ipc/msg.c

   1 /*
   2  * linux/ipc/msg.c
   3  * Copyright (C) 1992 Krishna Balasubramanian
   4  *
   5  * Removed all the remaining kerneld mess
   6  * Catch the -EFAULT stuff properly
   7  * Use GFP_KERNEL for messages as in 1.2
   8  * Fixed up the unchecked user space derefs
   9  * Copyright (C) 1998 Alan Cox & Andi Kleen
  10  *
  11  * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
  12  *
  13  * mostly rewritten, threaded and wake-one semantics added
  14  * MSGMAX limit removed, sysctl's added
  15  * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
  16  *
  17  * support for audit of ipc object properties and permission changes
  18  * Dustin Kirkland <dustin.kirkland@us.ibm.com>
  19  *
  20  * namespaces support
  21  * OpenVZ, SWsoft Inc.
  22  * Pavel Emelianov <xemul@openvz.org>
  23  */
  24
  25 #include <linux/capability.h>
  26 #include <linux/msg.h>
  27 #include <linux/spinlock.h>
  28 #include <linux/init.h>
  29 #include <linux/mm.h>
  30 #include <linux/proc_fs.h>
  31 #include <linux/list.h>
  32 #include <linux/security.h>
  33 #include <linux/sched.h>
  34 #include <linux/syscalls.h>
  35 #include <linux/audit.h>
  36 #include <linux/seq_file.h>
  37 #include <linux/rwsem.h>
  38 #include <linux/nsproxy.h>
  39 #include <linux/ipc_namespace.h>
  40
  41 #include <asm/current.h>
  42 #include <linux/uaccess.h>
  43 #include "util.h"
  44
  45 /* one msg_receiver structure for each sleeping receiver */
  46 struct msg_receiver {
  47         struct list_head        r_list;
  48         struct task_struct      *r_tsk;
  49
  50         int                     r_mode;
  51         long                    r_msgtype;
  52         long                    r_maxsize;
  53
  54         /*
  55          * Mark r_msg volatile so that the compiler
  56          * does not try to get smart and optimize
  57          * it. We rely on this for the lockless
  58          * receive algorithm.
  59          */
  60         struct msg_msg          *volatile r_msg;
  61 };
  62
  63 /* one msg_sender for each sleeping sender */
  64 struct msg_sender {
  65         struct list_head        list;
  66         struct task_struct      *tsk;
  67 };
  68
  69 #define SEARCH_ANY              1
  70 #define SEARCH_EQUAL            2
  71 #define SEARCH_NOTEQUAL         3
  72 #define SEARCH_LESSEQUAL        4
  73 #define SEARCH_NUMBER           5
  74
  75 #define msg_ids(ns)     ((ns)->ids[IPC_MSG_IDS])
  76
  77 static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
  78 {
  79         struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&msg_ids(ns), id);
  80
  81         if (IS_ERR(ipcp))
  82                 return ERR_CAST(ipcp);
  83
  84         return container_of(ipcp, struct msg_queue, q_perm);
  85 }
  86
  87 static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns,
  88                                                         int id)
  89 {
  90         struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id);
  91
  92         if (IS_ERR(ipcp))
  93                 return ERR_CAST(ipcp);
  94
  95         return container_of(ipcp, struct msg_queue, q_perm);
  96 }
  97
  98 static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
  99 {
 100         ipc_rmid(&msg_ids(ns), &s->q_perm);
 101 }
 102
 103 static void msg_rcu_free(struct rcu_head *head)
 104 {
 105         struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
 106         struct msg_queue *msq = ipc_rcu_to_struct(p);
 107
 108         security_msg_queue_free(msq);
 109         ipc_rcu_free(head);
 110 }
 111
 112 /**
 113  * newque - Create a new msg queue
 114  * @ns: namespace
 115  * @params: ptr to the structure that contains the key and msgflg
 116  *
 117  * Called with msg_ids.rwsem held (writer)
 118  */
 119 static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 120 {
 121         struct msg_queue *msq;
