net/rxrpc/recvmsg.c

   1 /* RxRPC recvmsg() implementation
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 #include <linux/net.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/export.h>
  17 #include <linux/sched/signal.h>
  18
  19 #include <net/sock.h>
  20 #include <net/af_rxrpc.h>
  21 #include "ar-internal.h"
  22
  23 /*
  24  * Post a call for attention by the socket or kernel service.  Further
  25  * notifications are suppressed by putting recvmsg_link on a dummy queue.
  26  */
  27 void rxrpc_notify_socket(struct rxrpc_call *call)
  28 {
  29         struct rxrpc_sock *rx;
  30         struct sock *sk;
  31
  32         _enter("%d", call->debug_id);
  33
  34         if (!list_empty(&call->recvmsg_link))
  35                 return;
  36
  37         rcu_read_lock();
  38
  39         rx = rcu_dereference(call->socket);
  40         sk = &rx->sk;
  41         if (rx && sk->sk_state < RXRPC_CLOSE) {
  42                 if (call->notify_rx) {
  43                         spin_lock_bh(&call->notify_lock);
  44                         call->notify_rx(sk, call, call->user_call_ID);
  45                         spin_unlock_bh(&call->notify_lock);
  46                 } else {
  47                         write_lock_bh(&rx->recvmsg_lock);
  48                         if (list_empty(&call->recvmsg_link)) {
  49                                 rxrpc_get_call(call, rxrpc_call_got);
  50                                 list_add_tail(&call->recvmsg_link, &rx->recvmsg_q);
  51                         }
  52                         write_unlock_bh(&rx->recvmsg_lock);
  53
  54                         if (!sock_flag(sk, SOCK_DEAD)) {
  55                                 _debug("call %ps", sk->sk_data_ready);
  56                                 sk->sk_data_ready(sk);
  57                         }
  58                 }
  59         }
  60
  61         rcu_read_unlock();
  62         _leave("");
  63 }
  64
  65 /*
  66  * Pass a call terminating message to userspace.
  67  */
  68 static int rxrpc_recvmsg_term(struct rxrpc_call *call, struct msghdr *msg)
  69 {
  70         u32 tmp = 0;
  71         int ret;
  72
  73         switch (call->completion) {
  74         case RXRPC_CALL_SUCCEEDED:
  75                 ret = 0;
  76                 if (rxrpc_is_service_call(call))
  77                         ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ACK, 0, &tmp);
  78                 break;
  79         case RXRPC_CALL_REMOTELY_ABORTED:
  80                 tmp = call->abort_code;
  81                 ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ABORT, 4, &tmp);
  82                 break;
  83         case RXRPC_CALL_LOCALLY_ABORTED:
  84                 tmp = call->abort_code;
  85                 ret = put_cmsg(msg, SOL_RXRPC, RXRPC_ABORT, 4, &tmp);
  86                 break;
  87         case RXRPC_CALL_NETWORK_ERROR:
  88                 tmp = -call->error;
  89                 ret = put_cmsg(msg, SOL_RXRPC, RXRPC_NET_ERROR, 4, &tmp);
  90                 break;
  91         case RXRPC_CALL_LOCAL_ERROR:
  92                 tmp = -call->error;
  93                 ret = put_cmsg(msg, SOL_RXRPC, RXRPC_LOCAL_ERROR, 4, &tmp);
  94                 break;
  95         default:
  96                 pr_err("Invalid terminal call state %u\n", call->state);
  97                 BUG();
  98                 break;
  99         }
 100
 101         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_terminal, call->rx_hard_ack,
 102                             call->rx_pkt_offset, call->rx_pkt_len, ret);
 103         return ret;
 104 }
 105
 106 /*
 107  * Pass back notification of a new call.  The call is added to the
 108  * to-be-accepted list.  This means that the next call to be accepted might not
 109  * be the last call seen awaiting acceptance, but unless we leave this on the
 110  * front of the queue and block all other messages until someone gives us a
 111  * user_ID for it, there's not a lot we can do.
