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 <manfreds@colorfullife.com>
  16  */
  17
  18 #include <linux/config.h>
  19 #include <linux/slab.h>
  20 #include <linux/msg.h>
  21 #include <linux/spinlock.h>
  22 #include <linux/init.h>
  23 #include <linux/proc_fs.h>
  24 #include <linux/list.h>
  25 #include <linux/security.h>
  26 #include <linux/sched.h>
  27 #include <linux/syscalls.h>
  28 #include <linux/audit.h>
  29 #include <asm/current.h>
  30 #include <asm/uaccess.h>
  31 #include "util.h"
  32
  33 /* sysctl: */
  34 int msg_ctlmax = MSGMAX;
  35 int msg_ctlmnb = MSGMNB;
  36 int msg_ctlmni = MSGMNI;
  37
  38 /* one msg_receiver structure for each sleeping receiver */
  39 struct msg_receiver {
  40         struct list_head r_list;
  41         struct task_struct* r_tsk;
  42
  43         int r_mode;
  44         long r_msgtype;
  45         long r_maxsize;
  46
  47         struct msg_msg* volatile r_msg;
  48 };
  49
  50 /* one msg_sender for each sleeping sender */
  51 struct msg_sender {
  52         struct list_head list;
  53         struct task_struct* tsk;
  54 };
  55
  56 #define SEARCH_ANY              1
  57 #define SEARCH_EQUAL            2
  58 #define SEARCH_NOTEQUAL         3
  59 #define SEARCH_LESSEQUAL        4
  60
  61 static atomic_t msg_bytes = ATOMIC_INIT(0);
  62 static atomic_t msg_hdrs = ATOMIC_INIT(0);
  63
  64 static struct ipc_ids msg_ids;
  65
  66 #define msg_lock(id)    ((struct msg_queue*)ipc_lock(&msg_ids,id))
  67 #define msg_unlock(msq) ipc_unlock(&(msq)->q_perm)
  68 #define msg_rmid(id)    ((struct msg_queue*)ipc_rmid(&msg_ids,id))
  69 #define msg_checkid(msq, msgid) \
  70         ipc_checkid(&msg_ids,&msq->q_perm,msgid)
  71 #define msg_buildid(id, seq) \
  72         ipc_buildid(&msg_ids, id, seq)
  73
  74 static void freeque (struct msg_queue *msq, int id);
  75 static int newque (key_t key, int msgflg);
  76 #ifdef CONFIG_PROC_FS
  77 static int sysvipc_msg_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data);
  78 #endif
  79
  80 void __init msg_init (void)
  81 {
  82         ipc_init_ids(&msg_ids,msg_ctlmni);
  83
  84 #ifdef CONFIG_PROC_FS
  85         create_proc_read_entry("sysvipc/msg", 0, NULL, sysvipc_msg_read_proc, NULL);
  86 #endif
  87 }
  88
  89 static int newque (key_t key, int msgflg)
  90 {
  91         int id;
  92         int retval;
  93         struct msg_queue *msq;
  94
  95         msq  = ipc_rcu_alloc(sizeof(*msq));
  96         if (!msq)
  97                 return -ENOMEM;
  98
  99         msq->q_perm.mode = (msgflg & S_IRWXUGO);
 100         msq->q_perm.key = key;
 101         msq->q_perm.xid = vx_current_xid();
 102
 103         msq->q_perm.security = NULL;
 104         retval = security_msg_queue_alloc(msq);
 105         if (retval) {
 106                 ipc_rcu_putref(msq);
 107                 return retval;
 108         }
 109
 110         id = ipc_addid(&msg_ids, &msq->q_perm, msg_ctlmni);
 111         if(id == -1) {
 112                 security_msg_queue_free(msq);
 113                 ipc_rcu_putref(msq);
 114                 return -ENOSPC;
 115         }
 116
 117         msq->q_stime = msq->q_rtime = 0;
 118         msq->q_ctime = get_seconds();
 119         msq->q_cbytes = msq->q_qnum = 0;
 120         msq->q_qbytes = msg_ctlmnb;
 121         msq->q_lspid = msq->q_lrpid = 0;
 122         INIT_LIST_HEAD(&msq->q_messages);
 123         INIT_LIST_HEAD(&msq->q_receivers);
 124         INIT_LIST_HEAD(&msq->q_senders);
 125         msg_unlock(msq);
 126
 127         return msg_buildid(id,msq->q_perm.seq);
 128 }
 129
 130 static inline void ss_add(struct msg_queue* msq, struct msg_sender* mss)
 131 {
 132         mss->tsk=current;
 133         current->state=TASK_INTERRUPTIBLE;
