ipc/msg.c

   1 /*
   2  * linux/ipc/msg.c
   3  * Copyright (C) 1992 Krishna Balasubramanian
   4  *
   5  * Removed all the remaining kerneld mess
   6  * Catch the -EFAULT stuff properly
   7  * Use GFP_KERNEL for messages as in 1.2
   8  * Fixed up the unchecked user space derefs
   9  * Copyright (C) 1998 Alan Cox & Andi Kleen
  10  *
  11  * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
  12  *
  13  * mostly rewritten, threaded and wake-one semantics added
  14  * MSGMAX limit removed, sysctl's added
  15  * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
  16  *
  17  * support for audit of ipc object properties and permission changes
  18  * Dustin Kirkland <dustin.kirkland@us.ibm.com>
  19  *
  20  * namespaces support
  21  * OpenVZ, SWsoft Inc.
  22  * Pavel Emelianov <xemul@openvz.org>
  23  */
  24
  25 #include <linux/capability.h>
  26 #include <linux/slab.h>
  27 #include <linux/msg.h>
  28 #include <linux/spinlock.h>
  29 #include <linux/init.h>
  30 #include <linux/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  */
  48 struct 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 */
  60 struct 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 #define msg_buildid(id, seq)    ipc_buildid(id, seq)
  74
  75 static void freeque(struct ipc_namespace *, struct kern_ipc_perm *);
  76 static int newque(struct ipc_namespace *, struct ipc_params *);
  77 #ifdef CONFIG_PROC_FS
  78 static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
  79 #endif
  80
  81 void msg_init_ns(struct ipc_namespace *ns)
  82 {
  83         ns->msg_ctlmax = MSGMAX;
  84         ns->msg_ctlmnb = MSGMNB;
  85         ns->msg_ctlmni = MSGMNI;
  86         atomic_set(&ns->msg_bytes, 0);
  87         atomic_set(&ns->msg_hdrs, 0);
  88         ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
  89 }
  90
  91 #ifdef CONFIG_IPC_NS
  92 void msg_exit_ns(struct ipc_namespace *ns)
  93 {
  94         free_ipcs(ns, &msg_ids(ns), freeque);
  95 }
  96 #endif
  97
  98 void __init msg_init(void)
  99 {
 100         msg_init_ns(&init_ipc_ns);
 101         ipc_init_proc_interface("sysvipc/msg",
 102                                 "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
 103                                 IPC_MSG_IDS, sysvipc_msg_proc_show);
 104 }
 105
 106 /*
 107  * This routine is called in the paths where the rw_mutex is held to protect
 108  * access to the idr tree.
 109  */
 110 static inline struct msg_queue *msg_lock_check_down(struct ipc_namespace *ns,
 111                                                 int id)
 112 {
 113         struct kern_ipc_perm *ipcp = ipc_lock_check_down(&msg_ids(ns), id);
 114
 115         if (IS_ERR(ipcp))
 116                 return (struct msg_queue *)ipcp;
 117
 118         return container_of(ipcp, struct msg_queue, q_perm);
 119 }
 120
 121 /*
 122  * msg_lock_(check_) routines are called in the paths where the rw_mutex
 123  * is not held.