 122         int id, retval;
 123         key_t key = params->key;
 124         int msgflg = params->flg;
 125
 126         msq = ipc_rcu_alloc(sizeof(*msq));
 127         if (!msq)
 128                 return -ENOMEM;
 129
 130         msq->q_perm.mode = msgflg & S_IRWXUGO;
 131         msq->q_perm.key = key;
 132
 133         msq->q_perm.security = NULL;
 134         retval = security_msg_queue_alloc(msq);
 135         if (retval) {
 136                 ipc_rcu_putref(msq, ipc_rcu_free);
 137                 return retval;
 138         }
 139
 140         msq->q_stime = msq->q_rtime = 0;
 141         msq->q_ctime = get_seconds();
 142         msq->q_cbytes = msq->q_qnum = 0;
 143         msq->q_qbytes = ns->msg_ctlmnb;
 144         msq->q_lspid = msq->q_lrpid = 0;
 145         INIT_LIST_HEAD(&msq->q_messages);
 146         INIT_LIST_HEAD(&msq->q_receivers);
 147         INIT_LIST_HEAD(&msq->q_senders);
 148
 149         /* ipc_addid() locks msq upon success. */
 150         id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
 151         if (id < 0) {
 152                 ipc_rcu_putref(msq, msg_rcu_free);
 153                 return id;
 154         }
 155
 156         ipc_unlock_object(&msq->q_perm);
 157         rcu_read_unlock();
 158
 159         return msq->q_perm.id;
 160 }
 161
 162 static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
 163 {
 164         mss->tsk = current;
 165         __set_current_state(TASK_INTERRUPTIBLE);
 166         list_add_tail(&mss->list, &msq->q_senders);
 167 }
 168
 169 static inline void ss_del(struct msg_sender *mss)
 170 {
 171         if (mss->list.next != NULL)
 172                 list_del(&mss->list);
 173 }
 174
 175 static void ss_wakeup(struct list_head *h, int kill)
 176 {
 177         struct msg_sender *mss, *t;
 178
 179         list_for_each_entry_safe(mss, t, h, list) {
 180                 if (kill)
 181                         mss->list.next = NULL;
 182                 wake_up_process(mss->tsk);
 183         }
 184 }
 185
 186 static void expunge_all(struct msg_queue *msq, int res)
 187 {
 188         struct msg_receiver *msr, *t;
 189
 190         list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
 191                 msr->r_msg = NULL; /* initialize expunge ordering */
 192                 wake_up_process(msr->r_tsk);
 193                 /*
 194                  * Ensure that the wakeup is visible before setting r_msg as
 195                  * the receiving end depends on it: either spinning on a nil,
 196                  * or dealing with -EAGAIN cases. See lockless receive part 1
 197                  * and 2 in do_msgrcv().
 198                  */
 199                 smp_wmb(); /* barrier (B) */
 200                 msr->r_msg = ERR_PTR(res);
 201         }
 202 }
 203
 204 /*
 205  * freeque() wakes up waiters on the sender and receiver waiting queue,
 206  * removes the message queue from message queue ID IDR, and cleans up all the
 207  * messages associated with this queue.
 208  *
 209  * msg_ids.rwsem (writer) and the spinlock for this message queue are held
 210  * before freeque() is called. msg_ids.rwsem remains locked on exit.
 211  */
 212 static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 213 {
 214         struct msg_msg *msg, *t;
 215         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 216
 217         expunge_all(msq, -EIDRM);
 218         ss_wakeup(&msq->q_senders, 1);
 219         msg_rmid(ns, msq);
 220         ipc_unlock_object(&msq->q_perm);
 221         rcu_read_unlock();
 222
 223         list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
 224                 atomic_dec(&ns->msg_hdrs);
 225                 free_msg(msg);
 226         }
 227         atomic_sub(msq->q_cbytes, &ns->msg_bytes);
 228         ipc_rcu_putref(msq, msg_rcu_free);
 229 }
 230
 231 /*
 232  * Called with msg_ids.rwsem and ipcp locked.