 112  */
 113 static int rxrpc_recvmsg_new_call(struct rxrpc_sock *rx,
 114                                   struct rxrpc_call *call,
 115                                   struct msghdr *msg, int flags)
 116 {
 117         int tmp = 0, ret;
 118
 119         ret = put_cmsg(msg, SOL_RXRPC, RXRPC_NEW_CALL, 0, &tmp);
 120
 121         if (ret == 0 && !(flags & MSG_PEEK)) {
 122                 _debug("to be accepted");
 123                 write_lock_bh(&rx->recvmsg_lock);
 124                 list_del_init(&call->recvmsg_link);
 125                 write_unlock_bh(&rx->recvmsg_lock);
 126
 127                 rxrpc_get_call(call, rxrpc_call_got);
 128                 write_lock(&rx->call_lock);
 129                 list_add_tail(&call->accept_link, &rx->to_be_accepted);
 130                 write_unlock(&rx->call_lock);
 131         }
 132
 133         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_to_be_accepted, 1, 0, 0, ret);
 134         return ret;
 135 }
 136
 137 /*
 138  * End the packet reception phase.
 139  */
 140 static void rxrpc_end_rx_phase(struct rxrpc_call *call, rxrpc_serial_t serial)
 141 {
 142         _enter("%d,%s", call->debug_id, rxrpc_call_states[call->state]);
 143
 144         trace_rxrpc_receive(call, rxrpc_receive_end, 0, call->rx_top);
 145         ASSERTCMP(call->rx_hard_ack, ==, call->rx_top);
 146
 147 #if 0 // TODO: May want to transmit final ACK under some circumstances anyway
 148         if (call->state == RXRPC_CALL_CLIENT_RECV_REPLY) {
 149                 rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, 0, serial, true, false,
 150                                   rxrpc_propose_ack_terminal_ack);
 151                 rxrpc_send_ack_packet(call, false, NULL);
 152         }
 153 #endif
 154
 155         write_lock_bh(&call->state_lock);
 156
 157         switch (call->state) {
 158         case RXRPC_CALL_CLIENT_RECV_REPLY:
 159                 __rxrpc_call_completed(call);
 160                 write_unlock_bh(&call->state_lock);
 161                 break;
 162
 163         case RXRPC_CALL_SERVER_RECV_REQUEST:
 164                 call->tx_phase = true;
 165                 call->state = RXRPC_CALL_SERVER_ACK_REQUEST;
 166                 call->expect_req_by = jiffies + MAX_JIFFY_OFFSET;
 167                 write_unlock_bh(&call->state_lock);
 168                 rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, 0, serial, false, true,
 169                                   rxrpc_propose_ack_processing_op);
 170                 break;
 171         default:
 172                 write_unlock_bh(&call->state_lock);
 173                 break;
 174         }
 175 }
 176
 177 /*
 178  * Discard a packet we've used up and advance the Rx window by one.
 179  */
 180 static void rxrpc_rotate_rx_window(struct rxrpc_call *call)
 181 {
 182         struct rxrpc_skb_priv *sp;
 183         struct sk_buff *skb;
 184         rxrpc_serial_t serial;
 185         rxrpc_seq_t hard_ack, top;
 186         u8 flags;
 187         int ix;
 188
 189         _enter("%d", call->debug_id);
 190
 191         hard_ack = call->rx_hard_ack;
 192         top = smp_load_acquire(&call->rx_top);
 193         ASSERT(before(hard_ack, top));
 194
 195         hard_ack++;
 196         ix = hard_ack & RXRPC_RXTX_BUFF_MASK;
 197         skb = call->rxtx_buffer[ix];
 198         rxrpc_see_skb(skb, rxrpc_skb_rx_rotated);
 199         sp = rxrpc_skb(skb);
 200         flags = sp->hdr.flags;
 201         serial = sp->hdr.serial;
 202         if (call->rxtx_annotations[ix] & RXRPC_RX_ANNO_JUMBO)
 203                 serial += (call->rxtx_annotations[ix] & RXRPC_RX_ANNO_JUMBO) - 1;
 204
 205         call->rxtx_buffer[ix] = NULL;
 206         call->rxtx_annotations[ix] = 0;
 207         /* Barrier against rxrpc_input_data(). */
 208         smp_store_release(&call->rx_hard_ack, hard_ack);
 209
 210         rxrpc_free_skb(skb, rxrpc_skb_rx_freed);
 211
 212         _debug("%u,%u,%02x", hard_ack, top, flags);
 213         trace_rxrpc_receive(call, rxrpc_receive_rotate, serial, hard_ack);
 214         if (flags & RXRPC_LAST_PACKET) {
