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 static void freeque(struct ipc_namespace *, struct kern_ipc_perm *);
  74 static int newque(struct ipc_namespace *, struct ipc_params *);
  75 #ifdef CONFIG_PROC_FS
  76 static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
  77 #endif
  78
  79 /*
  80  * Scale msgmni with the available lowmem size: the memory dedicated to msg
  81  * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
  82  * Also take into account the number of nsproxies created so far.
  83  * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
  84  */
  85 void recompute_msgmni(struct ipc_namespace *ns)
  86 {
  87         struct sysinfo i;
  88         unsigned long allowed;
  89         int nb_ns;
  90
  91         si_meminfo(&i);
  92         allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
  93                 / MSGMNB;
  94         nb_ns = atomic_read(&nr_ipc_ns);
  95         allowed /= nb_ns;
  96
  97         if (allowed < MSGMNI) {
  98                 ns->msg_ctlmni = MSGMNI;
  99                 return;
 100         }
 101
 102         if (allowed > IPCMNI / nb_ns) {
 103                 ns->msg_ctlmni = IPCMNI / nb_ns;
 104                 return;
 105         }
 106
 107         ns->msg_ctlmni = allowed;
 108 }
 109
 110 void msg_init_ns(struct ipc_namespace *ns)
 111 {
 112         ns->msg_ctlmax = MSGMAX;
 113         ns->msg_ctlmnb = MSGMNB;
 114
 115         recompute_msgmni(ns);
 116
 117         atomic_set(&ns->msg_bytes, 0);
 118         atomic_set(&ns->msg_hdrs, 0);
 119         ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
 120 }
 121
 122 #ifdef CONFIG_IPC_NS
 123 void msg_exit_ns(struct ipc_namespace *ns)
 124 {
 125         free_ipcs(ns, &msg_ids(ns), freeque);
 126         idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
 127 }
 128 #endif
 129
 130 void __init msg_init(void)
 131 {
 132         msg_init_ns(&init_ipc_ns);
 133
 134         printk(KERN_INFO "msgmni has been set to %d\n",
 135                 init_ipc_ns.msg_ctlmni);
 136
 137         ipc_init_proc_interface("sysvipc/msg",
 138                                 "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
 139                                 IPC_MSG_IDS, sysvipc_msg_proc_show);
 140 }
 141
 142 static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
 143 {
 144         struct kern_ipc_perm *ipcp = ipc_obtain_object(&msg_ids(ns), id);
 145
 146         if (IS_ERR(ipcp))
 147                 return ERR_CAST(ipcp);
 148
 149         return container_of(ipcp, struct msg_queue, q_perm);
 150 }
 151
 152 static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns,
 153                                                         int id)
 154 {
 155         struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id);
 156
 157         if (IS_ERR(ipcp))
 158                 return ERR_CAST(ipcp);
 159
 160         return container_of(ipcp, struct msg_queue, q_perm);
 161 }
 162
 163 static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
 164 {
 165         ipc_rmid(&msg_ids(ns), &s->q_perm);
 166 }
 167
 168 static void msg_rcu_free(struct rcu_head *head)
 169 {
 170         struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
 171         struct msg_queue *msq = ipc_rcu_to_struct(p);
 172
 173         security_msg_queue_free(msq);
 174         ipc_rcu_free(head);
 175 }
 176
 177 /**
 178  * newque - Create a new msg queue
 179  * @ns: namespace
 180  * @params: ptr to the structure that contains the key and msgflg
 181  *
 182  * Called with msg_ids.rwsem held (writer)
 183  */
