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         /*
  37          * WQ is singlethread because we need to serialize rekey operations.
  38          * Use a separate workqueue for security operations instead of the
  39          * wusbd workqueue because security operations may need to communicate
  40          * directly with downstream wireless devices using synchronous URBs.
  41          * If a device is not responding, this could block other host
  42          * controller operations.
  43          */
  44         wusbhc->wq_security = create_singlethread_workqueue("wusbd_security");
  45         if (wusbhc->wq_security == NULL) {
  46                 pr_err("WUSB-core: Cannot create wusbd_security workqueue\n");
  47                 return -ENOMEM;
  48         }
  49
  50         wusbhc->gtk.descr.bLength = sizeof(wusbhc->gtk.descr) +
  51                 sizeof(wusbhc->gtk.data);
  52         wusbhc->gtk.descr.bDescriptorType = USB_DT_KEY;
  53         wusbhc->gtk.descr.bReserved = 0;
  54         wusbhc->gtk_index = 0;
  55
  56         INIT_WORK(&wusbhc->gtk_rekey_work, wusbhc_gtk_rekey_work);
  57
  58         return 0;
  59 }
  60
  61
  62 /* Called when the HC is destroyed */
  63 void wusbhc_sec_destroy(struct wusbhc *wusbhc)
  64 {
  65         destroy_workqueue(wusbhc->wq_security);
  66 }
  67
  68
  69 /**
  70  * wusbhc_next_tkid - generate a new, currently unused, TKID
  71  * @wusbhc:   the WUSB host controller
  72  * @wusb_dev: the device whose PTK the TKID is for
  73  *            (or NULL for a TKID for a GTK)
  74  *
  75  * The generated TKID consists of two parts: the device's authenticated
  76  * address (or 0 or a GTK); and an incrementing number.  This ensures
  77  * that TKIDs cannot be shared between devices and by the time the
  78  * incrementing number wraps around the older TKIDs will no longer be
  79  * in use (a maximum of two keys may be active at any one time).
  80  */
  81 static u32 wusbhc_next_tkid(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev)
  82 {
  83         u32 *tkid;
  84         u32 addr;
  85
  86         if (wusb_dev == NULL) {
  87                 tkid = &wusbhc->gtk_tkid;
  88                 addr = 0;
  89         } else {
  90                 tkid = &wusb_port_by_idx(wusbhc, wusb_dev->port_idx)->ptk_tkid;
  91                 addr = wusb_dev->addr & 0x7f;
  92         }
  93
  94         *tkid = (addr << 8) | ((*tkid + 1) & 0xff);
  95
  96         return *tkid;
  97 }
  98
  99 static void wusbhc_generate_gtk(struct wusbhc *wusbhc)
 100 {
 101         const size_t key_size = sizeof(wusbhc->gtk.data);
 102         u32 tkid;
 103
 104         tkid = wusbhc_next_tkid(wusbhc, NULL);
 105
 106         wusbhc->gtk.descr.tTKID[0] = (tkid >>  0) & 0xff;
 107         wusbhc->gtk.descr.tTKID[1] = (tkid >>  8) & 0xff;
 108         wusbhc->gtk.descr.tTKID[2] = (tkid >> 16) & 0xff;
 109
 110         get_random_bytes(wusbhc->gtk.descr.bKeyData, key_size);
 111 }
 112
 113 /**
 114  * wusbhc_sec_start - start the security management process
 115  * @wusbhc: the WUSB host controller
 116  *
 117  * Generate and set an initial GTK on the host controller.
 118  *
 119  * Called when the HC is started.
 120  */
 121 int wusbhc_sec_start(struct wusbhc *wusbhc)
 122 {
 123         const size_t key_size = sizeof(wusbhc->gtk.data);
 124         int result;
 125
 126         wusbhc_generate_gtk(wusbhc);
 127
 128         result = wusbhc->set_gtk(wusbhc, wusbhc->gtk_tkid,
 129                                 &wusbhc->gtk.descr.bKeyData, key_size);
 130         if (result < 0)
 131                 dev_err(wusbhc->dev, "cannot set GTK for the host: %d\n",
 132                         result);
 133
 134         return result;
 135 }
 136
 137 /**
 138  * wusbhc_sec_stop - stop the security management process
 139  * @wusbhc: the WUSB host controller
 140  *
 141  * Wait for any pending GTK rekeys to stop.
