fs/ceph/auth_x.c

   1
   2 #include "ceph_debug.h"
   3
   4 #include <linux/err.h>
   5 #include <linux/module.h>
   6 #include <linux/random.h>
   7
   8 #include "auth_x.h"
   9 #include "auth_x_protocol.h"
  10 #include "crypto.h"
  11 #include "auth.h"
  12 #include "decode.h"
  13
  14 struct kmem_cache *ceph_x_ticketbuf_cachep;
  15
  16 #define TEMP_TICKET_BUF_LEN     256
  17
  18 static void ceph_x_validate_tickets(struct ceph_auth_client *ac, int *pneed);
  19
  20 static int ceph_x_is_authenticated(struct ceph_auth_client *ac)
  21 {
  22         struct ceph_x_info *xi = ac->private;
  23         int need;
  24
  25         ceph_x_validate_tickets(ac, &need);
  26         dout("ceph_x_is_authenticated want=%d need=%d have=%d\n",
  27              ac->want_keys, need, xi->have_keys);
  28         return (ac->want_keys & xi->have_keys) == ac->want_keys;
  29 }
  30
  31 static int ceph_x_encrypt(struct ceph_crypto_key *secret,
  32                           void *ibuf, int ilen, void *obuf, size_t olen)
  33 {
  34         struct ceph_x_encrypt_header head = {
  35                 .struct_v = 1,
  36                 .magic = cpu_to_le64(CEPHX_ENC_MAGIC)
  37         };
  38         size_t len = olen - sizeof(u32);
  39         int ret;
  40
  41         ret = ceph_encrypt2(secret, obuf + sizeof(u32), &len,
  42                             &head, sizeof(head), ibuf, ilen);
  43         if (ret)
  44                 return ret;
  45         ceph_encode_32(&obuf, len);
  46         return len + sizeof(u32);
  47 }
  48
  49 static int ceph_x_decrypt(struct ceph_crypto_key *secret,
  50                           void **p, void *end, void *obuf, size_t olen)
  51 {
  52         struct ceph_x_encrypt_header head;
  53         size_t head_len = sizeof(head);
  54         int len, ret;
  55
  56         len = ceph_decode_32(p);
  57         if (*p + len > end)
  58                 return -EINVAL;
  59
  60         dout("ceph_x_decrypt len %d\n", len);
  61         ret = ceph_decrypt2(secret, &head, &head_len, obuf, &olen,
  62                             *p, len);
  63         if (ret)
  64                 return ret;
  65         if (head.struct_v != 1 || le64_to_cpu(head.magic) != CEPHX_ENC_MAGIC)
  66                 return -EPERM;
  67         *p += len;
  68         return olen;
  69 }
  70
  71 /*
  72  * get existing (or insert new) ticket handler
  73  */
  74 struct ceph_x_ticket_handler *get_ticket_handler(struct ceph_auth_client *ac,
  75                                                  int service)
  76 {
  77         struct ceph_x_ticket_handler *th;
  78         struct ceph_x_info *xi = ac->private;
  79         struct rb_node *parent = NULL, **p = &xi->ticket_handlers.rb_node;
  80
  81         while (*p) {
  82                 parent = *p;
  83                 th = rb_entry(parent, struct ceph_x_ticket_handler, node);
  84                 if (service < th->service)
  85                         p = &(*p)->rb_left;
  86                 else if (service > th->service)
  87                         p = &(*p)->rb_right;
  88                 else
  89                         return th;
  90         }
  91
  92         /* add it */
  93         th = kzalloc(sizeof(*th), GFP_NOFS);
  94         if (!th)
  95                 return ERR_PTR(-ENOMEM);
  96         th->service = service;
  97         rb_link_node(&th->node, parent, p);
  98         rb_insert_color(&th->node, &xi->ticket_handlers);
  99         return th;
 100 }
 101
 102 static void remove_ticket_handler(struct ceph_auth_client *ac,
 103                                   struct ceph_x_ticket_handler *th)
 104 {
 105         struct ceph_x_info *xi = ac->private;
 106
 107         dout("remove_ticket_handler %p %d\n", th, th->service);
 108         rb_erase(&th->node, &xi->ticket_handlers);
 109         ceph_crypto_key_destroy(&th->session_key);
 110         if (th->ticket_blob)
 111                 ceph_buffer_put(th->ticket_blob);
 112         kfree(th);
 113 }
 114
 115 static int ceph_x_proc_ticket_reply(struct ceph_auth_client *ac,