 184 static int newque(struct ipc_namespace *ns, struct ipc_params *params)
 185 {
 186         struct msg_queue *msq;
 187         int id, retval;
 188         key_t key = params->key;
 189         int msgflg = params->flg;
 190
 191         msq = ipc_rcu_alloc(sizeof(*msq));
 192         if (!msq)
 193                 return -ENOMEM;
 194
 195         msq->q_perm.mode = msgflg & S_IRWXUGO;
 196         msq->q_perm.key = key;
 197
 198         msq->q_perm.security = NULL;
 199         retval = security_msg_queue_alloc(msq);
 200         if (retval) {
 201                 ipc_rcu_putref(msq, ipc_rcu_free);
 202                 return retval;
 203         }
 204
 205         /* ipc_addid() locks msq upon success. */
 206         id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
 207         if (id < 0) {
 208                 ipc_rcu_putref(msq, msg_rcu_free);
 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         ipc_unlock_object(&msq->q_perm);
 222         rcu_read_unlock();
 223
 224         return msq->q_perm.id;
 225 }
 226
 227 static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
 228 {
 229         mss->tsk = current;
 230         current->state = TASK_INTERRUPTIBLE;
 231         list_add_tail(&mss->list, &msq->q_senders);
 232 }
 233
 234 static inline void ss_del(struct msg_sender *mss)
 235 {
 236         if (mss->list.next != NULL)
 237                 list_del(&mss->list);
 238 }
 239
 240 static void ss_wakeup(struct list_head *h, int kill)
 241 {
 242         struct msg_sender *mss, *t;
 243
 244         list_for_each_entry_safe(mss, t, h, list) {
 245                 if (kill)
 246                         mss->list.next = NULL;
 247                 wake_up_process(mss->tsk);
 248         }
 249 }
 250
 251 static void expunge_all(struct msg_queue *msq, int res)
 252 {
 253         struct msg_receiver *msr, *t;
 254
 255         list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
 256                 msr->r_msg = NULL; /* initialize expunge ordering */
 257                 wake_up_process(msr->r_tsk);
 258                 /*
 259                  * Ensure that the wakeup is visible before setting r_msg as
 260                  * the receiving end depends on it: either spinning on a nil,
 261                  * or dealing with -EAGAIN cases. See lockless receive part 1
 262                  * and 2 in do_msgrcv().
 263                  */
 264                 smp_mb();
 265                 msr->r_msg = ERR_PTR(res);
 266         }
 267 }
 268
 269 /*
 270  * freeque() wakes up waiters on the sender and receiver waiting queue,
 271  * removes the message queue from message queue ID IDR, and cleans up all the
 272  * messages associated with this queue.
 273  *
 274  * msg_ids.rwsem (writer) and the spinlock for this message queue are held
 275  * before freeque() is called. msg_ids.rwsem remains locked on exit.
 276  */
 277 static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 278 {
 279         struct msg_msg *msg, *t;
 280         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 281
 282         expunge_all(msq, -EIDRM);
 283         ss_wakeup(&msq->q_senders, 1);
 284         msg_rmid(ns, msq);
 285         ipc_unlock_object(&msq->q_perm);
 286         rcu_read_unlock();
 287
 288         list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
 289                 atomic_dec(&ns->msg_hdrs);
 290                 free_msg(msg);
 291         }
 292         atomic_sub(msq->q_cbytes, &ns->msg_bytes);
 293         ipc_rcu_putref(msq, msg_rcu_free);
 294 }
 295
 296 /*
 297  * Called with msg_ids.rwsem and ipcp locked.