 233  */
 234 static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
 235 {
 236         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 237
 238         return security_msg_queue_associate(msq, msgflg);
 239 }
 240
 241 SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
 242 {
 243         struct ipc_namespace *ns;
 244         static const struct ipc_ops msg_ops = {
 245                 .getnew = newque,
 246                 .associate = msg_security,
 247         };
 248         struct ipc_params msg_params;
 249
 250         ns = current->nsproxy->ipc_ns;
 251
 252         msg_params.key = key;
 253         msg_params.flg = msgflg;
 254
 255         return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
 256 }
 257
 258 static inline unsigned long
 259 copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 260 {
 261         switch (version) {
 262         case IPC_64:
 263                 return copy_to_user(buf, in, sizeof(*in));
 264         case IPC_OLD:
 265         {
 266                 struct msqid_ds out;
 267
 268                 memset(&out, 0, sizeof(out));
 269
 270                 ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
 271
 272                 out.msg_stime           = in->msg_stime;
 273                 out.msg_rtime           = in->msg_rtime;
 274                 out.msg_ctime           = in->msg_ctime;
 275
 276                 if (in->msg_cbytes > USHRT_MAX)
 277                         out.msg_cbytes  = USHRT_MAX;
 278                 else
 279                         out.msg_cbytes  = in->msg_cbytes;
 280                 out.msg_lcbytes         = in->msg_cbytes;
 281
 282                 if (in->msg_qnum > USHRT_MAX)
 283                         out.msg_qnum    = USHRT_MAX;
 284                 else
 285                         out.msg_qnum    = in->msg_qnum;
 286
 287                 if (in->msg_qbytes > USHRT_MAX)
 288                         out.msg_qbytes  = USHRT_MAX;
 289                 else
 290                         out.msg_qbytes  = in->msg_qbytes;
 291                 out.msg_lqbytes         = in->msg_qbytes;
 292
 293                 out.msg_lspid           = in->msg_lspid;
 294                 out.msg_lrpid           = in->msg_lrpid;
 295
 296                 return copy_to_user(buf, &out, sizeof(out));
 297         }
 298         default:
 299                 return -EINVAL;
 300         }
 301 }
 302
 303 static inline unsigned long
 304 copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
 305 {
 306         switch (version) {
 307         case IPC_64:
 308                 if (copy_from_user(out, buf, sizeof(*out)))
 309                         return -EFAULT;
 310                 return 0;
 311         case IPC_OLD:
 312         {
 313                 struct msqid_ds tbuf_old;
 314
 315                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
 316                         return -EFAULT;
 317
 318                 out->msg_perm.uid       = tbuf_old.msg_perm.uid;
 319                 out->msg_perm.gid       = tbuf_old.msg_perm.gid;
 320                 out->msg_perm.mode      = tbuf_old.msg_perm.mode;
 321
 322                 if (tbuf_old.msg_qbytes == 0)
 323                         out->msg_qbytes = tbuf_old.msg_lqbytes;
 324                 else
 325                         out->msg_qbytes = tbuf_old.msg_qbytes;
 326
 327                 return 0;
 328         }
 329         default:
 330                 return -EINVAL;
 331         }
 332 }
 333
 334 /*
 335  * This function handles some msgctl commands which require the rwsem
 336  * to be held in write mode.
 337  * NOTE: no locks must be held, the rwsem is taken inside this function.
 338  */
 339 static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 340                        struct msqid_ds __user *buf, int version)
 341 {
 342         struct kern_ipc_perm *ipcp;
 343         struct msqid64_ds uninitialized_var(msqid64);
 344         struct msg_queue *msq;
 345         int err;
 346
 347         if (cmd == IPC_SET) {
 348                 if (copy_msqid_from_user(&msqid64, buf, version))
 349                         return -EFAULT;
 350         }
 351
 352         down_write(&msg_ids(ns).rwsem);
 353         rcu_read_lock();
 354
 355         ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
 356                                       &msqid64.msg_perm, msqid64.msg_qbytes);
 357         if (IS_ERR(ipcp)) {
 358                 err = PTR_ERR(ipcp);
 359                 goto out_unlock1;
 360         }
 361
 362         msq = container_of(ipcp, struct msg_queue, q_perm);
 363
 364         err = security_msg_queue_msgctl(msq, cmd);
 365         if (err)
 366                 goto out_unlock1;
 367
 368         switch (cmd) {
 369         case IPC_RMID:
 370                 ipc_lock_object(&msq->q_perm);
 371                 /* freeque unlocks the ipc object and rcu */
 372                 freeque(ns, ipcp);
 373                 goto out_up;
 374         case IPC_SET:
 375                 if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
 376                     !capable(CAP_SYS_RESOURCE)) {
 377                         err = -EPERM;
 378                         goto out_unlock1;
 379                 }
 380
 381                 ipc_lock_object(&msq->q_perm);
 382                 err = ipc_update_perm(&msqid64.msg_perm, ipcp);
 383                 if (err)
 384                         goto out_unlock0;
 385
 386                 msq->q_qbytes = msqid64.msg_qbytes;
 387
 388                 msq->q_ctime = get_seconds();
 389                 /* sleeping receivers might be excluded by
 390                  * stricter permissions.
 391                  */
 392                 expunge_all(msq, -EAGAIN);
 393                 /* sleeping senders might be able to send
 394                  * due to a larger queue size.
