb_dev->ccm1_etd.bEncryptionType),
 173                         wusb_dev->ccm1_etd.bEncryptionValue,  result);
 174         return result;
 175 }
 176
 177 /*
 178  * Set the GTK to be used by a device.
 179  *
 180  * The device must be authenticated.
 181  */
 182 static int wusb_dev_set_gtk(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev)
 183 {
 184         struct usb_device *usb_dev = wusb_dev->usb_dev;
 185         u8 key_index = wusb_key_index(wusbhc->gtk_index,
 186                 WUSB_KEY_INDEX_TYPE_GTK, WUSB_KEY_INDEX_ORIGINATOR_HOST);
 187
 188         return usb_control_msg(
 189                 usb_dev, usb_sndctrlpipe(usb_dev, 0),
 190                 USB_REQ_SET_DESCRIPTOR,
 191                 USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 192                 USB_DT_KEY << 8 | key_index, 0,
 193                 &wusbhc->gtk.descr, wusbhc->gtk.descr.bLength,
 194                 USB_CTRL_SET_TIMEOUT);
 195 }
 196
 197
 198 /* FIXME: prototype for adding security */
 199 int wusb_dev_sec_add(struct wusbhc *wusbhc,
 200                      struct usb_device *usb_dev, struct wusb_dev *wusb_dev)
 201 {
 202         int result, bytes, secd_size;
 203         struct device *dev = &usb_dev->dev;
 204         struct usb_security_descriptor *secd, *new_secd;
 205         const struct usb_encryption_descriptor *etd, *ccm1_etd = NULL;
 206         const void *itr, *top;
 207         char buf[64];
 208
 209         secd = kmalloc(sizeof(*secd), GFP_KERNEL);
 210         if (secd == NULL) {
 211                 result = -ENOMEM;
 212                 goto out;
 213         }
 214
 215         result = usb_get_descriptor(usb_dev, USB_DT_SECURITY,
 216                                     0, secd, sizeof(*secd));
 217         if (result < sizeof(*secd)) {
 218                 dev_err(dev, "Can't read security descriptor or "
 219                         "not enough data: %d\n", result);
 220                 goto out;
 221         }
 222         secd_size = le16_to_cpu(secd->wTotalLength);
 223         new_secd = krealloc(secd, secd_size, GFP_KERNEL);
 224         if (new_secd == NULL) {
 225                 dev_err(dev, "Can't allocate space for security descriptors\n");
 226                 goto out;
 227         }
 228         secd = new_secd;
 229         result = usb_get_descriptor(usb_dev, USB_DT_SECURITY,
 230                                     0, secd, secd_size);
 231         if (result < secd_size) {
 232                 dev_err(dev, "Can't read security descriptor or "
 233                         "not enough data: %d\n", result);
 234                 goto out;
 235         }
 236         bytes = 0;
 237         itr = &secd[1];
 238         top = (void *)secd + result;
 239         while (itr < top) {
 240                 etd = itr;
 241                 if (top - itr < sizeof(*etd)) {
 242                         dev_err(dev, "BUG: bad device security descriptor; "
 243                                 "not enough data (%zu vs %zu bytes left)\n",
 244                                 top - itr, sizeof(*etd));
 245                         break;
 246                 }
 247                 if (etd->bLength < sizeof(*etd)) {
 248                         dev_err(dev, "BUG: bad device encryption descriptor; "
 249                                 "descriptor is too short "
 250                                 "(%u vs %zu needed)\n",
 251                                 etd->bLength, sizeof(*etd));
 252                         break;
 253                 }
 254                 itr += etd->bLength;
 255                 bytes += snprintf(buf + bytes, sizeof(buf) - bytes,
 256                                   "%s (0x%02x/%02x) ",
 257                                   wusb_et_name(etd->bEncryptionType),
 258                                   etd->bEncryptionValue, etd->bAuthKeyIndex);
 259                 if (etd->bEncryptionType == USB_ENC_TYPE_CCM_1)
 260                         ccm1_etd = etd;
 261         }
 262         /* This code only supports CCM1 as of now. */
 263         /* FIXME: user has to choose which sec mode to use?
