linux/ipc/util.c
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   1/*
   2 * linux/ipc/util.c
   3 * Copyright (C) 1992 Krishna Balasubramanian
   4 *
   5 * Sep 1997 - Call suser() last after "normal" permission checks so we
   6 *            get BSD style process accounting right.
   7 *            Occurs in several places in the IPC code.
   8 *            Chris Evans, <chris@ferret.lmh.ox.ac.uk>
   9 * Nov 1999 - ipc helper functions, unified SMP locking
  10 *            Manfred Spraul <manfred@colorfullife.com>
  11 * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
  12 *            Mingming Cao <cmm@us.ibm.com>
  13 * Mar 2006 - support for audit of ipc object properties
  14 *            Dustin Kirkland <dustin.kirkland@us.ibm.com>
  15 * Jun 2006 - namespaces ssupport
  16 *            OpenVZ, SWsoft Inc.
  17 *            Pavel Emelianov <xemul@openvz.org>
  18 *
  19 * General sysv ipc locking scheme:
  20 *  when doing ipc id lookups, take the ids->rwsem
  21 *      rcu_read_lock()
  22 *          obtain the ipc object (kern_ipc_perm)
  23 *          perform security, capabilities, auditing and permission checks, etc.
  24 *          acquire the ipc lock (kern_ipc_perm.lock) throught ipc_lock_object()
  25 *             perform data updates (ie: SET, RMID, LOCK/UNLOCK commands)
  26 */
  27
  28#include <linux/mm.h>
  29#include <linux/shm.h>
  30#include <linux/init.h>
  31#include <linux/msg.h>
  32#include <linux/vmalloc.h>
  33#include <linux/slab.h>
  34#include <linux/notifier.h>
  35#include <linux/capability.h>
  36#include <linux/highuid.h>
  37#include <linux/security.h>
  38#include <linux/rcupdate.h>
  39#include <linux/workqueue.h>
  40#include <linux/seq_file.h>
  41#include <linux/proc_fs.h>
  42#include <linux/audit.h>
  43#include <linux/nsproxy.h>
  44#include <linux/rwsem.h>
  45#include <linux/memory.h>
  46#include <linux/ipc_namespace.h>
  47
  48#include <asm/unistd.h>
  49
  50#include "util.h"
  51
  52struct ipc_proc_iface {
  53        const char *path;
  54        const char *header;
  55        int ids;
  56        int (*show)(struct seq_file *, void *);
  57};
  58
  59static void ipc_memory_notifier(struct work_struct *work)
  60{
  61        ipcns_notify(IPCNS_MEMCHANGED);
  62}
  63
  64static int ipc_memory_callback(struct notifier_block *self,
  65                                unsigned long action, void *arg)
  66{
  67        static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
  68
  69        switch (action) {
  70        case MEM_ONLINE:    /* memory successfully brought online */
  71        case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
  72                /*
  73                 * This is done by invoking the ipcns notifier chain with the
  74                 * IPC_MEMCHANGED event.
  75                 * In order not to keep the lock on the hotplug memory chain
  76                 * for too long, queue a work item that will, when waken up,
  77                 * activate the ipcns notification chain.
  78                 * No need to keep several ipc work items on the queue.
  79                 */
  80                if (!work_pending(&ipc_memory_wq))
  81                        schedule_work(&ipc_memory_wq);
  82                break;
  83        case MEM_GOING_ONLINE:
  84        case MEM_GOING_OFFLINE:
  85        case MEM_CANCEL_ONLINE:
  86        case MEM_CANCEL_OFFLINE:
  87        default:
  88                break;
  89        }
  90
  91        return NOTIFY_OK;
  92}
  93
  94static struct notifier_block ipc_memory_nb = {
  95        .notifier_call = ipc_memory_callback,
  96        .priority = IPC_CALLBACK_PRI,
  97};
  98
  99/**
 100 *      ipc_init        -       initialise IPC subsystem
 101 *
 102 *      The various system5 IPC resources (semaphores, messages and shared
 103 *      memory) are initialised
 104 *      A callback routine is registered into the memory hotplug notifier
 105 *      chain: since msgmni scales to lowmem this callback routine will be
 106 *      called upon successful memory add / remove to recompute msmgni.