 134         list_add_tail(&mss->list,&msq->q_senders);
 135 }
 136
 137 static inline void ss_del(struct msg_sender* mss)
 138 {
 139         if(mss->list.next != NULL)
 140                 list_del(&mss->list);
 141 }
 142
 143 static void ss_wakeup(struct list_head* h, int kill)
 144 {
 145         struct list_head *tmp;
 146
 147         tmp = h->next;
 148         while (tmp != h) {
 149                 struct msg_sender* mss;
 150
 151                 mss = list_entry(tmp,struct msg_sender,list);
 152                 tmp = tmp->next;
 153                 if(kill)
 154                         mss->list.next=NULL;
 155                 wake_up_process(mss->tsk);
 156         }
 157 }
 158
 159 static void expunge_all(struct msg_queue* msq, int res)
 160 {
 161         struct list_head *tmp;
 162
 163         tmp = msq->q_receivers.next;
 164         while (tmp != &msq->q_receivers) {
 165                 struct msg_receiver* msr;
 166
 167                 msr = list_entry(tmp,struct msg_receiver,r_list);
 168                 tmp = tmp->next;
 169                 msr->r_msg = NULL;
 170                 wake_up_process(msr->r_tsk);
 171                 smp_mb();
 172                 msr->r_msg = ERR_PTR(res);
 173         }
 174 }
 175 /*
 176  * freeque() wakes up waiters on the sender and receiver waiting queue,
 177  * removes the message queue from message queue ID
 178  * array, and cleans up all the messages associated with this queue.
 179  *
 180  * msg_ids.sem and the spinlock for this message queue is hold
 181  * before freeque() is called. msg_ids.sem remains locked on exit.
 182  */
 183 static void freeque (struct msg_queue *msq, int id)
 184 {
 185         struct list_head *tmp;
 186
 187         expunge_all(msq,-EIDRM);
 188         ss_wakeup(&msq->q_senders,1);
 189         msq = msg_rmid(id);
 190         msg_unlock(msq);
 191
 192         tmp = msq->q_messages.next;
 193         while(tmp != &msq->q_messages) {
 194                 struct msg_msg* msg = list_entry(tmp,struct msg_msg,m_list);
 195                 tmp = tmp->next;
 196                 atomic_dec(&msg_hdrs);
 197                 free_msg(msg);
 198         }
 199         atomic_sub(msq->q_cbytes, &msg_bytes);
 200         security_msg_queue_free(msq);
 201         ipc_rcu_putref(msq);
 202 }
 203
 204 asmlinkage long sys_msgget (key_t key, int msgflg)
 205 {
 206         int id, ret = -EPERM;
 207         struct msg_queue *msq;
 208
 209         down(&msg_ids.sem);
 210         if (key == IPC_PRIVATE)
 211                 ret = newque(key, msgflg);
 212         else if ((id = ipc_findkey(&msg_ids, key)) == -1) { /* key not used */
 213                 if (!(msgflg & IPC_CREAT))
 214                         ret = -ENOENT;
 215                 else
 216                         ret = newque(key, msgflg);
 217         } else if (msgflg & IPC_CREAT && msgflg & IPC_EXCL) {
 218                 ret = -EEXIST;
 219         } else {
 220                 msq = msg_lock(id);
 221                 if(msq==NULL)
 222                         BUG();
 223                 if (ipcperms(&msq->q_perm, msgflg))
 224                         ret = -EACCES;
 225                 else {
 226                         int qid = msg_buildid(id, msq->q_perm.seq);
 227                         ret = security_msg_queue_associate(msq, msgflg);
 228                         if (!ret)
 229                                 ret = qid;
 230                 }
 231                 msg_unlock(msq);
 232         }
 233         up(&msg_ids.sem);
 234         return ret;
 235 }
 236
 237 static inline unsigned long copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 238 {
 239         switch(version) {
 240         case IPC_64:
 241                 return copy_to_user (buf, in, sizeof(*in));