 298  */
 299 static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
 300 {
 301         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
 302
 303         return security_msg_queue_associate(msq, msgflg);
 304 }
 305
 306 SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
 307 {
 308         struct ipc_namespace *ns;
 309         struct ipc_ops msg_ops;
 310         struct ipc_params msg_params;
 311
 312         ns = current->nsproxy->ipc_ns;
 313
 314         msg_ops.getnew = newque;
 315         msg_ops.associate = msg_security;
 316         msg_ops.more_checks = NULL;
 317
 318         msg_params.key = key;
 319         msg_params.flg = msgflg;
 320
 321         return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
 322 }
 323
 324 static inline unsigned long
 325 copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
 326 {
 327         switch (version) {
 328         case IPC_64:
 329                 return copy_to_user(buf, in, sizeof(*in));
 330         case IPC_OLD:
 331         {
 332                 struct msqid_ds out;
 333
 334                 memset(&out, 0, sizeof(out));
 335
 336                 ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
 337
 338                 out.msg_stime           = in->msg_stime;
 339                 out.msg_rtime           = in->msg_rtime;
 340                 out.msg_ctime           = in->msg_ctime;
 341
 342                 if (in->msg_cbytes > USHRT_MAX)
 343                         out.msg_cbytes  = USHRT_MAX;
 344                 else
 345                         out.msg_cbytes  = in->msg_cbytes;
 346                 out.msg_lcbytes         = in->msg_cbytes;
 347
 348                 if (in->msg_qnum > USHRT_MAX)
 349                         out.msg_qnum    = USHRT_MAX;
 350                 else
 351                         out.msg_qnum    = in->msg_qnum;
 352
 353                 if (in->msg_qbytes > USHRT_MAX)
 354                         out.msg_qbytes  = USHRT_MAX;
 355                 else
 356                         out.msg_qbytes  = in->msg_qbytes;
 357                 out.msg_lqbytes         = in->msg_qbytes;
 358
 359                 out.msg_lspid           = in->msg_lspid;
 360                 out.msg_lrpid           = in->msg_lrpid;
 361
 362                 return copy_to_user(buf, &out, sizeof(out));
 363         }
 364         default:
 365                 return -EINVAL;
 366         }
 367 }
 368
 369 static inline unsigned long
 370 copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
 371 {
 372         switch (version) {
 373         case IPC_64:
 374                 if (copy_from_user(out, buf, sizeof(*out)))
 375                         return -EFAULT;
 376                 return 0;
 377         case IPC_OLD:
 378         {
 379                 struct msqid_ds tbuf_old;
 380
 381                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
 382                         return -EFAULT;
 383
 384                 out->msg_perm.uid       = tbuf_old.msg_perm.uid;
 385                 out->msg_perm.gid       = tbuf_old.msg_perm.gid;
 386                 out->msg_perm.mode      = tbuf_old.msg_perm.mode;
 387
 388                 if (tbuf_old.msg_qbytes == 0)
 389                         out->msg_qbytes = tbuf_old.msg_lqbytes;
 390                 else
 391                         out->msg_qbytes = tbuf_old.msg_qbytes;
 392
 393                 return 0;
 394         }
 395         default:
 396                 return -EINVAL;
 397         }
 398 }
 399
 400 /*
 401  * This function handles some msgctl commands which require the rwsem
 402  * to be held in write mode.
 403  * NOTE: no locks must be held, the rwsem is taken inside this function.
 404  */
 405 static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
 406                        struct msqid_ds __user *buf, int version)
 407 {
 408         struct kern_ipc_perm *ipcp;
 409         struct msqid64_ds uninitialized_var(msqid64);
 410         struct msg_queue *msq;
 411         int err;
 412
 413         if (cmd == IPC_SET) {
 414                 if (copy_msqid_from_user(&msqid64, buf, version))
 415                         return -EFAULT;
 416         }
 417
 418         down_write(&msg_ids(ns).rwsem);
 419         rcu_read_lock();
 420
 421         ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
 422                                       &msqid64.msg_perm, msqid64.msg_qbytes);
 423         if (IS_ERR(ipcp)) {
 424                 err = PTR_ERR(ipcp);
 425                 goto out_unlock1;
 426         }
 427
 428         msq = container_of(ipcp, struct msg_queue, q_perm);
 429
 430         err = security_msg_queue_msgctl(msq, cmd);
 431         if (err)
 432                 goto out_unlock1;
 433
 434         switch (cmd) {
 435         case IPC_RMID:
 436                 ipc_lock_object(&msq->q_perm);
 437                 /* freeque unlocks the ipc object and rcu */
 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_unlock1;
 445                 }
 446
 447                 ipc_lock_object(&msq->q_perm);
 448                 err = ipc_update_perm(&msqid64.msg_perm, ipcp);
 449                 if (err)
 450                         goto out_unlock0;
 451
 452                 msq->q_qbytes = msqid64.msg_qbytes;
 453
 454                 msq->q_ctime = get_seconds();
 455                 /* sleeping receivers might be excluded by
 456                  * stricter permissions.