 395                  */
 396                 ss_wakeup(&msq->q_senders, 0);
 397                 break;
 398         default:
 399                 err = -EINVAL;
 400                 goto out_unlock1;
 401         }
 402
 403 out_unlock0:
 404         ipc_unlock_object(&msq->q_perm);
 405 out_unlock1:
 406         rcu_read_unlock();
 407 out_up:
 408         up_write(&msg_ids(ns).rwsem);
 409         return err;
 410 }
 411
 412 static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
 413                          int cmd, int version, void __user *buf)
 414 {
 415         int err;
 416         struct msg_queue *msq;
 417
 418         switch (cmd) {
 419         case IPC_INFO:
 420         case MSG_INFO:
 421         {
 422                 struct msginfo msginfo;
 423                 int max_id;
 424
 425                 if (!buf)
 426                         return -EFAULT;
 427
 428                 /*
 429                  * We must not return kernel stack data.
 430                  * due to padding, it's not enough
 431                  * to set all member fields.
 432                  */
 433                 err = security_msg_queue_msgctl(NULL, cmd);
 434                 if (err)
 435                         return err;
 436
 437                 memset(&msginfo, 0, sizeof(msginfo));
 438                 msginfo.msgmni = ns->msg_ctlmni;
 439                 msginfo.msgmax = ns->msg_ctlmax;
 440                 msginfo.msgmnb = ns->msg_ctlmnb;
 441                 msginfo.msgssz = MSGSSZ;
 442                 msginfo.msgseg = MSGSEG;
 443                 down_read(&msg_ids(ns).rwsem);
 444                 if (cmd == MSG_INFO) {
 445                         msginfo.msgpool = msg_ids(ns).in_use;
 446                         msginfo.msgmap = atomic_read(&ns->msg_hdrs);
 447                         msginfo.msgtql = atomic_read(&ns->msg_bytes);
 448                 } else {
 449                         msginfo.msgmap = MSGMAP;
 450                         msginfo.msgpool = MSGPOOL;
 451                         msginfo.msgtql = MSGTQL;
 452                 }
 453                 max_id = ipc_get_maxid(&msg_ids(ns));
 454                 up_read(&msg_ids(ns).rwsem);
 455                 if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
 456                         return -EFAULT;
 457                 return (max_id < 0) ? 0 : max_id;
 458         }
 459
 460         case MSG_STAT:
 461         case IPC_STAT:
 462         {
 463                 struct msqid64_ds tbuf;
 464                 int success_return;
 465
 466                 if (!buf)
 467                         return -EFAULT;
 468
 469                 memset(&tbuf, 0, sizeof(tbuf));
 470
 471                 rcu_read_lock();
 472                 if (cmd == MSG_STAT) {
 473                         msq = msq_obtain_object(ns, msqid);
 474                         if (IS_ERR(msq)) {
 475                                 err = PTR_ERR(msq);
 476                                 goto out_unlock;
 477                         }
 478                         success_return = msq->q_perm.id;
 479                 } else {
 480                         msq = msq_obtain_object_check(ns, msqid);
 481                         if (IS_ERR(msq)) {
 482                                 err = PTR_ERR(msq);
 483                                 goto out_unlock;
 484                         }
 485                         success_return = 0;
 486                 }
 487
 488                 err = -EACCES;
 489                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 490                         goto out_unlock;
 491
 492                 err = security_msg_queue_msgctl(msq, cmd);
 493                 if (err)
 494                         goto out_unlock;
 495
 496                 kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
 497                 tbuf.msg_stime  = msq->q_stime;
 498                 tbuf.msg_rtime  = msq->q_rtime;
 499                 tbuf.msg_ctime  = msq->q_ctime;
 500                 tbuf.msg_cbytes = msq->q_cbytes;
 501                 tbuf.msg_qnum   = msq->q_qnum;
 502                 tbuf.msg_qbytes = msq->q_qbytes;
 503                 tbuf.msg_lspid  = msq->q_lspid;
 504                 tbuf.msg_lrpid  = msq->q_lrpid;
 505                 rcu_read_unlock();
 506
 507                 if (copy_msqid_to_user(buf, &tbuf, version))
 508                         return -EFAULT;
 509                 return success_return;
 510         }
 511
 512         default:
 513                 return -EINVAL;
 514         }
 515
