linux/ipc/msg.c
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   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#define SEARCH_NUMBER           5
  70
  71#define msg_ids(ns)     ((ns)->ids[IPC_MSG_IDS])
  72
  73#define msg_unlock(msq)         ipc_unlock(&(msq)->q_perm)
  74
  75static void freeque(struct ipc_namespace *, struct kern_ipc_perm *);
  76static int newque(struct ipc_namespace *, struct ipc_params *);
  77#ifdef CONFIG_PROC_FS
  78static 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 */
  87void 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                return;
 102        }
 103
 104        if (allowed > IPCMNI / nb_ns) {
 105                ns->msg_ctlmni = IPCMNI / nb_ns;
 106                return;
 107        }
 108
 109        ns->msg_ctlmni = allowed;
 110}
 111
 112void msg_init_ns(struct ipc_namespace *ns)
 113{
 114        ns->msg_ctlmax = MSGMAX;
 115        ns->msg_ctlmnb = MSGMNB;
 116
 117        recompute_msgmni(ns);
 118
 119        atomic_set(&ns->msg_bytes, 0);
 120        atomic_set(&ns->msg_hdrs, 0);
 121        ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
 122}
 123
 124#ifdef CONFIG_IPC_NS
 125void msg_exit_ns(struct ipc_namespace *ns)
 126{
 127        free_ipcs(ns, &msg_ids(ns), freeque);
 128        idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
 129}
 130#endif
 131
 132void __init msg_init(void)
 133{
 134        msg_init_ns(&init_ipc_ns);
 135
 136        printk(KERN_INFO "msgmni has been set to %d\n",
 137                init_ipc_ns.msg_ctlmni);
 138
 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 */
 148static 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
 158static 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
 169static 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 */
 181static 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
 226static 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
 233static inline void ss_del(struct msg_sender *mss)
 234{
 235        if (mss->list.next != NULL)
 236                list_del(&mss->list);
 237}
 238
 239static void ss_wakeup(struct list_head *h, int kill)
 240{
 241        struct msg_sender *mss, *t;
 242
 243        list_for_each_entry_safe(mss, t, h, list) {
 244                if (kill)
 245                        mss->list.next = NULL;
 246                wake_up_process(mss->tsk);
 247        }
 248}
 249
 250static void expunge_all(struct msg_queue *msq, int res)
 251{
 252        struct msg_receiver *msr, *t;
 253
 254        list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
 255                msr->r_msg = NULL;
 256                wake_up_process(msr->r_tsk);
 257                smp_mb();
 258                msr->r_msg = ERR_PTR(res);
 259        }
 260}
 261
 262/*
 263 * freeque() wakes up waiters on the sender and receiver waiting queue,
 264 * removes the message queue from message queue ID IDR, and cleans up all the
 265 * messages associated with this queue.
 266 *
 267 * msg_ids.rw_mutex (writer) and the spinlock for this message queue are held
 268 * before freeque() is called. msg_ids.rw_mutex remains locked on exit.
 269 */
 270static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 271{
 272        struct msg_msg *msg, *t;
 273        struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 274
 275        expunge_all(msq, -EIDRM);
 276        ss_wakeup(&msq->q_senders, 1);
 277        msg_rmid(ns, msq);
 278        msg_unlock(msq);
 279
 280        list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
 281                atomic_dec(&ns->msg_hdrs);
 282                free_msg(msg);
 283        }
 284        atomic_sub(msq->q_cbytes, &ns->msg_bytes);
 285        security_msg_queue_free(msq);
 286        ipc_rcu_putref(msq);
 287}
 288
 289/*
 290 * Called with msg_ids.rw_mutex and ipcp locked.