 124  */
 125 static inline struct msg_queue *msg_lock(struct ipc_namespace *ns, int id)
 126 {
 127         struct kern_ipc_perm *ipcp = ipc_lock(&msg_ids(ns), id);
 128
 129         if (IS_ERR(ipcp))
 130                 return (struct msg_queue *)ipcp;
 131
 132         return container_of(ipcp, struct msg_queue, q_perm);
 133 }
 134
 135 static inline struct msg_queue *msg_lock_check(struct ipc_namespace *ns,
 136                                                 int id)
 137 {
 138         struct kern_ipc_perm *ipcp = ipc_lock_check(&msg_ids(ns), id);
 139
 140         if (IS_ERR(ipcp))
 141                 return (struct msg_queue *)ipcp;
 142
 143         return container_of(ipcp, struct msg_queue, q_perm);
 144 }
 145
 146 static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
 147 {
 148         ipc_rmid(&msg_ids(ns), &s->q_perm);
 149 }
 150
 151 /**
 152  * newque - Create a new msg queue
 153  * @ns: namespace
 154  * @params: ptr to the structure that contains the key and msgflg
 155  *
 156  * Called with msg_ids.rw_mutex held (writer)
 157  */
 158 static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 159 {
 160         struct msg_queue *msq;
 161         int id, retval;
 162         key_t key = params->key;
 163         int msgflg = params->flg;
 164
 165         msq = ipc_rcu_alloc(sizeof(*msq));
 166         if (!msq)
 167                 return -ENOMEM;
 168
 169         msq->q_perm.mode = msgflg & S_IRWXUGO;
 170         msq->q_perm.key = key;
 171
 172         msq->q_perm.security = NULL;
 173         retval = security_msg_queue_alloc(msq);
 174         if (retval) {
 175                 ipc_rcu_putref(msq);
 176                 return retval;
 177         }
 178
 179         /*
 180          * ipc_addid() locks msq
 181          */
 182         id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
 183         if (id < 0) {
 184                 security_msg_queue_free(msq);
 185                 ipc_rcu_putref(msq);
 186                 return id;
 187         }
 188
 189         msq->q_perm.id = msg_buildid(id, msq->q_perm.seq);
 190         msq->q_stime = msq->q_rtime = 0;
 191         msq->q_ctime = get_seconds();
 192         msq->q_cbytes = msq->q_qnum = 0;
 193         msq->q_qbytes = ns->msg_ctlmnb;
 194         msq->q_lspid = msq->q_lrpid = 0;
 195         INIT_LIST_HEAD(&msq->q_messages);
 196         INIT_LIST_HEAD(&msq->q_receivers);
 197         INIT_LIST_HEAD(&msq->q_senders);
 198
 199         msg_unlock(msq);
 200
 201         return msq->q_perm.id;
 202 }
 203
 204 static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
 205 {
 206         mss->tsk = current;
 207         current->state = TASK_INTERRUPTIBLE;
 208         list_add_tail(&mss->list, &msq->q_senders);
 209 }
 210
 211 static inline void ss_del(struct msg_sender *mss)
 212 {
 213         if (mss->list.next != NULL)
 214                 list_del(&mss->list);
 215 }
 216
 217 static void ss_wakeup(struct list_head *h, int kill)
 218 {
 219         struct list_head *tmp;
 220
 221         tmp = h->next;
 222         while (tmp != h) {
 223                 struct msg_sender *mss;
 224
 225                 mss = list_entry(tmp, struct msg_sender, list);
 226                 tmp = tmp->next;
 227                 if (kill)
 228                         mss->list.next = NULL;
 229                 wake_up_process(mss->tsk);
 230         }
 231 }
 232
 233 static void expunge_all(struct msg_queue *msq, int res)
 234 {
 235         struct list_head *tmp;
 236
 237         tmp = msq->q_receivers.next;
 238         while (tmp != &msq->q_receivers) {
 239                 struct msg_receiver *msr;
 240
 241                 msr = list_entry(tmp, struct msg_receiver, r_list);
 242                 tmp = tmp->next;
 243                 msr->r_msg = NULL;
 244                 wake_up_process(msr->r_tsk);
 245                 smp_mb();
 246                 msr->r_msg = ERR_PTR(res);
 247         }
 248 }
 249
 250 /*
 251  * freeque() wakes up waiters on the sender and receiver waiting queue,
 252  * removes the message queue from message queue ID IDR, and cleans up all the
 253  * messages associated with this queue.
 254  *
 255  * msg_ids.rw_mutex (writer) and the spinlock for this message queue are held
 256  * before freeque() is called. msg_ids.rw_mutex remains locked on exit.