 457                  */
 458                 expunge_all(msq, -EAGAIN);
 459                 /* sleeping senders might be able to send
 460                  * due to a larger queue size.
 461                  */
 462                 ss_wakeup(&msq->q_senders, 0);
 463                 break;
 464         default:
 465                 err = -EINVAL;
 466                 goto out_unlock1;
 467         }
 468
 469 out_unlock0:
 470         ipc_unlock_object(&msq->q_perm);
 471 out_unlock1:
 472         rcu_read_unlock();
 473 out_up:
 474         up_write(&msg_ids(ns).rwsem);
 475         return err;
 476 }
 477
 478 static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
 479                          int cmd, int version, void __user *buf)
 480 {
 481         int err;
 482         struct msg_queue *msq;
 483
 484         switch (cmd) {
 485         case IPC_INFO:
 486         case MSG_INFO:
 487         {
 488                 struct msginfo msginfo;
 489                 int max_id;
 490
 491                 if (!buf)
 492                         return -EFAULT;
 493
 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).rwsem);
 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).rwsem);
 521                 if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
 522                         return -EFAULT;
 523                 return (max_id < 0) ? 0 : max_id;
 524         }
 525
 526         case MSG_STAT:
 527         case IPC_STAT:
 528         {
 529                 struct msqid64_ds tbuf;
 530                 int success_return;
 531
 532                 if (!buf)
 533                         return -EFAULT;
 534
 535                 memset(&tbuf, 0, sizeof(tbuf));
 536
 537                 rcu_read_lock();
 538                 if (cmd == MSG_STAT) {
 539                         msq = msq_obtain_object(ns, msqid);
 540                         if (IS_ERR(msq)) {
 541                                 err = PTR_ERR(msq);
 542                                 goto out_unlock;
 543                         }
 544                         success_return = msq->q_perm.id;
 545                 } else {
 546                         msq = msq_obtain_object_check(ns, msqid);
 547                         if (IS_ERR(msq)) {
 548                                 err = PTR_ERR(msq);
 549                                 goto out_unlock;
 550                         }
 551                         success_return = 0;
 552                 }
 553
 554                 err = -EACCES;
 555                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 556                         goto out_unlock;
 557
 558                 err = security_msg_queue_msgctl(msq, cmd);
 559                 if (err)
 560                         goto out_unlock;
 561
 562                 kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
 563                 tbuf.msg_stime  = msq->q_stime;
 564                 tbuf.msg_rtime  = msq->q_rtime;
 565                 tbuf.msg_ctime  = msq->q_ctime;
 566                 tbuf.msg_cbytes = msq->q_cbytes;
 567                 tbuf.msg_qnum   = msq->q_qnum;
 568                 tbuf.msg_qbytes = msq->q_qbytes;
 569                 tbuf.msg_lspid  = msq->q_lspid;
 570                 tbuf.msg_lrpid  = msq->q_lrpid;
 571                 rcu_read_unlock();
 572
 573                 if (copy_msqid_to_user(buf, &tbuf, version))
 574                         return -EFAULT;
 575                 return success_return;
 576         }
 577
 578         default:
 579                 return -EINVAL;
 580         }
 581
 582         return err;
 583 out_unlock:
 584         rcu_read_unlock();
 585         return err;
 586 }
 587
 588 SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
 589 {
 590         int version;
 591         struct ipc_namespace *ns;
 592
 593         if (msqid < 0 || cmd < 0)
 594                 return -EINVAL;
 595
 596         version = ipc_parse_version(&cmd);
 597         ns = current->nsproxy->ipc_ns;
 598
 599         switch (cmd) {
 600         case IPC_INFO:
 601         case MSG_INFO:
 602         case MSG_STAT:  /* msqid is an index rather than a msg queue id */
 603         case IPC_STAT:
 604                 return msgctl_nolock(ns, msqid, cmd, version, buf);