 291 */
 292static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
 293{
 294        struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 295
 296        return security_msg_queue_associate(msq, msgflg);
 297}
 298
 299SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
 300{
 301        struct ipc_namespace *ns;
 302        struct ipc_ops msg_ops;
 303        struct ipc_params msg_params;
 304
 305        ns = current->nsproxy->ipc_ns;
 306
 307        msg_ops.getnew = newque;
 308        msg_ops.associate = msg_security;
 309        msg_ops.more_checks = NULL;
 310
 311        msg_params.key = key;
 312        msg_params.flg = msgflg;
 313
 314        return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
 315}
 316
 317static inline unsigned long
 318copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 319{
 320        switch(version) {
 321        case IPC_64:
 322                return copy_to_user(buf, in, sizeof(*in));
 323        case IPC_OLD:
 324        {
 325                struct msqid_ds out;
 326
 327                memset(&out, 0, sizeof(out));
 328
 329                ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
 330
 331                out.msg_stime           = in->msg_stime;
 332                out.msg_rtime           = in->msg_rtime;
 333                out.msg_ctime           = in->msg_ctime;
 334
 335                if (in->msg_cbytes > USHRT_MAX)
 336                        out.msg_cbytes  = USHRT_MAX;
 337                else
 338                        out.msg_cbytes  = in->msg_cbytes;
 339                out.msg_lcbytes         = in->msg_cbytes;
 340
 341                if (in->msg_qnum > USHRT_MAX)
 342                        out.msg_qnum    = USHRT_MAX;
 343                else
 344                        out.msg_qnum    = in->msg_qnum;
 345
 346                if (in->msg_qbytes > USHRT_MAX)
 347                        out.msg_qbytes  = USHRT_MAX;
 348                else
 349                        out.msg_qbytes  = in->msg_qbytes;
 350                out.msg_lqbytes         = in->msg_qbytes;
 351
 352                out.msg_lspid           = in->msg_lspid;
 353                out.msg_lrpid           = in->msg_lrpid;
 354
 355                return copy_to_user(buf, &out, sizeof(out));
 356        }
 357        default:
 358                return -EINVAL;
 359        }
 360}
 361
 362static inline unsigned long
 363copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
 364{
 365        switch(version) {
 366        case IPC_64:
 367                if (copy_from_user(out, buf, sizeof(*out)))
 368                        return -EFAULT;
 369                return 0;
 370        case IPC_OLD:
 371        {
 372                struct msqid_ds tbuf_old;
 373
 374                if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
 375                        return -EFAULT;
 376
 377                out->msg_perm.uid       = tbuf_old.msg_perm.uid;
 378                out->msg_perm.gid       = tbuf_old.msg_perm.gid;
 379                out->msg_perm.mode      = tbuf_old.msg_perm.mode;
 380
 381                if (tbuf_old.msg_qbytes == 0)
 382                        out->msg_qbytes = tbuf_old.msg_lqbytes;
 383                else
 384                        out->msg_qbytes = tbuf_old.msg_qbytes;
 385
 386                return 0;
 387        }
 388        default:
 389                return -EINVAL;
 390        }
 391}
 392
 393/*
 394 * This function handles some msgctl commands which require the rw_mutex
 395 * to be held in write mode.
 396 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
 397 */
 398static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 399                       struct msqid_ds __user *buf, int version)
 400{
 401        struct kern_ipc_perm *ipcp;
 402        struct msqid64_ds uninitialized_var(msqid64);
 403        struct msg_queue *msq;
 404        int err;
 405
 406        if (cmd == IPC_SET) {
 407                if (copy_msqid_from_user(&msqid64, buf, version))
 408                        return -EFAULT;
 409        }
 410
 411        ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,
 412                               &msqid64.msg_perm, msqid64.msg_qbytes);
 413        if (IS_ERR(ipcp))
 414                return PTR_ERR(ipcp);
 415
 416        msq = container_of(ipcp, struct msg_queue, q_perm);
 417
 418        err = security_msg_queue_msgctl(msq, cmd);
 419        if (err)
 420                goto out_unlock;
 421
 422        switch (cmd) {
 423        case IPC_RMID:
 424                freeque(ns, ipcp);
 425                goto out_up;
 426        case IPC_SET:
 427                if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
 428                    !capable(CAP_SYS_RESOURCE)) {
 429                        err = -EPERM;
 430                        goto out_unlock;
 431                }
 432
 433                err = ipc_update_perm(&msqid64.msg_perm, ipcp);
 434                if (err)
 435                        goto out_unlock;
 436
 437                msq->q_qbytes = msqid64.msg_qbytes;
 438
 439                msq->q_ctime = get_seconds();
 440                /* sleeping receivers might be excluded by
 441                 * stricter permissions.
 442                 */
 443                expunge_all(msq, -EAGAIN);
 444                /* sleeping senders might be able to send
 445                 * due to a larger queue size.
