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/slab.h>
  27 #include <linux/msg.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/init.h>
  30 #include <linux/mm.h>
  31 #include <linux/proc_fs.h>
  32 #include <linux/list.h>
  33 #include <linux/security.h>
  34 #include <linux/sched.h>
  35 #include <linux/syscalls.h>
  36 #include <linux/audit.h>
  37 #include <linux/seq_file.h>
  38 #include <linux/rwsem.h>
  39 #include <linux/nsproxy.h>
  40 #include <linux/ipc_namespace.h>
  41
  42 #include <asm/current.h>
  43 #include <asm/uaccess.h>
  44 #include "util.h"
  45
  46 /*
  47  * one msg_receiver structure for each sleeping receiver:
  48  */
  49 struct msg_receiver {
  50         struct list_head        r_list;
  51         struct task_struct      *r_tsk;
  52
  53         int                     r_mode;
  54         long                    r_msgtype;
  55         long                    r_maxsize;
  56
  57         struct msg_msg          *volatile r_msg;
  58 };
  59
  60 /* one msg_sender for each sleeping sender */
  61 struct msg_sender {
  62         struct list_head        list;
  63         struct task_struct      *tsk;
  64 };
  65
  66 #define SEARCH_ANY              1
  67 #define SEARCH_EQUAL            2
  68 #define SEARCH_NOTEQUAL         3
  69 #define SEARCH_LESSEQUAL        4
  70
  71 #define msg_ids(ns)     ((ns)->ids[IPC_MSG_IDS])
  72
  73 #define msg_unlock(msq)         ipc_unlock(&(msq)->q_perm)
  74
  75 static void freeque(struct ipc_namespace *, struct kern_ipc_perm *);
  76 static int newque(struct ipc_namespace *, struct ipc_params *);
  77 #ifdef CONFIG_PROC_FS
  78 static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
  79 #endif
  80
  81 /*
  82  * Scale msgmni with the available lowmem size: the memory dedicated to msg
  83  * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
  84  * Also take into account the number of nsproxies created so far.
  85  * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
  86  */
  87 void recompute_msgmni(struct ipc_namespace *ns)
  88 {
  89         struct sysinfo i;
  90         unsigned long allowed;
  91         int nb_ns;
  92
  93         si_meminfo(&i);
  94         allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
  95                 / MSGMNB;
  96         nb_ns = atomic_read(&nr_ipc_ns);
  97         allowed /= nb_ns;
  98
  99         if (allowed < MSGMNI) {
 100                 ns->msg_ctlmni = MSGMNI;
 101                 goto out_callback;
 102         }
 103
 104         if (allowed > IPCMNI / nb_ns) {
 105                 ns->msg_ctlmni = IPCMNI / nb_ns;
 106                 goto out_callback;
 107         }
 108
 109         ns->msg_ctlmni = allowed;
 110
 111 out_callback:
 112
 113         printk(KERN_INFO "msgmni has been set to %d for ipc namespace %p\n",
 114                 ns->msg_ctlmni, ns);
 115 }
 116
 117 void msg_init_ns(struct ipc_namespace *ns)
 118 {
 119         ns->msg_ctlmax = MSGMAX;
 120         ns->msg_ctlmnb = MSGMNB;
 121
 122         recompute_msgmni(ns);
 123
 124         atomic_set(&ns->msg_bytes, 0);
 125         atomic_set(&ns->msg_hdrs, 0);
 126         ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
 127 }
 128
 129 #ifdef CONFIG_IPC_NS
 130 void msg_exit_ns(struct ipc_namespace *ns)
 131 {
 132         free_ipcs(ns, &msg_ids(ns), freeque);
 133 }
 134 #endif
 135
 136 void __init msg_init(void)
 137 {
 138         msg_init_ns(&init_ipc_ns);
 139         ipc_init_proc_interface("sysvipc/msg",
 140                                 "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
 141                                 IPC_MSG_IDS, sysvipc_msg_proc_show);
 142 }
 143
 144 /*
 145  * msg_lock_(check_) routines are called in the paths where the rw_mutex
 146  * is not held.