 257  */
 258 static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 259 {
 260         struct list_head *tmp;
 261         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 262
 263         expunge_all(msq, -EIDRM);
 264         ss_wakeup(&msq->q_senders, 1);
 265         msg_rmid(ns, msq);
 266         msg_unlock(msq);
 267
 268         tmp = msq->q_messages.next;
 269         while (tmp != &msq->q_messages) {
 270                 struct msg_msg *msg = list_entry(tmp, struct msg_msg, m_list);
 271
 272                 tmp = tmp->next;
 273                 atomic_dec(&ns->msg_hdrs);
 274                 free_msg(msg);
 275         }
 276         atomic_sub(msq->q_cbytes, &ns->msg_bytes);
 277         security_msg_queue_free(msq);
 278         ipc_rcu_putref(msq);
 279 }
 280
 281 /*
 282  * Called with msg_ids.rw_mutex and ipcp locked.
 283  */
 284 static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
 285 {
 286         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 287
 288         return security_msg_queue_associate(msq, msgflg);
 289 }
 290
 291 asmlinkage long sys_msgget(key_t key, int msgflg)
 292 {
 293         struct ipc_namespace *ns;
 294         struct ipc_ops msg_ops;
 295         struct ipc_params msg_params;
 296
 297         ns = current->nsproxy->ipc_ns;
 298
 299         msg_ops.getnew = newque;
 300         msg_ops.associate = msg_security;
 301         msg_ops.more_checks = NULL;
 302
 303         msg_params.key = key;
 304         msg_params.flg = msgflg;
 305
 306         return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
 307 }
 308
 309 static inline unsigned long
 310 copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 311 {
 312         switch(version) {
 313         case IPC_64:
 314                 return copy_to_user(buf, in, sizeof(*in));
 315         case IPC_OLD:
 316         {
 317                 struct msqid_ds out;
 318
 319                 memset(&out, 0, sizeof(out));
 320
 321                 ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
 322
 323                 out.msg_stime           = in->msg_stime;
 324                 out.msg_rtime           = in->msg_rtime;
 325                 out.msg_ctime           = in->msg_ctime;
 326
 327                 if (in->msg_cbytes > USHRT_MAX)
 328                         out.msg_cbytes  = USHRT_MAX;
 329                 else
 330                         out.msg_cbytes  = in->msg_cbytes;
 331                 out.msg_lcbytes         = in->msg_cbytes;
 332
 333                 if (in->msg_qnum > USHRT_MAX)
 334                         out.msg_qnum    = USHRT_MAX;
 335                 else
 336                         out.msg_qnum    = in->msg_qnum;
 337
 338                 if (in->msg_qbytes > USHRT_MAX)
 339                         out.msg_qbytes  = USHRT_MAX;
 340                 else
 341                         out.msg_qbytes  = in->msg_qbytes;
 342                 out.msg_lqbytes         = in->msg_qbytes;
 343
 344                 out.msg_lspid           = in->msg_lspid;
 345                 out.msg_lrpid           = in->msg_lrpid;
 346
 347                 return copy_to_user(buf, &out, sizeof(out));
 348         }
 349         default:
 350                 return -EINVAL;
 351         }
 352 }
 353
 354 struct msq_setbuf {
 355         unsigned long   qbytes;
 356         uid_t           uid;
 357         gid_t           gid;
 358         mode_t          mode;
 359 };
 360
 361 static inline unsigned long
 362 copy_msqid_from_user(struct msq_setbuf *out, void __user *buf, int version)
 363 {
 364         switch(version) {
 365         case IPC_64:
 366         {
 367                 struct msqid64_ds tbuf;
 368
 369                 if (copy_from_user(&tbuf, buf, sizeof(tbuf)))
 370                         return -EFAULT;
 371
 372                 out->qbytes             = tbuf.msg_qbytes;
 373                 out->uid                = tbuf.msg_perm.uid;
 374                 out->gid                = tbuf.msg_perm.gid;
 375                 out->mode               = tbuf.msg_perm.mode;
 376
 377                 return 0;
 378         }
 379         case IPC_OLD:
 380         {
 381                 struct msqid_ds tbuf_old;
 382
 383                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
 384                         return -EFAULT;
 385
 386                 out->uid                = tbuf_old.msg_perm.uid;