 446                 */
 447                ss_wakeup(&msq->q_senders, 0);
 448                break;
 449        default:
 450                err = -EINVAL;
 451        }
 452out_unlock:
 453        msg_unlock(msq);
 454out_up:
 455        up_write(&msg_ids(ns).rw_mutex);
 456        return err;
 457}
 458
 459SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
 460{
 461        struct msg_queue *msq;
 462        int err, version;
 463        struct ipc_namespace *ns;
 464
 465        if (msqid < 0 || cmd < 0)
 466                return -EINVAL;
 467
 468        version = ipc_parse_version(&cmd);
 469        ns = current->nsproxy->ipc_ns;
 470
 471        switch (cmd) {
 472        case IPC_INFO:
 473        case MSG_INFO:
 474        {
 475                struct msginfo msginfo;
 476                int max_id;
 477
 478                if (!buf)
 479                        return -EFAULT;
 480                /*
 481                 * We must not return kernel stack data.
 482                 * due to padding, it's not enough
 483                 * to set all member fields.
 484                 */
 485                err = security_msg_queue_msgctl(NULL, cmd);
 486                if (err)
 487                        return err;
 488
 489                memset(&msginfo, 0, sizeof(msginfo));
 490                msginfo.msgmni = ns->msg_ctlmni;
 491                msginfo.msgmax = ns->msg_ctlmax;
 492                msginfo.msgmnb = ns->msg_ctlmnb;
 493                msginfo.msgssz = MSGSSZ;
 494                msginfo.msgseg = MSGSEG;
 495                down_read(&msg_ids(ns).rw_mutex);
 496                if (cmd == MSG_INFO) {
 497                        msginfo.msgpool = msg_ids(ns).in_use;
 498                        msginfo.msgmap = atomic_read(&ns->msg_hdrs);
 499                        msginfo.msgtql = atomic_read(&ns->msg_bytes);
 500                } else {
 501                        msginfo.msgmap = MSGMAP;
 502                        msginfo.msgpool = MSGPOOL;
 503                        msginfo.msgtql = MSGTQL;
 504                }
 505                max_id = ipc_get_maxid(&msg_ids(ns));
 506                up_read(&msg_ids(ns).rw_mutex);
 507                if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
 508                        return -EFAULT;
 509                return (max_id < 0) ? 0 : max_id;
 510        }
 511        case MSG_STAT:  /* msqid is an index rather than a msg queue id */
 512        case IPC_STAT:
 513        {
 514                struct msqid64_ds tbuf;
 515                int success_return;
 516
 517                if (!buf)
 518                        return -EFAULT;
 519
 520                if (cmd == MSG_STAT) {
 521                        msq = msg_lock(ns, msqid);
 522                        if (IS_ERR(msq))
 523                                return PTR_ERR(msq);
 524                        success_return = msq->q_perm.id;
 525                } else {
 526                        msq = msg_lock_check(ns, msqid);
 527                        if (IS_ERR(msq))
 528                                return PTR_ERR(msq);
 529                        success_return = 0;
 530                }
 531                err = -EACCES;
 532                if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 533                        goto out_unlock;
 534
 535                err = security_msg_queue_msgctl(msq, cmd);
 536                if (err)
 537                        goto out_unlock;
 538
 539                memset(&tbuf, 0, sizeof(tbuf));
 540
 541                kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
 542                tbuf.msg_stime  = msq->q_stime;
 543                tbuf.msg_rtime  = msq->q_rtime;
 544                tbuf.msg_ctime  = msq->q_ctime;
 545                tbuf.msg_cbytes = msq->q_cbytes;
 546                tbuf.msg_qnum   = msq->q_qnum;
 547                tbuf.msg_qbytes = msq->q_qbytes;
 548                tbuf.msg_lspid  = msq->q_lspid;
 549                tbuf.msg_lrpid  = msq->q_lrpid;
 550                msg_unlock(msq);
 551                if (copy_msqid_to_user(buf, &tbuf, version))
 552                        return -EFAULT;
 553                return success_return;
 554        }
 555        case IPC_SET:
 556        case IPC_RMID:
 557                err = msgctl_down(ns, msqid, cmd, buf, version);
 558                return err;
 559        default:
 560                return  -EINVAL;
 561        }
 562
 563out_unlock:
 564        msg_unlock(msq);
 565        return err;
 566}
 567
 568static int testmsg(struct msg_msg *msg, long type, int mode)
 569{
 570        switch(mode)
 571        {
 572                case SEARCH_ANY:
 573                case SEARCH_NUMBER:
 574                        return 1;
 575                case SEARCH_LESSEQUAL:
 576                        if (msg->m_type <=type)
 577                                return 1;
 578                        break;
 579                case SEARCH_EQUAL:
 580                        if (msg->m_type == type)
 581                                return 1;
 582                        break;
