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 <linux/uaccess.h>
  43#include "util.h"
  44
  45/* one msg_receiver structure for each sleeping receiver */
  46struct 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 */
  64struct 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
  77static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
  78{
  79        struct kern_ipc_perm *ipcp = ipc_obtain_object(&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
  87static 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
  98static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
  99{
 100        ipc_rmid(&msg_ids(ns), &s->q_perm);
 101}
 102
 103static 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 */
 119static 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        /* ipc_addid() locks msq upon success. */
 141        id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
 142        if (id < 0) {
 143                ipc_rcu_putref(msq, msg_rcu_free);
 144                return id;
 145        }
 146
 147        msq->q_stime = msq->q_rtime = 0;
 148        msq->q_ctime = get_seconds();
 149        msq->q_cbytes = msq->q_qnum = 0;
 150        msq->q_qbytes = ns->msg_ctlmnb;
 151        msq->q_lspid = msq->q_lrpid = 0;
 152        INIT_LIST_HEAD(&msq->q_messages);
 153        INIT_LIST_HEAD(&msq->q_receivers);
 154        INIT_LIST_HEAD(&msq->q_senders);
 155
 156        ipc_unlock_object(&msq->q_perm);
 157        rcu_read_unlock();
 158
 159        return msq->q_perm.id;
 160}
 161
 162static 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
 169static inline void ss_del(struct msg_sender *mss)
 170{
 171        if (mss->list.next != NULL)
 172                list_del(&mss->list);
 173}
 174
 175static 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
 186static 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_mb();
 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 */
 212static 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 */
 234static 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
 241SYSCALL_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
 258static inline unsigned long
 259copy_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
 303static inline unsigned long
 304copy_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 */
 339static 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
 403out_unlock0:
 404        ipc_unlock_object(&msq->q_perm);
 405out_unlock1:
 406        rcu_read_unlock();
 407out_up:
 408        up_write(&msg_ids(ns).rwsem);
 409        return err;
 410}
 411
 412static 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;
 517out_unlock:
 518        rcu_read_unlock();
 519        return err;
 520}
 521
 522SYSCALL_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
 547static 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
 569static 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                                smp_mb(); /* see barrier comment below */
 584                                msr->r_msg = ERR_PTR(-E2BIG);
 585                        } else {
 586                                msr->r_msg = NULL;
 587                                msq->q_lrpid = task_pid_vnr(msr->r_tsk);
 588                                msq->q_rtime = get_seconds();
 589                                wake_up_process(msr->r_tsk);
 590                                /*
 591                                 * Ensure that the wakeup is visible before
 592                                 * setting r_msg, as the receiving end depends
 593                                 * on it. See lockless receive part 1 and 2 in
 594                                 * do_msgrcv().
 595                                 */
 596                                smp_mb();
 597                                msr->r_msg = msg;
 598
 599                                return 1;
 600                        }
 601                }
 602        }
 603
 604        return 0;
 605}
 606
 607long do_msgsnd(int msqid, long mtype, void __user *mtext,
 608                size_t msgsz, int msgflg)
 609{
 610        struct msg_queue *msq;
 611        struct msg_msg *msg;
 612        int err;
 613        struct ipc_namespace *ns;
 614
 615        ns = current->nsproxy->ipc_ns;
 616
 617        if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 618                return -EINVAL;
 619        if (mtype < 1)
 620                return -EINVAL;
 621
 622        msg = load_msg(mtext, msgsz);
 623        if (IS_ERR(msg))
 624                return PTR_ERR(msg);
 625
 626        msg->m_type = mtype;
 627        msg->m_ts = msgsz;
 628
 629        rcu_read_lock();