 516         return err;
 517 out_unlock:
 518         rcu_read_unlock();
 519         return err;
 520 }
 521
 522 SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
 523 {
 524         int version;
 525         struct ipc_namespace *ns;
 526
 527         if (msqid < 0 || cmd < 0)
 528                 return -EINVAL;
 529
 530         version = ipc_parse_version(&cmd);
 531         ns = current->nsproxy->ipc_ns;
 532
 533         switch (cmd) {
 534         case IPC_INFO:
 535         case MSG_INFO:
 536         case MSG_STAT:  /* msqid is an index rather than a msg queue id */
 537         case IPC_STAT:
 538                 return msgctl_nolock(ns, msqid, cmd, version, buf);
 539         case IPC_SET:
 540         case IPC_RMID:
 541                 return msgctl_down(ns, msqid, cmd, buf, version);
 542         default:
 543                 return  -EINVAL;
 544         }
 545 }
 546
 547 static int testmsg(struct msg_msg *msg, long type, int mode)
 548 {
 549         switch (mode) {
 550         case SEARCH_ANY:
 551         case SEARCH_NUMBER:
 552                 return 1;
 553         case SEARCH_LESSEQUAL:
 554                 if (msg->m_type <= type)
 555                         return 1;
 556                 break;
 557         case SEARCH_EQUAL:
 558                 if (msg->m_type == type)
 559                         return 1;
 560                 break;
 561         case SEARCH_NOTEQUAL:
 562                 if (msg->m_type != type)
 563                         return 1;
 564                 break;
 565         }
 566         return 0;
 567 }
 568
 569 static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
 570 {
 571         struct msg_receiver *msr, *t;
 572
 573         list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
 574                 if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
 575                     !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
 576                                                msr->r_msgtype, msr->r_mode)) {
 577
 578                         list_del(&msr->r_list);
 579                         if (msr->r_maxsize < msg->m_ts) {
 580                                 /* initialize pipelined send ordering */
 581                                 msr->r_msg = NULL;
 582                                 wake_up_process(msr->r_tsk);
 583                                 /* barrier (B) see barrier comment below */
 584                                 smp_wmb();
 585                                 msr->r_msg = ERR_PTR(-E2BIG);
 586                         } else {
 587                                 msr->r_msg = NULL;
 588                                 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
 589                                 msq->q_rtime = get_seconds();
 590                                 wake_up_process(msr->r_tsk);
 591                                 /*
 592                                  * Ensure that the wakeup is visible before
 593                                  * setting r_msg, as the receiving can otherwise
 594                                  * exit - once r_msg is set, the receiver can
 595                                  * continue. See lockless receive part 1 and 2
 596                                  * in do_msgrcv(). Barrier (B).
 597                                  */
 598                                 smp_wmb();
 599                                 msr->r_msg = msg;
 600
 601                                 return 1;
 602                         }
 603                 }
 604         }
 605
 606         return 0;
 607 }
 608
 609 long do_msgsnd(int msqid, long mtype, void __user *mtext,
 610                 size_t msgsz, int msgflg)
 611 {
 612         struct msg_queue *msq;
 613         struct msg_msg *msg;
 614         int err;
 615         struct ipc_namespace *ns;
 616
 617         ns = current->nsproxy->ipc_ns;
 618
 619         if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 620                 return -EINVAL;
 621         if (mtype < 1)
 622                 return -EINVAL;
 623
 624         msg = load_msg(mtext, msgsz);
 625         if (IS_ERR(msg))
 626                 return PTR_ERR(msg);
 627
 628         msg->m_type = mtype;
 629         msg->m_ts = msgsz;
 630
 631         rcu_read_lock();
 632         msq = msq_obtain_object_check(ns, msqid);
 633         if (IS_ERR(msq)) {
 634                 err = PTR_ERR(msq);
 635                 goto out_unlock1;
 636         }
 637
 638         ipc_lock_object(&msq->q_perm);
 639
 640         for (;;) {
 641                 struct msg_sender s;