 142  */
 143 void wusbhc_sec_stop(struct wusbhc *wusbhc)
 144 {
 145         cancel_work_sync(&wusbhc->gtk_rekey_work);
 146 }
 147
 148
 149 /** @returns encryption type name */
 150 const char *wusb_et_name(u8 x)
 151 {
 152         switch (x) {
 153         case USB_ENC_TYPE_UNSECURE:     return "unsecure";
 154         case USB_ENC_TYPE_WIRED:        return "wired";
 155         case USB_ENC_TYPE_CCM_1:        return "CCM-1";
 156         case USB_ENC_TYPE_RSA_1:        return "RSA-1";
 157         default:                        return "unknown";
 158         }
 159 }
 160 EXPORT_SYMBOL_GPL(wusb_et_name);
 161
 162 /*
 163  * Set the device encryption method
 164  *
 165  * We tell the device which encryption method to use; we do this when
 166  * setting up the device's security.
 167  */
 168 static int wusb_dev_set_encryption(struct usb_device *usb_dev, int value)
 169 {
 170         int result;
 171         struct device *dev = &usb_dev->dev;
 172         struct wusb_dev *wusb_dev = usb_dev->wusb_dev;
 173
 174         if (value) {
 175                 value = wusb_dev->ccm1_etd.bEncryptionValue;
 176         } else {
 177                 /* FIXME: should be wusb_dev->etd[UNSECURE].bEncryptionValue */
 178                 value = 0;
 179         }
 180         /* Set device's */
 181         result = usb_control_msg(usb_dev, usb_sndctrlpipe(usb_dev, 0),
 182                         USB_REQ_SET_ENCRYPTION,
 183                         USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 184                         value, 0, NULL, 0, USB_CTRL_SET_TIMEOUT);
 185         if (result < 0)
 186                 dev_err(dev, "Can't set device's WUSB encryption to "
 187                         "%s (value %d): %d\n",
 188                         wusb_et_name(wusb_dev->ccm1_etd.bEncryptionType),
 189                         wusb_dev->ccm1_etd.bEncryptionValue,  result);
 190         return result;
 191 }
 192
 193 /*
 194  * Set the GTK to be used by a device.
 195  *
 196  * The device must be authenticated.
 197  */
 198 static int wusb_dev_set_gtk(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev)
 199 {
 200         struct usb_device *usb_dev = wusb_dev->usb_dev;
 201         u8 key_index = wusb_key_index(wusbhc->gtk_index,
 202                 WUSB_KEY_INDEX_TYPE_GTK, WUSB_KEY_INDEX_ORIGINATOR_HOST);
 203
 204         return usb_control_msg(
 205                 usb_dev, usb_sndctrlpipe(usb_dev, 0),
 206                 USB_REQ_SET_DESCRIPTOR,
 207                 USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 208                 USB_DT_KEY << 8 | key_index, 0,
 209                 &wusbhc->gtk.descr, wusbhc->gtk.descr.bLength,
 210                 USB_CTRL_SET_TIMEOUT);
 211 }
 212
 213
 214 /* FIXME: prototype for adding security */
 215 int wusb_dev_sec_add(struct wusbhc *wusbhc,
 216                      struct usb_device *usb_dev, struct wusb_dev *wusb_dev)
 217 {
 218         int result, bytes, secd_size;
 219         struct device *dev = &usb_dev->dev;
 220         struct usb_security_descriptor *secd, *new_secd;
 221         const struct usb_encryption_descriptor *etd, *ccm1_etd = NULL;
 222         const void *itr, *top;
 223         char buf[64];
 224
 225         secd = kmalloc(sizeof(*secd), GFP_KERNEL);
 226         if (secd == NULL) {
 227                 result = -ENOMEM;
 228                 goto out;
 229         }
 230
 231         result = usb_get_descriptor(usb_dev, USB_DT_SECURITY,
 232                                     0, secd, sizeof(*secd));
 233         if (result < (int)sizeof(*secd)) {
 234                 dev_err(dev, "Can't read security descriptor or "
 235                         "not enough data: %d\n", result);
 236                 goto out;
 237         }
 238         secd_size = le16_to_cpu(secd->wTotalLength);
 239         new_secd = krealloc(secd, secd_size, GFP_KERNEL);
 240         if (new_secd == NULL) {
 241                 dev_err(dev,
 242                         "Can't allocate space for security descriptors\n");
 243                 result = -ENOMEM;
 244                 goto out;
 245         }
 246         secd = new_secd;