 147  */
 148 static inline struct msg_queue *msg_lock(struct ipc_namespace *ns, int id)
 149 {
 150         struct kern_ipc_perm *ipcp = ipc_lock(&msg_ids(ns), id);
 151
 152         if (IS_ERR(ipcp))
 153                 return (struct msg_queue *)ipcp;
 154
 155         return container_of(ipcp, struct msg_queue, q_perm);
 156 }
 157
 158 static inline struct msg_queue *msg_lock_check(struct ipc_namespace *ns,
 159                                                 int id)
 160 {
 161         struct kern_ipc_perm *ipcp = ipc_lock_check(&msg_ids(ns), id);
 162
 163         if (IS_ERR(ipcp))
 164                 return (struct msg_queue *)ipcp;
 165
 166         return container_of(ipcp, struct msg_queue, q_perm);
 167 }
 168
 169 static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
 170 {
 171         ipc_rmid(&msg_ids(ns), &s->q_perm);
 172 }
 173
 174 /**
 175  * newque - Create a new msg queue
 176  * @ns: namespace
 177  * @params: ptr to the structure that contains the key and msgflg
 178  *
 179  * Called with msg_ids.rw_mutex held (writer)
 180  */
 181 static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 182 {
 183         struct msg_queue *msq;
 184         int id, retval;
 185         key_t key = params->key;
 186         int msgflg = params->flg;
 187
 188         msq = ipc_rcu_alloc(sizeof(*msq));
 189         if (!msq)
 190                 return -ENOMEM;
 191
 192         msq->q_perm.mode = msgflg & S_IRWXUGO;
 193         msq->q_perm.key = key;
 194
 195         msq->q_perm.security = NULL;
 196         retval = security_msg_queue_alloc(msq);
 197         if (retval) {
 198                 ipc_rcu_putref(msq);
 199                 return retval;
 200         }
 201
 202         /*
 203          * ipc_addid() locks msq
 204          */
 205         id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
 206         if (id < 0) {
 207                 security_msg_queue_free(msq);
 208                 ipc_rcu_putref(msq);
 209                 return id;
 210         }
 211
 212         msq->q_stime = msq->q_rtime = 0;
 213         msq->q_ctime = get_seconds();
 214         msq->q_cbytes = msq->q_qnum = 0;
 215         msq->q_qbytes = ns->msg_ctlmnb;
 216         msq->q_lspid = msq->q_lrpid = 0;
 217         INIT_LIST_HEAD(&msq->q_messages);
 218         INIT_LIST_HEAD(&msq->q_receivers);
 219         INIT_LIST_HEAD(&msq->q_senders);
 220
 221         msg_unlock(msq);
 222
 223         return msq->q_perm.id;
 224 }
 225
 226 static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
 227 {
 228         mss->tsk = current;
 229         current->state = TASK_INTERRUPTIBLE;
 230         list_add_tail(&mss->list, &msq->q_senders);
 231 }
 232
 233 static inline void ss_del(struct msg_sender *mss)
 234 {
 235         if (mss->list.next != NULL)
 236                 list_del(&mss->list);
 237 }
 238
 239 static void ss_wakeup(struct list_head *h, int kill)
 240 {
 241         struct list_head *tmp;
 242
 243         tmp = h->next;
 244         while (tmp != h) {
 245                 struct msg_sender *mss;
 246
 247                 mss = list_entry(tmp, struct msg_sender, list);
 248                 tmp = tmp->next;
 249                 if (kill)
 250                         mss->list.next = NULL;
 251                 wake_up_process(mss->tsk);
 252         }
 253 }
 254
 255 static void expunge_all(struct msg_queue *msq, int res)
 256 {
 257         struct list_head *tmp;
 258
 259         tmp = msq->q_receivers.next;
 260         while (tmp != &msq->q_receivers) {
 261                 struct msg_receiver *msr;
 262
 263                 msr = list_entry(tmp, struct msg_receiver, r_list);
 264                 tmp = tmp->next;
 265                 msr->r_msg = NULL;
 266                 wake_up_process(msr->r_tsk);
 267                 smp_mb();
 268                 msr->r_msg = ERR_PTR(res);
 269         }
 270 }
 271
 272 /*
 273  * freeque() wakes up waiters on the sender and receiver waiting queue,
 274  * removes the message queue from message queue ID IDR, and cleans up all the
 275  * messages associated with this queue.