 116                                     struct ceph_crypto_key *secret,
 117                                     void *buf, void *end)
 118 {
 119         struct ceph_x_info *xi = ac->private;
 120         int num;
 121         void *p = buf;
 122         int ret;
 123         char *dbuf;
 124         char *ticket_buf;
 125         u8 struct_v;
 126
 127         dbuf = kmem_cache_alloc(ceph_x_ticketbuf_cachep, GFP_NOFS | GFP_ATOMIC);
 128         if (!dbuf)
 129                 return -ENOMEM;
 130
 131         ret = -ENOMEM;
 132         ticket_buf = kmem_cache_alloc(ceph_x_ticketbuf_cachep,
 133                                       GFP_NOFS | GFP_ATOMIC);
 134         if (!ticket_buf)
 135                 goto out_dbuf;
 136
 137         ceph_decode_need(&p, end, 1 + sizeof(u32), bad);
 138         struct_v = ceph_decode_8(&p);
 139         if (struct_v != 1)
 140                 goto bad;
 141         num = ceph_decode_32(&p);
 142         dout("%d tickets\n", num);
 143         while (num--) {
 144                 int type;
 145                 u8 struct_v;
 146                 struct ceph_x_ticket_handler *th;
 147                 void *dp, *dend;
 148                 int dlen;
 149                 char is_enc;
 150                 struct timespec validity;
 151                 struct ceph_crypto_key old_key;
 152                 void *tp, *tpend;
 153
 154                 ceph_decode_need(&p, end, sizeof(u32) + 1, bad);
 155
 156                 type = ceph_decode_32(&p);
 157                 dout(" ticket type %d %s\n", type, ceph_entity_type_name(type));
 158
 159                 struct_v = ceph_decode_8(&p);
 160                 if (struct_v != 1)
 161                         goto bad;
 162
 163                 th = get_ticket_handler(ac, type);
 164                 if (IS_ERR(th)) {
 165                         ret = PTR_ERR(th);
 166                         goto out;
 167                 }
 168
 169                 /* blob for me */
 170                 dlen = ceph_x_decrypt(secret, &p, end, dbuf,
 171                                       TEMP_TICKET_BUF_LEN);
 172                 if (dlen <= 0) {
 173                         ret = dlen;
 174                         goto out;
 175                 }
 176                 dout(" decrypted %d bytes\n", dlen);
 177                 dend = dbuf + dlen;
 178                 dp = dbuf;
 179
 180                 struct_v = ceph_decode_8(&dp);
 181                 if (struct_v != 1)
 182                         goto bad;
 183
 184                 memcpy(&old_key, &th->session_key, sizeof(old_key));
 185                 ret = ceph_crypto_key_decode(&th->session_key, &dp, dend);
 186                 if (ret)
 187                         goto out;
 188
 189                 ceph_decode_copy(&dp, &th->validity, sizeof(th->validity));
 190                 ceph_decode_timespec(&validity, &th->validity);
 191                 th->expires = get_seconds() + validity.tv_sec;
 192                 th->renew_after = th->expires - (validity.tv_sec / 4);
 193                 dout(" expires=%lu renew_after=%lu\n", th->expires,
 194                      th->renew_after);
 195
 196                 /* ticket blob for service */
 197                 ceph_decode_8_safe(&p, end, is_enc, bad);
 198                 tp = ticket_buf;
 199                 if (is_enc) {
 200                         /* encrypted */
 201                         dout(" encrypted ticket\n");
 202                         dlen = ceph_x_decrypt(&old_key, &p, end, ticket_buf,
 203                                               TEMP_TICKET_BUF_LEN);
 204                         if (dlen < 0) {
 205                                 ret = dlen;
 206                                 goto out;
 207                         }
 208                         dlen = ceph_decode_32(&tp);
 209                 } else {
 210                         /* unencrypted */
 211                         ceph_decode_32_safe(&p, end, dlen, bad);
 212                         ceph_decode_need(&p, end, dlen, bad);
 213                         ceph_decode_copy(&p, ticket_buf, dlen);
