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
  20#include <linux/mm.h>
  21#include <linux/shm.h>
  22#include <linux/init.h>
  23#include <linux/msg.h>
  24#include <linux/vmalloc.h>
  25#include <linux/slab.h>
  26#include <linux/notifier.h>
  27#include <linux/capability.h>
  28#include <linux/highuid.h>
  29#include <linux/security.h>
  30#include <linux/rcupdate.h>
  31#include <linux/workqueue.h>
  32#include <linux/seq_file.h>
  33#include <linux/proc_fs.h>
  34#include <linux/audit.h>
  35#include <linux/nsproxy.h>
  36#include <linux/rwsem.h>
  37#include <linux/memory.h>
  38#include <linux/ipc_namespace.h>
  39
  40#include <asm/unistd.h>
  41
  42#include "util.h"
  43
  44struct ipc_proc_iface {
  45        const char *path;
  46        const char *header;
  47        int ids;
  48        int (*show)(struct seq_file *, void *);
  49};
  50
  51static void ipc_memory_notifier(struct work_struct *work)
  52{
  53        ipcns_notify(IPCNS_MEMCHANGED);
  54}
  55
  56static int ipc_memory_callback(struct notifier_block *self,
  57                                unsigned long action, void *arg)
  58{
  59        static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
  60
  61        switch (action) {
  62        case MEM_ONLINE:    /* memory successfully brought online */
  63        case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
  64                /*
  65                 * This is done by invoking the ipcns notifier chain with the
  66                 * IPC_MEMCHANGED event.
  67                 * In order not to keep the lock on the hotplug memory chain
  68                 * for too long, queue a work item that will, when waken up,
  69                 * activate the ipcns notification chain.
  70                 * No need to keep several ipc work items on the queue.
  71                 */
  72                if (!work_pending(&ipc_memory_wq))
  73                        schedule_work(&ipc_memory_wq);
  74                break;
  75        case MEM_GOING_ONLINE:
  76        case MEM_GOING_OFFLINE:
  77        case MEM_CANCEL_ONLINE:
  78        case MEM_CANCEL_OFFLINE:
  79        default:
  80                break;
  81        }
  82
  83        return NOTIFY_OK;
  84}
  85
  86static struct notifier_block ipc_memory_nb = {
  87        .notifier_call = ipc_memory_callback,
  88        .priority = IPC_CALLBACK_PRI,
  89};
  90
  91/**
  92 *      ipc_init        -       initialise IPC subsystem
  93 *
  94 *      The various system5 IPC resources (semaphores, messages and shared
  95 *      memory) are initialised
  96 *      A callback routine is registered into the memory hotplug notifier
  97 *      chain: since msgmni scales to lowmem this callback routine will be
  98 *      called upon successful memory add / remove to recompute msmgni.
  99 */
 100 
 101static int __init ipc_init(void)
 102{
 103        sem_init();
 104        msg_init();
 105        shm_init();
 106        register_hotmemory_notifier(&ipc_memory_nb);
 107        register_ipcns_notifier(&init_ipc_ns);
 108        return 0;
 109}
 110__initcall(ipc_init);
 111
 112/**
 113 *      ipc_init_ids            -       initialise IPC identifiers
 114 *      @ids: Identifier set
 115 *
 116 *      Set up the sequence range to use for the ipc identifier range (limited
 117 *      below IPCMNI) then initialise the ids idr.
 118 */
 119 
 120void ipc_init_ids(struct ipc_ids *ids)
 121{
 122        init_rwsem(&ids->rw_mutex);
 123
 124        ids->in_use = 0;
 125        ids->seq = 0;
 126        ids->next_id = -1;
 127        {
 128                int seq_limit = INT_MAX/SEQ_MULTIPLIER;
 129                if (seq_limit > USHRT_MAX)
 130                        ids->seq_max = USHRT_MAX;
 131                 else
 132                        ids->seq_max = seq_limit;
 133        }
 134
 135        idr_init(&ids->ipcs_idr);
 136}
 137
 138#ifdef CONFIG_PROC_FS
 139static const struct file_operations sysvipc_proc_fops;
 140/**
 141 *      ipc_init_proc_interface -  Create a proc interface for sysipc types using a seq_file interface.