 107 */
 108 
 109static int __init ipc_init(void)
 110{
 111        sem_init();
 112        msg_init();
 113        shm_init();
 114        register_hotmemory_notifier(&ipc_memory_nb);
 115        register_ipcns_notifier(&init_ipc_ns);
 116        return 0;
 117}
 118__initcall(ipc_init);
 119
 120/**
 121 *      ipc_init_ids            -       initialise IPC identifiers
 122 *      @ids: Identifier set
 123 *
 124 *      Set up the sequence range to use for the ipc identifier range (limited
 125 *      below IPCMNI) then initialise the ids idr.
 126 */
 127 
 128void ipc_init_ids(struct ipc_ids *ids)
 129{
 130        init_rwsem(&ids->rwsem);
 131
 132        ids->in_use = 0;
 133        ids->seq = 0;
 134        ids->next_id = -1;
 135        {
 136                int seq_limit = INT_MAX/SEQ_MULTIPLIER;
 137                if (seq_limit > USHRT_MAX)
 138                        ids->seq_max = USHRT_MAX;
 139                 else
 140                        ids->seq_max = seq_limit;
 141        }
 142
 143        idr_init(&ids->ipcs_idr);
 144}
 145
 146#ifdef CONFIG_PROC_FS
 147static const struct file_operations sysvipc_proc_fops;
 148/**
 149 *      ipc_init_proc_interface -  Create a proc interface for sysipc types using a seq_file interface.
 150 *      @path: Path in procfs
 151 *      @header: Banner to be printed at the beginning of the file.
 152 *      @ids: ipc id table to iterate.
 153 *      @show: show routine.
 154 */
 155void __init ipc_init_proc_interface(const char *path, const char *header,
 156                int ids, int (*show)(struct seq_file *, void *))
 157{
 158        struct proc_dir_entry *pde;
 159        struct ipc_proc_iface *iface;
 160
 161        iface = kmalloc(sizeof(*iface), GFP_KERNEL);
 162        if (!iface)
 163                return;
 164        iface->path     = path;
 165        iface->header   = header;
 166        iface->ids      = ids;
 167        iface->show     = show;
 168
 169        pde = proc_create_data(path,
 170                               S_IRUGO,        /* world readable */
 171                               NULL,           /* parent dir */
 172                               &sysvipc_proc_fops,
 173                               iface);
 174        if (!pde) {
 175                kfree(iface);
 176        }
 177}
 178#endif
 179
 180/**
 181 *      ipc_findkey     -       find a key in an ipc identifier set     
 182 *      @ids: Identifier set
 183 *      @key: The key to find
 184 *      
 185 *      Requires ipc_ids.rwsem locked.
 186 *      Returns the LOCKED pointer to the ipc structure if found or NULL
 187 *      if not.
 188 *      If key is found ipc points to the owning ipc structure
 189 */
 190 
 191static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 192{
 193        struct kern_ipc_perm *ipc;
 194        int next_id;
 195        int total;
 196
 197        for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
 198                ipc = idr_find(&ids->ipcs_idr, next_id);
 199
 200                if (ipc == NULL)
 201                        continue;
 202
 203                if (ipc->key != key) {
 204                        total++;
 205                        continue;
 206                }
 207
 208                rcu_read_lock();
 209                ipc_lock_object(ipc);
 210                return ipc;
 211        }
 212
 213        return NULL;
 214}
 215
 216/**
 217 *      ipc_get_maxid   -       get the last assigned id
 218 *      @ids: IPC identifier set
 219 *
 220 *      Called with ipc_ids.rwsem held.
 221 */
 222
 223int ipc_get_maxid(struct ipc_ids *ids)
 224{
 225        struct kern_ipc_perm *ipc;
 226        int max_id = -1;
 227        int total, id;
 228
 229        if (ids->in_use == 0)
 230                return -1;
 231
 232        if (ids->in_use == IPCMNI)
 233                return IPCMNI - 1;
 234
 235        /* Look for the last assigned id */
 236        total = 0;
 237        for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
 238                ipc = idr_find(&ids->ipcs_idr, id);
 239                if (ipc != NULL) {
 240                        max_id = id;
 241                        total++;
 242                }
 243        }
 244        return max_id;
 245}
 246
 247/**
 248 *      ipc_addid       -       add an IPC identifier
 249 *      @ids: IPC identifier set
 250 *      @new: new IPC permission set
 251 *      @size: limit for the number of used ids
 252 *
 253 *      Add an entry 'new' to the IPC ids idr. The permissions object is
 254 *      initialised and the first free entry is set up and the id assigned
 255 *      is returned. The 'new' entry is returned in a locked state on success.