 214                 }
 215                 tpend = tp + dlen;
 216                 dout(" ticket blob is %d bytes\n", dlen);
 217                 ceph_decode_need(&tp, tpend, 1 + sizeof(u64), bad);
 218                 struct_v = ceph_decode_8(&tp);
 219                 th->secret_id = ceph_decode_64(&tp);
 220                 ret = ceph_decode_buffer(&th->ticket_blob, &tp, tpend);
 221                 if (ret)
 222                         goto out;
 223                 dout(" got ticket service %d (%s) secret_id %lld len %d\n",
 224                      type, ceph_entity_type_name(type), th->secret_id,
 225                      (int)th->ticket_blob->vec.iov_len);
 226                 xi->have_keys |= th->service;
 227         }
 228
 229         ret = 0;
 230 out:
 231         kmem_cache_free(ceph_x_ticketbuf_cachep, ticket_buf);
 232 out_dbuf:
 233         kmem_cache_free(ceph_x_ticketbuf_cachep, dbuf);
 234         return ret;
 235
 236 bad:
 237         ret = -EINVAL;
 238         goto out;
 239 }
 240
 241 static int ceph_x_build_authorizer(struct ceph_auth_client *ac,
 242                                    struct ceph_x_ticket_handler *th,
 243                                    struct ceph_x_authorizer *au)
 244 {
 245         int len;
 246         struct ceph_x_authorize_a *msg_a;
 247         struct ceph_x_authorize_b msg_b;
 248         void *p, *end;
 249         int ret;
 250         int ticket_blob_len =
 251                 (th->ticket_blob ? th->ticket_blob->vec.iov_len : 0);
 252
 253         dout("build_authorizer for %s %p\n",
 254              ceph_entity_type_name(th->service), au);
 255
 256         len = sizeof(*msg_a) + sizeof(msg_b) + sizeof(u32) +
 257                 ticket_blob_len + 16;
 258         dout("  need len %d\n", len);
 259         if (au->buf && au->buf->alloc_len < len) {
 260                 ceph_buffer_put(au->buf);
 261                 au->buf = NULL;
 262         }
 263         if (!au->buf) {
 264                 au->buf = ceph_buffer_new(len, GFP_NOFS);
 265                 if (!au->buf)
 266                         return -ENOMEM;
 267         }
 268         au->service = th->service;
 269
 270         msg_a = au->buf->vec.iov_base;
 271         msg_a->struct_v = 1;
 272         msg_a->global_id = cpu_to_le64(ac->global_id);
 273         msg_a->service_id = cpu_to_le32(th->service);
 274         msg_a->ticket_blob.struct_v = 1;
 275         msg_a->ticket_blob.secret_id = cpu_to_le64(th->secret_id);
 276         msg_a->ticket_blob.blob_len = cpu_to_le32(ticket_blob_len);
 277         if (ticket_blob_len) {
 278                 memcpy(msg_a->ticket_blob.blob, th->ticket_blob->vec.iov_base,
 279                        th->ticket_blob->vec.iov_len);
 280         }
 281         dout(" th %p secret_id %lld %lld\n", th, th->secret_id,
 282              le64_to_cpu(msg_a->ticket_blob.secret_id));
 283
 284         p = msg_a + 1;
 285         p += ticket_blob_len;
 286         end = au->buf->vec.iov_base + au->buf->vec.iov_len;
 287
 288         get_random_bytes(&au->nonce, sizeof(au->nonce));
 289         msg_b.struct_v = 1;
 290         msg_b.nonce = cpu_to_le64(au->nonce);
 291         ret = ceph_x_encrypt(&th->session_key, &msg_b, sizeof(msg_b),
 292                              p, end - p);
 293         if (ret < 0)
 294                 goto out_buf;
 295         p += ret;
 296         au->buf->vec.iov_len = p - au->buf->vec.iov_base;
 297         dout(" built authorizer nonce %llx len %d\n", au->nonce,
 298              (int)au->buf->vec.iov_len);
 299         return 0;
 300
 301 out_buf:
 302         ceph_buffer_put(au->buf);
 303         au->buf = NULL;
 304         return ret;
 305 }
 306
 307 static int ceph_x_encode_ticket(struct ceph_x_ticket_handler *th,
 308                                 void **p, void *end)
 309 {
 310         ceph_decode_need(p, end, 1 + sizeof(u64), bad);
 311         ceph_encode_8(p, 1);
 312         ceph_encode_64(p, th->secret_id);
 313         if (th->ticket_blob) {
 314                 const char *buf = th->ticket_blob->vec.iov_base;