 142 *      @path: Path in procfs
 143 *      @header: Banner to be printed at the beginning of the file.
 144 *      @ids: ipc id table to iterate.
 145 *      @show: show routine.
 146 */
 147void __init ipc_init_proc_interface(const char *path, const char *header,
 148                int ids, int (*show)(struct seq_file *, void *))
 149{
 150        struct proc_dir_entry *pde;
 151        struct ipc_proc_iface *iface;
 152
 153        iface = kmalloc(sizeof(*iface), GFP_KERNEL);
 154        if (!iface)
 155                return;
 156        iface->path     = path;
 157        iface->header   = header;
 158        iface->ids      = ids;
 159        iface->show     = show;
 160
 161        pde = proc_create_data(path,
 162                               S_IRUGO,        /* world readable */
 163                               NULL,           /* parent dir */
 164                               &sysvipc_proc_fops,
 165                               iface);
 166        if (!pde) {
 167                kfree(iface);
 168        }
 169}
 170#endif
 171
 172/**
 173 *      ipc_findkey     -       find a key in an ipc identifier set     
 174 *      @ids: Identifier set
 175 *      @key: The key to find
 176 *      
 177 *      Requires ipc_ids.rw_mutex locked.
 178 *      Returns the LOCKED pointer to the ipc structure if found or NULL
 179 *      if not.
 180 *      If key is found ipc points to the owning ipc structure
 181 */
 182 
 183static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 184{
 185        struct kern_ipc_perm *ipc;
 186        int next_id;
 187        int total;
 188
 189        for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
 190                ipc = idr_find(&ids->ipcs_idr, next_id);
 191
 192                if (ipc == NULL)
 193                        continue;
 194
 195                if (ipc->key != key) {
 196                        total++;
 197                        continue;
 198                }
 199
 200                ipc_lock_by_ptr(ipc);
 201                return ipc;
 202        }
 203
 204        return NULL;
 205}
 206
 207/**
 208 *      ipc_get_maxid   -       get the last assigned id
 209 *      @ids: IPC identifier set
 210 *
 211 *      Called with ipc_ids.rw_mutex held.
 212 */
 213
 214int ipc_get_maxid(struct ipc_ids *ids)
 215{
 216        struct kern_ipc_perm *ipc;
 217        int max_id = -1;
 218        int total, id;
 219
 220        if (ids->in_use == 0)
 221                return -1;
 222
 223        if (ids->in_use == IPCMNI)
 224                return IPCMNI - 1;
 225
 226        /* Look for the last assigned id */
 227        total = 0;
 228        for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
 229                ipc = idr_find(&ids->ipcs_idr, id);
 230                if (ipc != NULL) {
 231                        max_id = id;
 232                        total++;
 233                }
 234        }
 235        return max_id;
 236}
 237
 238/**
 239 *      ipc_addid       -       add an IPC identifier
 240 *      @ids: IPC identifier set
 241 *      @new: new IPC permission set
 242 *      @size: limit for the number of used ids
 243 *
 244 *      Add an entry 'new' to the IPC ids idr. The permissions object is
 245 *      initialised and the first free entry is set up and the id assigned
 246 *      is returned. The 'new' entry is returned in a locked state on success.
 247 *      On failure the entry is not locked and a negative err-code is returned.
 248 *
 249 *      Called with ipc_ids.rw_mutex held as a writer.