 242         case IPC_OLD:
 243             {
 244                 struct msqid_ds out;
 245
 246                 memset(&out,0,sizeof(out));
 247
 248                 ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
 249
 250                 out.msg_stime           = in->msg_stime;
 251                 out.msg_rtime           = in->msg_rtime;
 252                 out.msg_ctime           = in->msg_ctime;
 253
 254                 if(in->msg_cbytes > USHRT_MAX)
 255                         out.msg_cbytes  = USHRT_MAX;
 256                 else
 257                         out.msg_cbytes  = in->msg_cbytes;
 258                 out.msg_lcbytes         = in->msg_cbytes;
 259
 260                 if(in->msg_qnum > USHRT_MAX)
 261                         out.msg_qnum    = USHRT_MAX;
 262                 else
 263                         out.msg_qnum    = in->msg_qnum;
 264
 265                 if(in->msg_qbytes > USHRT_MAX)
 266                         out.msg_qbytes  = USHRT_MAX;
 267                 else
 268                         out.msg_qbytes  = in->msg_qbytes;
 269                 out.msg_lqbytes         = in->msg_qbytes;
 270
 271                 out.msg_lspid           = in->msg_lspid;
 272                 out.msg_lrpid           = in->msg_lrpid;
 273
 274                 return copy_to_user (buf, &out, sizeof(out));
 275             }
 276         default:
 277                 return -EINVAL;
 278         }
 279 }
 280
 281 struct msq_setbuf {
 282         unsigned long   qbytes;
 283         uid_t           uid;
 284         gid_t           gid;
 285         mode_t          mode;
 286 };
 287
 288 static inline unsigned long copy_msqid_from_user(struct msq_setbuf *out, void __user *buf, int version)
 289 {
 290         switch(version) {
 291         case IPC_64:
 292             {
 293                 struct msqid64_ds tbuf;
 294
 295                 if (copy_from_user (&tbuf, buf, sizeof (tbuf)))
 296                         return -EFAULT;
 297
 298                 out->qbytes             = tbuf.msg_qbytes;
 299                 out->uid                = tbuf.msg_perm.uid;
 300                 out->gid                = tbuf.msg_perm.gid;
 301                 out->mode               = tbuf.msg_perm.mode;
 302
 303                 return 0;
 304             }
 305         case IPC_OLD:
 306             {
 307                 struct msqid_ds tbuf_old;
 308
 309                 if (copy_from_user (&tbuf_old, buf, sizeof (tbuf_old)))
 310                         return -EFAULT;
 311
 312                 out->uid                = tbuf_old.msg_perm.uid;
 313                 out->gid                = tbuf_old.msg_perm.gid;
 314                 out->mode               = tbuf_old.msg_perm.mode;
 315
 316                 if(tbuf_old.msg_qbytes == 0)
 317                         out->qbytes     = tbuf_old.msg_lqbytes;
 318                 else
 319                         out->qbytes     = tbuf_old.msg_qbytes;
 320
 321                 return 0;
 322             }
 323         default:
 324                 return -EINVAL;
 325         }
 326 }
 327
 328 asmlinkage long sys_msgctl (int msqid, int cmd, struct msqid_ds __user *buf)
 329 {
 330         int err, version;
 331         struct msg_queue *msq;
 332         struct msq_setbuf setbuf;
 333         struct kern_ipc_perm *ipcp;
 334
 335         if (msqid < 0 || cmd < 0)
 336                 return -EINVAL;
 337
 338         version = ipc_parse_version(&cmd);
 339
 340         switch (cmd) {
 341         case IPC_INFO:
 342         case MSG_INFO:
 343         {
 344                 struct msginfo msginfo;
 345                 int max_id;
 346                 if (!buf)
 347                         return -EFAULT;
 348                 /* We must not return kernel stack data.