 583                case SEARCH_NOTEQUAL:
 584                        if (msg->m_type != type)
 585                                return 1;
 586                        break;
 587        }
 588        return 0;
 589}
 590
 591static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
 592{
 593        struct msg_receiver *msr, *t;
 594
 595        list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
 596                if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
 597                    !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
 598                                               msr->r_msgtype, msr->r_mode)) {
 599
 600                        list_del(&msr->r_list);
 601                        if (msr->r_maxsize < msg->m_ts) {
 602                                msr->r_msg = NULL;
 603                                wake_up_process(msr->r_tsk);
 604                                smp_mb();
 605                                msr->r_msg = ERR_PTR(-E2BIG);
 606                        } else {
 607                                msr->r_msg = NULL;
 608                                msq->q_lrpid = task_pid_vnr(msr->r_tsk);
 609                                msq->q_rtime = get_seconds();
 610                                wake_up_process(msr->r_tsk);
 611                                smp_mb();
 612                                msr->r_msg = msg;
 613
 614                                return 1;
 615                        }
 616                }
 617        }
 618        return 0;
 619}
 620
 621long do_msgsnd(int msqid, long mtype, void __user *mtext,
 622                size_t msgsz, int msgflg)
 623{
 624        struct msg_queue *msq;
 625        struct msg_msg *msg;
 626        int err;
 627        struct ipc_namespace *ns;
 628
 629        ns = current->nsproxy->ipc_ns;
 630
 631        if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 632                return -EINVAL;
 633        if (mtype < 1)
 634                return -EINVAL;
 635
 636        msg = load_msg(mtext, msgsz);
 637        if (IS_ERR(msg))
 638                return PTR_ERR(msg);
 639
 640        msg->m_type = mtype;
 641        msg->m_ts = msgsz;
 642
 643        msq = msg_lock_check(ns, msqid);
 644        if (IS_ERR(msq)) {
 645                err = PTR_ERR(msq);
 646                goto out_free;
 647        }
 648
 649        for (;;) {
 650                struct msg_sender s;
 651
 652                err = -EACCES;
 653                if (ipcperms(ns, &msq->q_perm, S_IWUGO))
 654                        goto out_unlock_free;
 655
 656                err = security_msg_queue_msgsnd(msq, msg, msgflg);
 657                if (err)
 658                        goto out_unlock_free;
 659
 660                if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
 661                                1 + msq->q_qnum <= msq->q_qbytes) {
 662                        break;
 663                }
 664
 665                /* queue full, wait: */
 666                if (msgflg & IPC_NOWAIT) {
 667                        err = -EAGAIN;
 668                        goto out_unlock_free;
 669                }
 670                ss_add(msq, &s);
 671
 672                if (!ipc_rcu_getref(msq)) {
 673                        err = -EIDRM;
 674                        goto out_unlock_free;
 675                }
 676
 677                msg_unlock(msq);
 678                schedule();
 679
 680                ipc_lock_by_ptr(&msq->q_perm);
 681                ipc_rcu_putref(msq);
 682                if (msq->q_perm.deleted) {
 683                        err = -EIDRM;
 684                        goto out_unlock_free;
 685                }
 686                ss_del(&s);
 687
 688                if (signal_pending(current)) {
 689                        err = -ERESTARTNOHAND;
 690                        goto out_unlock_free;
 691                }
 692        }
 693
 694        msq->q_lspid = task_tgid_vnr(current);
 695        msq->q_stime = get_seconds();
 696
 697        if (!pipelined_send(msq, msg)) {
 698                /* no one is waiting for this message, enqueue it */
 699                list_add_tail(&msg->m_list, &msq->q_messages);
 700                msq->q_cbytes += msgsz;
 701                msq->q_qnum++;
 702                atomic_add(msgsz, &ns->msg_bytes);
 703                atomic_inc(&ns->msg_hdrs);
 704        }
 705
 706        err = 0;
 707        msg = NULL;
 708
 709out_unlock_free:
 710        msg_unlock(msq);
 711out_free:
 712        if (msg != NULL)
 713                free_msg(msg);
 714        return err;
 715}
 716
 717SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 718                int, msgflg)
 719{
 720        long mtype;
 721
 722        if (get_user(mtype, &msgp->mtype))
 723                return -EFAULT;
 724        return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
 725}
 726
 727static inline int convert_mode(long *msgtyp, int msgflg)
 728{
 729        if (msgflg & MSG_COPY)
 730                return SEARCH_NUMBER;
 731        /*
 732         *  find message of correct type.