 630        msq = msq_obtain_object_check(ns, msqid);
 631        if (IS_ERR(msq)) {
 632                err = PTR_ERR(msq);
 633                goto out_unlock1;
 634        }
 635
 636        ipc_lock_object(&msq->q_perm);
 637
 638        for (;;) {
 639                struct msg_sender s;
 640
 641                err = -EACCES;
 642                if (ipcperms(ns, &msq->q_perm, S_IWUGO))
 643                        goto out_unlock0;
 644
 645                /* raced with RMID? */
 646                if (!ipc_valid_object(&msq->q_perm)) {
 647                        err = -EIDRM;
 648                        goto out_unlock0;
 649                }
 650
 651                err = security_msg_queue_msgsnd(msq, msg, msgflg);
 652                if (err)
 653                        goto out_unlock0;
 654
 655                if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
 656                                1 + msq->q_qnum <= msq->q_qbytes) {
 657                        break;
 658                }
 659
 660                /* queue full, wait: */
 661                if (msgflg & IPC_NOWAIT) {
 662                        err = -EAGAIN;
 663                        goto out_unlock0;
 664                }
 665
 666                /* enqueue the sender and prepare to block */
 667                ss_add(msq, &s);
 668
 669                if (!ipc_rcu_getref(msq)) {
 670                        err = -EIDRM;
 671                        goto out_unlock0;
 672                }
 673
 674                ipc_unlock_object(&msq->q_perm);
 675                rcu_read_unlock();
 676                schedule();
 677
 678                rcu_read_lock();
 679                ipc_lock_object(&msq->q_perm);
 680
 681                ipc_rcu_putref(msq, ipc_rcu_free);
 682                /* raced with RMID? */
 683                if (!ipc_valid_object(&msq->q_perm)) {
 684                        err = -EIDRM;
 685                        goto out_unlock0;
 686                }
 687
 688                ss_del(&s);
 689
 690                if (signal_pending(current)) {
 691                        err = -ERESTARTNOHAND;
 692                        goto out_unlock0;
 693                }
 694
 695        }
 696        msq->q_lspid = task_tgid_vnr(current);
 697        msq->q_stime = get_seconds();
 698
 699        if (!pipelined_send(msq, msg)) {
 700                /* no one is waiting for this message, enqueue it */
 701                list_add_tail(&msg->m_list, &msq->q_messages);
 702                msq->q_cbytes += msgsz;
 703                msq->q_qnum++;
 704                atomic_add(msgsz, &ns->msg_bytes);
 705                atomic_inc(&ns->msg_hdrs);
 706        }
 707
 708        err = 0;
 709        msg = NULL;
 710
 711out_unlock0:
 712        ipc_unlock_object(&msq->q_perm);
 713out_unlock1:
 714        rcu_read_unlock();
 715        if (msg != NULL)
 716                free_msg(msg);
 717        return err;
 718}
 719
 720SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 721                int, msgflg)
 722{
 723        long mtype;
 724
 725        if (get_user(mtype, &msgp->mtype))
 726                return -EFAULT;
 727        return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
 728}
 729
 730static inline int convert_mode(long *msgtyp, int msgflg)
 731{
 732        if (msgflg & MSG_COPY)
 733                return SEARCH_NUMBER;
 734        /*
 735         *  find message of correct type.
 736         *  msgtyp = 0 => get first.
 737         *  msgtyp > 0 => get first message of matching type.
 738         *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 739         */
 740        if (*msgtyp == 0)
 741                return SEARCH_ANY;
 742        if (*msgtyp < 0) {
 743                *msgtyp = -*msgtyp;
 744                return SEARCH_LESSEQUAL;
 745        }
 746        if (msgflg & MSG_EXCEPT)
 747                return SEARCH_NOTEQUAL;
 748        return SEARCH_EQUAL;
 749}
 750
 751static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
 752{
 753        struct msgbuf __user *msgp = dest;
 754        size_t msgsz;
 755
 756        if (put_user(msg->m_type, &msgp->mtype))
 757                return -EFAULT;
 758
 759        msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
 760        if (store_msg(msgp->mtext, msg, msgsz))
 761                return -EFAULT;
 762        return msgsz;
 763}
 764
 765#ifdef CONFIG_CHECKPOINT_RESTORE
 766/*
 767 * This function creates new kernel message structure, large enough to store
 768 * bufsz message bytes.
 769 */
 770static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 771{
 772        struct msg_msg *copy;
 773
 774        /*
 775         * Create dummy message to copy real message to.