 349                  * due to padding, it's not enough
 350                  * to set all member fields.
 351                  */
 352
 353                 err = security_msg_queue_msgctl(NULL, cmd);
 354                 if (err)
 355                         return err;
 356
 357                 memset(&msginfo,0,sizeof(msginfo));
 358                 msginfo.msgmni = msg_ctlmni;
 359                 msginfo.msgmax = msg_ctlmax;
 360                 msginfo.msgmnb = msg_ctlmnb;
 361                 msginfo.msgssz = MSGSSZ;
 362                 msginfo.msgseg = MSGSEG;
 363                 down(&msg_ids.sem);
 364                 if (cmd == MSG_INFO) {
 365                         msginfo.msgpool = msg_ids.in_use;
 366                         msginfo.msgmap = atomic_read(&msg_hdrs);
 367                         msginfo.msgtql = atomic_read(&msg_bytes);
 368                 } else {
 369                         msginfo.msgmap = MSGMAP;
 370                         msginfo.msgpool = MSGPOOL;
 371                         msginfo.msgtql = MSGTQL;
 372                 }
 373                 max_id = msg_ids.max_id;
 374                 up(&msg_ids.sem);
 375                 if (copy_to_user (buf, &msginfo, sizeof(struct msginfo)))
 376                         return -EFAULT;
 377                 return (max_id < 0) ? 0: max_id;
 378         }
 379         case MSG_STAT:
 380         case IPC_STAT:
 381         {
 382                 struct msqid64_ds tbuf;
 383                 int success_return;
 384                 if (!buf)
 385                         return -EFAULT;
 386                 if(cmd == MSG_STAT && msqid >= msg_ids.entries->size)
 387                         return -EINVAL;
 388
 389                 memset(&tbuf,0,sizeof(tbuf));
 390
 391                 msq = msg_lock(msqid);
 392                 if (msq == NULL)
 393                         return -EINVAL;
 394
 395                 if(cmd == MSG_STAT) {
 396                         success_return = msg_buildid(msqid, msq->q_perm.seq);
 397                 } else {
 398                         err = -EIDRM;
 399                         if (msg_checkid(msq,msqid))
 400                                 goto out_unlock;
 401                         success_return = 0;
 402                 }
 403                 err = -EACCES;
 404                 if (ipcperms (&msq->q_perm, S_IRUGO))
 405                         goto out_unlock;
 406
 407                 err = security_msg_queue_msgctl(msq, cmd);
 408                 if (err)
 409                         goto out_unlock;
 410
 411                 kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
 412                 tbuf.msg_stime  = msq->q_stime;
 413                 tbuf.msg_rtime  = msq->q_rtime;
 414                 tbuf.msg_ctime  = msq->q_ctime;
 415                 tbuf.msg_cbytes = msq->q_cbytes;
 416                 tbuf.msg_qnum   = msq->q_qnum;
 417                 tbuf.msg_qbytes = msq->q_qbytes;
 418                 tbuf.msg_lspid  = msq->q_lspid;
 419                 tbuf.msg_lrpid  = msq->q_lrpid;
 420                 msg_unlock(msq);
 421                 if (copy_msqid_to_user(buf, &tbuf, version))
 422                         return -EFAULT;
 423                 return success_return;
 424         }
 425         case IPC_SET:
 426                 if (!buf)
 427                         return -EFAULT;
 428                 if (copy_msqid_from_user (&setbuf, buf, version))
 429                         return -EFAULT;
 430                 if ((err = audit_ipc_perms(setbuf.qbytes, setbuf.uid, setbuf.gid, setbuf.mode)))
 431                         return err;
 432                 break;
 433         case IPC_RMID:
 434                 break;
 435         default:
 436                 return  -EINVAL;
 437         }