 733         *  msgtyp = 0 => get first.
 734         *  msgtyp > 0 => get first message of matching type.
 735         *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 736         */
 737        if (*msgtyp == 0)
 738                return SEARCH_ANY;
 739        if (*msgtyp < 0) {
 740                *msgtyp = -*msgtyp;
 741                return SEARCH_LESSEQUAL;
 742        }
 743        if (msgflg & MSG_EXCEPT)
 744                return SEARCH_NOTEQUAL;
 745        return SEARCH_EQUAL;
 746}
 747
 748static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
 749{
 750        struct msgbuf __user *msgp = dest;
 751        size_t msgsz;
 752
 753        if (put_user(msg->m_type, &msgp->mtype))
 754                return -EFAULT;
 755
 756        msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
 757        if (store_msg(msgp->mtext, msg, msgsz))
 758                return -EFAULT;
 759        return msgsz;
 760}
 761
 762#ifdef CONFIG_CHECKPOINT_RESTORE
 763/*
 764 * This function creates new kernel message structure, large enough to store
 765 * bufsz message bytes.
 766 */
 767static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 768{
 769        struct msg_msg *copy;
 770
 771        /*
 772         * Create dummy message to copy real message to.
 773         */
 774        copy = load_msg(buf, bufsz);
 775        if (!IS_ERR(copy))
 776                copy->m_ts = bufsz;
 777        return copy;
 778}
 779
 780static inline void free_copy(struct msg_msg *copy)
 781{
 782        if (copy)
 783                free_msg(copy);
 784}
 785#else
 786static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 787{
 788        return ERR_PTR(-ENOSYS);
 789}
 790
 791static inline void free_copy(struct msg_msg *copy)
 792{
 793}
 794#endif
 795
 796static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
 797{
 798        struct msg_msg *msg;
 799        long count = 0;
 800
 801        list_for_each_entry(msg, &msq->q_messages, m_list) {
 802                if (testmsg(msg, *msgtyp, mode) &&
 803                    !security_msg_queue_msgrcv(msq, msg, current,
 804                                               *msgtyp, mode)) {
 805                        if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
 806                                *msgtyp = msg->m_type - 1;
 807                        } else if (mode == SEARCH_NUMBER) {
 808                                if (*msgtyp == count)
 809                                        return msg;
 810                        } else
 811                                return msg;
 812                        count++;
 813                }
 814        }
 815
 816        return ERR_PTR(-EAGAIN);
 817}
 818
 819
 820long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
 821               int msgflg,
 822               long (*msg_handler)(void __user *, struct msg_msg *, size_t))
 823{
 824        struct msg_queue *msq;
 825        struct msg_msg *msg;
 826        int mode;
 827        struct ipc_namespace *ns;
 828        struct msg_msg *copy = NULL;
 829
 830        ns = current->nsproxy->ipc_ns;
 831
 832        if (msqid < 0 || (long) bufsz < 0)
 833                return -EINVAL;
 834        if (msgflg & MSG_COPY) {
 835                copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
 836                if (IS_ERR(copy))
 837                        return PTR_ERR(copy);
 838        }
 839        mode = convert_mode(&msgtyp, msgflg);
 840
 841        msq = msg_lock_check(ns, msqid);
 842        if (IS_ERR(msq)) {
 843                free_copy(copy);
 844                return PTR_ERR(msq);
 845        }
 846
 847        for (;;) {
 848                struct msg_receiver msr_d;
 849
 850                msg = ERR_PTR(-EACCES);
 851                if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 852                        goto out_unlock;
 853
 854                msg = find_msg(msq, &msgtyp, mode);
 855
 856                if (!IS_ERR(msg)) {
 857                        /*
 858                         * Found a suitable message.
 859                         * Unlink it from the queue.
 860                         */
 861                        if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 862                                msg = ERR_PTR(-E2BIG);
 863                                goto out_unlock;
 864                        }
 865                        /*
 866                         * If we are copying, then do not unlink message and do
 867                         * not update queue parameters.