 256 *      On failure the entry is not locked and a negative err-code is returned.
 257 *
 258 *      Called with writer ipc_ids.rwsem held.
 259 */
 260int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 261{
 262        kuid_t euid;
 263        kgid_t egid;
 264        int id;
 265        int next_id = ids->next_id;
 266
 267        if (size > IPCMNI)
 268                size = IPCMNI;
 269
 270        if (ids->in_use >= size)
 271                return -ENOSPC;
 272
 273        idr_preload(GFP_KERNEL);
 274
 275        spin_lock_init(&new->lock);
 276        new->deleted = 0;
 277        rcu_read_lock();
 278        spin_lock(&new->lock);
 279
 280        id = idr_alloc(&ids->ipcs_idr, new,
 281                       (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
 282                       GFP_NOWAIT);
 283        idr_preload_end();
 284        if (id < 0) {
 285                spin_unlock(&new->lock);
 286                rcu_read_unlock();
 287                return id;
 288        }
 289
 290        ids->in_use++;
 291
 292        current_euid_egid(&euid, &egid);
 293        new->cuid = new->uid = euid;
 294        new->gid = new->cgid = egid;
 295
 296        if (next_id < 0) {
 297                new->seq = ids->seq++;
 298                if (ids->seq > ids->seq_max)
 299                        ids->seq = 0;
 300        } else {
 301                new->seq = ipcid_to_seqx(next_id);
 302                ids->next_id = -1;
 303        }
 304
 305        new->id = ipc_buildid(id, new->seq);
 306        return id;
 307}
 308
 309/**
 310 *      ipcget_new      -       create a new ipc object
 311 *      @ns: namespace
 312 *      @ids: IPC identifer set
 313 *      @ops: the actual creation routine to call
 314 *      @params: its parameters
 315 *
 316 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 317 *      when the key is IPC_PRIVATE.
 318 */
 319static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
 320                struct ipc_ops *ops, struct ipc_params *params)
 321{
 322        int err;
 323
 324        down_write(&ids->rwsem);
 325        err = ops->getnew(ns, params);
 326        up_write(&ids->rwsem);
 327        return err;
 328}
 329
 330/**
 331 *      ipc_check_perms -       check security and permissions for an IPC
 332 *      @ns: IPC namespace
 333 *      @ipcp: ipc permission set
 334 *      @ops: the actual security routine to call
 335 *      @params: its parameters
 336 *
 337 *      This routine is called by sys_msgget(), sys_semget() and sys_shmget()
 338 *      when the key is not IPC_PRIVATE and that key already exists in the
 339 *      ids IDR.
 340 *
 341 *      On success, the IPC id is returned.
 342 *
 343 *      It is called with ipc_ids.rwsem and ipcp->lock held.
 344 */
 345static int ipc_check_perms(struct ipc_namespace *ns,
 346                           struct kern_ipc_perm *ipcp,
 347                           struct ipc_ops *ops,
 348                           struct ipc_params *params)
 349{
 350        int err;
 351
 352        if (ipcperms(ns, ipcp, params->flg))
 353                err = -EACCES;
 354        else {
 355                err = ops->associate(ipcp, params->flg);
 356                if (!err)
 357                        err = ipcp->id;
 358        }
 359
 360        return err;
 361}
 362
 363/**
 364 *      ipcget_public   -       get an ipc object or create a new one
 365 *      @ns: namespace
 366 *      @ids: IPC identifer set
 367 *      @ops: the actual creation routine to call
 368 *      @params: its parameters
 369 *
 370 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 371 *      when the key is not IPC_PRIVATE.
 372 *      It adds a new entry if the key is not found and does some permission
 373 *      / security checkings if the key is found.
 374 *
 375 *      On success, the ipc id is returned.