 276  *
 277  * msg_ids.rw_mutex (writer) and the spinlock for this message queue are held
 278  * before freeque() is called. msg_ids.rw_mutex remains locked on exit.
 279  */
 280 static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 281 {
 282         struct list_head *tmp;
 283         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 284
 285         expunge_all(msq, -EIDRM);
 286         ss_wakeup(&msq->q_senders, 1);
 287         msg_rmid(ns, msq);
 288         msg_unlock(msq);
 289
 290         tmp = msq->q_messages.next;
 291         while (tmp != &msq->q_messages) {
 292                 struct msg_msg *msg = list_entry(tmp, struct msg_msg, m_list);
 293
 294                 tmp = tmp->next;
 295                 atomic_dec(&ns->msg_hdrs);
 296                 free_msg(msg);
 297         }
 298         atomic_sub(msq->q_cbytes, &ns->msg_bytes);
 299         security_msg_queue_free(msq);
 300         ipc_rcu_putref(msq);
 301 }
 302
 303 /*
 304  * Called with msg_ids.rw_mutex and ipcp locked.
 305  */
 306 static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
 307 {
 308         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 309
 310         return security_msg_queue_associate(msq, msgflg);
 311 }
 312
 313 asmlinkage long sys_msgget(key_t key, int msgflg)
 314 {
 315         struct ipc_namespace *ns;
 316         struct ipc_ops msg_ops;
 317         struct ipc_params msg_params;
 318
 319         ns = current->nsproxy->ipc_ns;
 320
 321         msg_ops.getnew = newque;
 322         msg_ops.associate = msg_security;
 323         msg_ops.more_checks = NULL;
 324
 325         msg_params.key = key;
 326         msg_params.flg = msgflg;
 327
 328         return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
 329 }
 330
 331 static inline unsigned long
 332 copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 333 {
 334         switch(version) {
 335         case IPC_64:
 336                 return copy_to_user(buf, in, sizeof(*in));
 337         case IPC_OLD:
 338         {
 339                 struct msqid_ds out;
 340
 341                 memset(&out, 0, sizeof(out));
 342
 343                 ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
 344
 345                 out.msg_stime           = in->msg_stime;
 346                 out.msg_rtime           = in->msg_rtime;
 347                 out.msg_ctime           = in->msg_ctime;
 348
 349                 if (in->msg_cbytes > USHORT_MAX)
 350                         out.msg_cbytes  = USHORT_MAX;
 351                 else
 352                         out.msg_cbytes  = in->msg_cbytes;
 353                 out.msg_lcbytes         = in->msg_cbytes;
 354
 355                 if (in->msg_qnum > USHORT_MAX)
 356                         out.msg_qnum    = USHORT_MAX;
 357                 else
 358                         out.msg_qnum    = in->msg_qnum;
 359
 360                 if (in->msg_qbytes > USHORT_MAX)
 361                         out.msg_qbytes  = USHORT_MAX;
 362                 else
 363                         out.msg_qbytes  = in->msg_qbytes;
 364                 out.msg_lqbytes         = in->msg_qbytes;
 365
 366                 out.msg_lspid           = in->msg_lspid;
 367                 out.msg_lrpid           = in->msg_lrpid;
 368
 369                 return copy_to_user(buf, &out, sizeof(out));
 370         }
 371         default:
 372                 return -EINVAL;
 373         }
 374 }
 375
 376 static inline unsigned long
 377 copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
 378 {
 379         switch(version) {
 380         case IPC_64:
 381                 if (copy_from_user(out, buf, sizeof(*out)))
 382                         return -EFAULT;
 383                 return 0;
 384         case IPC_OLD:
 385         {
 386                 struct msqid_ds tbuf_old;
 387
 388                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
 389                         return -EFAULT;
 390
 391                 out->msg_perm.uid       = tbuf_old.msg_perm.uid;
 392                 out->msg_perm.gid       = tbuf_old.msg_perm.gid;
 393                 out->msg_perm.mode      = tbuf_old.msg_perm.mode;
 394
 395                 if (tbuf_old.msg_qbytes == 0)
 396                         out->msg_qbytes = tbuf_old.msg_lqbytes;
 397                 else
 398                         out->msg_qbytes = tbuf_old.msg_qbytes;
 399
 400                 return 0;
 401         }
 402         default:
 403                 return -EINVAL;
 404         }
 405 }
 406
 407 /*
 408  * This function handles some msgctl commands which require the rw_mutex
 409  * to be held in write mode.
