linux/ipc/msg.c
<<
>>
Prefs
   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 <asm/uaccess.h>
  43#include "util.h"
  44
  45/*
  46 * one msg_receiver structure for each sleeping receiver:
  47 */
  48struct msg_receiver {
  49        struct list_head        r_list;
  50        struct task_struct      *r_tsk;
  51
  52        int                     r_mode;
  53        long                    r_msgtype;
  54        long                    r_maxsize;
  55
  56        struct msg_msg          *volatile r_msg;
  57};
  58
  59/* one msg_sender for each sleeping sender */
  60struct msg_sender {
  61        struct list_head        list;
  62        struct task_struct      *tsk;
  63};
  64
  65#define SEARCH_ANY              1
  66#define SEARCH_EQUAL            2
  67#define SEARCH_NOTEQUAL         3
  68#define SEARCH_LESSEQUAL        4
  69
  70#define msg_ids(ns)     ((ns)->ids[IPC_MSG_IDS])
  71
  72#define msg_unlock(msq)         ipc_unlock(&(msq)->q_perm)
  73
  74static void freeque(struct ipc_namespace *, struct kern_ipc_perm *);
  75static int newque(struct ipc_namespace *, struct ipc_params *);
  76#ifdef CONFIG_PROC_FS
  77static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
  78#endif
  79
  80/*
  81 * Scale msgmni with the available lowmem size: the memory dedicated to msg
  82 * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
  83 * Also take into account the number of nsproxies created so far.
  84 * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
  85 */
  86void recompute_msgmni(struct ipc_namespace *ns)
  87{
  88        struct sysinfo i;
  89        unsigned long allowed;
  90        int nb_ns;
  91
  92        si_meminfo(&i);
  93        allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
  94                / MSGMNB;
  95        nb_ns = atomic_read(&nr_ipc_ns);
  96        allowed /= nb_ns;
  97
  98        if (allowed < MSGMNI) {
  99                ns->msg_ctlmni = MSGMNI;
 100                return;
 101        }
 102
 103        if (allowed > IPCMNI / nb_ns) {
 104                ns->msg_ctlmni = IPCMNI / nb_ns;
 105                return;
 106        }
 107
 108        ns->msg_ctlmni = allowed;
 109}
 110
 111void msg_init_ns(struct ipc_namespace *ns)
 112{
 113        ns->msg_ctlmax = MSGMAX;
 114        ns->msg_ctlmnb = MSGMNB;
 115
 116        recompute_msgmni(ns);
 117
 118        atomic_set(&ns->msg_bytes, 0);
 119        atomic_set(&ns->msg_hdrs, 0);
 120        ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
 121}
 122
 123#ifdef CONFIG_IPC_NS
 124void msg_exit_ns(struct ipc_namespace *ns)
 125{
 126        free_ipcs(ns, &msg_ids(ns), freeque);
 127        idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
 128}
 129#endif
 130
 131void __init msg_init(void)
 132{
 133        msg_init_ns(&init_ipc_ns);
 134
 135        printk(KERN_INFO "msgmni has been set to %d\n",
 136                init_ipc_ns.msg_ctlmni);
 137
 138        ipc_init_proc_interface("sysvipc/msg",
 139                                "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
 140                                IPC_MSG_IDS, sysvipc_msg_proc_show);
 141}
 142
 143/*
 144 * msg_lock_(check_) routines are called in the paths where the rw_mutex
 145 * is not held.
