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/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  */
  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 #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
  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 /*
  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  */
  87 void 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
 112 void 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
 125 void 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
 132 void __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  */
 148 static 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
 158 static 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
 169 static 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  */
 181 static 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
 226 static 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
 233 static inline void ss_del(struct msg_sender *mss)
 234 {
 235         if (mss->list.next != NULL)
 236                 list_del(&mss->list);
 237 }
 238
 239 static void ss_wakeup(struct list_head *h, int kill)
 240 {
 241         struct list_head *tmp;
 242
 243         tmp = h->next;
 244         while (tmp != h) {
 245                 struct msg_sender *mss;
 246
 247                 mss = list_entry(tmp, struct msg_sender, list);
 248                 tmp = tmp->next;
 249                 if (kill)
 250                         mss->list.next = NULL;
 251                 wake_up_process(mss->tsk);
 252         }
 253 }
 254
 255 static void expunge_all(struct msg_queue *msq, int res)
 256 {
 257         struct list_head *tmp;
 258
 259         tmp = msq->q_receivers.next;
 260         while (tmp != &msq->q_receivers) {
 261                 struct msg_receiver *msr;
 262
 263                 msr = list_entry(tmp, struct msg_receiver, r_list);
 264                 tmp = tmp->next;
 265                 msr->r_msg = NULL;
 266                 wake_up_process(msr->r_tsk);
 267                 smp_mb();
 268                 msr->r_msg = ERR_PTR(res);
 269         }
 270 }
 271
 272 /*
 273  * freeque() wakes up waiters on the sender and receiver waiting queue,
 274  * removes the message queue from message queue ID IDR, and cleans up all the
 275  * messages associated with this queue.
 276  *
 277  * msg_ids.rw_mutex (writer) and the spinlock for this message queue are held
 278  * before freeque() is called. msg_ids.rw_mutex remains locked on exit.
 279  */
 280 static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 281 {
 282         struct list_head *tmp;
 283         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 284
 285         expunge_all(msq, -EIDRM);
 286         ss_wakeup(&msq->q_senders, 1);
 287         msg_rmid(ns, msq);
 288         msg_unlock(msq);
 289
 290         tmp = msq->q_messages.next;
 291         while (tmp != &msq->q_messages) {
 292                 struct msg_msg *msg = list_entry(tmp, struct msg_msg, m_list);
 293
 294                 tmp = tmp->next;
 295                 atomic_dec(&ns->msg_hdrs);
 296                 free_msg(msg);
 297         }
 298         atomic_sub(msq->q_cbytes, &ns->msg_bytes);
 299         security_msg_queue_free(msq);
 300         ipc_rcu_putref(msq);
 301 }
 302
 303 /*
 304  * Called with msg_ids.rw_mutex and ipcp locked.
 305  */
 306 static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
 307 {
 308         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 309
 310         return security_msg_queue_associate(msq, msgflg);
 311 }
 312
 313 SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
 314 {
 315         struct ipc_namespace *ns;
 316         struct ipc_ops msg_ops;
 317         struct ipc_params msg_params;
 318
 319         ns = current->nsproxy->ipc_ns;
 320
 321         msg_ops.getnew = newque;
 322         msg_ops.associate = msg_security;
 323         msg_ops.more_checks = NULL;
 324
 325         msg_params.key = key;
 326         msg_params.flg = msgflg;
 327
 328         return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
 329 }
 330
 331 static inline unsigned long
 332 copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 333 {
 334         switch(version) {
 335         case IPC_64:
 336                 return copy_to_user(buf, in, sizeof(*in));
 337         case IPC_OLD:
 338         {
 339                 struct msqid_ds out;
 340
 341                 memset(&out, 0, sizeof(out));
 342
 343                 ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
 344
 345                 out.msg_stime           = in->msg_stime;
 346                 out.msg_rtime           = in->msg_rtime;
 347                 out.msg_ctime           = in->msg_ctime;
 348
 349                 if (in->msg_cbytes > USHRT_MAX)
 350                         out.msg_cbytes  = USHRT_MAX;
 351                 else
 352                         out.msg_cbytes  = in->msg_cbytes;