 215                 rxrpc_end_rx_phase(call, serial);
 216         } else {
 217                 /* Check to see if there's an ACK that needs sending. */
 218                 if (after_eq(hard_ack, call->ackr_consumed + 2) ||
 219                     after_eq(top, call->ackr_seen + 2) ||
 220                     (hard_ack == top && after(hard_ack, call->ackr_consumed)))
 221                         rxrpc_propose_ACK(call, RXRPC_ACK_DELAY, 0, serial,
 222                                           true, true,
 223                                           rxrpc_propose_ack_rotate_rx);
 224                 if (call->ackr_reason && call->ackr_reason != RXRPC_ACK_DELAY)
 225                         rxrpc_send_ack_packet(call, false, NULL);
 226         }
 227 }
 228
 229 /*
 230  * Decrypt and verify a (sub)packet.  The packet's length may be changed due to
 231  * padding, but if this is the case, the packet length will be resident in the
 232  * socket buffer.  Note that we can't modify the master skb info as the skb may
 233  * be the home to multiple subpackets.
 234  */
 235 static int rxrpc_verify_packet(struct rxrpc_call *call, struct sk_buff *skb,
 236                                u8 annotation,
 237                                unsigned int offset, unsigned int len)
 238 {
 239         struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
 240         rxrpc_seq_t seq = sp->hdr.seq;
 241         u16 cksum = sp->hdr.cksum;
 242
 243         _enter("");
 244
 245         /* For all but the head jumbo subpacket, the security checksum is in a
 246          * jumbo header immediately prior to the data.
 247          */
 248         if ((annotation & RXRPC_RX_ANNO_JUMBO) > 1) {
 249                 __be16 tmp;
 250                 if (skb_copy_bits(skb, offset - 2, &tmp, 2) < 0)
 251                         BUG();
 252                 cksum = ntohs(tmp);
 253                 seq += (annotation & RXRPC_RX_ANNO_JUMBO) - 1;
 254         }
 255
 256         return call->conn->security->verify_packet(call, skb, offset, len,
 257                                                    seq, cksum);
 258 }
 259
 260 /*
 261  * Locate the data within a packet.  This is complicated by:
 262  *
 263  * (1) An skb may contain a jumbo packet - so we have to find the appropriate
 264  *     subpacket.
 265  *
 266  * (2) The (sub)packets may be encrypted and, if so, the encrypted portion
 267  *     contains an extra header which includes the true length of the data,
 268  *     excluding any encrypted padding.
 269  */
 270 static int rxrpc_locate_data(struct rxrpc_call *call, struct sk_buff *skb,
 271                              u8 *_annotation,
 272                              unsigned int *_offset, unsigned int *_len)
 273 {
 274         unsigned int offset = sizeof(struct rxrpc_wire_header);
 275         unsigned int len = *_len;
 276         int ret;
 277         u8 annotation = *_annotation;
 278
 279         /* Locate the subpacket */
 280         len = skb->len - offset;
 281         if ((annotation & RXRPC_RX_ANNO_JUMBO) > 0) {
 282                 offset += (((annotation & RXRPC_RX_ANNO_JUMBO) - 1) *
 283                            RXRPC_JUMBO_SUBPKTLEN);
 284                 len = (annotation & RXRPC_RX_ANNO_JLAST) ?
 285                         skb->len - offset : RXRPC_JUMBO_SUBPKTLEN;
 286         }
 287
 288         if (!(annotation & RXRPC_RX_ANNO_VERIFIED)) {
 289                 ret = rxrpc_verify_packet(call, skb, annotation, offset, len);
 290                 if (ret < 0)
 291                         return ret;
 292                 *_annotation |= RXRPC_RX_ANNO_VERIFIED;
 293         }
 294
 295         *_offset = offset;
 296         *_len = len;
 297         call->conn->security->locate_data(call, skb, _offset, _len);
 298         return 0;
 299 }
 300
 301 /*
 302  * Deliver messages to a call.  This keeps processing packets until the buffer
 303  * is filled and we find either more DATA (returns 0) or the end of the DATA
 304  * (returns 1).  If more packets are required, it returns -EAGAIN.