 438
 439         down(&msg_ids.sem);
 440         msq = msg_lock(msqid);
 441         err=-EINVAL;
 442         if (msq == NULL)
 443                 goto out_up;
 444
 445         err = -EIDRM;
 446         if (msg_checkid(msq,msqid))
 447                 goto out_unlock_up;
 448         ipcp = &msq->q_perm;
 449         err = -EPERM;
 450         if (current->euid != ipcp->cuid &&
 451             current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN))
 452             /* We _could_ check for CAP_CHOWN above, but we don't */
 453                 goto out_unlock_up;
 454
 455         err = security_msg_queue_msgctl(msq, cmd);
 456         if (err)
 457                 goto out_unlock_up;
 458
 459         switch (cmd) {
 460         case IPC_SET:
 461         {
 462                 err = -EPERM;
 463                 if (setbuf.qbytes > msg_ctlmnb && !capable(CAP_SYS_RESOURCE))
 464                         goto out_unlock_up;
 465
 466                 msq->q_qbytes = setbuf.qbytes;
 467
 468                 ipcp->uid = setbuf.uid;
 469                 ipcp->gid = setbuf.gid;
 470                 ipcp->mode = (ipcp->mode & ~S_IRWXUGO) |
 471                         (S_IRWXUGO & setbuf.mode);
 472                 msq->q_ctime = get_seconds();
 473                 /* sleeping receivers might be excluded by
 474                  * stricter permissions.
 475                  */
 476                 expunge_all(msq,-EAGAIN);
 477                 /* sleeping senders might be able to send
 478                  * due to a larger queue size.
 479                  */
 480                 ss_wakeup(&msq->q_senders,0);
 481                 msg_unlock(msq);
 482                 break;
 483         }
 484         case IPC_RMID:
 485                 freeque (msq, msqid);
 486                 break;
 487         }
 488         err = 0;
 489 out_up:
 490         up(&msg_ids.sem);
 491         return err;
 492 out_unlock_up:
 493         msg_unlock(msq);
 494         goto out_up;
 495 out_unlock:
 496         msg_unlock(msq);
 497         return err;
 498 }
 499
 500 static int testmsg(struct msg_msg* msg,long type,int mode)
 501 {
 502         switch(mode)
 503         {
 504                 case SEARCH_ANY:
 505                         return 1;
 506                 case SEARCH_LESSEQUAL:
 507                         if(msg->m_type <=type)
 508                                 return 1;
 509                         break;
 510                 case SEARCH_EQUAL:
 511                         if(msg->m_type == type)
 512                                 return 1;
 513                         break;
 514                 case SEARCH_NOTEQUAL:
 515                         if(msg->m_type != type)
 516                                 return 1;
 517                         break;
 518         }
 519         return 0;
 520 }
 521
 522 static inline int pipelined_send(struct msg_queue* msq, struct msg_msg* msg)
 523 {
 524         struct list_head* tmp;
 525
 526         tmp = msq->q_receivers.next;
 527         while (tmp != &msq->q_receivers) {
 528                 struct msg_receiver* msr;
 529                 msr = list_entry(tmp,struct msg_receiver,r_list);
 530                 tmp = tmp->next;
 531                 if(testmsg(msg,msr->r_msgtype,msr->r_mode) &&
 532                    !security_msg_queue_msgrcv(msq, msg, msr->r_tsk, msr->r_msgtype, msr->r_mode)) {
 533                         list_del(&msr->r_list);
 534                         if(msr->r_maxsize < msg->m_ts) {
 535                                 msr->r_msg = NULL;
 536                                 wake_up_process(msr->r_tsk);
 537                                 smp_mb();
 538                                 msr->r_msg = ERR_PTR(-E2BIG);
 539                         } else {