 353                 out.msg_lcbytes         = in->msg_cbytes;
 354
 355                 if (in->msg_qnum > USHRT_MAX)
 356                         out.msg_qnum    = USHRT_MAX;
 357                 else
 358                         out.msg_qnum    = in->msg_qnum;
 359
 360                 if (in->msg_qbytes > USHRT_MAX)
 361                         out.msg_qbytes  = USHRT_MAX;
 362                 else
 363                         out.msg_qbytes  = in->msg_qbytes;
 364                 out.msg_lqbytes         = in->msg_qbytes;
 365
 366                 out.msg_lspid           = in->msg_lspid;
 367                 out.msg_lrpid           = in->msg_lrpid;
 368
 369                 return copy_to_user(buf, &out, sizeof(out));
 370         }
 371         default:
 372                 return -EINVAL;
 373         }
 374 }
 375
 376 static inline unsigned long
 377 copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
 378 {
 379         switch(version) {
 380         case IPC_64:
 381                 if (copy_from_user(out, buf, sizeof(*out)))
 382                         return -EFAULT;
 383                 return 0;
 384         case IPC_OLD:
 385         {
 386                 struct msqid_ds tbuf_old;
 387
 388                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
 389                         return -EFAULT;
 390
 391                 out->msg_perm.uid       = tbuf_old.msg_perm.uid;
 392                 out->msg_perm.gid       = tbuf_old.msg_perm.gid;
 393                 out->msg_perm.mode      = tbuf_old.msg_perm.mode;
 394
 395                 if (tbuf_old.msg_qbytes == 0)
 396                         out->msg_qbytes = tbuf_old.msg_lqbytes;
 397                 else
 398                         out->msg_qbytes = tbuf_old.msg_qbytes;
 399
 400                 return 0;
 401         }
 402         default:
 403                 return -EINVAL;
 404         }
 405 }
 406
 407 /*
 408  * This function handles some msgctl commands which require the rw_mutex
 409  * to be held in write mode.
 410  * NOTE: no locks must be held, the rw_mutex is taken inside this function.
 411  */
 412 static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 413                        struct msqid_ds __user *buf, int version)
 414 {
 415         struct kern_ipc_perm *ipcp;
 416         struct msqid64_ds uninitialized_var(msqid64);
 417         struct msg_queue *msq;
 418         int err;
 419
 420         if (cmd == IPC_SET) {
 421                 if (copy_msqid_from_user(&msqid64, buf, version))
 422                         return -EFAULT;
 423         }
 424
 425         ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,
 426                                &msqid64.msg_perm, msqid64.msg_qbytes);
 427         if (IS_ERR(ipcp))
 428                 return PTR_ERR(ipcp);
 429
 430         msq = container_of(ipcp, struct msg_queue, q_perm);
 431
 432         err = security_msg_queue_msgctl(msq, cmd);
 433         if (err)
 434                 goto out_unlock;
 435
 436         switch (cmd) {
 437         case IPC_RMID:
 438                 freeque(ns, ipcp);
 439                 goto out_up;
 440         case IPC_SET:
 441                 if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
 442                     !capable(CAP_SYS_RESOURCE)) {
 443                         err = -EPERM;
 444                         goto out_unlock;
 445                 }
 446
 447                 err = ipc_update_perm(&msqid64.msg_perm, ipcp);
 448                 if (err)
 449                         goto out_unlock;
 450
 451                 msq->q_qbytes = msqid64.msg_qbytes;
 452
 453                 msq->q_ctime = get_seconds();
 454                 /* sleeping receivers might be excluded by
 455                  * stricter permissions.
 456                  */
 457                 expunge_all(msq, -EAGAIN);
 458                 /* sleeping senders might be able to send
 459                  * due to a larger queue size.
 460                  */
 461                 ss_wakeup(&msq->q_senders, 0);
 462                 break;
 463         default:
 464                 err = -EINVAL;
 465         }
 466 out_unlock:
 467         msg_unlock(msq);
 468 out_up:
 469         up_write(&msg_ids(ns).rw_mutex);
 470         return err;
 471 }
 472
 473 SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
 474 {
 475         struct msg_queue *msq;
 476         int err, version;
 477         struct ipc_namespace *ns;
 478
 479         if (msqid < 0 || cmd < 0)
 480                 return -EINVAL;
 481
 482         version = ipc_parse_version(&cmd);
 483         ns = current->nsproxy->ipc_ns;
 484
 485         switch (cmd) {
 486         case IPC_INFO:
 487         case MSG_INFO:
 488         {
 489                 struct msginfo msginfo;
 490                 int max_id;
 491
 492                 if (!buf)
 493                         return -EFAULT;
 494                 /*
 495                  * We must not return kernel stack data.