 305  */
 306 static int rxrpc_recvmsg_data(struct socket *sock, struct rxrpc_call *call,
 307                               struct msghdr *msg, struct iov_iter *iter,
 308                               size_t len, int flags, size_t *_offset)
 309 {
 310         struct rxrpc_skb_priv *sp;
 311         struct sk_buff *skb;
 312         rxrpc_seq_t hard_ack, top, seq;
 313         size_t remain;
 314         bool last;
 315         unsigned int rx_pkt_offset, rx_pkt_len;
 316         int ix, copy, ret = -EAGAIN, ret2;
 317
 318         rx_pkt_offset = call->rx_pkt_offset;
 319         rx_pkt_len = call->rx_pkt_len;
 320
 321         if (call->state >= RXRPC_CALL_SERVER_ACK_REQUEST) {
 322                 seq = call->rx_hard_ack;
 323                 ret = 1;
 324                 goto done;
 325         }
 326
 327         /* Barriers against rxrpc_input_data(). */
 328         hard_ack = call->rx_hard_ack;
 329         seq = hard_ack + 1;
 330         while (top = smp_load_acquire(&call->rx_top),
 331                before_eq(seq, top)
 332                ) {
 333                 ix = seq & RXRPC_RXTX_BUFF_MASK;
 334                 skb = call->rxtx_buffer[ix];
 335                 if (!skb) {
 336                         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_hole, seq,
 337                                             rx_pkt_offset, rx_pkt_len, 0);
 338                         break;
 339                 }
 340                 smp_rmb();
 341                 rxrpc_see_skb(skb, rxrpc_skb_rx_seen);
 342                 sp = rxrpc_skb(skb);
 343
 344                 if (!(flags & MSG_PEEK))
 345                         trace_rxrpc_receive(call, rxrpc_receive_front,
 346                                             sp->hdr.serial, seq);
 347
 348                 if (msg)
 349                         sock_recv_timestamp(msg, sock->sk, skb);
 350
 351                 if (rx_pkt_offset == 0) {
 352                         ret2 = rxrpc_locate_data(call, skb,
 353                                                  &call->rxtx_annotations[ix],
 354                                                  &rx_pkt_offset, &rx_pkt_len);
 355                         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_next, seq,
 356                                             rx_pkt_offset, rx_pkt_len, ret2);
 357                         if (ret2 < 0) {
 358                                 ret = ret2;
 359                                 goto out;
 360                         }
 361                 } else {
 362                         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_cont, seq,
 363                                             rx_pkt_offset, rx_pkt_len, 0);
 364                 }
 365
 366                 /* We have to handle short, empty and used-up DATA packets. */
 367                 remain = len - *_offset;
 368                 copy = rx_pkt_len;
 369                 if (copy > remain)
 370                         copy = remain;
 371                 if (copy > 0) {
 372                         ret2 = skb_copy_datagram_iter(skb, rx_pkt_offset, iter,
 373                                                       copy);
 374                         if (ret2 < 0) {
 375                                 ret = ret2;
 376                                 goto out;
 377                         }
 378
 379                         /* handle piecemeal consumption of data packets */
 380                         rx_pkt_offset += copy;
 381                         rx_pkt_len -= copy;
 382                         *_offset += copy;
 383                 }
 384
 385                 if (rx_pkt_len > 0) {
 386                         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_full, seq,
 387                                             rx_pkt_offset, rx_pkt_len, 0);
 388                         ASSERTCMP(*_offset, ==, len);
 389                         ret = 0;
 390                         break;
 391                 }
 392