 250 */
 251 
 252int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 253{
 254        kuid_t euid;
 255        kgid_t egid;
 256        int id;
 257        int next_id = ids->next_id;
 258
 259        if (size > IPCMNI)
 260                size = IPCMNI;
 261
 262        if (ids->in_use >= size)
 263                return -ENOSPC;
 264
 265        idr_preload(GFP_KERNEL);
 266
 267        spin_lock_init(&new->lock);
 268        new->deleted = 0;
 269        rcu_read_lock();
 270        spin_lock(&new->lock);
 271
 272        id = idr_alloc(&ids->ipcs_idr, new,
 273                       (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
 274                       GFP_NOWAIT);
 275        idr_preload_end();
 276        if (id < 0) {
 277                spin_unlock(&new->lock);
 278                rcu_read_unlock();
 279                return id;
 280        }
 281
 282        ids->in_use++;
 283
 284        current_euid_egid(&euid, &egid);
 285        new->cuid = new->uid = euid;
 286        new->gid = new->cgid = egid;
 287
 288        if (next_id < 0) {
 289                new->seq = ids->seq++;
 290                if (ids->seq > ids->seq_max)
 291                        ids->seq = 0;
 292        } else {
 293                new->seq = ipcid_to_seqx(next_id);
 294                ids->next_id = -1;
 295        }
 296
 297        new->id = ipc_buildid(id, new->seq);
 298        return id;
 299}
 300
 301/**
 302 *      ipcget_new      -       create a new ipc object
 303 *      @ns: namespace
 304 *      @ids: IPC identifer set
 305 *      @ops: the actual creation routine to call
 306 *      @params: its parameters
 307 *
 308 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 309 *      when the key is IPC_PRIVATE.
 310 */
 311static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
 312                struct ipc_ops *ops, struct ipc_params *params)
 313{
 314        int err;
 315
 316        down_write(&ids->rw_mutex);
 317        err = ops->getnew(ns, params);
 318        up_write(&ids->rw_mutex);
 319        return err;
 320}
 321
 322/**
 323 *      ipc_check_perms -       check security and permissions for an IPC
 324 *      @ns: IPC namespace
 325 *      @ipcp: ipc permission set
 326 *      @ops: the actual security routine to call
 327 *      @params: its parameters
 328 *
 329 *      This routine is called by sys_msgget(), sys_semget() and sys_shmget()
 330 *      when the key is not IPC_PRIVATE and that key already exists in the
 331 *      ids IDR.
 332 *
 333 *      On success, the IPC id is returned.
 334 *
 335 *      It is called with ipc_ids.rw_mutex and ipcp->lock held.
 336 */
 337static int ipc_check_perms(struct ipc_namespace *ns,
 338                           struct kern_ipc_perm *ipcp,
 339                           struct ipc_ops *ops,
 340                           struct ipc_params *params)
 341{
 342        int err;
 343
 344        if (ipcperms(ns, ipcp, params->flg))
 345                err = -EACCES;
 346        else {
 347                err = ops->associate(ipcp, params->flg);
 348                if (!err)
 349                        err = ipcp->id;
 350        }
 351
 352        return err;
 353}
 354
 355/**
 356 *      ipcget_public   -       get an ipc object or create a new one
 357 *      @ns: namespace
 358 *      @ids: IPC identifer set
 359 *      @ops: the actual creation routine to call
 360 *      @params: its parameters
 361 *
 362 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 363 *      when the key is not IPC_PRIVATE.
 364 *      It adds a new entry if the key is not found and does some permission
 365 *      / security checkings if the key is found.
 366 *
 367 *      On success, the ipc id is returned.