 264          * In theory we want CCM */
 265         if (ccm1_etd == NULL) {
 266                 dev_err(dev, "WUSB device doesn't support CCM1 encryption, "
 267                         "can't use!\n");
 268                 result = -EINVAL;
 269                 goto out;
 270         }
 271         wusb_dev->ccm1_etd = *ccm1_etd;
 272         dev_dbg(dev, "supported encryption: %s; using %s (0x%02x/%02x)\n",
 273                 buf, wusb_et_name(ccm1_etd->bEncryptionType),
 274                 ccm1_etd->bEncryptionValue, ccm1_etd->bAuthKeyIndex);
 275         result = 0;
 276 out:
 277         kfree(secd);
 278         return result;
 279 }
 280
 281 void wusb_dev_sec_rm(struct wusb_dev *wusb_dev)
 282 {
 283         /* Nothing so far */
 284 }
 285
 286 /**
 287  * Update the address of an unauthenticated WUSB device
 288  *
 289  * Once we have successfully authenticated, we take it to addr0 state
 290  * and then to a normal address.
 291  *
 292  * Before the device's address (as known by it) was usb_dev->devnum |
 293  * 0x80 (unauthenticated address). With this we update it to usb_dev->devnum.
 294  */
 295 int wusb_dev_update_address(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev)
 296 {
 297         int result = -ENOMEM;
 298         struct usb_device *usb_dev = wusb_dev->usb_dev;
 299         struct device *dev = &usb_dev->dev;
 300         u8 new_address = wusb_dev->addr & 0x7F;
 301
 302         /* Set address 0 */
 303         result = usb_control_msg(usb_dev, usb_sndctrlpipe(usb_dev, 0),
 304                         USB_REQ_SET_ADDRESS,
 305                         USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 306                          0, 0, NULL, 0, USB_CTRL_SET_TIMEOUT);
 307         if (result < 0) {
 308                 dev_err(dev, "auth failed: can't set address 0: %d\n",
 309                         result);
 310                 goto error_addr0;
 311         }
 312         result = wusb_set_dev_addr(wusbhc, wusb_dev, 0);
 313         if (result < 0)
 314                 goto error_addr0;
 315         usb_set_device_state(usb_dev, USB_STATE_DEFAULT);
 316         usb_ep0_reinit(usb_dev);
 317
 318         /* Set new (authenticated) address. */
 319         result = usb_control_msg(usb_dev, usb_sndctrlpipe(usb_dev, 0),
 320                         USB_REQ_SET_ADDRESS,
 321                         USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 322                         new_address, 0, NULL, 0,
 323                         USB_CTRL_SET_TIMEOUT);
 324         if (result < 0) {
 325                 dev_err(dev, "auth failed: can't set address %u: %d\n",
 326                         new_address, result);
 327                 goto error_addr;
 328         }
 329         result = wusb_set_dev_addr(wusbhc, wusb_dev, new_address);
 330         if (result < 0)
 331                 goto error_addr;
 332         usb_set_device_state(usb_dev, USB_STATE_ADDRESS);
 333         usb_ep0_reinit(usb_dev);
 334         usb_dev->authenticated = 1;
 335 error_addr:
 336 error_addr0:
 337         return result;
 338 }
 339
 340 /*
 341  *
 342  *
 343  */
 344 /* FIXME: split and cleanup */
 345 int wusb_dev_4way_handshake(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev,
 346                             struct wusb_ckhdid *ck)
 347 {
 348         int result = -ENOMEM;
 349         struct usb_device *usb_dev = wusb_dev->usb_dev;
 350         struct device *dev = &usb_dev->dev;
 351         u32 tkid;
 352         __le32 tkid_le;
 353         struct usb_handshake *hs;
 354         struct aes_ccm_nonce ccm_n;