 315                 u32 len = th->ticket_blob->vec.iov_len;
 316
 317                 ceph_encode_32_safe(p, end, len, bad);
 318                 ceph_encode_copy_safe(p, end, buf, len, bad);
 319         } else {
 320                 ceph_encode_32_safe(p, end, 0, bad);
 321         }
 322
 323         return 0;
 324 bad:
 325         return -ERANGE;
 326 }
 327
 328 static void ceph_x_validate_tickets(struct ceph_auth_client *ac, int *pneed)
 329 {
 330         int want = ac->want_keys;
 331         struct ceph_x_info *xi = ac->private;
 332         int service;
 333
 334         *pneed = ac->want_keys & ~(xi->have_keys);
 335
 336         for (service = 1; service <= want; service <<= 1) {
 337                 struct ceph_x_ticket_handler *th;
 338
 339                 if (!(ac->want_keys & service))
 340                         continue;
 341
 342                 if (*pneed & service)
 343                         continue;
 344
 345                 th = get_ticket_handler(ac, service);
 346
 347                 if (!th) {
 348                         *pneed |= service;
 349                         continue;
 350                 }
 351
 352                 if (get_seconds() >= th->renew_after)
 353                         *pneed |= service;
 354                 if (get_seconds() >= th->expires)
 355                         xi->have_keys &= ~service;
 356         }
 357 }
 358
 359
 360 static int ceph_x_build_request(struct ceph_auth_client *ac,
 361                                 void *buf, void *end)
 362 {
 363         struct ceph_x_info *xi = ac->private;
 364         int need;
 365         struct ceph_x_request_header *head = buf;
 366         int ret;
 367         struct ceph_x_ticket_handler *th =
 368                 get_ticket_handler(ac, CEPH_ENTITY_TYPE_AUTH);
 369
 370         ceph_x_validate_tickets(ac, &need);
 371
 372         dout("build_request want %x have %x need %x\n",
 373              ac->want_keys, xi->have_keys, need);
 374
 375         if (need & CEPH_ENTITY_TYPE_AUTH) {
 376                 struct ceph_x_authenticate *auth = (void *)(head + 1);
 377                 void *p = auth + 1;
 378                 struct ceph_x_challenge_blob tmp;
 379                 char tmp_enc[40];
 380                 u64 *u;
 381
 382                 if (p > end)
 383                         return -ERANGE;
 384
 385                 dout(" get_auth_session_key\n");
 386                 head->op = cpu_to_le16(CEPHX_GET_AUTH_SESSION_KEY);
 387
 388                 /* encrypt and hash */
 389                 get_random_bytes(&auth->client_challenge, sizeof(u64));
 390                 tmp.client_challenge = auth->client_challenge;
 391                 tmp.server_challenge = cpu_to_le64(xi->server_challenge);
 392                 ret = ceph_x_encrypt(&xi->secret, &tmp, sizeof(tmp),
 393                                      tmp_enc, sizeof(tmp_enc));
 394                 if (ret < 0)
 395                         return ret;
 396
 397                 auth->struct_v = 1;
 398                 auth->key = 0;
 399                 for (u = (u64 *)tmp_enc; u + 1 <= (u64 *)(tmp_enc + ret); u++)
 400                         auth->key ^= *u;
 401                 dout(" server_challenge %llx client_challenge %llx key %llx\n",
 402                      xi->server_challenge, le64_to_cpu(auth->client_challenge),
 403                      le64_to_cpu(auth->key));
 404
 405                 /* now encode the old ticket if exists */
 406                 ret = ceph_x_encode_ticket(th, &p, end);
 407                 if (ret < 0)
 408                         return ret;
 409
 410                 return p - buf;
 411         }
 412
 413         if (need) {
 414                 void *p = head + 1;
 415                 struct ceph_x_service_ticket_request *req;
 416
 417                 if (p > end)
 418                         return -ERANGE;
 419                 head->op = cpu_to_le16(CEPHX_GET_PRINCIPAL_SESSION_KEY);
 420
 421                 BUG_ON(!th);
 422                 ret = ceph_x_build_authorizer(ac, th, &xi->auth_authorizer);
 423                 if (ret)