 247         result = usb_get_descriptor(usb_dev, USB_DT_SECURITY,
 248                                     0, secd, secd_size);
 249         if (result < secd_size) {
 250                 dev_err(dev, "Can't read security descriptor or "
 251                         "not enough data: %d\n", result);
 252                 goto out;
 253         }
 254         bytes = 0;
 255         itr = &secd[1];
 256         top = (void *)secd + result;
 257         while (itr < top) {
 258                 etd = itr;
 259                 if (top - itr < sizeof(*etd)) {
 260                         dev_err(dev, "BUG: bad device security descriptor; "
 261                                 "not enough data (%zu vs %zu bytes left)\n",
 262                                 top - itr, sizeof(*etd));
 263                         break;
 264                 }
 265                 if (etd->bLength < sizeof(*etd)) {
 266                         dev_err(dev, "BUG: bad device encryption descriptor; "
 267                                 "descriptor is too short "
 268                                 "(%u vs %zu needed)\n",
 269                                 etd->bLength, sizeof(*etd));
 270                         break;
 271                 }
 272                 itr += etd->bLength;
 273                 bytes += snprintf(buf + bytes, sizeof(buf) - bytes,
 274                                   "%s (0x%02x/%02x) ",
 275                                   wusb_et_name(etd->bEncryptionType),
 276                                   etd->bEncryptionValue, etd->bAuthKeyIndex);
 277                 if (etd->bEncryptionType == USB_ENC_TYPE_CCM_1)
 278                         ccm1_etd = etd;
 279         }
 280         /* This code only supports CCM1 as of now. */
 281         /* FIXME: user has to choose which sec mode to use?
 282          * In theory we want CCM */
 283         if (ccm1_etd == NULL) {
 284                 dev_err(dev, "WUSB device doesn't support CCM1 encryption, "
 285                         "can't use!\n");
 286                 result = -EINVAL;
 287                 goto out;
 288         }
 289         wusb_dev->ccm1_etd = *ccm1_etd;
 290         dev_dbg(dev, "supported encryption: %s; using %s (0x%02x/%02x)\n",
 291                 buf, wusb_et_name(ccm1_etd->bEncryptionType),
 292                 ccm1_etd->bEncryptionValue, ccm1_etd->bAuthKeyIndex);
 293         result = 0;
 294 out:
 295         kfree(secd);
 296         return result;
 297 }
 298
 299 void wusb_dev_sec_rm(struct wusb_dev *wusb_dev)
 300 {
 301         /* Nothing so far */
 302 }
 303
 304 /**
 305  * Update the address of an unauthenticated WUSB device
 306  *
 307  * Once we have successfully authenticated, we take it to addr0 state
 308  * and then to a normal address.
 309  *
 310  * Before the device's address (as known by it) was usb_dev->devnum |
 311  * 0x80 (unauthenticated address). With this we update it to usb_dev->devnum.
 312  */
 313 int wusb_dev_update_address(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev)
 314 {
 315         int result = -ENOMEM;
 316         struct usb_device *usb_dev = wusb_dev->usb_dev;
 317         struct device *dev = &usb_dev->dev;
 318         u8 new_address = wusb_dev->addr & 0x7F;
 319
 320         /* Set address 0 */
 321         result = usb_control_msg(usb_dev, usb_sndctrlpipe(usb_dev, 0),
 322                         USB_REQ_SET_ADDRESS,
 323                         USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 324                          0, 0, NULL, 0, USB_CTRL_SET_TIMEOUT);
 325         if (result < 0) {
 326                 dev_err(dev, "auth failed: can't set address 0: %d\n",
 327                         result);
 328                 goto error_addr0;
 329         }
 330         result = wusb_set_dev_addr(wusbhc, wusb_dev, 0);
 331         if (result < 0)
 332                 goto error_addr0;
 333         usb_set_device_state(usb_dev, USB_STATE_DEFAULT);
 334         usb_ep0_reinit(usb_dev);
 335
 336         /* Set new (authenticated) address. */
 337         result = usb_control_msg(usb_dev, usb_sndctrlpipe(usb_dev, 0),
 338                         USB_REQ_SET_ADDRESS,