 410  * NOTE: no locks must be held, the rw_mutex is taken inside this function.
 411  */
 412 static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 413                        struct msqid_ds __user *buf, int version)
 414 {
 415         struct kern_ipc_perm *ipcp;
 416         struct msqid64_ds msqid64;
 417         struct msg_queue *msq;
 418         int err;
 419
 420         if (cmd == IPC_SET) {
 421                 if (copy_msqid_from_user(&msqid64, buf, version))
 422                         return -EFAULT;
 423         }
 424
 425         ipcp = ipcctl_pre_down(&msg_ids(ns), msqid, cmd,
 426                                &msqid64.msg_perm, msqid64.msg_qbytes);
 427         if (IS_ERR(ipcp))
 428                 return PTR_ERR(ipcp);
 429
 430         msq = container_of(ipcp, struct msg_queue, q_perm);
 431
 432         err = security_msg_queue_msgctl(msq, cmd);
 433         if (err)
 434                 goto out_unlock;
 435
 436         switch (cmd) {
 437         case IPC_RMID:
 438                 freeque(ns, ipcp);
 439                 goto out_up;
 440         case IPC_SET:
 441                 if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
 442                     !capable(CAP_SYS_RESOURCE)) {
 443                         err = -EPERM;
 444                         goto out_unlock;
 445                 }
 446
 447                 msq->q_qbytes = msqid64.msg_qbytes;
 448
 449                 ipc_update_perm(&msqid64.msg_perm, ipcp);
 450                 msq->q_ctime = get_seconds();
 451                 /* sleeping receivers might be excluded by
 452                  * stricter permissions.
 453                  */
 454                 expunge_all(msq, -EAGAIN);
 455                 /* sleeping senders might be able to send
 456                  * due to a larger queue size.
 457                  */
 458                 ss_wakeup(&msq->q_senders, 0);
 459                 break;
 460         default:
 461                 err = -EINVAL;
 462         }
 463 out_unlock:
 464         msg_unlock(msq);
 465 out_up:
 466         up_write(&msg_ids(ns).rw_mutex);
 467         return err;
 468 }
 469
 470 asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
 471 {
 472         struct msg_queue *msq;
 473         int err, version;
 474         struct ipc_namespace *ns;
 475
 476         if (msqid < 0 || cmd < 0)
 477                 return -EINVAL;
 478
 479         version = ipc_parse_version(&cmd);
 480         ns = current->nsproxy->ipc_ns;
 481
 482         switch (cmd) {
 483         case IPC_INFO:
 484         case MSG_INFO:
 485         {
 486                 struct msginfo msginfo;
 487                 int max_id;
 488
 489                 if (!buf)
 490                         return -EFAULT;
 491                 /*
 492                  * We must not return kernel stack data.
 493                  * due to padding, it's not enough
 494                  * to set all member fields.