 424                         return ret;
 425                 ceph_encode_copy(&p, xi->auth_authorizer.buf->vec.iov_base,
 426                                  xi->auth_authorizer.buf->vec.iov_len);
 427
 428                 req = p;
 429                 req->keys = cpu_to_le32(need);
 430                 p += sizeof(*req);
 431                 return p - buf;
 432         }
 433
 434         return 0;
 435 }
 436
 437 static int ceph_x_handle_reply(struct ceph_auth_client *ac, int result,
 438                                void *buf, void *end)
 439 {
 440         struct ceph_x_info *xi = ac->private;
 441         struct ceph_x_reply_header *head = buf;
 442         struct ceph_x_ticket_handler *th;
 443         int len = end - buf;
 444         int op;
 445         int ret;
 446
 447         if (result)
 448                 return result;  /* XXX hmm? */
 449
 450         if (xi->starting) {
 451                 /* it's a hello */
 452                 struct ceph_x_server_challenge *sc = buf;
 453
 454                 if (len != sizeof(*sc))
 455                         return -EINVAL;
 456                 xi->server_challenge = le64_to_cpu(sc->server_challenge);
 457                 dout("handle_reply got server challenge %llx\n",
 458                      xi->server_challenge);
 459                 xi->starting = false;
 460                 xi->have_keys &= ~CEPH_ENTITY_TYPE_AUTH;
 461                 return -EAGAIN;
 462         }
 463
 464         op = le32_to_cpu(head->op);
 465         result = le32_to_cpu(head->result);
 466         dout("handle_reply op %d result %d\n", op, result);
 467         switch (op) {
 468         case CEPHX_GET_AUTH_SESSION_KEY:
 469                 /* verify auth key */
 470                 ret = ceph_x_proc_ticket_reply(ac, &xi->secret,
 471                                                buf + sizeof(*head), end);
 472                 break;
 473
 474         case CEPHX_GET_PRINCIPAL_SESSION_KEY:
 475                 th = get_ticket_handler(ac, CEPH_ENTITY_TYPE_AUTH);
 476                 BUG_ON(!th);
 477                 ret = ceph_x_proc_ticket_reply(ac, &th->session_key,
 478                                                buf + sizeof(*head), end);
 479                 break;
 480
 481         default:
 482                 return -EINVAL;
 483         }
 484         if (ret)
 485                 return ret;
 486         if (ac->want_keys == xi->have_keys)
 487                 return 0;
 488         return -EAGAIN;
 489 }
 490
 491 static int ceph_x_create_authorizer(
 492         struct ceph_auth_client *ac, int peer_type,
 493         struct ceph_authorizer **a,
 494         void **buf, size_t *len,
 495         void **reply_buf, size_t *reply_len)
 496 {
 497         struct ceph_x_authorizer *au;
 498         struct ceph_x_ticket_handler *th;
 499         int ret;
 500
 501         th = get_ticket_handler(ac, peer_type);
 502         if (IS_ERR(th))
 503                 return PTR_ERR(th);
 504
 505         au = kzalloc(sizeof(*au), GFP_NOFS);
 506         if (!au)
 507                 return -ENOMEM;
 508
 509         ret = ceph_x_build_authorizer(ac, th, au);
 510         if (ret) {
 511                 kfree(au);
 512                 return ret;
 513         }
 514
 515         *a = (struct ceph_authorizer *)au;
 516         *buf = au->buf->vec.iov_base;
 517         *len = au->buf->vec.iov_len;
 518         *reply_buf = au->reply_buf;
 519         *reply_len = sizeof(au->reply_buf);
 520         return 0;
 521 }
 522
 523 static int ceph_x_verify_authorizer_reply(struct ceph_auth_client *ac,
 524                                           struct ceph_authorizer *a, size_t len)
 525 {
 526         struct ceph_x_authorizer *au = (void *)a;
 527         struct ceph_x_ticket_handler *th;
 528         int ret = 0;
 529         struct ceph_x_authorize_reply reply;
 530         void *p = au->reply_buf;
 531         void *end = p + sizeof(au->reply_buf);
 532
 533         th = get_ticket_handler(ac, au->service);
 534         if (!th)
 535                 return -EIO;  /* hrm! */