 355         u8 mic[8];
 356         struct wusb_keydvt_in keydvt_in;
 357         struct wusb_keydvt_out keydvt_out;
 358
 359         hs = kcalloc(3, sizeof(hs[0]), GFP_KERNEL);
 360         if (hs == NULL) {
 361                 dev_err(dev, "can't allocate handshake data\n");
 362                 goto error_kzalloc;
 363         }
 364
 365         /* We need to turn encryption before beginning the 4way
 366          * hshake (WUSB1.0[.3.2.2]) */
 367         result = wusb_dev_set_encryption(usb_dev, 1);
 368         if (result < 0)
 369                 goto error_dev_set_encryption;
 370
 371         tkid = wusbhc_next_tkid(wusbhc, wusb_dev);
 372         tkid_le = cpu_to_le32(tkid);
 373
 374         hs[0].bMessageNumber = 1;
 375         hs[0].bStatus = 0;
 376         memcpy(hs[0].tTKID, &tkid_le, sizeof(hs[0].tTKID));
 377         hs[0].bReserved = 0;
 378         memcpy(hs[0].CDID, &wusb_dev->cdid, sizeof(hs[0].CDID));
 379         get_random_bytes(&hs[0].nonce, sizeof(hs[0].nonce));
 380         memset(hs[0].MIC, 0, sizeof(hs[0].MIC));        /* Per WUSB1.0[T7-22] */
 381
 382         result = usb_control_msg(
 383                 usb_dev, usb_sndctrlpipe(usb_dev, 0),
 384                 USB_REQ_SET_HANDSHAKE,
 385                 USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 386                 1, 0, &hs[0], sizeof(hs[0]), USB_CTRL_SET_TIMEOUT);
 387         if (result < 0) {
 388                 dev_err(dev, "Handshake1: request failed: %d\n", result);
 389                 goto error_hs1;
 390         }
 391
 392         /* Handshake 2, from the device -- need to verify fields */
 393         result = usb_control_msg(
 394                 usb_dev, usb_rcvctrlpipe(usb_dev, 0),
 395                 USB_REQ_GET_HANDSHAKE,
 396                 USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 397                 2, 0, &hs[1], sizeof(hs[1]), USB_CTRL_GET_TIMEOUT);
 398         if (result < 0) {
 399                 dev_err(dev, "Handshake2: request failed: %d\n", result);
 400                 goto error_hs2;
 401         }
 402
 403         result = -EINVAL;
 404         if (hs[1].bMessageNumber != 2) {
 405                 dev_err(dev, "Handshake2 failed: bad message number %u\n",
 406                         hs[1].bMessageNumber);
 407                 goto error_hs2;
 408         }
 409         if (hs[1].bStatus != 0) {
 410                 dev_err(dev, "Handshake2 failed: bad status %u\n",
 411                         hs[1].bStatus);
 412                 goto error_hs2;
 413         }
 414         if (memcmp(hs[0].tTKID, hs[1].tTKID, sizeof(hs[0].tTKID))) {
 415                 dev_err(dev, "Handshake2 failed: TKID mismatch "
 416                         "(#1 0x%02x%02x%02x vs #2 0x%02x%02x%02x)\n",
 417                         hs[0].tTKID[0], hs[0].tTKID[1], hs[0].tTKID[2],
 418                         hs[1].tTKID[0], hs[1].tTKID[1], hs[1].tTKID[2]);
 419                 goto error_hs2;
 420         }
 421         if (memcmp(hs[0].CDID, hs[1].CDID, sizeof(hs[0].CDID))) {
 422                 dev_err(dev, "Handshake2 failed: CDID mismatch\n");
 423                 goto error_hs2;
 424         }
 425
 426         /* Setup the CCM nonce */
 427         memset(&ccm_n.sfn, 0, sizeof(ccm_n.sfn));       /* Per WUSB1.0[6.5.2] */
 428         memcpy(ccm_n.tkid, &tkid_le, sizeof(ccm_n.tkid));
 429         ccm_n.src_addr = wusbhc->uwb_rc->uwb_dev.dev_addr;
 430         ccm_n.dest_addr.data[0] = wusb_dev->addr;
 431         ccm_n.dest_addr.data[1] = 0;
 432
 433         /* Derive the KCK and PTK from CK, the CCM, H and D nonces */