 376 */
 377static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 378                struct ipc_ops *ops, struct ipc_params *params)
 379{
 380        struct kern_ipc_perm *ipcp;
 381        int flg = params->flg;
 382        int err;
 383
 384        /*
 385         * Take the lock as a writer since we are potentially going to add
 386         * a new entry + read locks are not "upgradable"
 387         */
 388        down_write(&ids->rwsem);
 389        ipcp = ipc_findkey(ids, params->key);
 390        if (ipcp == NULL) {
 391                /* key not used */
 392                if (!(flg & IPC_CREAT))
 393                        err = -ENOENT;
 394                else
 395                        err = ops->getnew(ns, params);
 396        } else {
 397                /* ipc object has been locked by ipc_findkey() */
 398
 399                if (flg & IPC_CREAT && flg & IPC_EXCL)
 400                        err = -EEXIST;
 401                else {
 402                        err = 0;
 403                        if (ops->more_checks)
 404                                err = ops->more_checks(ipcp, params);
 405                        if (!err)
 406                                /*
 407                                 * ipc_check_perms returns the IPC id on
 408                                 * success
 409                                 */
 410                                err = ipc_check_perms(ns, ipcp, ops, params);
 411                }
 412                ipc_unlock(ipcp);
 413        }
 414        up_write(&ids->rwsem);
 415
 416        return err;
 417}
 418
 419
 420/**
 421 *      ipc_rmid        -       remove an IPC identifier
 422 *      @ids: IPC identifier set
 423 *      @ipcp: ipc perm structure containing the identifier to remove
 424 *
 425 *      ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
 426 *      before this function is called, and remain locked on the exit.
 427 */
 428 
 429void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 430{
 431        int lid = ipcid_to_idx(ipcp->id);
 432
 433        idr_remove(&ids->ipcs_idr, lid);
 434
 435        ids->in_use--;
 436
 437        ipcp->deleted = 1;
 438
 439        return;
 440}
 441
 442/**
 443 *      ipc_alloc       -       allocate ipc space
 444 *      @size: size desired
 445 *
 446 *      Allocate memory from the appropriate pools and return a pointer to it.
 447 *      NULL is returned if the allocation fails
 448 */
 449 
 450void *ipc_alloc(int size)
 451{
 452        void *out;
 453        if(size > PAGE_SIZE)
 454                out = vmalloc(size);
 455        else
 456                out = kmalloc(size, GFP_KERNEL);
 457        return out;
 458}
 459
 460/**
 461 *      ipc_free        -       free ipc space
 462 *      @ptr: pointer returned by ipc_alloc
 463 *      @size: size of block
 464 *
 465 *      Free a block created with ipc_alloc(). The caller must know the size
 466 *      used in the allocation call.
 467 */
 468
 469void ipc_free(void* ptr, int size)
 470{
 471        if(size > PAGE_SIZE)
 472                vfree(ptr);
 473        else
 474                kfree(ptr);
 475}
 476
 477/**
 478 *      ipc_rcu_alloc   -       allocate ipc and rcu space 
 479 *      @size: size desired
 480 *
 481 *      Allocate memory for the rcu header structure +  the object.
 482 *      Returns the pointer to the object or NULL upon failure.
 483 */
 484void *ipc_rcu_alloc(int size)
 485{
 486        /*
 487         * We prepend the allocation with the rcu struct
 488         */
 489        struct ipc_rcu *out = ipc_alloc(sizeof(struct ipc_rcu) + size);
 490        if (unlikely(!out))
 491                return NULL;
 492        atomic_set(&out->refcount, 1);
 493        return out + 1;
 494}
 495
 496int ipc_rcu_getref(void *ptr)
 497{
 498        struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;
 499
 500        return atomic_inc_not_zero(&p->refcount);
 501}
 502
 503void ipc_rcu_putref(void *ptr, void (*func)(struct rcu_head *head))
 504{
 505        struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;
 506
 507        if (!atomic_dec_and_test(&p->refcount))
 508                return;
 509
 510        call_rcu(&p->rcu, func);
 511}
 512
 513void ipc_rcu_free(struct rcu_head *head)
 514{
 515        struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
 516
 517        if (is_vmalloc_addr(p))
 518                vfree(p);
 519        else
 520                kfree(p);
 521}
 522
 523/**
 524 *      ipcperms        -       check IPC permissions
 525 *      @ns: IPC namespace
 526 *      @ipcp: IPC permission set
 527 *      @flag: desired permission set.