 146 */
 147static inline struct msg_queue *msg_lock(struct ipc_namespace *ns, int id)
 148{
 149        struct kern_ipc_perm *ipcp = ipc_lock(&msg_ids(ns), id);
 150
 151        if (IS_ERR(ipcp))
 152                return (struct msg_queue *)ipcp;
 153
 154        return container_of(ipcp, struct msg_queue, q_perm);
 155}
 156
 157static inline struct msg_queue *msg_lock_check(struct ipc_namespace *ns,
 158                                                int id)
 159{
 160        struct kern_ipc_perm *ipcp = ipc_lock_check(&msg_ids(ns), id);
 161
 162        if (IS_ERR(ipcp))
 163                return (struct msg_queue *)ipcp;
 164
 165        return container_of(ipcp, struct msg_queue, q_perm);
 166}
 167
 168static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
 169{
 170        ipc_rmid(&msg_ids(ns), &s->q_perm);
 171}
 172
 173/**
 174 * newque - Create a new msg queue
 175 * @ns: namespace
 176 * @params: ptr to the structure that contains the key and msgflg
 177 *
 178 * Called with msg_ids.rw_mutex held (writer)
 179 */
 180static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 181{
 182        struct msg_queue *msq;
 183        int id, retval;
 184        key_t key = params->key;
 185        int msgflg = params->flg;
 186
 187        msq = ipc_rcu_alloc(sizeof(*msq));
 188        if (!msq)
 189                return -ENOMEM;
 190
 191        msq->q_perm.mode = msgflg & S_IRWXUGO;
 192        msq->q_perm.key = key;
 193
 194        msq->q_perm.security = NULL;
 195        retval = security_msg_queue_alloc(msq);
 196        if (retval) {
 197                ipc_rcu_putref(msq);
 198                return retval;
 199        }
 200
 201        /*
 202         * ipc_addid() locks msq
 203         */
 204        id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
 205        if (id < 0) {
 206                security_msg_queue_free(msq);
 207                ipc_rcu_putref(msq);
 208                return id;
 209        }
 210
 211        msq->q_stime = msq->q_rtime = 0;
 212        msq->q_ctime = get_seconds();
 213        msq->q_cbytes = msq->q_qnum = 0;
 214        msq->q_qbytes = ns->msg_ctlmnb;
 215        msq->q_lspid = msq->q_lrpid = 0;
 216        INIT_LIST_HEAD(&msq->q_messages);
 217        INIT_LIST_HEAD(&msq->q_receivers);
 218        INIT_LIST_HEAD(&msq->q_senders);
 219
 220        msg_unlock(msq);
 221
 222        return msq->q_perm.id;
 223}
 224
 225static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
 226{
 227        mss->tsk = current;
 228        current->state = TASK_INTERRUPTIBLE;
 229        list_add_tail(&mss->list, &msq->q_senders);
 230}
 231
 232static inline void ss_del(struct msg_sender *mss)
 233{
 234        if (mss->list.next != NULL)
 235                list_del(&mss->list);
 236}
 237
 238static void ss_wakeup(struct list_head *h, int kill)
 239{
 240        struct list_head *tmp;
 241
 242        tmp = h->next;
 243        while (tmp != h) {
 244                struct msg_sender *mss;
 245
 246                mss = list_entry(tmp, struct msg_sender, list);
 247                tmp = tmp->next;
 248                if (kill)
 249                        mss->list.next = NULL;
 250                wake_up_process(mss->tsk);
 251        }
 252}
 253
 254static void expunge_all(struct msg_queue *msq, int res)
 255{
 256        struct list_head *tmp;
 257
 258        tmp = msq->q_receivers.next;
 259        while (tmp != &msq->q_receivers) {
 260                struct msg_receiver *msr;
 261
 262                msr = list_entry(tmp, struct msg_receiver, r_list);
 263                tmp = tmp->next;
 264                msr->r_msg = NULL;
 265                wake_up_process(msr->r_tsk);
 266                smp_mb();
 267                msr->r_msg = ERR_PTR(res);
 268        }
 269}
 270
 271/*
 272 * freeque() wakes up waiters on the sender and receiver waiting queue,
 273 * removes the message queue from message queue ID IDR, and cleans up all the
 274 * messages associated with this queue.
 275 *
 276 * msg_ids.rw_mutex (writer) and the spinlock for this message queue are held
 277 * before freeque() is called. msg_ids.rw_mutex remains locked on exit.
 278 */
 279static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 280{
 281        struct list_head *tmp;
 282        struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 283
 284        expunge_all(msq, -EIDRM);
 285        ss_wakeup(&msq->q_senders, 1);
 286        msg_rmid(ns, msq);
 287        msg_unlock(msq);
 288
 289        tmp = msq->q_messages.next;
 290        while (tmp != &msq->q_messages) {
 291                struct msg_msg *msg = list_entry(tmp, struct msg_msg, m_list);
 292
 293                tmp = tmp->next;
 294                atomic_dec(&ns->msg_hdrs);
 295                free_msg(msg);
 296        }
 297        atomic_sub(msq->q_cbytes, &ns->msg_bytes);
 298        security_msg_queue_free(msq);
 299        ipc_rcu_putref(msq);
 300}
 301
 302/*
 303 * Called with msg_ids.rw_mutex and ipcp locked.