 776         */
 777        copy = load_msg(buf, bufsz);
 778        if (!IS_ERR(copy))
 779                copy->m_ts = bufsz;
 780        return copy;
 781}
 782
 783static inline void free_copy(struct msg_msg *copy)
 784{
 785        if (copy)
 786                free_msg(copy);
 787}
 788#else
 789static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 790{
 791        return ERR_PTR(-ENOSYS);
 792}
 793
 794static inline void free_copy(struct msg_msg *copy)
 795{
 796}
 797#endif
 798
 799static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
 800{
 801        struct msg_msg *msg, *found = NULL;
 802        long count = 0;
 803
 804        list_for_each_entry(msg, &msq->q_messages, m_list) {
 805                if (testmsg(msg, *msgtyp, mode) &&
 806                    !security_msg_queue_msgrcv(msq, msg, current,
 807                                               *msgtyp, mode)) {
 808                        if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
 809                                *msgtyp = msg->m_type - 1;
 810                                found = msg;
 811                        } else if (mode == SEARCH_NUMBER) {
 812                                if (*msgtyp == count)
 813                                        return msg;
 814                        } else
 815                                return msg;
 816                        count++;
 817                }
 818        }
 819
 820        return found ?: ERR_PTR(-EAGAIN);
 821}
 822
 823long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
 824               long (*msg_handler)(void __user *, struct msg_msg *, size_t))
 825{
 826        int mode;
 827        struct msg_queue *msq;
 828        struct ipc_namespace *ns;
 829        struct msg_msg *msg, *copy = NULL;
 830
 831        ns = current->nsproxy->ipc_ns;
 832
 833        if (msqid < 0 || (long) bufsz < 0)
 834                return -EINVAL;
 835
 836        if (msgflg & MSG_COPY) {
 837                if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
 838                        return -EINVAL;
 839                copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
 840                if (IS_ERR(copy))
 841                        return PTR_ERR(copy);
 842        }
 843        mode = convert_mode(&msgtyp, msgflg);
 844
 845        rcu_read_lock();
 846        msq = msq_obtain_object_check(ns, msqid);
 847        if (IS_ERR(msq)) {
 848                rcu_read_unlock();
 849                free_copy(copy);
 850                return PTR_ERR(msq);
 851        }
 852
 853        for (;;) {
 854                struct msg_receiver msr_d;
 855
 856                msg = ERR_PTR(-EACCES);
 857                if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 858                        goto out_unlock1;
 859
 860                ipc_lock_object(&msq->q_perm);
 861
 862                /* raced with RMID? */
 863                if (!ipc_valid_object(&msq->q_perm)) {
 864                        msg = ERR_PTR(-EIDRM);
 865                        goto out_unlock0;
 866                }
 867
 868                msg = find_msg(msq, &msgtyp, mode);
 869                if (!IS_ERR(msg)) {
 870                        /*
 871                         * Found a suitable message.
 872                         * Unlink it from the queue.
 873                         */
 874                        if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 875                                msg = ERR_PTR(-E2BIG);
 876                                goto out_unlock0;
 877                        }
 878                        /*
 879                         * If we are copying, then do not unlink message and do
 880                         * not update queue parameters.
 881                         */
 882                        if (msgflg & MSG_COPY) {
 883                                msg = copy_msg(msg, copy);
 884                                goto out_unlock0;
 885                        }
 886
 887                        list_del(&msg->m_list);
 888                        msq->q_qnum--;
 889                        msq->q_rtime = get_seconds();
 890                        msq->q_lrpid = task_tgid_vnr(current);
 891                        msq->q_cbytes -= msg->m_ts;
 892                        atomic_sub(msg->m_ts, &ns->msg_bytes);
 893                        atomic_dec(&ns->msg_hdrs);
 894                        ss_wakeup(&msq->q_senders, 0);
 895
 896                        goto out_unlock0;
 897                }
 898
 899                /* No message waiting. Wait for a message */
 900                if (msgflg & IPC_NOWAIT) {
 901                        msg = ERR_PTR(-ENOMSG);
 902                        goto out_unlock0;
 903                }
 904
 905                list_add_tail(&msr_d.r_list, &msq->q_receivers);
 906                msr_d.r_tsk = current;
 907                msr_d.r_msgtype = msgtyp;
 908                msr_d.r_mode = mode;
 909                if (msgflg & MSG_NOERROR)
 910                        msr_d.r_maxsize = INT_MAX;
 911                else
 912                        msr_d.r_maxsize = bufsz;
 913                msr_d.r_msg = ERR_PTR(-EAGAIN);
 914                __set_current_state(TASK_INTERRUPTIBLE);
 915
 916                ipc_unlock_object(&msq->q_perm);
 917                rcu_read_unlock();
 918                schedule();
 919
 920                /* Lockless receive, part 1:
 921                 * Disable preemption.  We don't hold a reference to the queue
 922                 * and getting a reference would defeat the idea of a lockless
 923                 * operation, thus the code relies on rcu to guarantee the
 924                 * existence of msq:
 925                 * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 926                 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 927                 * rcu_read_lock() prevents preemption between reading r_msg
 928                 * and acquiring the q_perm.lock in ipc_lock_object().