 528 *
 529 *      Check user, group, other permissions for access
 530 *      to ipc resources. return 0 if allowed
 531 *
 532 *      @flag will most probably be 0 or S_...UGO from <linux/stat.h>
 533 */
 534 
 535int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
 536{
 537        kuid_t euid = current_euid();
 538        int requested_mode, granted_mode;
 539
 540        audit_ipc_obj(ipcp);
 541        requested_mode = (flag >> 6) | (flag >> 3) | flag;
 542        granted_mode = ipcp->mode;
 543        if (uid_eq(euid, ipcp->cuid) ||
 544            uid_eq(euid, ipcp->uid))
 545                granted_mode >>= 6;
 546        else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 547                granted_mode >>= 3;
 548        /* is there some bit set in requested_mode but not in granted_mode? */
 549        if ((requested_mode & ~granted_mode & 0007) && 
 550            !ns_capable(ns->user_ns, CAP_IPC_OWNER))
 551                return -1;
 552
 553        return security_ipc_permission(ipcp, flag);
 554}
 555
 556/*
 557 * Functions to convert between the kern_ipc_perm structure and the
 558 * old/new ipc_perm structures
 559 */
 560
 561/**
 562 *      kernel_to_ipc64_perm    -       convert kernel ipc permissions to user
 563 *      @in: kernel permissions
 564 *      @out: new style IPC permissions
 565 *
 566 *      Turn the kernel object @in into a set of permissions descriptions
 567 *      for returning to userspace (@out).
 568 */
 569 
 570
 571void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
 572{
 573        out->key        = in->key;
 574        out->uid        = from_kuid_munged(current_user_ns(), in->uid);
 575        out->gid        = from_kgid_munged(current_user_ns(), in->gid);
 576        out->cuid       = from_kuid_munged(current_user_ns(), in->cuid);
 577        out->cgid       = from_kgid_munged(current_user_ns(), in->cgid);
 578        out->mode       = in->mode;
 579        out->seq        = in->seq;
 580}
 581
 582/**
 583 *      ipc64_perm_to_ipc_perm  -       convert new ipc permissions to old
 584 *      @in: new style IPC permissions
 585 *      @out: old style IPC permissions
 586 *
 587 *      Turn the new style permissions object @in into a compatibility
 588 *      object and store it into the @out pointer.
 589 */
 590 
 591void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
 592{
 593        out->key        = in->key;
 594        SET_UID(out->uid, in->uid);
 595        SET_GID(out->gid, in->gid);
 596        SET_UID(out->cuid, in->cuid);
 597        SET_GID(out->cgid, in->cgid);
 598        out->mode       = in->mode;
 599        out->seq        = in->seq;
 600}
 601
 602/**
 603 * ipc_obtain_object
 604 * @ids: ipc identifier set
 605 * @id: ipc id to look for
 606 *
 607 * Look for an id in the ipc ids idr and return associated ipc object.
 608 *
 609 * Call inside the RCU critical section.
 610 * The ipc object is *not* locked on exit.
 611 */
 612struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id)
 613{
 614        struct kern_ipc_perm *out;
 615        int lid = ipcid_to_idx(id);
 616
 617        out = idr_find(&ids->ipcs_idr, lid);
 618        if (!out)
 619                return ERR_PTR(-EINVAL);
 620
 621        return out;
 622}
 623
 624/**
 625 * ipc_lock - Lock an ipc structure without rwsem held
 626 * @ids: IPC identifier set
 627 * @id: ipc id to look for
 628 *
 629 * Look for an id in the ipc ids idr and lock the associated ipc object.
 630 *
 631 * The ipc object is locked on successful exit.
 632 */
 633struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
 634{
 635        struct kern_ipc_perm *out;
 636
 637        rcu_read_lock();
 638        out = ipc_obtain_object(ids, id);
 639        if (IS_ERR(out))
 640                goto err1;
 641
 642        spin_lock(&out->lock);
 643
 644        /* ipc_rmid() may have already freed the ID while ipc_lock
 645         * was spinning: here verify that the structure is still valid
 646         */
 647        if (!out->deleted)
 648                return out;
 649
 650        spin_unlock(&out->lock);
 651        out = ERR_PTR(-EINVAL);
 652err1:
 653        rcu_read_unlock();
 654        return out;
 655}
 656
 657/**
 658 * ipc_obtain_object_check
 659 * @ids: ipc identifier set
 660 * @id: ipc id to look for
 661 *
 662 * Similar to ipc_obtain_object() but also checks
 663 * the ipc object reference counter.
 664 *
 665 * Call inside the RCU critical section.
 666 * The ipc object is *not* locked on exit.