 387                 out->gid                = tbuf_old.msg_perm.gid;
 388                 out->mode               = tbuf_old.msg_perm.mode;
 389
 390                 if (tbuf_old.msg_qbytes == 0)
 391                         out->qbytes     = tbuf_old.msg_lqbytes;
 392                 else
 393                         out->qbytes     = tbuf_old.msg_qbytes;
 394
 395                 return 0;
 396         }
 397         default:
 398                 return -EINVAL;
 399         }
 400 }
 401
 402 asmlinkage long sys_msgctl(int msqid, int cmd, struct msqid_ds __user *buf)
 403 {
 404         struct kern_ipc_perm *ipcp;
 405         struct msq_setbuf uninitialized_var(setbuf);
 406         struct msg_queue *msq;
 407         int err, version;
 408         struct ipc_namespace *ns;
 409
 410         if (msqid < 0 || cmd < 0)
 411                 return -EINVAL;
 412
 413         version = ipc_parse_version(&cmd);
 414         ns = current->nsproxy->ipc_ns;
 415
 416         switch (cmd) {
 417         case IPC_INFO:
 418         case MSG_INFO:
 419         {
 420                 struct msginfo msginfo;
 421                 int max_id;
 422
 423                 if (!buf)
 424                         return -EFAULT;
 425                 /*
 426                  * We must not return kernel stack data.
 427                  * due to padding, it's not enough
 428                  * to set all member fields.
 429                  */
 430                 err = security_msg_queue_msgctl(NULL, cmd);
 431                 if (err)
 432                         return err;
 433
 434                 memset(&msginfo, 0, sizeof(msginfo));
 435                 msginfo.msgmni = ns->msg_ctlmni;
 436                 msginfo.msgmax = ns->msg_ctlmax;
 437                 msginfo.msgmnb = ns->msg_ctlmnb;
 438                 msginfo.msgssz = MSGSSZ;
 439                 msginfo.msgseg = MSGSEG;
 440                 down_read(&msg_ids(ns).rw_mutex);
 441                 if (cmd == MSG_INFO) {
 442                         msginfo.msgpool = msg_ids(ns).in_use;
 443                         msginfo.msgmap = atomic_read(&ns->msg_hdrs);
 444                         msginfo.msgtql = atomic_read(&ns->msg_bytes);
 445                 } else {
 446                         msginfo.msgmap = MSGMAP;
 447                         msginfo.msgpool = MSGPOOL;
 448                         msginfo.msgtql = MSGTQL;
 449                 }
 450                 max_id = ipc_get_maxid(&msg_ids(ns));
 451                 up_read(&msg_ids(ns).rw_mutex);
 452                 if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
 453                         return -EFAULT;
 454                 return (max_id < 0) ? 0 : max_id;
 455         }
 456         case MSG_STAT:  /* msqid is an index rather than a msg queue id */
 457         case IPC_STAT:
 458         {
 459                 struct msqid64_ds tbuf;
 460                 int success_return;
 461
 462                 if (!buf)
 463                         return -EFAULT;
 464
 465                 if (cmd == MSG_STAT) {
 466                         msq = msg_lock(ns, msqid);
 467                         if (IS_ERR(msq))
 468                                 return PTR_ERR(msq);
 469                         success_return = msq->q_perm.id;
 470                 } else {
 471                         msq = msg_lock_check(ns, msqid);
 472                         if (IS_ERR(msq))
 473                                 return PTR_ERR(msq);
 474                         success_return = 0;
 475                 }
 476                 err = -EACCES;
 477                 if (ipcperms(&msq->q_perm, S_IRUGO))
 478                         goto out_unlock;
 479
 480                 err = security_msg_queue_msgctl(msq, cmd);
 481                 if (err)
 482                         goto out_unlock;
 483
 484                 memset(&tbuf, 0, sizeof(tbuf));
 485
 486                 kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
 487                 tbuf.msg_stime  = msq->q_stime;
 488                 tbuf.msg_rtime  = msq->q_rtime;
 489                 tbuf.msg_ctime  = msq->q_ctime;
 490                 tbuf.msg_cbytes = msq->q_cbytes;
 491                 tbuf.msg_qnum   = msq->q_qnum;
 492                 tbuf.msg_qbytes = msq->q_qbytes;
 493                 tbuf.msg_lspid  = msq->q_lspid;
 494                 tbuf.msg_lrpid  = msq->q_lrpid;