 339                         USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 340                         new_address, 0, NULL, 0,
 341                         USB_CTRL_SET_TIMEOUT);
 342         if (result < 0) {
 343                 dev_err(dev, "auth failed: can't set address %u: %d\n",
 344                         new_address, result);
 345                 goto error_addr;
 346         }
 347         result = wusb_set_dev_addr(wusbhc, wusb_dev, new_address);
 348         if (result < 0)
 349                 goto error_addr;
 350         usb_set_device_state(usb_dev, USB_STATE_ADDRESS);
 351         usb_ep0_reinit(usb_dev);
 352         usb_dev->authenticated = 1;
 353 error_addr:
 354 error_addr0:
 355         return result;
 356 }
 357
 358 /*
 359  *
 360  *
 361  */
 362 /* FIXME: split and cleanup */
 363 int wusb_dev_4way_handshake(struct wusbhc *wusbhc, struct wusb_dev *wusb_dev,
 364                             struct wusb_ckhdid *ck)
 365 {
 366         int result = -ENOMEM;
 367         struct usb_device *usb_dev = wusb_dev->usb_dev;
 368         struct device *dev = &usb_dev->dev;
 369         u32 tkid;
 370         __le32 tkid_le;
 371         struct usb_handshake *hs;
 372         struct aes_ccm_nonce ccm_n;
 373         u8 mic[8];
 374         struct wusb_keydvt_in keydvt_in;
 375         struct wusb_keydvt_out keydvt_out;
 376
 377         hs = kcalloc(3, sizeof(hs[0]), GFP_KERNEL);
 378         if (!hs)
 379                 goto error_kzalloc;
 380
 381         /* We need to turn encryption before beginning the 4way
 382          * hshake (WUSB1.0[.3.2.2]) */
 383         result = wusb_dev_set_encryption(usb_dev, 1);
 384         if (result < 0)
 385                 goto error_dev_set_encryption;
 386
 387         tkid = wusbhc_next_tkid(wusbhc, wusb_dev);
 388         tkid_le = cpu_to_le32(tkid);
 389
 390         hs[0].bMessageNumber = 1;
 391         hs[0].bStatus = 0;
 392         memcpy(hs[0].tTKID, &tkid_le, sizeof(hs[0].tTKID));
 393         hs[0].bReserved = 0;
 394         memcpy(hs[0].CDID, &wusb_dev->cdid, sizeof(hs[0].CDID));
 395         get_random_bytes(&hs[0].nonce, sizeof(hs[0].nonce));
 396         memset(hs[0].MIC, 0, sizeof(hs[0].MIC)); /* Per WUSB1.0[T7-22] */
 397
 398         result = usb_control_msg(
 399                 usb_dev, usb_sndctrlpipe(usb_dev, 0),
 400                 USB_REQ_SET_HANDSHAKE,
 401                 USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 402                 1, 0, &hs[0], sizeof(hs[0]), USB_CTRL_SET_TIMEOUT);
 403         if (result < 0) {
 404                 dev_err(dev, "Handshake1: request failed: %d\n", result);
 405                 goto error_hs1;
 406         }
 407
 408         /* Handshake 2, from the device -- need to verify fields */
 409         result = usb_control_msg(
 410                 usb_dev, usb_rcvctrlpipe(usb_dev, 0),
 411                 USB_REQ_GET_HANDSHAKE,
 412                 USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 413                 2, 0, &hs[1], sizeof(hs[1]), USB_CTRL_GET_TIMEOUT);
 414         if (result < 0) {
 415                 dev_err(dev, "Handshake2: request failed: %d\n", result);
 416                 goto error_hs2;
 417         }
 418
 419         result = -EINVAL;
 420         if (hs[1].bMessageNumber != 2) {
 421                 dev_err(dev, "Handshake2 failed: bad message number %u\n",
 422                         hs[1].bMessageNumber);
 423                 goto error_hs2;
 424         }
 425         if (hs[1].bStatus != 0) {
 426                 dev_err(dev, "Handshake2 failed: bad status %u\n",
 427                         hs[1].bStatus);
 428                 goto error_hs2;
 429         }
 430         if (memcmp(hs[0].tTKID, hs[1].tTKID, sizeof(hs[0].tTKID))) {
 431                 dev_err(dev, "Handshake2 failed: TKID mismatch "
 432                         "(#1 0x%02x%02x%02x vs #2 0x%02x%02x%02x)\n",
 433                         hs[0].tTKID[0], hs[0].tTKID[1], hs[0].tTKID[2],
 434                         hs[1].tTKID[0], hs[1].tTKID[1], hs[1].tTKID[2]);
 435                 goto error_hs2;
 436         }
 437         if (memcmp(hs[0].CDID, hs[1].CDID, sizeof(hs[0].CDID))) {