 667 */
 668struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
 669{
 670        struct kern_ipc_perm *out = ipc_obtain_object(ids, id);
 671
 672        if (IS_ERR(out))
 673                goto out;
 674
 675        if (ipc_checkid(out, id))
 676                return ERR_PTR(-EIDRM);
 677out:
 678        return out;
 679}
 680
 681/**
 682 * ipcget - Common sys_*get() code
 683 * @ns : namsepace
 684 * @ids : IPC identifier set
 685 * @ops : operations to be called on ipc object creation, permission checks
 686 *        and further checks
 687 * @params : the parameters needed by the previous operations.
 688 *
 689 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
 690 */
 691int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
 692                        struct ipc_ops *ops, struct ipc_params *params)
 693{
 694        if (params->key == IPC_PRIVATE)
 695                return ipcget_new(ns, ids, ops, params);
 696        else
 697                return ipcget_public(ns, ids, ops, params);
 698}
 699
 700/**
 701 * ipc_update_perm - update the permissions of an IPC.
 702 * @in:  the permission given as input.
 703 * @out: the permission of the ipc to set.
 704 */
 705int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 706{
 707        kuid_t uid = make_kuid(current_user_ns(), in->uid);
 708        kgid_t gid = make_kgid(current_user_ns(), in->gid);
 709        if (!uid_valid(uid) || !gid_valid(gid))
 710                return -EINVAL;
 711
 712        out->uid = uid;
 713        out->gid = gid;
 714        out->mode = (out->mode & ~S_IRWXUGO)
 715                | (in->mode & S_IRWXUGO);
 716
 717        return 0;
 718}
 719
 720/**
 721 * ipcctl_pre_down_nolock - retrieve an ipc and check permissions for some IPC_XXX cmd
 722 * @ns:  the ipc namespace
 723 * @ids:  the table of ids where to look for the ipc
 724 * @id:   the id of the ipc to retrieve
 725 * @cmd:  the cmd to check
 726 * @perm: the permission to set
 727 * @extra_perm: one extra permission parameter used by msq
 728 *
 729 * This function does some common audit and permissions check for some IPC_XXX
 730 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
 731 * It must be called without any lock held and
 732 *  - retrieves the ipc with the given id in the given table.
 733 *  - performs some audit and permission check, depending on the given cmd
 734 *  - returns a pointer to the ipc object or otherwise, the corresponding error.
 735 *
 736 * Call holding the both the rwsem and the rcu read lock.
 737 */
 738struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
 739                                        struct ipc_ids *ids, int id, int cmd,
 740                                        struct ipc64_perm *perm, int extra_perm)
 741{
 742        kuid_t euid;
 743        int err = -EPERM;
 744        struct kern_ipc_perm *ipcp;
 745
 746        ipcp = ipc_obtain_object_check(ids, id);
 747        if (IS_ERR(ipcp)) {
 748                err = PTR_ERR(ipcp);
 749                goto err;
 750        }
 751
 752        audit_ipc_obj(ipcp);
 753        if (cmd == IPC_SET)
 754                audit_ipc_set_perm(extra_perm, perm->uid,
 755                                   perm->gid, perm->mode);
 756
 757        euid = current_euid();
 758        if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
 759            ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 760                return ipcp; /* successful lookup */
 761err:
 762        return ERR_PTR(err);
 763}
 764
 765#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
 766
 767
 768/**
 769 *      ipc_parse_version       -       IPC call version
 770 *      @cmd: pointer to command
 771 *
 772 *      Return IPC_64 for new style IPC and IPC_OLD for old style IPC. 
 773 *      The @cmd value is turned from an encoding command and version into
 774 *      just the command code.
 775 */
 776 
 777int ipc_parse_version (int *cmd)
 778{
 779        if (*cmd & IPC_64) {
 780                *cmd ^= IPC_64;
 781                return IPC_64;
 782        } else {
 783                return IPC_OLD;
 784        }
 785}
 786
 787#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
 788
 789#ifdef CONFIG_PROC_FS
 790struct ipc_proc_iter {
 791        struct ipc_namespace *ns;
 792        struct ipc_proc_iface *iface;
 793};
 794
 795/*
 796 * This routine locks the ipc structure found at least at position pos.