 495                 msg_unlock(msq);
 496                 if (copy_msqid_to_user(buf, &tbuf, version))
 497                         return -EFAULT;
 498                 return success_return;
 499         }
 500         case IPC_SET:
 501                 if (!buf)
 502                         return -EFAULT;
 503                 if (copy_msqid_from_user(&setbuf, buf, version))
 504                         return -EFAULT;
 505                 break;
 506         case IPC_RMID:
 507                 break;
 508         default:
 509                 return  -EINVAL;
 510         }
 511
 512         down_write(&msg_ids(ns).rw_mutex);
 513         msq = msg_lock_check_down(ns, msqid);
 514         if (IS_ERR(msq)) {
 515                 err = PTR_ERR(msq);
 516                 goto out_up;
 517         }
 518
 519         ipcp = &msq->q_perm;
 520
 521         err = audit_ipc_obj(ipcp);
 522         if (err)
 523                 goto out_unlock_up;
 524         if (cmd == IPC_SET) {
 525                 err = audit_ipc_set_perm(setbuf.qbytes, setbuf.uid, setbuf.gid,
 526                                          setbuf.mode);
 527                 if (err)
 528                         goto out_unlock_up;
 529         }
 530
 531         err = -EPERM;
 532         if (current->euid != ipcp->cuid &&
 533             current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN))
 534                 /* We _could_ check for CAP_CHOWN above, but we don't */
 535                 goto out_unlock_up;
 536
 537         err = security_msg_queue_msgctl(msq, cmd);
 538         if (err)
 539                 goto out_unlock_up;
 540
 541         switch (cmd) {
 542         case IPC_SET:
 543         {
 544                 err = -EPERM;
 545                 if (setbuf.qbytes > ns->msg_ctlmnb && !capable(CAP_SYS_RESOURCE))
 546                         goto out_unlock_up;
 547
 548                 msq->q_qbytes = setbuf.qbytes;
 549
 550                 ipcp->uid = setbuf.uid;
 551                 ipcp->gid = setbuf.gid;
 552                 ipcp->mode = (ipcp->mode & ~S_IRWXUGO) |
 553                              (S_IRWXUGO & setbuf.mode);
 554                 msq->q_ctime = get_seconds();
 555                 /* sleeping receivers might be excluded by
 556                  * stricter permissions.
 557                  */
 558                 expunge_all(msq, -EAGAIN);
 559                 /* sleeping senders might be able to send
 560                  * due to a larger queue size.
 561                  */
 562                 ss_wakeup(&msq->q_senders, 0);
 563                 msg_unlock(msq);
 564                 break;
 565         }
 566         case IPC_RMID:
 567                 freeque(ns, &msq->q_perm);
 568                 break;
 569         }
 570         err = 0;
 571 out_up:
 572         up_write(&msg_ids(ns).rw_mutex);
 573         return err;
 574 out_unlock_up:
 575         msg_unlock(msq);
 576         goto out_up;
 577 out_unlock:
 578         msg_unlock(msq);
 579         return err;
 580 }
 581
 582 static int testmsg(struct msg_msg *msg, long type, int mode)
 583 {
 584         switch(mode)
 585         {
 586                 case SEARCH_ANY:
 587                         return 1;
 588                 case SEARCH_LESSEQUAL:
 589                         if (msg->m_type <=type)
 590                                 return 1;
 591                         break;
 592                 case SEARCH_EQUAL:
 593                         if (msg->m_type == type)
 594                                 return 1;
 595                         break;
 596                 case SEARCH_NOTEQUAL:
 597                         if (msg->m_type != type)
 598                                 return 1;
 599                         break;
 600         }
 601         return 0;
 602 }
 603
 604 static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
 605 {
 606         struct list_head *tmp;
 607
 608         tmp = msq->q_receivers.next;
 609         while (tmp != &msq->q_receivers) {
 610                 struct msg_receiver *msr;
 611
 612                 msr = list_entry(tmp, struct msg_receiver, r_list);
 613                 tmp = tmp->next;
 614                 if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
 615                     !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
 616                                                msr->r_msgtype, msr->r_mode)) {