 540                                 msr->r_msg = NULL;
 541                                 msq->q_lrpid = msr->r_tsk->pid;
 542                                 msq->q_rtime = get_seconds();
 543                                 wake_up_process(msr->r_tsk);
 544                                 smp_mb();
 545                                 msr->r_msg = msg;
 546                                 return 1;
 547                         }
 548                 }
 549         }
 550         return 0;
 551 }
 552
 553 asmlinkage long sys_msgsnd (int msqid, struct msgbuf __user *msgp, size_t msgsz, int msgflg)
 554 {
 555         struct msg_queue *msq;
 556         struct msg_msg *msg;
 557         long mtype;
 558         int err;
 559
 560         if (msgsz > msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 561                 return -EINVAL;
 562         if (get_user(mtype, &msgp->mtype))
 563                 return -EFAULT;
 564         if (mtype < 1)
 565                 return -EINVAL;
 566
 567         msg = load_msg(msgp->mtext, msgsz);
 568         if(IS_ERR(msg))
 569                 return PTR_ERR(msg);
 570
 571         msg->m_type = mtype;
 572         msg->m_ts = msgsz;
 573
 574         msq = msg_lock(msqid);
 575         err=-EINVAL;
 576         if(msq==NULL)
 577                 goto out_free;
 578
 579         err= -EIDRM;
 580         if (msg_checkid(msq,msqid))
 581                 goto out_unlock_free;
 582
 583         for (;;) {
 584                 struct msg_sender s;
 585
 586                 err=-EACCES;
 587                 if (ipcperms(&msq->q_perm, S_IWUGO))
 588                         goto out_unlock_free;
 589
 590                 err = security_msg_queue_msgsnd(msq, msg, msgflg);
 591                 if (err)
 592                         goto out_unlock_free;
 593
 594                 if(msgsz + msq->q_cbytes <= msq->q_qbytes &&
 595                                 1 + msq->q_qnum <= msq->q_qbytes) {
 596                         break;
 597                 }
 598
 599                 /* queue full, wait: */
 600                 if(msgflg&IPC_NOWAIT) {
 601                         err=-EAGAIN;
 602                         goto out_unlock_free;
 603                 }
 604                 ss_add(msq, &s);
 605                 ipc_rcu_getref(msq);
 606                 msg_unlock(msq);
 607                 schedule();
 608
 609                 ipc_lock_by_ptr(&msq->q_perm);
 610                 ipc_rcu_putref(msq);
 611                 if (msq->q_perm.deleted) {
 612                         err = -EIDRM;
 613                         goto out_unlock_free;
 614                 }
 615                 ss_del(&s);
 616
 617                 if (signal_pending(current)) {
 618                         err=-ERESTARTNOHAND;
 619                         goto out_unlock_free;
 620                 }
 621         }
 622
 623         msq->q_lspid = current->tgid;
 624         msq->q_stime = get_seconds();
 625
 626         if(!pipelined_send(msq,msg)) {
 627                 /* noone is waiting for this message, enqueue it */
 628                 list_add_tail(&msg->m_list,&msq->q_messages);
 629                 msq->q_cbytes += msgsz;
 630                 msq->q_qnum++;
 631                 atomic_add(msgsz,&msg_bytes);
 632                 atomic_inc(&msg_hdrs);
 633         }
 634
 635         err = 0;
 636         msg = NULL;
 637
 638 out_unlock_free:
 639         msg_unlock(msq);
 640 out_free:
 641         if(msg!=NULL)
 642                 free_msg(msg);
 643         return err;
 644 }
 645
 646 static inline int convert_mode(long* msgtyp, int msgflg)
 647 {
 648         /*
 649          *  find message of correct type.
 650          *  msgtyp = 0 => get first.
 651          *  msgtyp > 0 => get first message of matching type.