 368 */
 369static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 370                struct ipc_ops *ops, struct ipc_params *params)
 371{
 372        struct kern_ipc_perm *ipcp;
 373        int flg = params->flg;
 374        int err;
 375
 376        /*
 377         * Take the lock as a writer since we are potentially going to add
 378         * a new entry + read locks are not "upgradable"
 379         */
 380        down_write(&ids->rw_mutex);
 381        ipcp = ipc_findkey(ids, params->key);
 382        if (ipcp == NULL) {
 383                /* key not used */
 384                if (!(flg & IPC_CREAT))
 385                        err = -ENOENT;
 386                else
 387                        err = ops->getnew(ns, params);
 388        } else {
 389                /* ipc object has been locked by ipc_findkey() */
 390
 391                if (flg & IPC_CREAT && flg & IPC_EXCL)
 392                        err = -EEXIST;
 393                else {
 394                        err = 0;
 395                        if (ops->more_checks)
 396                                err = ops->more_checks(ipcp, params);
 397                        if (!err)
 398                                /*
 399                                 * ipc_check_perms returns the IPC id on
 400                                 * success
 401                                 */
 402                                err = ipc_check_perms(ns, ipcp, ops, params);
 403                }
 404                ipc_unlock(ipcp);
 405        }
 406        up_write(&ids->rw_mutex);
 407
 408        return err;
 409}
 410
 411
 412/**
 413 *      ipc_rmid        -       remove an IPC identifier
 414 *      @ids: IPC identifier set
 415 *      @ipcp: ipc perm structure containing the identifier to remove
 416 *
 417 *      ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
 418 *      before this function is called, and remain locked on the exit.
 419 */
 420 
 421void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 422{
 423        int lid = ipcid_to_idx(ipcp->id);
 424
 425        idr_remove(&ids->ipcs_idr, lid);
 426
 427        ids->in_use--;
 428
 429        ipcp->deleted = 1;
 430
 431        return;
 432}
 433
 434/**
 435 *      ipc_alloc       -       allocate ipc space
 436 *      @size: size desired
 437 *
 438 *      Allocate memory from the appropriate pools and return a pointer to it.
 439 *      NULL is returned if the allocation fails
 440 */
 441 
 442void *ipc_alloc(int size)
 443{
 444        void *out;
 445        if(size > PAGE_SIZE)
 446                out = vmalloc(size);
 447        else
 448                out = kmalloc(size, GFP_KERNEL);
 449        return out;
 450}
 451
 452/**
 453 *      ipc_free        -       free ipc space
 454 *      @ptr: pointer returned by ipc_alloc
 455 *      @size: size of block
 456 *
 457 *      Free a block created with ipc_alloc(). The caller must know the size
 458 *      used in the allocation call.
 459 */
 460
 461void ipc_free(void* ptr, int size)
 462{
 463        if(size > PAGE_SIZE)
 464                vfree(ptr);
 465        else
 466                kfree(ptr);
 467}
 468
 469struct ipc_rcu {
 470        struct rcu_head rcu;
 471        atomic_t refcount;
 472        /* "void *" makes sure alignment of following data is sane. */
 473        void *data[0];
 474};
 475
 476/**
 477 *      ipc_rcu_alloc   -       allocate ipc and rcu space 
 478 *      @size: size desired
 479 *
 480 *      Allocate memory for the rcu header structure +  the object.
 481 *      Returns the pointer to the object or NULL upon failure.
 482 */
 483void *ipc_rcu_alloc(int size)
 484{
 485        /*
 486         * We prepend the allocation with the rcu struct
 487         */
 488        struct ipc_rcu *out = ipc_alloc(sizeof(struct ipc_rcu) + size);
 489        if (unlikely(!out))
 490                return NULL;
 491        atomic_set(&out->refcount, 1);
 492        return out->data;
 493}
 494
 495int ipc_rcu_getref(void *ptr)
 496{
 497        return atomic_inc_not_zero(&container_of(ptr, struct ipc_rcu, data)->refcount);
 498}
 499
 500/**
 501 * ipc_schedule_free - free ipc + rcu space
 502 * @head: RCU callback structure for queued work
 503 */
 504static void ipc_schedule_free(struct rcu_head *head)
 505{
 506        vfree(container_of(head, struct ipc_rcu, rcu));
 507}
 508
 509void ipc_rcu_putref(void *ptr)
 510{
 511        struct ipc_rcu *p = container_of(ptr, struct ipc_rcu, data);
 512
 513        if (!atomic_dec_and_test(&p->refcount))
 514                return;
 515
 516        if (is_vmalloc_addr(ptr)) {
 517                call_rcu(&p->rcu, ipc_schedule_free);
 518        } else {
 519                kfree_rcu(p, rcu);
 520        }
 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 rw_mutex 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
 681struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
 682{
 683        struct kern_ipc_perm *out;
 684
 685        out = ipc_lock(ids, id);
 686        if (IS_ERR(out))
 687                return out;
 688
 689        if (ipc_checkid(out, id)) {
 690                ipc_unlock(out);
 691                return ERR_PTR(-EIDRM);
 692        }
 693
 694        return out;
 695}
 696
 697/**
 698 * ipcget - Common sys_*get() code
 699 * @ns : namsepace
 700 * @ids : IPC identifier set
 701 * @ops : operations to be called on ipc object creation, permission checks
 702 *        and further checks
 703 * @params : the parameters needed by the previous operations.