 605         case IPC_SET:
 606         case IPC_RMID:
 607                 return msgctl_down(ns, msqid, cmd, buf, version);
 608         default:
 609                 return  -EINVAL;
 610         }
 611 }
 612
 613 static int testmsg(struct msg_msg *msg, long type, int mode)
 614 {
 615         switch (mode)
 616         {
 617                 case SEARCH_ANY:
 618                 case SEARCH_NUMBER:
 619                         return 1;
 620                 case SEARCH_LESSEQUAL:
 621                         if (msg->m_type <= type)
 622                                 return 1;
 623                         break;
 624                 case SEARCH_EQUAL:
 625                         if (msg->m_type == type)
 626                                 return 1;
 627                         break;
 628                 case SEARCH_NOTEQUAL:
 629                         if (msg->m_type != type)
 630                                 return 1;
 631                         break;
 632         }
 633         return 0;
 634 }
 635
 636 static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
 637 {
 638         struct msg_receiver *msr, *t;
 639
 640         list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
 641                 if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
 642                     !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
 643                                                msr->r_msgtype, msr->r_mode)) {
 644
 645                         list_del(&msr->r_list);
 646                         if (msr->r_maxsize < msg->m_ts) {
 647                                 /* initialize pipelined send ordering */
 648                                 msr->r_msg = NULL;
 649                                 wake_up_process(msr->r_tsk);
 650                                 smp_mb(); /* see barrier comment below */
 651                                 msr->r_msg = ERR_PTR(-E2BIG);
 652                         } else {
 653                                 msr->r_msg = NULL;
 654                                 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
 655                                 msq->q_rtime = get_seconds();
 656                                 wake_up_process(msr->r_tsk);
 657                                 /*
 658                                  * Ensure that the wakeup is visible before
 659                                  * setting r_msg, as the receiving end depends
 660                                  * on it. See lockless receive part 1 and 2 in
 661                                  * do_msgrcv().
 662                                  */
 663                                 smp_mb();
 664                                 msr->r_msg = msg;
 665
 666                                 return 1;
 667                         }
 668                 }
 669         }
 670
 671         return 0;
 672 }
 673
 674 long do_msgsnd(int msqid, long mtype, void __user *mtext,
 675                 size_t msgsz, int msgflg)
 676 {
 677         struct msg_queue *msq;
 678         struct msg_msg *msg;
 679         int err;
 680         struct ipc_namespace *ns;
 681
 682         ns = current->nsproxy->ipc_ns;
 683
 684         if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
 685                 return -EINVAL;
 686         if (mtype < 1)
 687                 return -EINVAL;
 688
 689         msg = load_msg(mtext, msgsz);
 690         if (IS_ERR(msg))
 691                 return PTR_ERR(msg);
 692
 693         msg->m_type = mtype;
 694         msg->m_ts = msgsz;
 695
 696         rcu_read_lock();
 697         msq = msq_obtain_object_check(ns, msqid);
 698         if (IS_ERR(msq)) {
 699                 err = PTR_ERR(msq);
 700                 goto out_unlock1;
 701         }
 702
 703         ipc_lock_object(&msq->q_perm);
 704
 705         for (;;) {
 706                 struct msg_sender s;
 707
 708                 err = -EACCES;
 709                 if (ipcperms(ns, &msq->q_perm, S_IWUGO))
 710                         goto out_unlock0;
 711
 712                 /* raced with RMID? */
 713                 if (!ipc_valid_object(&msq->q_perm)) {
 714                         err = -EIDRM;