 304 */
 305static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
 306{
 307        struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 308
 309        return security_msg_queue_associate(msq, msgflg);
 310}
 311
 312SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
 313{
 314        struct ipc_namespace *ns;
 315        struct ipc_ops msg_ops;
 316        struct ipc_params msg_params;
 317
 318        ns = current->nsproxy->ipc_ns;
 319
 320        msg_ops.getnew = newque;
 321        msg_ops.associate = msg_security;
 322        msg_ops.more_checks = NULL;
 323
 324        msg_params.key = key;
 325        msg_params.flg = msgflg;
 326
 327        return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
 328}
 329
 330static inline unsigned long
 331copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 332{
 333        switch(version) {
 334        case IPC_64:
 335                return copy_to_user(buf, in, sizeof(*in));
 336        case IPC_OLD:
 337        {
 338                struct msqid_ds out;
 339
 340                memset(&out, 0, sizeof(out));
 341
 342                ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
 343
 344                out.msg_stime           = in->msg_stime;
 345                out.msg_rtime           = in->msg_rtime;
 346                out.msg_ctime           = in->msg_ctime;
 347
 348                if (in->msg_cbytes > USHRT_MAX)
 349                        out.msg_cbytes  = USHRT_MAX;
 350                else
 351                        out.msg_cbytes  = in->msg_cbytes;
 352                out.msg_lcbytes         = in->msg_cbytes;
 353
 354                if (in->msg_qnum > USHRT_MAX)
 355                        out.msg_qnum    = USHRT_MAX;
 356                else
 357                        out.msg_qnum    = in->msg_qnum;
 358
 359                if (in->msg_qbytes > USHRT_MAX)
 360                        out.msg_qbytes  = USHRT_MAX;
 361                else
 362                        out.msg_qbytes  = in->msg_qbytes;
 363                out.msg_lqbytes         = in->msg_qbytes;
 364
 365                out.msg_lspid           = in->msg_lspid;
 366                out.msg_lrpid           = in->msg_lrpid;
 367
 368                return copy_to_user(buf, &out, sizeof(out));
 369        }
 370        default:
 371                return -EINVAL;
 372        }
 373}
 374
 375static inline unsigned long
 376copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
 377{
 378        switch(version) {
 379        case IPC_64:
 380                if (copy_from_user(out, buf, sizeof(*out)))
 381                        return -EFAULT;
 382                return 0;
 383        case IPC_OLD:
 384        {
 385                struct msqid_ds tbuf_old;
 386
 387                if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
 388                        return -EFAULT;
 389
 390                out->msg_perm.uid       = tbuf_old.msg_perm.uid;
 391                out->msg_perm.gid       = tbuf_old.msg_perm.gid;
 392                out->msg_perm.mode      = tbuf_old.msg_perm.mode;
 393
 394                if (tbuf_old.msg_qbytes == 0)
 395                        out->msg_qbytes = tbuf_old.msg_lqbytes;
 396                else
 397                        out->msg_qbytes = tbuf_old.msg_qbytes;
 398
 399                return 0;
 400        }
 401        default:
 402                return -EINVAL;
 403        }
 404}
 405
 406/*
 407 * This function handles some msgctl commands which require the rw_mutex
 408 * to be held in write mode.
 409 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
 410 */
 411static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 412                       struct msqid_ds __user *buf, int version)
 413{
 414        struct kern_ipc_perm *ipcp;
 415        struct msqid64_ds uninitialized_var(msqid64);
 416        struct msg_queue *msq;
 417        int err;
 418
 419        if (cmd == IPC_SET) {
 420                if (copy_msqid_from_user(&msqid64, buf, version))
 421                        return -EFAULT;
 422        }
 423
 424        ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,
 425                               &msqid64.msg_perm, msqid64.msg_qbytes);
 426        if (IS_ERR(ipcp))
 427                return PTR_ERR(ipcp);
 428
 429        msq = container_of(ipcp, struct msg_queue, q_perm);
 430
 431        err = security_msg_queue_msgctl(msq, cmd);
 432        if (err)
 433                goto out_unlock;
 434
 435        switch (cmd) {
 436        case IPC_RMID:
 437                freeque(ns, ipcp);
 438                goto out_up;
 439        case IPC_SET:
 440                if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
 441                    !capable(CAP_SYS_RESOURCE)) {
 442                        err = -EPERM;
 443                        goto out_unlock;
 444                }
 445
 446                msq->q_qbytes = msqid64.msg_qbytes;
 447
 448                ipc_update_perm(&msqid64.msg_perm, ipcp);
 449                msq->q_ctime = get_seconds();
 450                /* sleeping receivers might be excluded by
 451                 * stricter permissions.