 617
 618                         list_del(&msr->r_list);
 619                         if (msr->r_maxsize < msg->m_ts) {
 620                                 msr->r_msg = NULL;
 621                                 wake_up_process(msr->r_tsk);
 622                                 smp_mb();
 623                                 msr->r_msg = ERR_PTR(-E2BIG);
 624                         } else {
 625                                 msr->r_msg = NULL;
 626                                 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
 627                                 msq->q_rtime = get_seconds();
 628                                 wake_up_process(msr->r_tsk);
 629                                 smp_mb();
 630                                 msr->r_msg = msg;
 631
 632                                 return 1;
 633                         }
 634                 }
 635         }
 636         return 0;
 637 }
 638
 639 long do_msgsnd(int msqid, long mtype, void __user *mtext,
 640                 size_t msgsz, int msgflg)
 641 {
 642         struct msg_queue *msq;
 643         struct msg_msg *msg;
 644         int err;
 645         struct ipc_namespace *ns;
 646
 647         ns = current->nsproxy->ipc_ns;
 648
 649         if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 650                 return -EINVAL;
 651         if (mtype < 1)
 652                 return -EINVAL;
 653
 654         msg = load_msg(mtext, msgsz);
 655         if (IS_ERR(msg))
 656                 return PTR_ERR(msg);
 657
 658         msg->m_type = mtype;
 659         msg->m_ts = msgsz;
 660
 661         msq = msg_lock_check(ns, msqid);
 662         if (IS_ERR(msq)) {
 663                 err = PTR_ERR(msq);
 664                 goto out_free;
 665         }
 666
 667         for (;;) {
 668                 struct msg_sender s;
 669
 670                 err = -EACCES;
 671                 if (ipcperms(&msq->q_perm, S_IWUGO))
 672                         goto out_unlock_free;
 673
 674                 err = security_msg_queue_msgsnd(msq, msg, msgflg);
 675                 if (err)
 676                         goto out_unlock_free;
 677
 678                 if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
 679                                 1 + msq->q_qnum <= msq->q_qbytes) {
 680                         break;
 681                 }
 682
 683                 /* queue full, wait: */
 684                 if (msgflg & IPC_NOWAIT) {
 685                         err = -EAGAIN;
 686                         goto out_unlock_free;
 687                 }
 688                 ss_add(msq, &s);
 689                 ipc_rcu_getref(msq);
 690                 msg_unlock(msq);
 691                 schedule();
 692
 693                 ipc_lock_by_ptr(&msq->q_perm);
 694                 ipc_rcu_putref(msq);
 695                 if (msq->q_perm.deleted) {
 696                         err = -EIDRM;
 697                         goto out_unlock_free;
 698                 }
 699                 ss_del(&s);
 700
 701                 if (signal_pending(current)) {
 702                         err = -ERESTARTNOHAND;
 703                         goto out_unlock_free;
 704                 }
 705         }
 706
 707         msq->q_lspid = task_tgid_vnr(current);
 708         msq->q_stime = get_seconds();
 709
 710         if (!pipelined_send(msq, msg)) {
 711                 /* noone is waiting for this message, enqueue it */
 712                 list_add_tail(&msg->m_list, &msq->q_messages);
 713                 msq->q_cbytes += msgsz;
 714                 msq->q_qnum++;
 715                 atomic_add(msgsz, &ns->msg_bytes);
 716                 atomic_inc(&ns->msg_hdrs);
 717         }
 718
 719         err = 0;
 720         msg = NULL;
 721
 722 out_unlock_free:
 723         msg_unlock(msq);
 724 out_free:
 725         if (msg != NULL)
 726                 free_msg(msg);
 727         return err;
 728 }
 729
 730 asmlinkage long
 731 sys_msgsnd(int msqid, struct msgbuf __user *msgp, size_t msgsz, int msgflg)
 732 {
 733         long mtype;
 734
 735         if (get_user(mtype, &msgp->mtype))
 736                 return -EFAULT;
 737         return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
 738 }
 739
 740 static inline int convert_mode(long *msgtyp, int msgflg)
 741 {
 742         /*
 743          *  find message of correct type.