 797 */
 798static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 799                                              loff_t *new_pos)
 800{
 801        struct kern_ipc_perm *ipc;
 802        int total, id;
 803
 804        total = 0;
 805        for (id = 0; id < pos && total < ids->in_use; id++) {
 806                ipc = idr_find(&ids->ipcs_idr, id);
 807                if (ipc != NULL)
 808                        total++;
 809        }
 810
 811        if (total >= ids->in_use)
 812                return NULL;
 813
 814        for ( ; pos < IPCMNI; pos++) {
 815                ipc = idr_find(&ids->ipcs_idr, pos);
 816                if (ipc != NULL) {
 817                        *new_pos = pos + 1;
 818                        rcu_read_lock();
 819                        ipc_lock_object(ipc);
 820                        return ipc;
 821                }
 822        }
 823
 824        /* Out of range - return NULL to terminate iteration */
 825        return NULL;
 826}
 827
 828static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 829{
 830        struct ipc_proc_iter *iter = s->private;
 831        struct ipc_proc_iface *iface = iter->iface;
 832        struct kern_ipc_perm *ipc = it;
 833
 834        /* If we had an ipc id locked before, unlock it */
 835        if (ipc && ipc != SEQ_START_TOKEN)
 836                ipc_unlock(ipc);
 837
 838        return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 839}
 840
 841/*
 842 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
 843 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
 844 */
 845static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 846{
 847        struct ipc_proc_iter *iter = s->private;
 848        struct ipc_proc_iface *iface = iter->iface;
 849        struct ipc_ids *ids;
 850
 851        ids = &iter->ns->ids[iface->ids];
 852
 853        /*
 854         * Take the lock - this will be released by the corresponding
 855         * call to stop().
 856         */
 857        down_read(&ids->rwsem);
 858
 859        /* pos < 0 is invalid */
 860        if (*pos < 0)
 861                return NULL;
 862
 863        /* pos == 0 means header */
 864        if (*pos == 0)
 865                return SEQ_START_TOKEN;
 866
 867        /* Find the (pos-1)th ipc */
 868        return sysvipc_find_ipc(ids, *pos - 1, pos);
 869}
 870
 871static void sysvipc_proc_stop(struct seq_file *s, void *it)
 872{
 873        struct kern_ipc_perm *ipc = it;
 874        struct ipc_proc_iter *iter = s->private;
 875        struct ipc_proc_iface *iface = iter->iface;
 876        struct ipc_ids *ids;
 877
 878        /* If we had a locked structure, release it */
 879        if (ipc && ipc != SEQ_START_TOKEN)
 880                ipc_unlock(ipc);
 881
 882        ids = &iter->ns->ids[iface->ids];
 883        /* Release the lock we took in start() */
 884        up_read(&ids->rwsem);
 885}
 886
 887static int sysvipc_proc_show(struct seq_file *s, void *it)
 888{
 889        struct ipc_proc_iter *iter = s->private;
 890        struct ipc_proc_iface *iface = iter->iface;
 891
 892        if (it == SEQ_START_TOKEN)
 893                return seq_puts(s, iface->header);
 894
 895        return iface->show(s, it);
 896}
 897
 898static const struct seq_operations sysvipc_proc_seqops = {
 899        .start = sysvipc_proc_start,
 900        .stop  = sysvipc_proc_stop,
 901        .next  = sysvipc_proc_next,
 902        .show  = sysvipc_proc_show,
 903};
 904
 905static int sysvipc_proc_open(struct inode *inode, struct file *file)
 906{
 907        int ret;
 908        struct seq_file *seq;
 909        struct ipc_proc_iter *iter;
 910
 911        ret = -ENOMEM;
 912        iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 913        if (!iter)
 914                goto out;
 915
 916        ret = seq_open(file, &sysvipc_proc_seqops);
 917        if (ret)
 918                goto out_kfree;
 919
 920        seq = file->private_data;
 921        seq->private = iter;
 922
 923        iter->iface = PDE_DATA(inode);
 924        iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 925out:
 926        return ret;
 927out_kfree:
 928        kfree(iter);
 929        goto out;
 930}
 931
 932static int sysvipc_proc_release(struct inode *inode, struct file *file)
 933{
 934        struct seq_file *seq = file->private_data;
 935        struct ipc_proc_iter *iter = seq->private;
 936        put_ipc_ns(iter->ns);
 937        return seq_release_private(inode, file);
 938}
 939
 940static const struct file_operations sysvipc_proc_fops = {
 941        .open    = sysvipc_proc_open,
 942        .read    = seq_read,
 943        .llseek  = seq_lseek,
 944        .release = sysvipc_proc_release,
 945};
 946#endif /* CONFIG_PROC_FS */
 947