 452                 */
 453                expunge_all(msq, -EAGAIN);
 454                /* sleeping senders might be able to send
 455                 * due to a larger queue size.
 456                 */
 457                ss_wakeup(&msq->q_senders, 0);
 458                break;
 459        default:
 460                err = -EINVAL;
 461        }
 462out_unlock:
 463        msg_unlock(msq);
 464out_up:
 465        up_write(&msg_ids(ns).rw_mutex);
 466        return err;
 467}
 468
 469SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
 470{
 471        struct msg_queue *msq;
 472        int err, version;
 473        struct ipc_namespace *ns;
 474
 475        if (msqid < 0 || cmd < 0)
 476                return -EINVAL;
 477
 478        version = ipc_parse_version(&cmd);
 479        ns = current->nsproxy->ipc_ns;
 480
 481        switch (cmd) {
 482        case IPC_INFO:
 483        case MSG_INFO:
 484        {
 485                struct msginfo msginfo;
 486                int max_id;
 487
 488                if (!buf)
 489                        return -EFAULT;
 490                /*
 491                 * We must not return kernel stack data.
 492                 * due to padding, it's not enough
 493                 * to set all member fields.
 494                 */
 495                err = security_msg_queue_msgctl(NULL, cmd);
 496                if (err)
 497                        return err;
 498
 499                memset(&msginfo, 0, sizeof(msginfo));
 500                msginfo.msgmni = ns->msg_ctlmni;
 501                msginfo.msgmax = ns->msg_ctlmax;
 502                msginfo.msgmnb = ns->msg_ctlmnb;
 503                msginfo.msgssz = MSGSSZ;
 504                msginfo.msgseg = MSGSEG;
 505                down_read(&msg_ids(ns).rw_mutex);
 506                if (cmd == MSG_INFO) {
 507                        msginfo.msgpool = msg_ids(ns).in_use;
 508                        msginfo.msgmap = atomic_read(&ns->msg_hdrs);
 509                        msginfo.msgtql = atomic_read(&ns->msg_bytes);
 510                } else {
 511                        msginfo.msgmap = MSGMAP;
 512                        msginfo.msgpool = MSGPOOL;
 513                        msginfo.msgtql = MSGTQL;
 514                }
 515                max_id = ipc_get_maxid(&msg_ids(ns));
 516                up_read(&msg_ids(ns).rw_mutex);
 517                if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
 518                        return -EFAULT;
 519                return (max_id < 0) ? 0 : max_id;
 520        }
 521        case MSG_STAT:  /* msqid is an index rather than a msg queue id */
 522        case IPC_STAT:
 523        {
 524                struct msqid64_ds tbuf;
 525                int success_return;
 526
 527                if (!buf)
 528                        return -EFAULT;
 529
 530                if (cmd == MSG_STAT) {
 531                        msq = msg_lock(ns, msqid);
 532                        if (IS_ERR(msq))
 533                                return PTR_ERR(msq);
 534                        success_return = msq->q_perm.id;
 535                } else {
 536                        msq = msg_lock_check(ns, msqid);
 537                        if (IS_ERR(msq))
 538                                return PTR_ERR(msq);
 539                        success_return = 0;
 540                }
 541                err = -EACCES;
 542                if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 543                        goto out_unlock;
 544
 545                err = security_msg_queue_msgctl(msq, cmd);
 546                if (err)
 547                        goto out_unlock;
 548
 549                memset(&tbuf, 0, sizeof(tbuf));
 550
 551                kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
 552                tbuf.msg_stime  = msq->q_stime;
 553                tbuf.msg_rtime  = msq->q_rtime;
 554                tbuf.msg_ctime  = msq->q_ctime;
 555                tbuf.msg_cbytes = msq->q_cbytes;
 556                tbuf.msg_qnum   = msq->q_qnum;
 557                tbuf.msg_qbytes = msq->q_qbytes;
 558                tbuf.msg_lspid  = msq->q_lspid;
 559                tbuf.msg_lrpid  = msq->q_lrpid;
 560                msg_unlock(msq);
 561                if (copy_msqid_to_user(buf, &tbuf, version))