 495                  */
 496                 err = security_msg_queue_msgctl(NULL, cmd);
 497                 if (err)
 498                         return err;
 499
 500                 memset(&msginfo, 0, sizeof(msginfo));
 501                 msginfo.msgmni = ns->msg_ctlmni;
 502                 msginfo.msgmax = ns->msg_ctlmax;
 503                 msginfo.msgmnb = ns->msg_ctlmnb;
 504                 msginfo.msgssz = MSGSSZ;
 505                 msginfo.msgseg = MSGSEG;
 506                 down_read(&msg_ids(ns).rw_mutex);
 507                 if (cmd == MSG_INFO) {
 508                         msginfo.msgpool = msg_ids(ns).in_use;
 509                         msginfo.msgmap = atomic_read(&ns->msg_hdrs);
 510                         msginfo.msgtql = atomic_read(&ns->msg_bytes);
 511                 } else {
 512                         msginfo.msgmap = MSGMAP;
 513                         msginfo.msgpool = MSGPOOL;
 514                         msginfo.msgtql = MSGTQL;
 515                 }
 516                 max_id = ipc_get_maxid(&msg_ids(ns));
 517                 up_read(&msg_ids(ns).rw_mutex);
 518                 if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
 519                         return -EFAULT;
 520                 return (max_id < 0) ? 0 : max_id;
 521         }
 522         case MSG_STAT:  /* msqid is an index rather than a msg queue id */
 523         case IPC_STAT:
 524         {
 525                 struct msqid64_ds tbuf;
 526                 int success_return;
 527
 528                 if (!buf)
 529                         return -EFAULT;
 530
 531                 if (cmd == MSG_STAT) {
 532                         msq = msg_lock(ns, msqid);
 533                         if (IS_ERR(msq))
 534                                 return PTR_ERR(msq);
 535                         success_return = msq->q_perm.id;
 536                 } else {
 537                         msq = msg_lock_check(ns, msqid);
 538                         if (IS_ERR(msq))
 539                                 return PTR_ERR(msq);
 540                         success_return = 0;
 541                 }
 542                 err = -EACCES;
 543                 if (ipcperms(&msq->q_perm, S_IRUGO))
 544                         goto out_unlock;
 545
 546                 err = security_msg_queue_msgctl(msq, cmd);
 547                 if (err)
 548                         goto out_unlock;
 549
 550                 memset(&tbuf, 0, sizeof(tbuf));
 551
 552                 kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
 553                 tbuf.msg_stime  = msq->q_stime;
 554                 tbuf.msg_rtime  = msq->q_rtime;
 555                 tbuf.msg_ctime  = msq->q_ctime;
 556                 tbuf.msg_cbytes = msq->q_cbytes;
 557                 tbuf.msg_qnum   = msq->q_qnum;
 558                 tbuf.msg_qbytes = msq->q_qbytes;
 559                 tbuf.msg_lspid  = msq->q_lspid;
 560                 tbuf.msg_lrpid  = msq->q_lrpid;
 561                 msg_unlock(msq);
 562                 if (copy_msqid_to_user(buf, &tbuf, version))
 563                         return -EFAULT;
 564                 return success_return;
 565         }
 566         case IPC_SET:
 567         case IPC_RMID:
 568                 err = msgctl_down(ns, msqid, cmd, buf, version);
 569                 return err;
 570         default:
 571                 return  -EINVAL;
 572         }
 573
 574 out_unlock:
 575         msg_unlock(msq);
 576         return err;
 577 }
 578
 579 static int testmsg(struct msg_msg *msg, long type, int mode)
 580 {
 581         switch(mode)
 582         {
 583                 case SEARCH_ANY:
 584                         return 1;
 585                 case SEARCH_LESSEQUAL:
 586                         if (msg->m_type <=type)
 587                                 return 1;
 588                         break;
 589                 case SEARCH_EQUAL:
 590                         if (msg->m_type == type)
 591                                 return 1;
 592                         break;
 593                 case SEARCH_NOTEQUAL:
 594                         if (msg->m_type != type)
 595                                 return 1;
 596                         break;
 597         }
 598         return 0;
 599 }
 600
 601 static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
 602 {
 603         struct list_head *tmp;
 604
 605         tmp = msq->q_receivers.next;
 606         while (tmp != &msq->q_receivers) {
 607                 struct msg_receiver *msr;
 608
 609                 msr = list_entry(tmp, struct msg_receiver, r_list);