 868                         */
 869                        if (msgflg & MSG_COPY) {
 870                                msg = copy_msg(msg, copy);
 871                                goto out_unlock;
 872                        }
 873                        list_del(&msg->m_list);
 874                        msq->q_qnum--;
 875                        msq->q_rtime = get_seconds();
 876                        msq->q_lrpid = task_tgid_vnr(current);
 877                        msq->q_cbytes -= msg->m_ts;
 878                        atomic_sub(msg->m_ts, &ns->msg_bytes);
 879                        atomic_dec(&ns->msg_hdrs);
 880                        ss_wakeup(&msq->q_senders, 0);
 881                        msg_unlock(msq);
 882                        break;
 883                }
 884                /* No message waiting. Wait for a message */
 885                if (msgflg & IPC_NOWAIT) {
 886                        msg = ERR_PTR(-ENOMSG);
 887                        goto out_unlock;
 888                }
 889                list_add_tail(&msr_d.r_list, &msq->q_receivers);
 890                msr_d.r_tsk = current;
 891                msr_d.r_msgtype = msgtyp;
 892                msr_d.r_mode = mode;
 893                if (msgflg & MSG_NOERROR)
 894                        msr_d.r_maxsize = INT_MAX;
 895                else
 896                        msr_d.r_maxsize = bufsz;
 897                msr_d.r_msg = ERR_PTR(-EAGAIN);
 898                current->state = TASK_INTERRUPTIBLE;
 899                msg_unlock(msq);
 900
 901                schedule();
 902
 903                /* Lockless receive, part 1:
 904                 * Disable preemption.  We don't hold a reference to the queue
 905                 * and getting a reference would defeat the idea of a lockless
 906                 * operation, thus the code relies on rcu to guarantee the
 907                 * existence of msq:
 908                 * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 909                 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 910                 * rcu_read_lock() prevents preemption between reading r_msg
 911                 * and the spin_lock() inside ipc_lock_by_ptr().
 912                 */
 913                rcu_read_lock();
 914
 915                /* Lockless receive, part 2:
 916                 * Wait until pipelined_send or expunge_all are outside of
 917                 * wake_up_process(). There is a race with exit(), see
 918                 * ipc/mqueue.c for the details.
 919                 */
 920                msg = (struct msg_msg*)msr_d.r_msg;
 921                while (msg == NULL) {
 922                        cpu_relax();
 923                        msg = (struct msg_msg *)msr_d.r_msg;
 924                }
 925
 926                /* Lockless receive, part 3:
 927                 * If there is a message or an error then accept it without
 928                 * locking.
 929                 */
 930                if (msg != ERR_PTR(-EAGAIN)) {
 931                        rcu_read_unlock();
 932                        break;
 933                }
 934
 935                /* Lockless receive, part 3:
 936                 * Acquire the queue spinlock.
 937                 */
 938                ipc_lock_by_ptr(&msq->q_perm);
 939                rcu_read_unlock();
 940
 941                /* Lockless receive, part 4:
 942                 * Repeat test after acquiring the spinlock.
 943                 */
 944                msg = (struct msg_msg*)msr_d.r_msg;
 945                if (msg != ERR_PTR(-EAGAIN))
 946                        goto out_unlock;
 947
 948                list_del(&msr_d.r_list);
 949                if (signal_pending(current)) {
 950                        msg = ERR_PTR(-ERESTARTNOHAND);
 951out_unlock:
 952                        msg_unlock(msq);
 953                        break;
 954                }
 955        }
 956        if (IS_ERR(msg)) {
 957                free_copy(copy);
 958                return PTR_ERR(msg);
 959        }
 960
 961        bufsz = msg_handler(buf, msg, bufsz);
 962        free_msg(msg);
 963
 964        return bufsz;
 965}
 966
 967SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 968                long, msgtyp, int, msgflg)
 969{
 970        return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
 971}
 972
 973#ifdef CONFIG_PROC_FS
 974static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
 975{
 976        struct user_namespace *user_ns = seq_user_ns(s);
 977        struct msg_queue *msq = it;
 978
 979        return seq_printf(s,
 980                        "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
 981                        msq->q_perm.key,
 982                        msq->q_perm.id,
 983                        msq->q_perm.mode,
 984                        msq->q_cbytes,
 985                        msq->q_qnum,
 986                        msq->q_lspid,
 987                        msq->q_lrpid,
 988                        from_kuid_munged(user_ns, msq->q_perm.uid),
 989                        from_kgid_munged(user_ns, msq->q_perm.gid),
 990                        from_kuid_munged(user_ns, msq->q_perm.cuid),
 991                        from_kgid_munged(user_ns, msq->q_perm.cgid),
 992                        msq->q_stime,
 993                        msq->q_rtime,
 994                        msq->q_ctime);
 995}
 996#endif
 997
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