 434         memcpy(keydvt_in.hnonce, hs[0].nonce, sizeof(keydvt_in.hnonce));
 435         memcpy(keydvt_in.dnonce, hs[1].nonce, sizeof(keydvt_in.dnonce));
 436         result = wusb_key_derive(&keydvt_out, ck->data, &ccm_n, &keydvt_in);
 437         if (result < 0) {
 438                 dev_err(dev, "Handshake2 failed: cannot derive keys: %d\n",
 439                         result);
 440                 goto error_hs2;
 441         }
 442
 443         /* Compute MIC and verify it */
 444         result = wusb_oob_mic(mic, keydvt_out.kck, &ccm_n, &hs[1]);
 445         if (result < 0) {
 446                 dev_err(dev, "Handshake2 failed: cannot compute MIC: %d\n",
 447                         result);
 448                 goto error_hs2;
 449         }
 450
 451         if (memcmp(hs[1].MIC, mic, sizeof(hs[1].MIC))) {
 452                 dev_err(dev, "Handshake2 failed: MIC mismatch\n");
 453                 goto error_hs2;
 454         }
 455
 456         /* Send Handshake3 */
 457         hs[2].bMessageNumber = 3;
 458         hs[2].bStatus = 0;
 459         memcpy(hs[2].tTKID, &tkid_le, sizeof(hs[2].tTKID));
 460         hs[2].bReserved = 0;
 461         memcpy(hs[2].CDID, &wusb_dev->cdid, sizeof(hs[2].CDID));
 462         memcpy(hs[2].nonce, hs[0].nonce, sizeof(hs[2].nonce));
 463         result = wusb_oob_mic(hs[2].MIC, keydvt_out.kck, &ccm_n, &hs[2]);
 464         if (result < 0) {
 465                 dev_err(dev, "Handshake3 failed: cannot compute MIC: %d\n",
 466                         result);
 467                 goto error_hs2;
 468         }
 469
 470         result = usb_control_msg(
 471                 usb_dev, usb_sndctrlpipe(usb_dev, 0),
 472                 USB_REQ_SET_HANDSHAKE,
 473                 USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 474                 3, 0, &hs[2], sizeof(hs[2]), USB_CTRL_SET_TIMEOUT);
 475         if (result < 0) {
 476                 dev_err(dev, "Handshake3: request failed: %d\n", result);
 477                 goto error_hs3;
 478         }
 479
 480         result = wusbhc->set_ptk(wusbhc, wusb_dev->port_idx, tkid,
 481                                  keydvt_out.ptk, sizeof(keydvt_out.ptk));
 482         if (result < 0)
 483                 goto error_wusbhc_set_ptk;
 484
 485         result = wusb_dev_set_gtk(wusbhc, wusb_dev);
 486         if (result < 0) {
 487                 dev_err(dev, "Set GTK for device: request failed: %d\n",
 488                         result);
 489                 goto error_wusbhc_set_gtk;
 490         }
 491
 492         /* Update the device's address from unauth to auth */
 493         if (usb_dev->authenticated == 0) {
 494                 result = wusb_dev_update_address(wusbhc, wusb_dev);
 495                 if (result < 0)
 496                         goto error_dev_update_address;
 497         }
 498         result = 0;
 499         dev_info(dev, "device authenticated\n");
 500
 501 error_dev_update_address:
 502 error_wusbhc_set_gtk:
 503 error_wusbhc_set_ptk:
 504 error_hs3:
 505 error_hs2:
 506 error_hs1:
 507         memset(hs, 0, 3*sizeof(hs[0]));
 508         memset(&keydvt_out, 0, sizeof(keydvt_out));
 509         memset(&keydvt_in, 0, sizeof(keydvt_in));
 510         memset(&ccm_n, 0, sizeof(ccm_n));
 511         memset(mic, 0, sizeof(mic));
 512         if (result < 0)
 513                 wusb_dev_set_encryption(usb_dev, 0);
 514 error_dev_set_encryption:
 515         kfree(hs);
 516 error_kzalloc:
 517         return result;
 518 }
 519
 520 /*
 521  * Once all connected and authenticated devices have received the new
 522  * GTK, switch the host to using it.