 562                        return -EFAULT;
 563                return success_return;
 564        }
 565        case IPC_SET:
 566        case IPC_RMID:
 567                err = msgctl_down(ns, msqid, cmd, buf, version);
 568                return err;
 569        default:
 570                return  -EINVAL;
 571        }
 572
 573out_unlock:
 574        msg_unlock(msq);
 575        return err;
 576}
 577
 578static int testmsg(struct msg_msg *msg, long type, int mode)
 579{
 580        switch(mode)
 581        {
 582                case SEARCH_ANY:
 583                        return 1;
 584                case SEARCH_LESSEQUAL:
 585                        if (msg->m_type <=type)
 586                                return 1;
 587                        break;
 588                case SEARCH_EQUAL:
 589                        if (msg->m_type == type)
 590                                return 1;
 591                        break;
 592                case SEARCH_NOTEQUAL:
 593                        if (msg->m_type != type)
 594                                return 1;
 595                        break;
 596        }
 597        return 0;
 598}
 599
 600static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
 601{
 602        struct list_head *tmp;
 603
 604        tmp = msq->q_receivers.next;
 605        while (tmp != &msq->q_receivers) {
 606                struct msg_receiver *msr;
 607
 608                msr = list_entry(tmp, struct msg_receiver, r_list);
 609                tmp = tmp->next;
 610                if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
 611                    !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
 612                                               msr->r_msgtype, msr->r_mode)) {
 613
 614                        list_del(&msr->r_list);
 615                        if (msr->r_maxsize < msg->m_ts) {
 616                                msr->r_msg = NULL;
 617                                wake_up_process(msr->r_tsk);
 618                                smp_mb();
 619                                msr->r_msg = ERR_PTR(-E2BIG);
 620                        } else {
 621                                msr->r_msg = NULL;
 622                                msq->q_lrpid = task_pid_vnr(msr->r_tsk);
 623                                msq->q_rtime = get_seconds();
 624                                wake_up_process(msr->r_tsk);
 625                                smp_mb();
 626                                msr->r_msg = msg;
 627
 628                                return 1;
 629                        }
 630                }
 631        }
 632        return 0;
 633}
 634
 635long do_msgsnd(int msqid, long mtype, void __user *mtext,
 636                size_t msgsz, int msgflg)
 637{
 638        struct msg_queue *msq;
 639        struct msg_msg *msg;
 640        int err;
 641        struct ipc_namespace *ns;
 642
 643        ns = current->nsproxy->ipc_ns;
 644
 645        if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 646                return -EINVAL;
 647        if (mtype < 1)
 648                return -EINVAL;
 649
 650        msg = load_msg(mtext, msgsz);
 651        if (IS_ERR(msg))
 652                return PTR_ERR(msg);
 653
 654        msg->m_type = mtype;
 655        msg->m_ts = msgsz;
 656
 657        msq = msg_lock_check(ns, msqid);
 658        if (IS_ERR(msq)) {
 659                err = PTR_ERR(msq);
 660                goto out_free;
 661        }
 662
 663        for (;;) {
 664                struct msg_sender s;
 665
 666                err = -EACCES;
 667                if (ipcperms(ns, &msq->q_perm, S_IWUGO))
 668                        goto out_unlock_free;
 669
 670                err = security_msg_queue_msgsnd(msq, msg, msgflg);
 671                if (err)
 672                        goto out_unlock_free;
 673
 674                if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
 675                                1 + msq->q_qnum <= msq->q_qbytes) {
 676                        break;
 677                }
 678
 679                /* queue full, wait: */
 680                if (msgflg & IPC_NOWAIT) {
 681                        err = -EAGAIN;
 682                        goto out_unlock_free;
 683                }
 684                ss_add(msq, &s);
 685                ipc_rcu_getref(msq);