 744          *  msgtyp = 0 => get first.
 745          *  msgtyp > 0 => get first message of matching type.
 746          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 747          */
 748         if (*msgtyp == 0)
 749                 return SEARCH_ANY;
 750         if (*msgtyp < 0) {
 751                 *msgtyp = -*msgtyp;
 752                 return SEARCH_LESSEQUAL;
 753         }
 754         if (msgflg & MSG_EXCEPT)
 755                 return SEARCH_NOTEQUAL;
 756         return SEARCH_EQUAL;
 757 }
 758
 759 long do_msgrcv(int msqid, long *pmtype, void __user *mtext,
 760                 size_t msgsz, long msgtyp, int msgflg)
 761 {
 762         struct msg_queue *msq;
 763         struct msg_msg *msg;
 764         int mode;
 765         struct ipc_namespace *ns;
 766
 767         if (msqid < 0 || (long) msgsz < 0)
 768                 return -EINVAL;
 769         mode = convert_mode(&msgtyp, msgflg);
 770         ns = current->nsproxy->ipc_ns;
 771
 772         msq = msg_lock_check(ns, msqid);
 773         if (IS_ERR(msq))
 774                 return PTR_ERR(msq);
 775
 776         for (;;) {
 777                 struct msg_receiver msr_d;
 778                 struct list_head *tmp;
 779
 780                 msg = ERR_PTR(-EACCES);
 781                 if (ipcperms(&msq->q_perm, S_IRUGO))
 782                         goto out_unlock;
 783
 784                 msg = ERR_PTR(-EAGAIN);
 785                 tmp = msq->q_messages.next;
 786                 while (tmp != &msq->q_messages) {
 787                         struct msg_msg *walk_msg;
 788
 789                         walk_msg = list_entry(tmp, struct msg_msg, m_list);
 790                         if (testmsg(walk_msg, msgtyp, mode) &&
 791                             !security_msg_queue_msgrcv(msq, walk_msg, current,
 792                                                        msgtyp, mode)) {
 793
 794                                 msg = walk_msg;
 795                                 if (mode == SEARCH_LESSEQUAL &&
 796                                                 walk_msg->m_type != 1) {
 797                                         msg = walk_msg;
 798                                         msgtyp = walk_msg->m_type - 1;
 799                                 } else {
 800                                         msg = walk_msg;
 801                                         break;
 802                                 }
 803                         }
 804                         tmp = tmp->next;
 805                 }
 806                 if (!IS_ERR(msg)) {
 807                         /*
 808                          * Found a suitable message.
 809                          * Unlink it from the queue.
 810                          */
 811                         if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 812                                 msg = ERR_PTR(-E2BIG);
 813                                 goto out_unlock;
 814                         }
 815                         list_del(&msg->m_list);
 816                         msq->q_qnum--;
 817                         msq->q_rtime = get_seconds();
 818                         msq->q_lrpid = task_tgid_vnr(current);
 819                         msq->q_cbytes -= msg->m_ts;
 820                         atomic_sub(msg->m_ts, &ns->msg_bytes);
 821                         atomic_dec(&ns->msg_hdrs);
 822                         ss_wakeup(&msq->q_senders, 0);
 823                         msg_unlock(msq);
 824                         break;
 825                 }
 826                 /* No message waiting. Wait for a message */
 827                 if (msgflg & IPC_NOWAIT) {
 828                         msg = ERR_PTR(-ENOMSG);
 829                         goto out_unlock;
 830                 }
 831                 list_add_tail(&msr_d.r_list, &msq->q_receivers);
 832                 msr_d.r_tsk = current;
 833                 msr_d.r_msgtype = msgtyp;
 834                 msr_d.r_mode = mode;
 835                 if (msgflg & MSG_NOERROR)
 836                         msr_d.r_maxsize = INT_MAX;
 837                 else
 838                         msr_d.r_maxsize = msgsz;
 839                 msr_d.r_msg = ERR_PTR(-EAGAIN);
 840                 current->state = TASK_INTERRUPTIBLE;
 841                 msg_unlock(msq);
 842
 843                 schedule();
 844
 845                 /* Lockless receive, part 1:
 846                  * Disable preemption.  We don't hold a reference to the queue
 847                  * and getting a reference would defeat the idea of a lockless
 848                  * operation, thus the code relies on rcu to guarantee the
 849                  * existance of msq:
 850                  * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 851                  * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 852                  * rcu_read_lock() prevents preemption between reading r_msg
 853                  * and the spin_lock() inside ipc_lock_by_ptr().