 652          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 653          */
 654         if(*msgtyp==0)
 655                 return SEARCH_ANY;
 656         if(*msgtyp<0) {
 657                 *msgtyp=-(*msgtyp);
 658                 return SEARCH_LESSEQUAL;
 659         }
 660         if(msgflg & MSG_EXCEPT)
 661                 return SEARCH_NOTEQUAL;
 662         return SEARCH_EQUAL;
 663 }
 664
 665 asmlinkage long sys_msgrcv (int msqid, struct msgbuf __user *msgp, size_t msgsz,
 666                             long msgtyp, int msgflg)
 667 {
 668         struct msg_queue *msq;
 669         struct msg_msg *msg;
 670         int mode;
 671
 672         if (msqid < 0 || (long) msgsz < 0)
 673                 return -EINVAL;
 674         mode = convert_mode(&msgtyp,msgflg);
 675
 676         msq = msg_lock(msqid);
 677         if(msq==NULL)
 678                 return -EINVAL;
 679
 680         msg = ERR_PTR(-EIDRM);
 681         if (msg_checkid(msq,msqid))
 682                 goto out_unlock;
 683
 684         for (;;) {
 685                 struct msg_receiver msr_d;
 686                 struct list_head* tmp;
 687
 688                 msg = ERR_PTR(-EACCES);
 689                 if (ipcperms (&msq->q_perm, S_IRUGO))
 690                         goto out_unlock;
 691
 692                 msg = ERR_PTR(-EAGAIN);
 693                 tmp = msq->q_messages.next;
 694                 while (tmp != &msq->q_messages) {
 695                         struct msg_msg *walk_msg;
 696                         walk_msg = list_entry(tmp,struct msg_msg,m_list);
 697                         if(testmsg(walk_msg,msgtyp,mode) &&
 698                            !security_msg_queue_msgrcv(msq, walk_msg, current, msgtyp, mode)) {
 699                                 msg = walk_msg;
 700                                 if(mode == SEARCH_LESSEQUAL && walk_msg->m_type != 1) {
 701                                         msg=walk_msg;
 702                                         msgtyp=walk_msg->m_type-1;
 703                                 } else {
 704                                         msg=walk_msg;
 705                                         break;
 706                                 }
 707                         }
 708                         tmp = tmp->next;
 709                 }
 710                 if(!IS_ERR(msg)) {
 711                         /* Found a suitable message. Unlink it from the queue. */
 712                         if ((msgsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 713                                 msg = ERR_PTR(-E2BIG);
 714                                 goto out_unlock;
 715                         }
 716                         list_del(&msg->m_list);
 717                         msq->q_qnum--;
 718                         msq->q_rtime = get_seconds();
 719                         msq->q_lrpid = current->tgid;
 720                         msq->q_cbytes -= msg->m_ts;
 721                         atomic_sub(msg->m_ts,&msg_bytes);
 722                         atomic_dec(&msg_hdrs);
 723                         ss_wakeup(&msq->q_senders,0);
 724                         msg_unlock(msq);
 725                         break;
 726                 }
 727                 /* No message waiting. Wait for a message */
 728                 if (msgflg & IPC_NOWAIT) {
 729                         msg = ERR_PTR(-ENOMSG);
 730                         goto out_unlock;
 731                 }
 732                 list_add_tail(&msr_d.r_list,&msq->q_receivers);
 733                 msr_d.r_tsk = current;
 734                 msr_d.r_msgtype = msgtyp;
 735                 msr_d.r_mode = mode;
 736                 if(msgflg & MSG_NOERROR)
 737                         msr_d.r_maxsize = INT_MAX;
 738                  else
 739                         msr_d.r_maxsize = msgsz;
 740                 msr_d.r_msg = ERR_PTR(-EAGAIN);
 741                 current->state = TASK_INTERRUPTIBLE;
 742                 msg_unlock(msq);
 743
 744                 schedule();
 745
 746                 /* Lockless receive, part 1:
 747                  * Disable preemption.  We don't hold a reference to the queue
 748                  * and getting a reference would defeat the idea of a lockless
 749                  * operation, thus the code relies on rcu to guarantee the
 750                  * existance of msq:
 751                  * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 752                  * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 753                  * rcu_read_lock() prevents preemption between reading r_msg
 754                  * and the spin_lock() inside ipc_lock_by_ptr().