 523  */
 524 static void wusbhc_gtk_rekey_work(struct work_struct *work)
 525 {
 526         struct wusbhc *wusbhc = container_of(work,
 527                                         struct wusbhc, gtk_rekey_work);
 528         size_t key_size = sizeof(wusbhc->gtk.data);
 529         int port_idx;
 530         struct wusb_dev *wusb_dev, *wusb_dev_next;
 531         LIST_HEAD(rekey_list);
 532
 533         mutex_lock(&wusbhc->mutex);
 534         /* generate the new key */
 535         wusbhc_generate_gtk(wusbhc);
 536         /* roll the gtk index. */
 537         wusbhc->gtk_index = (wusbhc->gtk_index + 1) % (WUSB_KEY_INDEX_MAX + 1);
 538         /*
 539          * Save all connected devices on a list while holding wusbhc->mutex and
 540          * take a reference to each one.  Then submit the set key request to
 541          * them after releasing the lock in order to avoid a deadlock.
 542          */
 543         for (port_idx = 0; port_idx < wusbhc->ports_max; port_idx++) {
 544                 wusb_dev = wusbhc->port[port_idx].wusb_dev;
 545                 if (!wusb_dev || !wusb_dev->usb_dev
 546                         || !wusb_dev->usb_dev->authenticated)
 547                         continue;
 548
 549                 wusb_dev_get(wusb_dev);
 550                 list_add_tail(&wusb_dev->rekey_node, &rekey_list);
 551         }
 552         mutex_unlock(&wusbhc->mutex);
 553
 554         /* Submit the rekey requests without holding wusbhc->mutex. */
 555         list_for_each_entry_safe(wusb_dev, wusb_dev_next, &rekey_list,
 556                 rekey_node) {
 557                 list_del_init(&wusb_dev->rekey_node);
 558                 dev_dbg(&wusb_dev->usb_dev->dev, "%s: rekey device at port %d\n",
 559                         __func__, wusb_dev->port_idx);
 560
 561                 if (wusb_dev_set_gtk(wusbhc, wusb_dev) < 0) {
 562                         dev_err(&wusb_dev->usb_dev->dev, "%s: rekey device at port %d failed\n",
 563                                 __func__, wusb_dev->port_idx);
 564                 }
 565                 wusb_dev_put(wusb_dev);
 566         }
 567
 568         /* Switch the host controller to use the new GTK. */
 569         mutex_lock(&wusbhc->mutex);
 570         wusbhc->set_gtk(wusbhc, wusbhc->gtk_tkid,
 571                 &wusbhc->gtk.descr.bKeyData, key_size);
 572         mutex_unlock(&wusbhc->mutex);
 573 }
 574
 575 /**
 576  * wusbhc_gtk_rekey - generate and distribute a new GTK
 577  * @wusbhc: the WUSB host controller
 578  *
 579  * Generate a new GTK and distribute it to all connected and
 580  * authenticated devices.  When all devices have the new GTK, the host
 581  * starts using it.
 582  *
 583  * This must be called after every device disconnect (see [WUSB]
 584  * section 6.2.11.2).
 585  */
 586 void wusbhc_gtk_rekey(struct wusbhc *wusbhc)
 587 {
 588         /*
 589          * We need to submit a URB to the downstream WUSB devices in order to
 590          * change the group key.  This can't be done while holding the
 591          * wusbhc->mutex since that is also taken in the urb_enqueue routine
 592          * and will cause a deadlock.  Instead, queue a work item to do
 593          * it when the lock is not held
 594          */
 595         queue_work(wusbd, &wusbhc->gtk_rekey_work);
 596 }