 536         ret = ceph_x_decrypt(&th->session_key, &p, end, &reply, sizeof(reply));
 537         if (ret < 0)
 538                 return ret;
 539         if (ret != sizeof(reply))
 540                 return -EPERM;
 541
 542         if (au->nonce + 1 != le64_to_cpu(reply.nonce_plus_one))
 543                 ret = -EPERM;
 544         else
 545                 ret = 0;
 546         dout("verify_authorizer_reply nonce %llx got %llx ret %d\n",
 547              au->nonce, le64_to_cpu(reply.nonce_plus_one), ret);
 548         return ret;
 549 }
 550
 551 static void ceph_x_destroy_authorizer(struct ceph_auth_client *ac,
 552                                       struct ceph_authorizer *a)
 553 {
 554         struct ceph_x_authorizer *au = (void *)a;
 555
 556         ceph_buffer_put(au->buf);
 557         kfree(au);
 558 }
 559
 560
 561 static void ceph_x_reset(struct ceph_auth_client *ac)
 562 {
 563         struct ceph_x_info *xi = ac->private;
 564
 565         dout("reset\n");
 566         xi->starting = true;
 567         xi->server_challenge = 0;
 568 }
 569
 570 static void ceph_x_destroy(struct ceph_auth_client *ac)
 571 {
 572         struct ceph_x_info *xi = ac->private;
 573         struct rb_node *p;
 574
 575         dout("ceph_x_destroy %p\n", ac);
 576         ceph_crypto_key_destroy(&xi->secret);
 577
 578         while ((p = rb_first(&xi->ticket_handlers)) != NULL) {
 579                 struct ceph_x_ticket_handler *th =
 580                         rb_entry(p, struct ceph_x_ticket_handler, node);
 581                 remove_ticket_handler(ac, th);
 582         }
 583
 584         kmem_cache_destroy(ceph_x_ticketbuf_cachep);
 585
 586         kfree(ac->private);
 587         ac->private = NULL;
 588 }
 589
 590 static void ceph_x_invalidate_authorizer(struct ceph_auth_client *ac,
 591                                    int peer_type)
 592 {
 593         struct ceph_x_ticket_handler *th;
 594
 595         th = get_ticket_handler(ac, peer_type);
 596         if (th && !IS_ERR(th))
 597                 remove_ticket_handler(ac, th);
 598 }
 599
 600
 601 static const struct ceph_auth_client_ops ceph_x_ops = {
 602         .is_authenticated = ceph_x_is_authenticated,
 603         .build_request = ceph_x_build_request,
 604         .handle_reply = ceph_x_handle_reply,
 605         .create_authorizer = ceph_x_create_authorizer,
 606         .verify_authorizer_reply = ceph_x_verify_authorizer_reply,
 607         .destroy_authorizer = ceph_x_destroy_authorizer,
 608         .invalidate_authorizer = ceph_x_invalidate_authorizer,
 609         .reset =  ceph_x_reset,
 610         .destroy = ceph_x_destroy,
 611 };
 612
 613
 614 int ceph_x_init(struct ceph_auth_client *ac)
 615 {
 616         struct ceph_x_info *xi;
 617         int ret;
 618
 619         dout("ceph_x_init %p\n", ac);
 620         xi = kzalloc(sizeof(*xi), GFP_NOFS);
 621         if (!xi)
 622                 return -ENOMEM;
 623
 624         ret = -ENOMEM;
 625         ceph_x_ticketbuf_cachep = kmem_cache_create("ceph_x_ticketbuf",
 626                                       TEMP_TICKET_BUF_LEN, 8,
 627                                       (SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD),
 628                                       NULL);
 629         if (!ceph_x_ticketbuf_cachep)
 630                 goto done_nomem;
 631         ret = -EINVAL;
 632         if (!ac->secret) {
 633                 pr_err("no secret set (for auth_x protocol)\n");
 634                 goto done_nomem;
 635         }
 636
 637         ret = ceph_crypto_key_unarmor(&xi->secret, ac->secret);
 638         if (ret)
 639                 goto done_nomem;
 640
 641         xi->starting = true;
 642         xi->ticket_handlers = RB_ROOT;
 643
 644         ac->protocol = CEPH_AUTH_CEPHX;
 645         ac->private = xi;
 646         ac->ops = &ceph_x_ops;
 647         return 0;
 648
 649 done_nomem:
 650         kfree(xi);
 651         if (ceph_x_ticketbuf_cachep)
 652                 kmem_cache_destroy(ceph_x_ticketbuf_cachep);
 653         return ret;
 654 }
 655
 656