 755                  */
 756                 rcu_read_lock();
 757
 758                 /* Lockless receive, part 2:
 759                  * Wait until pipelined_send or expunge_all are outside of
 760                  * wake_up_process(). There is a race with exit(), see
 761                  * ipc/mqueue.c for the details.
 762                  */
 763                 msg = (struct msg_msg*) msr_d.r_msg;
 764                 while (msg == NULL) {
 765                         cpu_relax();
 766                         msg = (struct msg_msg*) msr_d.r_msg;
 767                 }
 768
 769                 /* Lockless receive, part 3:
 770                  * If there is a message or an error then accept it without
 771                  * locking.
 772                  */
 773                 if(msg != ERR_PTR(-EAGAIN)) {
 774                         rcu_read_unlock();
 775                         break;
 776                 }
 777
 778                 /* Lockless receive, part 3:
 779                  * Acquire the queue spinlock.
 780                  */
 781                 ipc_lock_by_ptr(&msq->q_perm);
 782                 rcu_read_unlock();
 783
 784                 /* Lockless receive, part 4:
 785                  * Repeat test after acquiring the spinlock.
 786                  */
 787                 msg = (struct msg_msg*)msr_d.r_msg;
 788                 if(msg != ERR_PTR(-EAGAIN))
 789                         goto out_unlock;
 790
 791                 list_del(&msr_d.r_list);
 792                 if (signal_pending(current)) {
 793                         msg = ERR_PTR(-ERESTARTNOHAND);
 794 out_unlock:
 795                         msg_unlock(msq);
 796                         break;
 797                 }
 798         }
 799         if (IS_ERR(msg))
 800                 return PTR_ERR(msg);
 801
 802         msgsz = (msgsz > msg->m_ts) ? msg->m_ts : msgsz;
 803         if (put_user (msg->m_type, &msgp->mtype) ||
 804             store_msg(msgp->mtext, msg, msgsz)) {
 805                     msgsz = -EFAULT;
 806         }
 807         free_msg(msg);
 808         return msgsz;
 809 }
 810
 811 #ifdef CONFIG_PROC_FS
 812 static int sysvipc_msg_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data)
 813 {
 814         off_t pos = 0;
 815         off_t begin = 0;
 816         int i, len = 0;
 817
 818         down(&msg_ids.sem);
 819         len += sprintf(buffer, "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n");
 820
 821         for(i = 0; i <= msg_ids.max_id; i++) {
 822                 struct msg_queue * msq;
 823                 msq = msg_lock(i);
 824                 if (msq) {
 825                         if (!vx_check(msq->q_perm.xid, VX_IDENT)) {
 826                                 msg_unlock(msq);
 827                                 continue;
 828                         }
 829                         len += sprintf(buffer + len, "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
 830                                 msq->q_perm.key,
 831                                 msg_buildid(i,msq->q_perm.seq),
 832                                 msq->q_perm.mode,
 833                                 msq->q_cbytes,
 834                                 msq->q_qnum,
 835                                 msq->q_lspid,
 836                                 msq->q_lrpid,
 837                                 msq->q_perm.uid,
 838                                 msq->q_perm.gid,
 839                                 msq->q_perm.cuid,
 840                                 msq->q_perm.cgid,
 841                                 msq->q_stime,
 842                                 msq->q_rtime,
 843                                 msq->q_ctime);
 844                         msg_unlock(msq);
 845
 846                         pos += len;
 847                         if(pos < offset) {
 848                                 len = 0;
 849                                 begin = pos;
 850                         }
 851                         if(pos > offset + length)
 852                                 goto done;
 853                 }
 854
 855         }
 856         *eof = 1;
 857 done:
 858         up(&msg_ids.sem);
 859         *start = buffer + (offset - begin);
 860         len -= (offset - begin);
 861         if(len > length)
 862                 len = length;
 863         if(len < 0)
 864                 len = 0;
 865         return len;
 866 }
 867 #endif