 496                  * due to padding, it's not enough
 497                  * to set all member fields.
 498                  */
 499                 err = security_msg_queue_msgctl(NULL, cmd);
 500                 if (err)
 501                         return err;
 502
 503                 memset(&msginfo, 0, sizeof(msginfo));
 504                 msginfo.msgmni = ns->msg_ctlmni;
 505                 msginfo.msgmax = ns->msg_ctlmax;
 506                 msginfo.msgmnb = ns->msg_ctlmnb;
 507                 msginfo.msgssz = MSGSSZ;
 508                 msginfo.msgseg = MSGSEG;
 509                 down_read(&msg_ids(ns).rw_mutex);
 510                 if (cmd == MSG_INFO) {
 511                         msginfo.msgpool = msg_ids(ns).in_use;
 512                         msginfo.msgmap = atomic_read(&ns->msg_hdrs);
 513                         msginfo.msgtql = atomic_read(&ns->msg_bytes);
 514                 } else {
 515                         msginfo.msgmap = MSGMAP;
 516                         msginfo.msgpool = MSGPOOL;
 517                         msginfo.msgtql = MSGTQL;
 518                 }
 519                 max_id = ipc_get_maxid(&msg_ids(ns));
 520                 up_read(&msg_ids(ns).rw_mutex);
 521                 if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
 522                         return -EFAULT;
 523                 return (max_id < 0) ? 0 : max_id;
 524         }
 525         case MSG_STAT:  /* msqid is an index rather than a msg queue id */
 526         case IPC_STAT:
 527         {
 528                 struct msqid64_ds tbuf;
 529                 int success_return;
 530
 531                 if (!buf)
 532                         return -EFAULT;
 533
 534                 if (cmd == MSG_STAT) {
 535                         msq = msg_lock(ns, msqid);
 536                         if (IS_ERR(msq))
 537                                 return PTR_ERR(msq);
 538                         success_return = msq->q_perm.id;
 539                 } else {
 540                         msq = msg_lock_check(ns, msqid);
 541                         if (IS_ERR(msq))
 542                                 return PTR_ERR(msq);
 543                         success_return = 0;
 544                 }
 545                 err = -EACCES;
 546                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 547                         goto out_unlock;
 548
 549                 err = security_msg_queue_msgctl(msq, cmd);
 550                 if (err)
 551                         goto out_unlock;
 552
 553                 memset(&tbuf, 0, sizeof(tbuf));
 554
 555                 kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
 556                 tbuf.msg_stime  = msq->q_stime;
 557                 tbuf.msg_rtime  = msq->q_rtime;
 558                 tbuf.msg_ctime  = msq->q_ctime;
 559                 tbuf.msg_cbytes = msq->q_cbytes;
 560                 tbuf.msg_qnum   = msq->q_qnum;
 561                 tbuf.msg_qbytes = msq->q_qbytes;
 562                 tbuf.msg_lspid  = msq->q_lspid;
 563                 tbuf.msg_lrpid  = msq->q_lrpid;
 564                 msg_unlock(msq);
 565                 if (copy_msqid_to_user(buf, &tbuf, version))
 566                         return -EFAULT;
 567                 return success_return;
 568         }
 569         case IPC_SET:
 570         case IPC_RMID:
 571                 err = msgctl_down(ns, msqid, cmd, buf, version);
 572                 return err;
 573         default:
 574                 return  -EINVAL;
 575         }
 576
 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                 case SEARCH_NUMBER:
 588                         return 1;
 589                 case SEARCH_LESSEQUAL:
 590                         if (msg->m_type <=type)
 591                                 return 1;
 592                         break;
 593                 case SEARCH_EQUAL:
 594                         if (msg->m_type == type)
 595                                 return 1;
 596                         break;
 597                 case SEARCH_NOTEQUAL:
 598                         if (msg->m_type != type)
 599                                 return 1;
 600                         break;
 601         }
 602         return 0;
 603 }
 604
 605 static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
 606 {
 607         struct list_head *tmp;
 608
 609         tmp = msq->q_receivers.next;
 610         while (tmp != &msq->q_receivers) {
 611                 struct msg_receiver *msr;
 612
 613                 msr = list_entry(tmp, struct msg_receiver, r_list);
 614                 tmp = tmp->next;
 615                 if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