 642
 643                 err = -EACCES;
 644                 if (ipcperms(ns, &msq->q_perm, S_IWUGO))
 645                         goto out_unlock0;
 646
 647                 /* raced with RMID? */
 648                 if (!ipc_valid_object(&msq->q_perm)) {
 649                         err = -EIDRM;
 650                         goto out_unlock0;
 651                 }
 652
 653                 err = security_msg_queue_msgsnd(msq, msg, msgflg);
 654                 if (err)
 655                         goto out_unlock0;
 656
 657                 if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
 658                                 1 + msq->q_qnum <= msq->q_qbytes) {
 659                         break;
 660                 }
 661
 662                 /* queue full, wait: */
 663                 if (msgflg & IPC_NOWAIT) {
 664                         err = -EAGAIN;
 665                         goto out_unlock0;
 666                 }
 667
 668                 /* enqueue the sender and prepare to block */
 669                 ss_add(msq, &s);
 670
 671                 if (!ipc_rcu_getref(msq)) {
 672                         err = -EIDRM;
 673                         goto out_unlock0;
 674                 }
 675
 676                 ipc_unlock_object(&msq->q_perm);
 677                 rcu_read_unlock();
 678                 schedule();
 679
 680                 rcu_read_lock();
 681                 ipc_lock_object(&msq->q_perm);
 682
 683                 ipc_rcu_putref(msq, ipc_rcu_free);
 684                 /* raced with RMID? */
 685                 if (!ipc_valid_object(&msq->q_perm)) {
 686                         err = -EIDRM;
 687                         goto out_unlock0;
 688                 }
 689
 690                 ss_del(&s);
 691
 692                 if (signal_pending(current)) {
 693                         err = -ERESTARTNOHAND;
 694                         goto out_unlock0;
 695                 }
 696
 697         }
 698         msq->q_lspid = task_tgid_vnr(current);
 699         msq->q_stime = get_seconds();
 700
 701         if (!pipelined_send(msq, msg)) {
 702                 /* no one is waiting for this message, enqueue it */
 703                 list_add_tail(&msg->m_list, &msq->q_messages);
 704                 msq->q_cbytes += msgsz;
 705                 msq->q_qnum++;
 706                 atomic_add(msgsz, &ns->msg_bytes);
 707                 atomic_inc(&ns->msg_hdrs);
 708         }
 709
 710         err = 0;
 711         msg = NULL;
 712
 713 out_unlock0:
 714         ipc_unlock_object(&msq->q_perm);
 715 out_unlock1:
 716         rcu_read_unlock();
 717         if (msg != NULL)
 718                 free_msg(msg);
 719         return err;
 720 }
 721
 722 SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 723                 int, msgflg)
 724 {
 725         long mtype;
 726
 727         if (get_user(mtype, &msgp->mtype))
 728                 return -EFAULT;
 729         return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
 730 }
 731
 732 static inline int convert_mode(long *msgtyp, int msgflg)
 733 {
 734         if (msgflg & MSG_COPY)
 735                 return SEARCH_NUMBER;
 736         /*
 737          *  find message of correct type.
 738          *  msgtyp = 0 => get first.
 739          *  msgtyp > 0 => get first message of matching type.
 740          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 741          */
 742         if (*msgtyp == 0)
 743                 return SEARCH_ANY;
 744         if (*msgtyp < 0) {
 745                 *msgtyp = -*msgtyp;
 746                 return SEARCH_LESSEQUAL;
 747         }
 748         if (msgflg & MSG_EXCEPT)
 749                 return SEARCH_NOTEQUAL;
 750         return SEARCH_EQUAL;
 751 }
 752
 753 static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
 754 {
 755         struct msgbuf __user *msgp = dest;
 756         size_t msgsz;
 757
 758         if (put_user(msg->m_type, &msgp->mtype))
 759                 return -EFAULT;
 760
 761         msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
 762         if (store_msg(msgp->mtext, msg, msgsz))
 763                 return -EFAULT;
 764         return msgsz;
 765 }
 766
 767 #ifdef CONFIG_CHECKPOINT_RESTORE
 768 /*
 769  * This function creates new kernel message structure, large enough to store
 770  * bufsz message bytes.
 771  */
 772 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 773 {
 774         struct msg_msg *copy;
 775
 776         /*
 777          * Create dummy message to copy real message to.