 854                  */
 855                 rcu_read_lock();
 856
 857                 /* Lockless receive, part 2:
 858                  * Wait until pipelined_send or expunge_all are outside of
 859                  * wake_up_process(). There is a race with exit(), see
 860                  * ipc/mqueue.c for the details.
 861                  */
 862                 msg = (struct msg_msg*)msr_d.r_msg;
 863                 while (msg == NULL) {
 864                         cpu_relax();
 865                         msg = (struct msg_msg *)msr_d.r_msg;
 866                 }
 867
 868                 /* Lockless receive, part 3:
 869                  * If there is a message or an error then accept it without
 870                  * locking.
 871                  */
 872                 if (msg != ERR_PTR(-EAGAIN)) {
 873                         rcu_read_unlock();
 874                         break;
 875                 }
 876
 877                 /* Lockless receive, part 3:
 878                  * Acquire the queue spinlock.
 879                  */
 880                 ipc_lock_by_ptr(&msq->q_perm);
 881                 rcu_read_unlock();
 882
 883                 /* Lockless receive, part 4:
 884                  * Repeat test after acquiring the spinlock.
 885                  */
 886                 msg = (struct msg_msg*)msr_d.r_msg;
 887                 if (msg != ERR_PTR(-EAGAIN))
 888                         goto out_unlock;
 889
 890                 list_del(&msr_d.r_list);
 891                 if (signal_pending(current)) {
 892                         msg = ERR_PTR(-ERESTARTNOHAND);
 893 out_unlock:
 894                         msg_unlock(msq);
 895                         break;
 896                 }
 897         }
 898         if (IS_ERR(msg))
 899                 return PTR_ERR(msg);
 900
 901         msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz;
 902         *pmtype = msg->m_type;
 903         if (store_msg(mtext, msg, msgsz))
 904                 msgsz = -EFAULT;
 905
 906         free_msg(msg);
 907
 908         return msgsz;
 909 }
 910
 911 asmlinkage long sys_msgrcv(int msqid, struct msgbuf __user *msgp, size_t msgsz,
 912                            long msgtyp, int msgflg)
 913 {
 914         long err, mtype;
 915
 916         err =  do_msgrcv(msqid, &mtype, msgp->mtext, msgsz, msgtyp, msgflg);
 917         if (err < 0)
 918                 goto out;
 919
 920         if (put_user(mtype, &msgp->mtype))
 921                 err = -EFAULT;
 922 out:
 923         return err;
 924 }
 925
 926 #ifdef CONFIG_PROC_FS
 927 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
 928 {
 929         struct msg_queue *msq = it;
 930
 931         return seq_printf(s,
 932                         "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
 933                         msq->q_perm.key,
 934                         msq->q_perm.id,
 935                         msq->q_perm.mode,
 936                         msq->q_cbytes,
 937                         msq->q_qnum,
 938                         msq->q_lspid,
 939                         msq->q_lrpid,
 940                         msq->q_perm.uid,
 941                         msq->q_perm.gid,
 942                         msq->q_perm.cuid,
 943                         msq->q_perm.cgid,
 944                         msq->q_stime,
 945                         msq->q_rtime,
 946                         msq->q_ctime);
 947 }
 948 #endif