 610                 tmp = tmp->next;
 611                 if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
 612                     !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
 613                                                msr->r_msgtype, msr->r_mode)) {
 614
 615                         list_del(&msr->r_list);
 616                         if (msr->r_maxsize < msg->m_ts) {
 617                                 msr->r_msg = NULL;
 618                                 wake_up_process(msr->r_tsk);
 619                                 smp_mb();
 620                                 msr->r_msg = ERR_PTR(-E2BIG);
 621                         } else {
 622                                 msr->r_msg = NULL;
 623                                 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
 624                                 msq->q_rtime = get_seconds();
 625                                 wake_up_process(msr->r_tsk);
 626                                 smp_mb();
 627                                 msr->r_msg = msg;
 628
 629                                 return 1;
 630                         }
 631                 }
 632         }
 633         return 0;
 634 }
 635
 636 long do_msgsnd(int msqid, long mtype, void __user *mtext,
 637                 size_t msgsz, int msgflg)
 638 {
 639         struct msg_queue *msq;
 640         struct msg_msg *msg;
 641         int err;
 642         struct ipc_namespace *ns;
 643
 644         ns = current->nsproxy->ipc_ns;
 645
 646         if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 647                 return -EINVAL;
 648         if (mtype < 1)
 649                 return -EINVAL;
 650
 651         msg = load_msg(mtext, msgsz);
 652         if (IS_ERR(msg))
 653                 return PTR_ERR(msg);
 654
 655         msg->m_type = mtype;
 656         msg->m_ts = msgsz;
 657
 658         msq = msg_lock_check(ns, msqid);
 659         if (IS_ERR(msq)) {
 660                 err = PTR_ERR(msq);
 661                 goto out_free;
 662         }
 663
 664         for (;;) {
 665                 struct msg_sender s;
 666
 667                 err = -EACCES;
 668                 if (ipcperms(&msq->q_perm, S_IWUGO))
 669                         goto out_unlock_free;
 670
 671                 err = security_msg_queue_msgsnd(msq, msg, msgflg);
 672                 if (err)
 673                         goto out_unlock_free;
 674
 675                 if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
 676                                 1 + msq->q_qnum <= msq->q_qbytes) {
 677                         break;
 678                 }
 679
 680                 /* queue full, wait: */
 681                 if (msgflg & IPC_NOWAIT) {
 682                         err = -EAGAIN;
 683                         goto out_unlock_free;
 684                 }
 685                 ss_add(msq, &s);
 686                 ipc_rcu_getref(msq);
 687                 msg_unlock(msq);
 688                 schedule();
 689
 690                 ipc_lock_by_ptr(&msq->q_perm);
 691                 ipc_rcu_putref(msq);
 692                 if (msq->q_perm.deleted) {
 693                         err = -EIDRM;
 694                         goto out_unlock_free;
 695                 }
 696                 ss_del(&s);
 697
 698                 if (signal_pending(current)) {
 699                         err = -ERESTARTNOHAND;
 700                         goto out_unlock_free;
 701                 }
 702         }
 703
 704         msq->q_lspid = task_tgid_vnr(current);
 705         msq->q_stime = get_seconds();
 706
 707         if (!pipelined_send(msq, msg)) {
 708                 /* noone is waiting for this message, enqueue it */
 709                 list_add_tail(&msg->m_list, &msq->q_messages);
 710                 msq->q_cbytes += msgsz;
 711                 msq->q_qnum++;
 712                 atomic_add(msgsz, &ns->msg_bytes);
 713                 atomic_inc(&ns->msg_hdrs);
 714         }
 715
 716         err = 0;
 717         msg = NULL;
 718
 719 out_unlock_free:
 720         msg_unlock(msq);
 721 out_free:
 722         if (msg != NULL)
 723                 free_msg(msg);
 724         return err;
 725 }
 726
 727 asmlinkage long
 728 sys_msgsnd(int msqid, struct msgbuf __user *msgp, size_t msgsz, int msgflg)
 729 {
 730         long mtype;
 731
 732         if (get_user(mtype, &msgp->mtype))
 733                 return -EFAULT;
 734         return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
 735 }
 736
 737 static inline int convert_mode(long *msgtyp, int msgflg)
 738 {
 739         /*
 740          *  find message of correct type.