 686                msg_unlock(msq);
 687                schedule();
 688
 689                ipc_lock_by_ptr(&msq->q_perm);
 690                ipc_rcu_putref(msq);
 691                if (msq->q_perm.deleted) {
 692                        err = -EIDRM;
 693                        goto out_unlock_free;
 694                }
 695                ss_del(&s);
 696
 697                if (signal_pending(current)) {
 698                        err = -ERESTARTNOHAND;
 699                        goto out_unlock_free;
 700                }
 701        }
 702
 703        msq->q_lspid = task_tgid_vnr(current);
 704        msq->q_stime = get_seconds();
 705
 706        if (!pipelined_send(msq, msg)) {
 707                /* no one is waiting for this message, enqueue it */
 708                list_add_tail(&msg->m_list, &msq->q_messages);
 709                msq->q_cbytes += msgsz;
 710                msq->q_qnum++;
 711                atomic_add(msgsz, &ns->msg_bytes);
 712                atomic_inc(&ns->msg_hdrs);
 713        }
 714
 715        err = 0;
 716        msg = NULL;
 717
 718out_unlock_free:
 719        msg_unlock(msq);
 720out_free:
 721        if (msg != NULL)
 722                free_msg(msg);
 723        return err;
 724}
 725
 726SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 727                int, msgflg)
 728{
 729        long mtype;
 730
 731        if (get_user(mtype, &msgp->mtype))
 732                return -EFAULT;
 733        return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
 734}
 735
 736static inline int convert_mode(long *msgtyp, int msgflg)
 737{
 738        /*
 739         *  find message of correct type.
 740         *  msgtyp = 0 => get first.
 741         *  msgtyp > 0 => get first message of matching type.
 742         *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 743         */
 744        if (*msgtyp == 0)
 745                return SEARCH_ANY;
 746        if (*msgtyp < 0) {
 747                *msgtyp = -*msgtyp;
 748                return SEARCH_LESSEQUAL;
 749        }
 750        if (msgflg & MSG_EXCEPT)
 751                return SEARCH_NOTEQUAL;
 752        return SEARCH_EQUAL;
 753}
 754
 755long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
 756                size_t msgsz, long msgtyp, int msgflg)
 757{
 758        struct msg_queue *msq;
 759        struct msg_msg *msg;
 760        int mode;
 761        struct ipc_namespace *ns;
 762
 763        if (msqid < 0 || (long) msgsz < 0)
 764                return -EINVAL;
 765        mode = convert_mode(&msgtyp, msgflg);
 766        ns = current->nsproxy->ipc_ns;
 767
 768        msq = msg_lock_check(ns, msqid);
 769        if (IS_ERR(msq))
 770                return PTR_ERR(msq);
 771
 772        for (;;) {
 773                struct msg_receiver msr_d;
 774                struct list_head *tmp;
 775
 776                msg = ERR_PTR(-EACCES);
 777                if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 778                        goto out_unlock;
 779
 780                msg = ERR_PTR(-EAGAIN);
 781                tmp = msq->q_messages.next;
 782                while (tmp != &msq->q_messages) {
 783                        struct msg_msg *walk_msg;
 784
 785                        walk_msg = list_entry(tmp, struct msg_msg, m_list);
 786                        if (testmsg(walk_msg, msgtyp, mode) &&
 787                            !security_msg_queue_msgrcv(msq, walk_msg, current,
 788                                                       msgtyp, mode)) {
 789
 790                                msg = walk_msg;
 791                                if (mode == SEARCH_LESSEQUAL &&
 792                                                walk_msg->m_type != 1) {
 793                                        msg = walk_msg;
 794                                        msgtyp = walk_msg->m_type - 1;
 795                                } else {
 796                                        msg = walk_msg;
 797                                        break;
 798                                }
 799                        }
 800                        tmp = tmp->next;
 801                }
 802                if (!IS_ERR(msg)) {
 803                        /*
 804                         * Found a suitable message.
 805                         * Unlink it from the queue.