 715                         goto out_unlock0;
 716                 }
 717
 718                 err = security_msg_queue_msgsnd(msq, msg, msgflg);
 719                 if (err)
 720                         goto out_unlock0;
 721
 722                 if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
 723                                 1 + msq->q_qnum <= msq->q_qbytes) {
 724                         break;
 725                 }
 726
 727                 /* queue full, wait: */
 728                 if (msgflg & IPC_NOWAIT) {
 729                         err = -EAGAIN;
 730                         goto out_unlock0;
 731                 }
 732
 733                 /* enqueue the sender and prepare to block */
 734                 ss_add(msq, &s);
 735
 736                 if (!ipc_rcu_getref(msq)) {
 737                         err = -EIDRM;
 738                         goto out_unlock0;
 739                 }
 740
 741                 ipc_unlock_object(&msq->q_perm);
 742                 rcu_read_unlock();
 743                 schedule();
 744
 745                 rcu_read_lock();
 746                 ipc_lock_object(&msq->q_perm);
 747
 748                 ipc_rcu_putref(msq, ipc_rcu_free);
 749                 /* raced with RMID? */
 750                 if (!ipc_valid_object(&msq->q_perm)) {
 751                         err = -EIDRM;
 752                         goto out_unlock0;
 753                 }
 754
 755                 ss_del(&s);
 756
 757                 if (signal_pending(current)) {
 758                         err = -ERESTARTNOHAND;
 759                         goto out_unlock0;
 760                 }
 761
 762         }
 763         msq->q_lspid = task_tgid_vnr(current);
 764         msq->q_stime = get_seconds();
 765
 766         if (!pipelined_send(msq, msg)) {
 767                 /* no one is waiting for this message, enqueue it */
 768                 list_add_tail(&msg->m_list, &msq->q_messages);
 769                 msq->q_cbytes += msgsz;
 770                 msq->q_qnum++;
 771                 atomic_add(msgsz, &ns->msg_bytes);
 772                 atomic_inc(&ns->msg_hdrs);
 773         }
 774
 775         err = 0;
 776         msg = NULL;
 777
 778 out_unlock0:
 779         ipc_unlock_object(&msq->q_perm);
 780 out_unlock1:
 781         rcu_read_unlock();
 782         if (msg != NULL)
 783                 free_msg(msg);
 784         return err;
 785 }
 786
 787 SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
 788                 int, msgflg)
 789 {
 790         long mtype;
 791
 792         if (get_user(mtype, &msgp->mtype))
 793                 return -EFAULT;
 794         return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
 795 }
 796
 797 static inline int convert_mode(long *msgtyp, int msgflg)
 798 {
 799         if (msgflg & MSG_COPY)
 800                 return SEARCH_NUMBER;
 801         /*
 802          *  find message of correct type.
 803          *  msgtyp = 0 => get first.
 804          *  msgtyp > 0 => get first message of matching type.
 805          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
 806          */
 807         if (*msgtyp == 0)
 808                 return SEARCH_ANY;
 809         if (*msgtyp < 0) {
 810                 *msgtyp = -*msgtyp;
 811                 return SEARCH_LESSEQUAL;
 812         }
 813         if (msgflg & MSG_EXCEPT)
 814                 return SEARCH_NOTEQUAL;
 815         return SEARCH_EQUAL;
 816 }
 817
 818 static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
 819 {
 820         struct msgbuf __user *msgp = dest;
 821         size_t msgsz;
 822
 823         if (put_user(msg->m_type, &msgp->mtype))
 824                 return -EFAULT;
 825
 826         msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
 827         if (store_msg(msgp->mtext, msg, msgsz))
 828                 return -EFAULT;
 829         return msgsz;
 830 }
 831
 832 #ifdef CONFIG_CHECKPOINT_RESTORE
 833 /*
 834  * This function creates new kernel message structure, large enough to store
 835  * bufsz message bytes.
 836  */
 837 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 838 {
 839         struct msg_msg *copy;
 840
 841         /*
 842          * Create dummy message to copy real message to.