 616                     !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
 617                                                msr->r_msgtype, msr->r_mode)) {
 618
 619                         list_del(&msr->r_list);
 620                         if (msr->r_maxsize < msg->m_ts) {
 621                                 msr->r_msg = NULL;
 622                                 wake_up_process(msr->r_tsk);
 623                                 smp_mb();
 624                                 msr->r_msg = ERR_PTR(-E2BIG);
 625                         } else {
 626                                 msr->r_msg = NULL;
 627                                 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
 628                                 msq->q_rtime = get_seconds();
 629                                 wake_up_process(msr->r_tsk);
 630                                 smp_mb();
 631                                 msr->r_msg = msg;
 632
 633                                 return 1;
 634                         }
 635                 }
 636         }
 637         return 0;
 638 }
 639
 640 long do_msgsnd(int msqid, long mtype, void __user *mtext,
 641                 size_t msgsz, int msgflg)
 642 {
 643         struct msg_queue *msq;
 644         struct msg_msg *msg;
 645         int err;
 646         struct ipc_namespace *ns;
 647
 648         ns = current->nsproxy->ipc_ns;
 649
 650         if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 651                 return -EINVAL;
 652         if (mtype < 1)
 653                 return -EINVAL;
 654
 655         msg = load_msg(mtext, msgsz);
 656         if (IS_ERR(msg))
 657                 return PTR_ERR(msg);
 658
 659         msg->m_type = mtype;
 660         msg->m_ts = msgsz;
 661
 662         msq = msg_lock_check(ns, msqid);
 663         if (IS_ERR(msq)) {
 664                 err = PTR_ERR(msq);
 665                 goto out_free;
 666         }
 667
 668         for (;;) {
 669                 struct msg_sender s;
 670
 671                 err = -EACCES;
 672                 if (ipcperms(ns, &msq->q_perm, S_IWUGO))
 673                         goto out_unlock_free;
 674
 675                 err = security_msg_queue_msgsnd(msq, msg, msgflg);
 676                 if (err)
 677                         goto out_unlock_free;
 678
 679                 if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
 680                                 1 + msq->q_qnum <= msq->q_qbytes) {
 681                         break;
 682                 }
 683
 684                 /* queue full, wait: */
 685                 if (msgflg & IPC_NOWAIT) {
 686                         err = -EAGAIN;
 687                         goto out_unlock_free;
 688                 }
 689                 ss_add(msq, &s);
 690                 ipc_rcu_getref(msq);
 691                 msg_unlock(msq);
 692                 schedule();
 693
 694                 ipc_lock_by_ptr(&msq->q_perm);
 695                 ipc_rcu_putref(msq);
 696                 if (msq->q_perm.deleted) {
 697                         err = -EIDRM;
 698                         goto out_unlock_free;
 699                 }
 700                 ss_del(&s);
 701
 702                 if (signal_pending(current)) {
 703                         err = -ERESTARTNOHAND;
 704                         goto out_unlock_free;
 705                 }
 706         }
 707
 708         msq->q_lspid = task_tgid_vnr(current);
 709         msq->q_stime = get_seconds();
 710
 711         if (!pipelined_send(msq, msg)) {
 712                 /* no one is waiting for this message, enqueue it */
 713                 list_add_tail(&msg->m_list, &msq->q_messages);
 714                 msq->q_cbytes += msgsz;
 715                 msq->q_qnum++;
 716                 atomic_add(msgsz, &ns->msg_bytes);
 717                 atomic_inc(&ns->msg_hdrs);
 718         }
 719
 720         err = 0;
 721         msg = NULL;
 722
 723 out_unlock_free:
 724         msg_unlock(msq);
 725 out_free:
 726         if (msg != NULL)
 727                 free_msg(msg);
 728         return err;
 729 }
 730
 731 SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 732                 int, msgflg)
 733 {
 734         long mtype;
 735
 736         if (get_user(mtype, &msgp->mtype))
 737                 return -EFAULT;
 738         return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
 739 }
 740
 741 static inline int convert_mode(long *msgtyp, int msgflg)
 742 {
 743         if (msgflg & MSG_COPY)
 744                 return SEARCH_NUMBER;
 745         /*
 746          *  find message of correct type.
 747          *  msgtyp = 0 => get first.
 748          *  msgtyp > 0 => get first message of matching type.