 778          */
 779         copy = load_msg(buf, bufsz);
 780         if (!IS_ERR(copy))
 781                 copy->m_ts = bufsz;
 782         return copy;
 783 }
 784
 785 static inline void free_copy(struct msg_msg *copy)
 786 {
 787         if (copy)
 788                 free_msg(copy);
 789 }
 790 #else
 791 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 792 {
 793         return ERR_PTR(-ENOSYS);
 794 }
 795
 796 static inline void free_copy(struct msg_msg *copy)
 797 {
 798 }
 799 #endif
 800
 801 static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
 802 {
 803         struct msg_msg *msg, *found = NULL;
 804         long count = 0;
 805
 806         list_for_each_entry(msg, &msq->q_messages, m_list) {
 807                 if (testmsg(msg, *msgtyp, mode) &&
 808                     !security_msg_queue_msgrcv(msq, msg, current,
 809                                                *msgtyp, mode)) {
 810                         if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
 811                                 *msgtyp = msg->m_type - 1;
 812                                 found = msg;
 813                         } else if (mode == SEARCH_NUMBER) {
 814                                 if (*msgtyp == count)
 815                                         return msg;
 816                         } else
 817                                 return msg;
 818                         count++;
 819                 }
 820         }
 821
 822         return found ?: ERR_PTR(-EAGAIN);
 823 }
 824
 825 long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
 826                long (*msg_handler)(void __user *, struct msg_msg *, size_t))
 827 {
 828         int mode;
 829         struct msg_queue *msq;
 830         struct ipc_namespace *ns;
 831         struct msg_msg *msg, *copy = NULL;
 832
 833         ns = current->nsproxy->ipc_ns;
 834
 835         if (msqid < 0 || (long) bufsz < 0)
 836                 return -EINVAL;
 837
 838         if (msgflg & MSG_COPY) {
 839                 if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
 840                         return -EINVAL;
 841                 copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
 842                 if (IS_ERR(copy))
 843                         return PTR_ERR(copy);
 844         }
 845         mode = convert_mode(&msgtyp, msgflg);
 846
 847         rcu_read_lock();
 848         msq = msq_obtain_object_check(ns, msqid);
 849         if (IS_ERR(msq)) {
 850                 rcu_read_unlock();
 851                 free_copy(copy);
 852                 return PTR_ERR(msq);
 853         }
 854
 855         for (;;) {
 856                 struct msg_receiver msr_d;
 857
 858                 msg = ERR_PTR(-EACCES);
 859                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 860                         goto out_unlock1;
 861
 862                 ipc_lock_object(&msq->q_perm);
 863
 864                 /* raced with RMID? */
 865                 if (!ipc_valid_object(&msq->q_perm)) {
 866                         msg = ERR_PTR(-EIDRM);
 867                         goto out_unlock0;
 868                 }
 869
 870                 msg = find_msg(msq, &msgtyp, mode);
 871                 if (!IS_ERR(msg)) {
 872                         /*
 873                          * Found a suitable message.
 874                          * Unlink it from the queue.
 875                          */
 876                         if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 877                                 msg = ERR_PTR(-E2BIG);
 878                                 goto out_unlock0;
 879                         }
 880                         /*
 881                          * If we are copying, then do not unlink message and do
 882                          * not update queue parameters.
 883                          */
 884                         if (msgflg & MSG_COPY) {
 885                                 msg = copy_msg(msg, copy);
 886                                 goto out_unlock0;
 887                         }
 888
 889                         list_del(&msg->m_list);
 890                         msq->q_qnum--;
 891                         msq->q_rtime = get_seconds();
 892                         msq->q_lrpid = task_tgid_vnr(current);
 893                         msq->q_cbytes -= msg->m_ts;
 894                         atomic_sub(msg->m_ts, &ns->msg_bytes);
 895                         atomic_dec(&ns->msg_hdrs);
 896                         ss_wakeup(&msq->q_senders, 0);
 897
 898                         goto out_unlock0;
 899                 }
 900
 901                 /* No message waiting. Wait for a message */
 902                 if (msgflg & IPC_NOWAIT) {
 903                         msg = ERR_PTR(-ENOMSG);
 904                         goto out_unlock0;
 905                 }
 906
 907                 list_add_tail(&msr_d.r_list, &msq->q_receivers);
 908                 msr_d.r_tsk = current;
 909                 msr_d.r_msgtype = msgtyp;
 910                 msr_d.r_mode = mode;
 911                 if (msgflg & MSG_NOERROR)
 912                         msr_d.r_maxsize = INT_MAX;
 913                 else
 914                         msr_d.r_maxsize = bufsz;
 915                 msr_d.r_msg = ERR_PTR(-EAGAIN);
 916                 __set_current_state(TASK_INTERRUPTIBLE);
 917
 918                 ipc_unlock_object(&msq->q_perm);
 919                 rcu_read_unlock();
 920                 schedule();
 921
 922                 /* Lockless receive, part 1:
 923                  * Disable preemption.  We don't hold a reference to the queue
 924                  * and getting a reference would defeat the idea of a lockless
 925                  * operation, thus the code relies on rcu to guarantee the
 926                  * existence of msq:
 927                  * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 928                  * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 929                  * rcu_read_lock() prevents preemption between reading r_msg
 930                  * and acquiring the q_perm.lock in ipc_lock_object().
 931                  */
 932                 rcu_read_lock();
 933
 934                 /* Lockless receive, part 2:
 935                  * Wait until pipelined_send or expunge_all are outside of
 936                  * wake_up_process(). There is a race with exit(), see
 937                  * ipc/mqueue.c for the details. The correct serialization
 938                  * ensures that a receiver cannot continue without the wakeup
 939                  * being visibible _before_ setting r_msg:
 940                  *
 941                  * CPU 0                             CPU 1
 942                  * <loop receiver>
 943                  *   smp_rmb(); (A) <-- pair -.      <waker thread>
 944                  *   <load ->r_msg>           |        msr->r_msg = NULL;
 945                  *                            |        wake_up_process();
 946                  * <continue>                 `------> smp_wmb(); (B)
 947                  *                                     msr->r_msg = msg;
 948                  *
 949                  * Where (A) orders the message value read and where (B) orders
 950                  * the write to the r_msg -- done in both pipelined_send and
 951                  * expunge_all.