 741          *  msgtyp = 0 => get first.
 742          *  msgtyp > 0 => get first message of matching type.
 743          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 744          */
 745         if (*msgtyp == 0)
 746                 return SEARCH_ANY;
 747         if (*msgtyp < 0) {
 748                 *msgtyp = -*msgtyp;
 749                 return SEARCH_LESSEQUAL;
 750         }
 751         if (msgflg & MSG_EXCEPT)
 752                 return SEARCH_NOTEQUAL;
 753         return SEARCH_EQUAL;
 754 }
 755
 756 long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
 757                 size_t msgsz, long msgtyp, int msgflg)
 758 {
 759         struct msg_queue *msq;
 760         struct msg_msg *msg;
 761         int mode;
 762         struct ipc_namespace *ns;
 763
 764         if (msqid < 0 || (long) msgsz < 0)
 765                 return -EINVAL;
 766         mode = convert_mode(&msgtyp, msgflg);
 767         ns = current->nsproxy->ipc_ns;
 768
 769         msq = msg_lock_check(ns, msqid);
 770         if (IS_ERR(msq))
 771                 return PTR_ERR(msq);
 772
 773         for (;;) {
 774                 struct msg_receiver msr_d;
 775                 struct list_head *tmp;
 776
 777                 msg = ERR_PTR(-EACCES);
 778                 if (ipcperms(&msq->q_perm, S_IRUGO))
 779                         goto out_unlock;
 780
 781                 msg = ERR_PTR(-EAGAIN);
 782                 tmp = msq->q_messages.next;
 783                 while (tmp != &msq->q_messages) {
 784                         struct msg_msg *walk_msg;
 785
 786                         walk_msg = list_entry(tmp, struct msg_msg, m_list);
 787                         if (testmsg(walk_msg, msgtyp, mode) &&
 788                             !security_msg_queue_msgrcv(msq, walk_msg, current,
 789                                                        msgtyp, mode)) {
 790
 791                                 msg = walk_msg;
 792                                 if (mode == SEARCH_LESSEQUAL &&
 793                                                 walk_msg->m_type != 1) {
 794                                         msg = walk_msg;
 795                                         msgtyp = walk_msg->m_type - 1;
 796                                 } else {
 797                                         msg = walk_msg;
 798                                         break;
 799                                 }
 800                         }
 801                         tmp = tmp->next;
 802                 }
 803                 if (!IS_ERR(msg)) {
 804                         /*
 805                          * Found a suitable message.
 806                          * Unlink it from the queue.
 807                          */
 808                         if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 809                                 msg = ERR_PTR(-E2BIG);
 810                                 goto out_unlock;
 811                         }
 812                         list_del(&msg->m_list);
 813                         msq->q_qnum--;
 814                         msq->q_rtime = get_seconds();
 815                         msq->q_lrpid = task_tgid_vnr(current);
 816                         msq->q_cbytes -= msg->m_ts;
 817                         atomic_sub(msg->m_ts, &ns->msg_bytes);
 818                         atomic_dec(&ns->msg_hdrs);
 819                         ss_wakeup(&msq->q_senders, 0);
 820                         msg_unlock(msq);
 821                         break;
 822                 }
 823                 /* No message waiting. Wait for a message */
 824                 if (msgflg & IPC_NOWAIT) {
 825                         msg = ERR_PTR(-ENOMSG);
 826                         goto out_unlock;
 827                 }
 828                 list_add_tail(&msr_d.r_list, &msq->q_receivers);
 829                 msr_d.r_tsk = current;
 830                 msr_d.r_msgtype = msgtyp;
 831                 msr_d.r_mode = mode;
 832                 if (msgflg & MSG_NOERROR)
 833                         msr_d.r_maxsize = INT_MAX;
 834                 else
 835                         msr_d.r_maxsize = msgsz;
 836                 msr_d.r_msg = ERR_PTR(-EAGAIN);
 837                 current->state = TASK_INTERRUPTIBLE;
 838                 msg_unlock(msq);
 839
 840                 schedule();
 841
 842                 /* Lockless receive, part 1:
 843                  * Disable preemption.  We don't hold a reference to the queue
 844                  * and getting a reference would defeat the idea of a lockless
 845                  * operation, thus the code relies on rcu to guarantee the
 846                  * existance of msq:
 847                  * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 848                  * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 849                  * rcu_read_lock() prevents preemption between reading r_msg
 850                  * and the spin_lock() inside ipc_lock_by_ptr().