 929                 */
 930                rcu_read_lock();
 931
 932                /* Lockless receive, part 2:
 933                 * Wait until pipelined_send or expunge_all are outside of
 934                 * wake_up_process(). There is a race with exit(), see
 935                 * ipc/mqueue.c for the details.
 936                 */
 937                msg = (struct msg_msg *)msr_d.r_msg;
 938                while (msg == NULL) {
 939                        cpu_relax();
 940                        msg = (struct msg_msg *)msr_d.r_msg;
 941                }
 942
 943                /* Lockless receive, part 3:
 944                 * If there is a message or an error then accept it without
 945                 * locking.
 946                 */
 947                if (msg != ERR_PTR(-EAGAIN))
 948                        goto out_unlock1;
 949
 950                /* Lockless receive, part 3:
 951                 * Acquire the queue spinlock.
 952                 */
 953                ipc_lock_object(&msq->q_perm);
 954
 955                /* Lockless receive, part 4:
 956                 * Repeat test after acquiring the spinlock.
 957                 */
 958                msg = (struct msg_msg *)msr_d.r_msg;
 959                if (msg != ERR_PTR(-EAGAIN))
 960                        goto out_unlock0;
 961
 962                list_del(&msr_d.r_list);
 963                if (signal_pending(current)) {
 964                        msg = ERR_PTR(-ERESTARTNOHAND);
 965                        goto out_unlock0;
 966                }
 967
 968                ipc_unlock_object(&msq->q_perm);
 969        }
 970
 971out_unlock0:
 972        ipc_unlock_object(&msq->q_perm);
 973out_unlock1:
 974        rcu_read_unlock();
 975        if (IS_ERR(msg)) {
 976                free_copy(copy);
 977                return PTR_ERR(msg);
 978        }
 979
 980        bufsz = msg_handler(buf, msg, bufsz);
 981        free_msg(msg);
 982
 983        return bufsz;
 984}
 985
 986SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 987                long, msgtyp, int, msgflg)
 988{
 989        return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
 990}
 991
 992
 993void msg_init_ns(struct ipc_namespace *ns)
 994{
 995        ns->msg_ctlmax = MSGMAX;
 996        ns->msg_ctlmnb = MSGMNB;
 997        ns->msg_ctlmni = MSGMNI;
 998
 999        atomic_set(&ns->msg_bytes, 0);
1000        atomic_set(&ns->msg_hdrs, 0);
1001        ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
1002}
1003
1004#ifdef CONFIG_IPC_NS
1005void msg_exit_ns(struct ipc_namespace *ns)
1006{
1007        free_ipcs(ns, &msg_ids(ns), freeque);
1008        idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
1009}
1010#endif
1011
1012#ifdef CONFIG_PROC_FS
1013static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
1014{
1015        struct user_namespace *user_ns = seq_user_ns(s);
1016        struct msg_queue *msq = it;
1017
1018        return seq_printf(s,
1019                        "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1020                        msq->q_perm.key,
1021                        msq->q_perm.id,
1022                        msq->q_perm.mode,
1023                        msq->q_cbytes,
1024                        msq->q_qnum,
1025                        msq->q_lspid,
1026                        msq->q_lrpid,
1027                        from_kuid_munged(user_ns, msq->q_perm.uid),
1028                        from_kgid_munged(user_ns, msq->q_perm.gid),
1029                        from_kuid_munged(user_ns, msq->q_perm.cuid),
1030                        from_kgid_munged(user_ns, msq->q_perm.cgid),
1031                        msq->q_stime,
1032                        msq->q_rtime,
1033                        msq->q_ctime);
1034}
1035#endif
1036
1037void __init msg_init(void)
1038{
1039        msg_init_ns(&init_ipc_ns);
1040
1041        ipc_init_proc_interface("sysvipc/msg",
1042                                "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
1043                                IPC_MSG_IDS, sysvipc_msg_proc_show);
1044}
1045
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.