 749          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 750          */
 751         if (*msgtyp == 0)
 752                 return SEARCH_ANY;
 753         if (*msgtyp < 0) {
 754                 *msgtyp = -*msgtyp;
 755                 return SEARCH_LESSEQUAL;
 756         }
 757         if (msgflg & MSG_EXCEPT)
 758                 return SEARCH_NOTEQUAL;
 759         return SEARCH_EQUAL;
 760 }
 761
 762 static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
 763 {
 764         struct msgbuf __user *msgp = dest;
 765         size_t msgsz;
 766
 767         if (put_user(msg->m_type, &msgp->mtype))
 768                 return -EFAULT;
 769
 770         msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
 771         if (store_msg(msgp->mtext, msg, msgsz))
 772                 return -EFAULT;
 773         return msgsz;
 774 }
 775
 776 #ifdef CONFIG_CHECKPOINT_RESTORE
 777 /*
 778  * This function creates new kernel message structure, large enough to store
 779  * bufsz message bytes.
 780  */
 781 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 782 {
 783         struct msg_msg *copy;
 784
 785         /*
 786          * Create dummy message to copy real message to.
 787          */
 788         copy = load_msg(buf, bufsz);
 789         if (!IS_ERR(copy))
 790                 copy->m_ts = bufsz;
 791         return copy;
 792 }
 793
 794 static inline void free_copy(struct msg_msg *copy)
 795 {
 796         if (copy)
 797                 free_msg(copy);
 798 }
 799 #else
 800 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 801 {
 802         return ERR_PTR(-ENOSYS);
 803 }
 804
 805 static inline void free_copy(struct msg_msg *copy)
 806 {
 807 }
 808 #endif
 809
 810 static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
 811 {
 812         struct msg_msg *msg;
 813         long count = 0;
 814
 815         list_for_each_entry(msg, &msq->q_messages, m_list) {
 816                 if (testmsg(msg, *msgtyp, mode) &&
 817                     !security_msg_queue_msgrcv(msq, msg, current,
 818                                                *msgtyp, mode)) {
 819                         if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
 820                                 *msgtyp = msg->m_type - 1;
 821                         } else if (mode == SEARCH_NUMBER) {
 822                                 if (*msgtyp == count)
 823                                         return msg;
 824                         } else
 825                                 return msg;
 826                         count++;
 827                 }
 828         }
 829
 830         return ERR_PTR(-EAGAIN);
 831 }
 832
 833
 834 long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp,
 835                int msgflg,
 836                long (*msg_handler)(void __user *, struct msg_msg *, size_t))
 837 {
 838         struct msg_queue *msq;
 839         struct msg_msg *msg;
 840         int mode;
 841         struct ipc_namespace *ns;
 842         struct msg_msg *copy = NULL;
 843
 844         ns = current->nsproxy->ipc_ns;
 845
 846         if (msqid < 0 || (long) bufsz < 0)
 847                 return -EINVAL;
 848         if (msgflg & MSG_COPY) {
 849                 copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
 850                 if (IS_ERR(copy))
 851                         return PTR_ERR(copy);
 852         }
 853         mode = convert_mode(&msgtyp, msgflg);
 854
 855         msq = msg_lock_check(ns, msqid);
 856         if (IS_ERR(msq)) {
 857                 free_copy(copy);
 858                 return PTR_ERR(msq);
 859         }
 860
 861         for (;;) {
 862                 struct msg_receiver msr_d;
 863
 864                 msg = ERR_PTR(-EACCES);
 865                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 866                         goto out_unlock;
 867
 868                 msg = find_msg(msq, &msgtyp, mode);
 869
 870                 if (!IS_ERR(msg)) {
 871                         /*
 872                          * Found a suitable message.
 873                          * Unlink it from the queue.
 874                          */
 875                         if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 876                                 msg = ERR_PTR(-E2BIG);
 877                                 goto out_unlock;
 878                         }
 879                         /*
 880                          * If we are copying, then do not unlink message and do
 881                          * not update queue parameters.