 393                 /* The whole packet has been transferred. */
 394                 last = sp->hdr.flags & RXRPC_LAST_PACKET;
 395                 if (!(flags & MSG_PEEK))
 396                         rxrpc_rotate_rx_window(call);
 397                 rx_pkt_offset = 0;
 398                 rx_pkt_len = 0;
 399
 400                 if (last) {
 401                         ASSERTCMP(seq, ==, READ_ONCE(call->rx_top));
 402                         ret = 1;
 403                         goto out;
 404                 }
 405
 406                 seq++;
 407         }
 408
 409 out:
 410         if (!(flags & MSG_PEEK)) {
 411                 call->rx_pkt_offset = rx_pkt_offset;
 412                 call->rx_pkt_len = rx_pkt_len;
 413         }
 414 done:
 415         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_data_return, seq,
 416                             rx_pkt_offset, rx_pkt_len, ret);
 417         return ret;
 418 }
 419
 420 /*
 421  * Receive a message from an RxRPC socket
 422  * - we need to be careful about two or more threads calling recvmsg
 423  *   simultaneously
 424  */
 425 int rxrpc_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 426                   int flags)
 427 {
 428         struct rxrpc_call *call;
 429         struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
 430         struct list_head *l;
 431         size_t copied = 0;
 432         long timeo;
 433         int ret;
 434
 435         DEFINE_WAIT(wait);
 436
 437         trace_rxrpc_recvmsg(NULL, rxrpc_recvmsg_enter, 0, 0, 0, 0);
 438
 439         if (flags & (MSG_OOB | MSG_TRUNC))
 440                 return -EOPNOTSUPP;
 441
 442         timeo = sock_rcvtimeo(&rx->sk, flags & MSG_DONTWAIT);
 443
 444 try_again:
 445         lock_sock(&rx->sk);
 446
 447         /* Return immediately if a client socket has no outstanding calls */
 448         if (RB_EMPTY_ROOT(&rx->calls) &&
 449             list_empty(&rx->recvmsg_q) &&
 450             rx->sk.sk_state != RXRPC_SERVER_LISTENING) {
 451                 release_sock(&rx->sk);
 452                 return -ENODATA;
 453         }
 454
 455         if (list_empty(&rx->recvmsg_q)) {
 456                 ret = -EWOULDBLOCK;
 457                 if (timeo == 0) {
 458                         call = NULL;
 459                         goto error_no_call;
 460                 }
 461
 462                 release_sock(&rx->sk);
 463
 464                 /* Wait for something to happen */
 465                 prepare_to_wait_exclusive(sk_sleep(&rx->sk), &wait,
 466                                           TASK_INTERRUPTIBLE);
 467                 ret = sock_error(&rx->sk);
 468                 if (ret)
 469                         goto wait_error;
 470
 471                 if (list_empty(&rx->recvmsg_q)) {
 472                         if (signal_pending(current))
 473                                 goto wait_interrupted;
 474                         trace_rxrpc_recvmsg(NULL, rxrpc_recvmsg_wait,
 475                                             0, 0, 0, 0);
 476                         timeo = schedule_timeout(timeo);
 477                 }
 478                 finish_wait(sk_sleep(&rx->sk), &wait);
 479                 goto try_again;
 480         }
 481
 482         /* Find the next call and dequeue it if we're not just peeking.  If we
 483          * do dequeue it, that comes with a ref that we will need to release.
 484          */
 485         write_lock_bh(&rx->recvmsg_lock);
 486         l = rx->recvmsg_q.next;
 487         call = list_entry(l, struct rxrpc_call, recvmsg_link);
 488         if (!(flags & MSG_PEEK))
 489                 list_del_init(&call->recvmsg_link);
 490         else
 491                 rxrpc_get_call(call, rxrpc_call_got);
 492         write_unlock_bh(&rx->recvmsg_lock);
 493
 494         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_dequeue, 0, 0, 0, 0);
 495
 496         /* We're going to drop the socket lock, so we need to lock the call
 497          * against interference by sendmsg.