 438                 dev_err(dev, "Handshake2 failed: CDID mismatch\n");
 439                 goto error_hs2;
 440         }
 441
 442         /* Setup the CCM nonce */
 443         memset(&ccm_n.sfn, 0, sizeof(ccm_n.sfn)); /* Per WUSB1.0[6.5.2] */
 444         memcpy(ccm_n.tkid, &tkid_le, sizeof(ccm_n.tkid));
 445         ccm_n.src_addr = wusbhc->uwb_rc->uwb_dev.dev_addr;
 446         ccm_n.dest_addr.data[0] = wusb_dev->addr;
 447         ccm_n.dest_addr.data[1] = 0;
 448
 449         /* Derive the KCK and PTK from CK, the CCM, H and D nonces */
 450         memcpy(keydvt_in.hnonce, hs[0].nonce, sizeof(keydvt_in.hnonce));
 451         memcpy(keydvt_in.dnonce, hs[1].nonce, sizeof(keydvt_in.dnonce));
 452         result = wusb_key_derive(&keydvt_out, ck->data, &ccm_n, &keydvt_in);
 453         if (result < 0) {
 454                 dev_err(dev, "Handshake2 failed: cannot derive keys: %d\n",
 455                         result);
 456                 goto error_hs2;
 457         }
 458
 459         /* Compute MIC and verify it */
 460         result = wusb_oob_mic(mic, keydvt_out.kck, &ccm_n, &hs[1]);
 461         if (result < 0) {
 462                 dev_err(dev, "Handshake2 failed: cannot compute MIC: %d\n",
 463                         result);
 464                 goto error_hs2;
 465         }
 466
 467         if (memcmp(hs[1].MIC, mic, sizeof(hs[1].MIC))) {
 468                 dev_err(dev, "Handshake2 failed: MIC mismatch\n");
 469                 goto error_hs2;
 470         }
 471
 472         /* Send Handshake3 */
 473         hs[2].bMessageNumber = 3;
 474         hs[2].bStatus = 0;
 475         memcpy(hs[2].tTKID, &tkid_le, sizeof(hs[2].tTKID));
 476         hs[2].bReserved = 0;
 477         memcpy(hs[2].CDID, &wusb_dev->cdid, sizeof(hs[2].CDID));
 478         memcpy(hs[2].nonce, hs[0].nonce, sizeof(hs[2].nonce));
 479         result = wusb_oob_mic(hs[2].MIC, keydvt_out.kck, &ccm_n, &hs[2]);
 480         if (result < 0) {
 481                 dev_err(dev, "Handshake3 failed: cannot compute MIC: %d\n",
 482                         result);
 483                 goto error_hs2;
 484         }
 485
 486         result = usb_control_msg(
 487                 usb_dev, usb_sndctrlpipe(usb_dev, 0),
 488                 USB_REQ_SET_HANDSHAKE,
 489                 USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
 490                 3, 0, &hs[2], sizeof(hs[2]), USB_CTRL_SET_TIMEOUT);
 491         if (result < 0) {
 492                 dev_err(dev, "Handshake3: request failed: %d\n", result);
 493                 goto error_hs3;
 494         }
 495
 496         result = wusbhc->set_ptk(wusbhc, wusb_dev->port_idx, tkid,
 497                                  keydvt_out.ptk, sizeof(keydvt_out.ptk));
 498         if (result < 0)
 499                 goto error_wusbhc_set_ptk;
 500
 501         result = wusb_dev_set_gtk(wusbhc, wusb_dev);
 502         if (result < 0) {
 503                 dev_err(dev, "Set GTK for device: request failed: %d\n",
 504                         result);
 505                 goto error_wusbhc_set_gtk;
 506         }
 507
 508         /* Update the device's address from unauth to auth */
 509         if (usb_dev->authenticated == 0) {
 510                 result = wusb_dev_update_address(wusbhc, wusb_dev);
 511                 if (result < 0)
 512                         goto error_dev_update_address;
 513         }
 514         result = 0;
 515         dev_info(dev, "device authenticated\n");
 516
 517 error_dev_update_address:
 518 error_wusbhc_set_gtk:
 519 error_wusbhc_set_ptk:
 520 error_hs3:
 521 error_hs2:
 522 error_hs1:
 523         memset(hs, 0, 3*sizeof(hs[0]));
 524         memzero_explicit(&keydvt_out, sizeof(keydvt_out));
 525         memzero_explicit(&keydvt_in, sizeof(keydvt_in));
 526         memzero_explicit(&ccm_n, sizeof(ccm_n));
 527         memzero_explicit(mic, sizeof(mic));
 528         if (result < 0)
 529                 wusb_dev_set_encryption(usb_dev, 0);
 530 error_dev_set_encryption:
 531         kfree(hs);
 532 error_kzalloc:
 533         return result;
 534 }
 535
 536 /*
 537  * Once all connected and authenticated devices have received the new
 538  * GTK, switch the host to using it.