 882                          */
 883                         if (msgflg & MSG_COPY) {
 884                                 msg = copy_msg(msg, copy);
 885                                 goto out_unlock;
 886                         }
 887                         list_del(&msg->m_list);
 888                         msq->q_qnum--;
 889                         msq->q_rtime = get_seconds();
 890                         msq->q_lrpid = task_tgid_vnr(current);
 891                         msq->q_cbytes -= msg->m_ts;
 892                         atomic_sub(msg->m_ts, &ns->msg_bytes);
 893                         atomic_dec(&ns->msg_hdrs);
 894                         ss_wakeup(&msq->q_senders, 0);
 895                         msg_unlock(msq);
 896                         break;
 897                 }
 898                 /* No message waiting. Wait for a message */
 899                 if (msgflg & IPC_NOWAIT) {
 900                         msg = ERR_PTR(-ENOMSG);
 901                         goto out_unlock;
 902                 }
 903                 list_add_tail(&msr_d.r_list, &msq->q_receivers);
 904                 msr_d.r_tsk = current;
 905                 msr_d.r_msgtype = msgtyp;
 906                 msr_d.r_mode = mode;
 907                 if (msgflg & MSG_NOERROR)
 908                         msr_d.r_maxsize = INT_MAX;
 909                 else
 910                         msr_d.r_maxsize = bufsz;
 911                 msr_d.r_msg = ERR_PTR(-EAGAIN);
 912                 current->state = TASK_INTERRUPTIBLE;
 913                 msg_unlock(msq);
 914
 915                 schedule();
 916
 917                 /* Lockless receive, part 1:
 918                  * Disable preemption.  We don't hold a reference to the queue
 919                  * and getting a reference would defeat the idea of a lockless
 920                  * operation, thus the code relies on rcu to guarantee the
 921                  * existence of msq:
 922                  * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 923                  * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 924                  * rcu_read_lock() prevents preemption between reading r_msg
 925                  * and the spin_lock() inside ipc_lock_by_ptr().
 926                  */
 927                 rcu_read_lock();
 928
 929                 /* Lockless receive, part 2:
 930                  * Wait until pipelined_send or expunge_all are outside of
 931                  * wake_up_process(). There is a race with exit(), see
 932                  * ipc/mqueue.c for the details.
 933                  */
 934                 msg = (struct msg_msg*)msr_d.r_msg;
 935                 while (msg == NULL) {
 936                         cpu_relax();
 937                         msg = (struct msg_msg *)msr_d.r_msg;
 938                 }
 939
 940                 /* Lockless receive, part 3:
 941                  * If there is a message or an error then accept it without
 942                  * locking.
 943                  */
 944                 if (msg != ERR_PTR(-EAGAIN)) {
 945                         rcu_read_unlock();
 946                         break;
 947                 }
 948
 949                 /* Lockless receive, part 3:
 950                  * Acquire the queue spinlock.
 951                  */
 952                 ipc_lock_by_ptr(&msq->q_perm);
 953                 rcu_read_unlock();
 954
 955                 /* Lockless receive, part 4:
 956                  * Repeat test after acquiring the spinlock.
 957                  */
 958                 msg = (struct msg_msg*)msr_d.r_msg;
 959                 if (msg != ERR_PTR(-EAGAIN))
 960                         goto out_unlock;
 961
 962                 list_del(&msr_d.r_list);
 963                 if (signal_pending(current)) {
 964                         msg = ERR_PTR(-ERESTARTNOHAND);
 965 out_unlock:
 966                         msg_unlock(msq);
 967                         break;
 968                 }
 969         }
 970         if (IS_ERR(msg)) {
 971                 free_copy(copy);
 972                 return PTR_ERR(msg);
 973         }
 974
 975         bufsz = msg_handler(buf, msg, bufsz);
 976         free_msg(msg);
 977
 978         return bufsz;
 979 }
 980
 981 SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 982                 long, msgtyp, int, msgflg)
 983 {
 984         return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
 985 }
 986
 987 #ifdef CONFIG_PROC_FS
 988 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
 989 {
 990         struct user_namespace *user_ns = seq_user_ns(s);
 991         struct msg_queue *msq = it;
 992
 993         return seq_printf(s,
 994                         "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
 995                         msq->q_perm.key,
 996                         msq->q_perm.id,
 997                         msq->q_perm.mode,
 998                         msq->q_cbytes,
 999                         msq->q_qnum,
1000                         msq->q_lspid,
1001                         msq->q_lrpid,
1002                         from_kuid_munged(user_ns, msq->q_perm.uid),
1003                         from_kgid_munged(user_ns, msq->q_perm.gid),
1004                         from_kuid_munged(user_ns, msq->q_perm.cuid),
1005                         from_kgid_munged(user_ns, msq->q_perm.cgid),
1006                         msq->q_stime,
1007                         msq->q_rtime,
1008                         msq->q_ctime);
1009 }
1010 #endif