 498          */
 499         if (!mutex_trylock(&call->user_mutex)) {
 500                 ret = -EWOULDBLOCK;
 501                 if (flags & MSG_DONTWAIT)
 502                         goto error_requeue_call;
 503                 ret = -ERESTARTSYS;
 504                 if (mutex_lock_interruptible(&call->user_mutex) < 0)
 505                         goto error_requeue_call;
 506         }
 507
 508         release_sock(&rx->sk);
 509
 510         if (test_bit(RXRPC_CALL_RELEASED, &call->flags))
 511                 BUG();
 512
 513         if (test_bit(RXRPC_CALL_HAS_USERID, &call->flags)) {
 514                 if (flags & MSG_CMSG_COMPAT) {
 515                         unsigned int id32 = call->user_call_ID;
 516
 517                         ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID,
 518                                        sizeof(unsigned int), &id32);
 519                 } else {
 520                         unsigned long idl = call->user_call_ID;
 521
 522                         ret = put_cmsg(msg, SOL_RXRPC, RXRPC_USER_CALL_ID,
 523                                        sizeof(unsigned long), &idl);
 524                 }
 525                 if (ret < 0)
 526                         goto error_unlock_call;
 527         }
 528
 529         if (msg->msg_name) {
 530                 struct sockaddr_rxrpc *srx = msg->msg_name;
 531                 size_t len = sizeof(call->peer->srx);
 532
 533                 memcpy(msg->msg_name, &call->peer->srx, len);
 534                 srx->srx_service = call->service_id;
 535                 msg->msg_namelen = len;
 536         }
 537
 538         switch (READ_ONCE(call->state)) {
 539         case RXRPC_CALL_SERVER_ACCEPTING:
 540                 ret = rxrpc_recvmsg_new_call(rx, call, msg, flags);
 541                 break;
 542         case RXRPC_CALL_CLIENT_RECV_REPLY:
 543         case RXRPC_CALL_SERVER_RECV_REQUEST:
 544         case RXRPC_CALL_SERVER_ACK_REQUEST:
 545                 ret = rxrpc_recvmsg_data(sock, call, msg, &msg->msg_iter, len,
 546                                          flags, &copied);
 547                 if (ret == -EAGAIN)
 548                         ret = 0;
 549
 550                 if (after(call->rx_top, call->rx_hard_ack) &&
 551                     call->rxtx_buffer[(call->rx_hard_ack + 1) & RXRPC_RXTX_BUFF_MASK])
 552                         rxrpc_notify_socket(call);
 553                 break;
 554         default:
 555                 ret = 0;
 556                 break;
 557         }
 558
 559         if (ret < 0)
 560                 goto error_unlock_call;
 561
 562         if (call->state == RXRPC_CALL_COMPLETE) {
 563                 ret = rxrpc_recvmsg_term(call, msg);
 564                 if (ret < 0)
 565                         goto error_unlock_call;
 566                 if (!(flags & MSG_PEEK))
 567                         rxrpc_release_call(rx, call);
 568                 msg->msg_flags |= MSG_EOR;
 569                 ret = 1;
 570         }
 571
 572         if (ret == 0)
 573                 msg->msg_flags |= MSG_MORE;
 574         else
 575                 msg->msg_flags &= ~MSG_MORE;
 576         ret = copied;
 577
 578 error_unlock_call:
 579         mutex_unlock(&call->user_mutex);
 580         rxrpc_put_call(call, rxrpc_call_put);
 581         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_return, 0, 0, 0, ret);
 582         return ret;
 583
 584 error_requeue_call:
 585         if (!(flags & MSG_PEEK)) {
 586                 write_lock_bh(&rx->recvmsg_lock);
 587                 list_add(&call->recvmsg_link, &rx->recvmsg_q);
 588                 write_unlock_bh(&rx->recvmsg_lock);
 589                 trace_rxrpc_recvmsg(call, rxrpc_recvmsg_requeue, 0, 0, 0, 0);
 590         } else {
 591                 rxrpc_put_call(call, rxrpc_call_put);
 592         }
 593 error_no_call:
 594         release_sock(&rx->sk);
 595         trace_rxrpc_recvmsg(call, rxrpc_recvmsg_return, 0, 0, 0, ret);
 596         return ret;
 597
 598 wait_interrupted:
 599         ret = sock_intr_errno(timeo);
 600 wait_error:
 601         finish_wait(sk_sleep(&rx->sk), &wait);
 602         call = NULL;
 603         goto error_no_call;
 604 }
 605
 606 /**
 607  * rxrpc_kernel_recv_data - Allow a kernel service to receive data/info
 608  * @sock: The socket that the call exists on
 609  * @call: The call to send data through
 610  * @buf: The buffer to receive into
 611  * @size: The size of the buffer, including data already read
 612  * @_offset: The running offset into the buffer.