 843          */
 844         copy = load_msg(buf, bufsz);
 845         if (!IS_ERR(copy))
 846                 copy->m_ts = bufsz;
 847         return copy;
 848 }
 849
 850 static inline void free_copy(struct msg_msg *copy)
 851 {
 852         if (copy)
 853                 free_msg(copy);
 854 }
 855 #else
 856 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
 857 {
 858         return ERR_PTR(-ENOSYS);
 859 }
 860
 861 static inline void free_copy(struct msg_msg *copy)
 862 {
 863 }
 864 #endif
 865
 866 static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
 867 {
 868         struct msg_msg *msg, *found = NULL;
 869         long count = 0;
 870
 871         list_for_each_entry(msg, &msq->q_messages, m_list) {
 872                 if (testmsg(msg, *msgtyp, mode) &&
 873                     !security_msg_queue_msgrcv(msq, msg, current,
 874                                                *msgtyp, mode)) {
 875                         if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
 876                                 *msgtyp = msg->m_type - 1;
 877                                 found = msg;
 878                         } else if (mode == SEARCH_NUMBER) {
 879                                 if (*msgtyp == count)
 880                                         return msg;
 881                         } else
 882                                 return msg;
 883                         count++;
 884                 }
 885         }
 886
 887         return found ?: ERR_PTR(-EAGAIN);
 888 }
 889
 890 long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
 891                long (*msg_handler)(void __user *, struct msg_msg *, size_t))
 892 {
 893         int mode;
 894         struct msg_queue *msq;
 895         struct ipc_namespace *ns;
 896         struct msg_msg *msg, *copy = NULL;
 897
 898         ns = current->nsproxy->ipc_ns;
 899
 900         if (msqid < 0 || (long) bufsz < 0)
 901                 return -EINVAL;
 902
 903         if (msgflg & MSG_COPY) {
 904                 if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
 905                         return -EINVAL;
 906                 copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
 907                 if (IS_ERR(copy))
 908                         return PTR_ERR(copy);
 909         }
 910         mode = convert_mode(&msgtyp, msgflg);
 911
 912         rcu_read_lock();
 913         msq = msq_obtain_object_check(ns, msqid);
 914         if (IS_ERR(msq)) {
 915                 rcu_read_unlock();
 916                 free_copy(copy);
 917                 return PTR_ERR(msq);
 918         }
 919
 920         for (;;) {
 921                 struct msg_receiver msr_d;
 922
 923                 msg = ERR_PTR(-EACCES);
 924                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
 925                         goto out_unlock1;
 926
 927                 ipc_lock_object(&msq->q_perm);
 928
 929                 /* raced with RMID? */
 930                 if (!ipc_valid_object(&msq->q_perm)) {
 931                         msg = ERR_PTR(-EIDRM);
 932                         goto out_unlock0;
 933                 }
 934
 935                 msg = find_msg(msq, &msgtyp, mode);
 936                 if (!IS_ERR(msg)) {
 937                         /*
 938                          * Found a suitable message.
 939                          * Unlink it from the queue.
 940                          */
 941                         if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
 942                                 msg = ERR_PTR(-E2BIG);
 943                                 goto out_unlock0;
 944                         }
 945                         /*
 946                          * If we are copying, then do not unlink message and do
 947                          * not update queue parameters.
 948                          */
 949                         if (msgflg & MSG_COPY) {
 950                                 msg = copy_msg(msg, copy);
 951                                 goto out_unlock0;
 952                         }
 953
 954                         list_del(&msg->m_list);
 955                         msq->q_qnum--;
 956                         msq->q_rtime = get_seconds();
 957                         msq->q_lrpid = task_tgid_vnr(current);
 958                         msq->q_cbytes -= msg->m_ts;
 959                         atomic_sub(msg->m_ts, &ns->msg_bytes);
 960                         atomic_dec(&ns->msg_hdrs);
 961                         ss_wakeup(&msq->q_senders, 0);
 962
 963                         goto out_unlock0;
 964                 }
 965
 966                 /* No message waiting. Wait for a message */
 967                 if (msgflg & IPC_NOWAIT) {
 968                         msg = ERR_PTR(-ENOMSG);
 969                         goto out_unlock0;
 970                 }
 971
 972                 list_add_tail(&msr_d.r_list, &msq->q_receivers);
 973                 msr_d.r_tsk = current;
 974                 msr_d.r_msgtype = msgtyp;
 975                 msr_d.r_mode = mode;
 976                 if (msgflg & MSG_NOERROR)
 977                         msr_d.r_maxsize = INT_MAX;
 978                 else
 979                         msr_d.r_maxsize = bufsz;
 980                 msr_d.r_msg = ERR_PTR(-EAGAIN);
 981                 current->state = TASK_INTERRUPTIBLE;
 982
 983                 ipc_unlock_object(&msq->q_perm);
 984                 rcu_read_unlock();
 985                 schedule();
 986
 987                 /* Lockless receive, part 1:
 988                  * Disable preemption.  We don't hold a reference to the queue
 989                  * and getting a reference would defeat the idea of a lockless
 990                  * operation, thus the code relies on rcu to guarantee the
 991                  * existence of msq:
 992                  * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
 993                  * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
 994                  * rcu_read_lock() prevents preemption between reading r_msg
 995                  * and acquiring the q_perm.lock in ipc_lock_object().