 952                  */
 953                 for (;;) {
 954                         /*
 955                          * Pairs with writer barrier in pipelined_send
 956                          * or expunge_all.
 957                          */
 958                         smp_rmb(); /* barrier (A) */
 959                         msg = (struct msg_msg *)msr_d.r_msg;
 960                         if (msg)
 961                                 break;
 962
 963                         /*
 964                          * The cpu_relax() call is a compiler barrier
 965                          * which forces everything in this loop to be
 966                          * re-loaded.
 967                          */
 968                         cpu_relax();
 969                 }
 970
 971                 /* Lockless receive, part 3:
 972                  * If there is a message or an error then accept it without
 973                  * locking.
 974                  */
 975                 if (msg != ERR_PTR(-EAGAIN))
 976                         goto out_unlock1;
 977
 978                 /* Lockless receive, part 3:
 979                  * Acquire the queue spinlock.
 980                  */
 981                 ipc_lock_object(&msq->q_perm);
 982
 983                 /* Lockless receive, part 4:
 984                  * Repeat test after acquiring the spinlock.
 985                  */
 986                 msg = (struct msg_msg *)msr_d.r_msg;
 987                 if (msg != ERR_PTR(-EAGAIN))
 988                         goto out_unlock0;
 989
 990                 list_del(&msr_d.r_list);
 991                 if (signal_pending(current)) {
 992                         msg = ERR_PTR(-ERESTARTNOHAND);
 993                         goto out_unlock0;
 994                 }
 995
 996                 ipc_unlock_object(&msq->q_perm);
 997         }
 998
 999 out_unlock0:
1000         ipc_unlock_object(&msq->q_perm);
1001 out_unlock1:
1002         rcu_read_unlock();
1003         if (IS_ERR(msg)) {
1004                 free_copy(copy);
1005                 return PTR_ERR(msg);
1006         }
1007
1008         bufsz = msg_handler(buf, msg, bufsz);
1009         free_msg(msg);
1010
1011         return bufsz;
1012 }
1013
1014 SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
1015                 long, msgtyp, int, msgflg)
1016 {
1017         return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
1018 }
1019
1020
1021 void msg_init_ns(struct ipc_namespace *ns)
1022 {
1023         ns->msg_ctlmax = MSGMAX;
1024         ns->msg_ctlmnb = MSGMNB;
1025         ns->msg_ctlmni = MSGMNI;
1026
1027         atomic_set(&ns->msg_bytes, 0);
1028         atomic_set(&ns->msg_hdrs, 0);
1029         ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
1030 }
1031
1032 #ifdef CONFIG_IPC_NS
1033 void msg_exit_ns(struct ipc_namespace *ns)
1034 {
1035         free_ipcs(ns, &msg_ids(ns), freeque);
1036         idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
1037 }
1038 #endif
1039
1040 #ifdef CONFIG_PROC_FS
1041 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
1042 {
1043         struct user_namespace *user_ns = seq_user_ns(s);
1044         struct msg_queue *msq = it;
1045
1046         seq_printf(s,
1047                    "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1048                    msq->q_perm.key,
1049                    msq->q_perm.id,
1050                    msq->q_perm.mode,
1051                    msq->q_cbytes,
1052                    msq->q_qnum,
1053                    msq->q_lspid,
1054                    msq->q_lrpid,
1055                    from_kuid_munged(user_ns, msq->q_perm.uid),
1056                    from_kgid_munged(user_ns, msq->q_perm.gid),
1057                    from_kuid_munged(user_ns, msq->q_perm.cuid),
1058                    from_kgid_munged(user_ns, msq->q_perm.cgid),
1059                    msq->q_stime,
1060                    msq->q_rtime,
1061                    msq->q_ctime);
1062
1063         return 0;
1064 }
1065 #endif
1066
1067 void __init msg_init(void)
1068 {
1069         msg_init_ns(&init_ipc_ns);
1070
1071         ipc_init_proc_interface("sysvipc/msg",
1072                                 "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
1073                                 IPC_MSG_IDS, sysvipc_msg_proc_show);
1074 }