 851                  */
 852                 rcu_read_lock();
 853
 854                 /* Lockless receive, part 2:
 855                  * Wait until pipelined_send or expunge_all are outside of
 856                  * wake_up_process(). There is a race with exit(), see
 857                  * ipc/mqueue.c for the details.
 858                  */
 859                 msg = (struct msg_msg*)msr_d.r_msg;
 860                 while (msg == NULL) {
 861                         cpu_relax();
 862                         msg = (struct msg_msg *)msr_d.r_msg;
 863                 }
 864
 865                 /* Lockless receive, part 3:
 866                  * If there is a message or an error then accept it without
 867                  * locking.
 868                  */
 869                 if (msg != ERR_PTR(-EAGAIN)) {
 870                         rcu_read_unlock();
 871                         break;
 872                 }
 873
 874                 /* Lockless receive, part 3:
 875                  * Acquire the queue spinlock.
 876                  */
 877                 ipc_lock_by_ptr(&msq->q_perm);
 878                 rcu_read_unlock();
 879
 880                 /* Lockless receive, part 4:
 881                  * Repeat test after acquiring the spinlock.
 882                  */
 883                 msg = (struct msg_msg*)msr_d.r_msg;
 884                 if (msg != ERR_PTR(-EAGAIN))
 885                         goto out_unlock;
 886
 887                 list_del(&msr_d.r_list);
 888                 if (signal_pending(current)) {
 889                         msg = ERR_PTR(-ERESTARTNOHAND);
 890 out_unlock:
 891                         msg_unlock(msq);
 892                         break;
 893                 }
 894         }
 895         if (IS_ERR(msg))
 896                 return PTR_ERR(msg);
 897
 898         msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz;
 899         *pmtype = msg->m_type;
 900         if (store_msg(mtext, msg, msgsz))
 901                 msgsz = -EFAULT;
 902
 903         free_msg(msg);
 904
 905         return msgsz;
 906 }
 907
 908 asmlinkage long sys_msgrcv(int msqid, struct msgbuf __user *msgp, size_t msgsz,
 909                            long msgtyp, int msgflg)
 910 {
 911         long err, mtype;
 912
 913         err =  do_msgrcv(msqid, &mtype, msgp->mtext, msgsz, msgtyp, msgflg);
 914         if (err < 0)
 915                 goto out;
 916
 917         if (put_user(mtype, &msgp->mtype))
 918                 err = -EFAULT;
 919 out:
 920         return err;
 921 }
 922
 923 #ifdef CONFIG_PROC_FS
 924 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
 925 {
 926         struct msg_queue *msq = it;
 927
 928         return seq_printf(s,
 929                         "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
 930                         msq->q_perm.key,
 931                         msq->q_perm.id,
 932                         msq->q_perm.mode,
 933                         msq->q_cbytes,
 934                         msq->q_qnum,
 935                         msq->q_lspid,
 936                         msq->q_lrpid,
 937                         msq->q_perm.uid,
 938                         msq->q_perm.gid,
 939                         msq->q_perm.cuid,
 940                         msq->q_perm.cgid,
 941                         msq->q_stime,
 942                         msq->q_rtime,
 943                         msq->q_ctime);
 944 }
 945 #endif