 539  */
 540 static void wusbhc_gtk_rekey_work(struct work_struct *work)
 541 {
 542         struct wusbhc *wusbhc = container_of(work,
 543                                         struct wusbhc, gtk_rekey_work);
 544         size_t key_size = sizeof(wusbhc->gtk.data);
 545         int port_idx;
 546         struct wusb_dev *wusb_dev, *wusb_dev_next;
 547         LIST_HEAD(rekey_list);
 548
 549         mutex_lock(&wusbhc->mutex);
 550         /* generate the new key */
 551         wusbhc_generate_gtk(wusbhc);
 552         /* roll the gtk index. */
 553         wusbhc->gtk_index = (wusbhc->gtk_index + 1) % (WUSB_KEY_INDEX_MAX + 1);
 554         /*
 555          * Save all connected devices on a list while holding wusbhc->mutex and
 556          * take a reference to each one.  Then submit the set key request to
 557          * them after releasing the lock in order to avoid a deadlock.
 558          */
 559         for (port_idx = 0; port_idx < wusbhc->ports_max; port_idx++) {
 560                 wusb_dev = wusbhc->port[port_idx].wusb_dev;
 561                 if (!wusb_dev || !wusb_dev->usb_dev
 562                         || !wusb_dev->usb_dev->authenticated)
 563                         continue;
 564
 565                 wusb_dev_get(wusb_dev);
 566                 list_add_tail(&wusb_dev->rekey_node, &rekey_list);
 567         }
 568         mutex_unlock(&wusbhc->mutex);
 569
 570         /* Submit the rekey requests without holding wusbhc->mutex. */
 571         list_for_each_entry_safe(wusb_dev, wusb_dev_next, &rekey_list,
 572                 rekey_node) {
 573                 list_del_init(&wusb_dev->rekey_node);
 574                 dev_dbg(&wusb_dev->usb_dev->dev,
 575                         "%s: rekey device at port %d\n",
 576                         __func__, wusb_dev->port_idx);
 577
 578                 if (wusb_dev_set_gtk(wusbhc, wusb_dev) < 0) {
 579                         dev_err(&wusb_dev->usb_dev->dev,
 580                                 "%s: rekey device at port %d failed\n",
 581                                 __func__, wusb_dev->port_idx);
 582                 }
 583                 wusb_dev_put(wusb_dev);
 584         }
 585
 586         /* Switch the host controller to use the new GTK. */
 587         mutex_lock(&wusbhc->mutex);
 588         wusbhc->set_gtk(wusbhc, wusbhc->gtk_tkid,
 589                 &wusbhc->gtk.descr.bKeyData, key_size);
 590         mutex_unlock(&wusbhc->mutex);
 591 }
 592
 593 /**
 594  * wusbhc_gtk_rekey - generate and distribute a new GTK
 595  * @wusbhc: the WUSB host controller
 596  *
 597  * Generate a new GTK and distribute it to all connected and
 598  * authenticated devices.  When all devices have the new GTK, the host
 599  * starts using it.
 600  *
 601  * This must be called after every device disconnect (see [WUSB]
 602  * section 6.2.11.2).
 603  */
 604 void wusbhc_gtk_rekey(struct wusbhc *wusbhc)
 605 {
 606         /*
 607          * We need to submit a URB to the downstream WUSB devices in order to
 608          * change the group key.  This can't be done while holding the
 609          * wusbhc->mutex since that is also taken in the urb_enqueue routine
 610          * and will cause a deadlock.  Instead, queue a work item to do
 611          * it when the lock is not held
 612          */
 613         queue_work(wusbhc->wq_security, &wusbhc->gtk_rekey_work);
 614 }