 806                         */
 807                        if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 808                                msg = ERR_PTR(-E2BIG);
 809                                goto out_unlock;
 810                        }
 811                        list_del(&msg->m_list);
 812                        msq->q_qnum--;
 813                        msq->q_rtime = get_seconds();
 814                        msq->q_lrpid = task_tgid_vnr(current);
 815                        msq->q_cbytes -= msg->m_ts;
 816                        atomic_sub(msg->m_ts, &ns->msg_bytes);
 817                        atomic_dec(&ns->msg_hdrs);
 818                        ss_wakeup(&msq->q_senders, 0);
 819                        msg_unlock(msq);
 820                        break;
 821                }
 822                /* No message waiting. Wait for a message */
 823                if (msgflg & IPC_NOWAIT) {
 824                        msg = ERR_PTR(-ENOMSG);
 825                        goto out_unlock;
 826                }
 827                list_add_tail(&msr_d.r_list, &msq->q_receivers);
 828                msr_d.r_tsk = current;
 829                msr_d.r_msgtype = msgtyp;
 830                msr_d.r_mode = mode;
 831                if (msgflg & MSG_NOERROR)
 832                        msr_d.r_maxsize = INT_MAX;
 833                else
 834                        msr_d.r_maxsize = msgsz;
 835                msr_d.r_msg = ERR_PTR(-EAGAIN);
 836                current->state = TASK_INTERRUPTIBLE;
 837                msg_unlock(msq);
 838
 839                schedule();
 840
 841                /* Lockless receive, part 1:
 842                 * Disable preemption.  We don't hold a reference to the queue
 843                 * and getting a reference would defeat the idea of a lockless
 844                 * operation, thus the code relies on rcu to guarantee the
 845                 * existence of msq:
 846                 * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 847                 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 848                 * rcu_read_lock() prevents preemption between reading r_msg
 849                 * and the spin_lock() inside ipc_lock_by_ptr().
 850                 */
 851                rcu_read_lock();
 852
 853                /* Lockless receive, part 2:
 854                 * Wait until pipelined_send or expunge_all are outside of
 855                 * wake_up_process(). There is a race with exit(), see
 856                 * ipc/mqueue.c for the details.
 857                 */
 858                msg = (struct msg_msg*)msr_d.r_msg;
 859                while (msg == NULL) {
 860                        cpu_relax();
 861                        msg = (struct msg_msg *)msr_d.r_msg;
 862                }
 863
 864                /* Lockless receive, part 3:
 865                 * If there is a message or an error then accept it without
 866                 * locking.
 867                 */
 868                if (msg != ERR_PTR(-EAGAIN)) {
 869                        rcu_read_unlock();
 870                        break;
 871                }
 872
 873                /* Lockless receive, part 3:
 874                 * Acquire the queue spinlock.
 875                 */
 876                ipc_lock_by_ptr(&msq->q_perm);
 877                rcu_read_unlock();
 878
 879                /* Lockless receive, part 4:
 880                 * Repeat test after acquiring the spinlock.
 881                 */
 882                msg = (struct msg_msg*)msr_d.r_msg;
 883                if (msg != ERR_PTR(-EAGAIN))
 884                        goto out_unlock;
 885
 886                list_del(&msr_d.r_list);
 887                if (signal_pending(current)) {
 888                        msg = ERR_PTR(-ERESTARTNOHAND);
 889out_unlock:
 890                        msg_unlock(msq);
 891                        break;
 892                }
 893        }
 894        if (IS_ERR(msg))
 895                return PTR_ERR(msg);
 896
 897        msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz;
 898        *pmtype = msg->m_type;
 899        if (store_msg(mtext, msg, msgsz))
 900                msgsz = -EFAULT;
 901
 902        free_msg(msg);
 903
 904        return msgsz;
 905}
 906
 907SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 908                long, msgtyp, int, msgflg)
 909{
 910        long err, mtype;
 911
 912        err =  do_msgrcv(msqid, &mtype, msgp->mtext, msgsz, msgtyp, msgflg);
 913        if (err < 0)
 914                goto out;
 915
 916        if (put_user(mtype, &msgp->mtype))
 917                err = -EFAULT;
 918out:
 919        return err;
 920}
 921
 922#ifdef CONFIG_PROC_FS
 923static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
 924{
 925        struct msg_queue *msq = it;
 926
 927        return seq_printf(s,
 928                        "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
 929                        msq->q_perm.key,
 930                        msq->q_perm.id,
 931                        msq->q_perm.mode,
 932                        msq->q_cbytes,
 933                        msq->q_qnum,
 934                        msq->q_lspid,
 935                        msq->q_lrpid,
 936                        msq->q_perm.uid,
 937                        msq->q_perm.gid,
 938                        msq->q_perm.cuid,
 939                        msq->q_perm.cgid,
 940                        msq->q_stime,
 941                        msq->q_rtime,
 942                        msq->q_ctime);
 943}
 944#endif
 945
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.