 613  * @want_more: True if more data is expected to be read
 614  * @_abort: Where the abort code is stored if -ECONNABORTED is returned
 615  * @_service: Where to store the actual service ID (may be upgraded)
 616  *
 617  * Allow a kernel service to receive data and pick up information about the
 618  * state of a call.  Returns 0 if got what was asked for and there's more
 619  * available, 1 if we got what was asked for and we're at the end of the data
 620  * and -EAGAIN if we need more data.
 621  *
 622  * Note that we may return -EAGAIN to drain empty packets at the end of the
 623  * data, even if we've already copied over the requested data.
 624  *
 625  * This function adds the amount it transfers to *_offset, so this should be
 626  * precleared as appropriate.  Note that the amount remaining in the buffer is
 627  * taken to be size - *_offset.
 628  *
 629  * *_abort should also be initialised to 0.
 630  */
 631 int rxrpc_kernel_recv_data(struct socket *sock, struct rxrpc_call *call,
 632                            void *buf, size_t size, size_t *_offset,
 633                            bool want_more, u32 *_abort, u16 *_service)
 634 {
 635         struct iov_iter iter;
 636         struct kvec iov;
 637         int ret;
 638
 639         _enter("{%d,%s},%zu/%zu,%d",
 640                call->debug_id, rxrpc_call_states[call->state],
 641                *_offset, size, want_more);
 642
 643         ASSERTCMP(*_offset, <=, size);
 644         ASSERTCMP(call->state, !=, RXRPC_CALL_SERVER_ACCEPTING);
 645
 646         iov.iov_base = buf + *_offset;
 647         iov.iov_len = size - *_offset;
 648         iov_iter_kvec(&iter, ITER_KVEC | READ, &iov, 1, size - *_offset);
 649
 650         mutex_lock(&call->user_mutex);
 651
 652         switch (READ_ONCE(call->state)) {
 653         case RXRPC_CALL_CLIENT_RECV_REPLY:
 654         case RXRPC_CALL_SERVER_RECV_REQUEST:
 655         case RXRPC_CALL_SERVER_ACK_REQUEST:
 656                 ret = rxrpc_recvmsg_data(sock, call, NULL, &iter, size, 0,
 657                                          _offset);
 658                 if (ret < 0)
 659                         goto out;
 660
 661                 /* We can only reach here with a partially full buffer if we
 662                  * have reached the end of the data.  We must otherwise have a
 663                  * full buffer or have been given -EAGAIN.
 664                  */
 665                 if (ret == 1) {
 666                         if (*_offset < size)
 667                                 goto short_data;
 668                         if (!want_more)
 669                                 goto read_phase_complete;
 670                         ret = 0;
 671                         goto out;
 672                 }
 673
 674                 if (!want_more)
 675                         goto excess_data;
 676                 goto out;
 677
 678         case RXRPC_CALL_COMPLETE:
 679                 goto call_complete;
 680
 681         default:
 682                 ret = -EINPROGRESS;
 683                 goto out;
 684         }
 685
 686 read_phase_complete:
 687         ret = 1;
 688 out:
 689         if (_service)
 690                 *_service = call->service_id;
 691         mutex_unlock(&call->user_mutex);
 692         _leave(" = %d [%zu,%d]", ret, *_offset, *_abort);
 693         return ret;
 694
 695 short_data:
 696         trace_rxrpc_rx_eproto(call, 0, tracepoint_string("short_data"));
 697         ret = -EBADMSG;
 698         goto out;
 699 excess_data:
 700         trace_rxrpc_rx_eproto(call, 0, tracepoint_string("excess_data"));
 701         ret = -EMSGSIZE;
 702         goto out;
 703 call_complete:
 704         *_abort = call->abort_code;
 705         ret = call->error;
 706         if (call->completion == RXRPC_CALL_SUCCEEDED) {
 707                 ret = 1;
 708                 if (size > 0)
 709                         ret = -ECONNRESET;
 710         }
 711         goto out;
 712 }
 713 EXPORT_SYMBOL(rxrpc_kernel_recv_data);