 996                  */
 997                 rcu_read_lock();
 998
 999                 /* Lockless receive, part 2:
1000                  * Wait until pipelined_send or expunge_all are outside of
1001                  * wake_up_process(). There is a race with exit(), see
1002                  * ipc/mqueue.c for the details.
1003                  */
1004                 msg = (struct msg_msg *)msr_d.r_msg;
1005                 while (msg == NULL) {
1006                         cpu_relax();
1007                         msg = (struct msg_msg *)msr_d.r_msg;
1008                 }
1009
1010                 /* Lockless receive, part 3:
1011                  * If there is a message or an error then accept it without
1012                  * locking.
1013                  */
1014                 if (msg != ERR_PTR(-EAGAIN))
1015                         goto out_unlock1;
1016
1017                 /* Lockless receive, part 3:
1018                  * Acquire the queue spinlock.
1019                  */
1020                 ipc_lock_object(&msq->q_perm);
1021
1022                 /* Lockless receive, part 4:
1023                  * Repeat test after acquiring the spinlock.
1024                  */
1025                 msg = (struct msg_msg *)msr_d.r_msg;
1026                 if (msg != ERR_PTR(-EAGAIN))
1027                         goto out_unlock0;
1028
1029                 list_del(&msr_d.r_list);
1030                 if (signal_pending(current)) {
1031                         msg = ERR_PTR(-ERESTARTNOHAND);
1032                         goto out_unlock0;
1033                 }
1034
1035                 ipc_unlock_object(&msq->q_perm);
1036         }
1037
1038 out_unlock0:
1039         ipc_unlock_object(&msq->q_perm);
1040 out_unlock1:
1041         rcu_read_unlock();
1042         if (IS_ERR(msg)) {
1043                 free_copy(copy);
1044                 return PTR_ERR(msg);
1045         }
1046
1047         bufsz = msg_handler(buf, msg, bufsz);
1048         free_msg(msg);
1049
1050         return bufsz;
1051 }
1052
1053 SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
1054                 long, msgtyp, int, msgflg)
1055 {
1056         return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
1057 }
1058
1059 #ifdef CONFIG_PROC_FS
1060 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
1061 {
1062         struct user_namespace *user_ns = seq_user_ns(s);
1063         struct msg_queue *msq = it;
1064
1065         return seq_printf(s,
1066                         "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1067                         msq->q_perm.key,
1068                         msq->q_perm.id,
1069                         msq->q_perm.mode,
1070                         msq->q_cbytes,
1071                         msq->q_qnum,
1072                         msq->q_lspid,
1073                         msq->q_lrpid,
1074                         from_kuid_munged(user_ns, msq->q_perm.uid),
1075                         from_kgid_munged(user_ns, msq->q_perm.gid),
1076                         from_kuid_munged(user_ns, msq->q_perm.cuid),
1077                         from_kgid_munged(user_ns, msq->q_perm.cgid),
1078                         msq->q_stime,
1079                         msq->q_rtime,
1080                         msq->q_ctime);
1081 }
1082 #endif