 704 *
 705 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
 706 */
 707int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
 708                        struct ipc_ops *ops, struct ipc_params *params)
 709{
 710        if (params->key == IPC_PRIVATE)
 711                return ipcget_new(ns, ids, ops, params);
 712        else
 713                return ipcget_public(ns, ids, ops, params);
 714}
 715
 716/**
 717 * ipc_update_perm - update the permissions of an IPC.
 718 * @in:  the permission given as input.
 719 * @out: the permission of the ipc to set.
 720 */
 721int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 722{
 723        kuid_t uid = make_kuid(current_user_ns(), in->uid);
 724        kgid_t gid = make_kgid(current_user_ns(), in->gid);
 725        if (!uid_valid(uid) || !gid_valid(gid))
 726                return -EINVAL;
 727
 728        out->uid = uid;
 729        out->gid = gid;
 730        out->mode = (out->mode & ~S_IRWXUGO)
 731                | (in->mode & S_IRWXUGO);
 732
 733        return 0;
 734}
 735
 736/**
 737 * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
 738 * @ns:  the ipc namespace
 739 * @ids:  the table of ids where to look for the ipc
 740 * @id:   the id of the ipc to retrieve
 741 * @cmd:  the cmd to check
 742 * @perm: the permission to set
 743 * @extra_perm: one extra permission parameter used by msq
 744 *
 745 * This function does some common audit and permissions check for some IPC_XXX
 746 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
 747 * It must be called without any lock held and
 748 *  - retrieves the ipc with the given id in the given table.
 749 *  - performs some audit and permission check, depending on the given cmd
 750 *  - returns the ipc with both ipc and rw_mutex locks held in case of success
 751 *    or an err-code without any lock held otherwise.
 752 */
 753struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
 754                                      struct ipc_ids *ids, int id, int cmd,
 755                                      struct ipc64_perm *perm, int extra_perm)
 756{
 757        struct kern_ipc_perm *ipcp;
 758
 759        ipcp = ipcctl_pre_down_nolock(ns, ids, id, cmd, perm, extra_perm);
 760        if (IS_ERR(ipcp))
 761                goto out;
 762
 763        spin_lock(&ipcp->lock);
 764out:
 765        return ipcp;
 766}
 767
 768struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
 769                                             struct ipc_ids *ids, int id, int cmd,
 770                                             struct ipc64_perm *perm, int extra_perm)
 771{
 772        kuid_t euid;
 773        int err = -EPERM;
 774        struct kern_ipc_perm *ipcp;
 775
 776        down_write(&ids->rw_mutex);
 777        rcu_read_lock();
 778
 779        ipcp = ipc_obtain_object_check(ids, id);
 780        if (IS_ERR(ipcp)) {
 781                err = PTR_ERR(ipcp);
 782                goto out_up;
 783        }
 784
 785        audit_ipc_obj(ipcp);
 786        if (cmd == IPC_SET)
 787                audit_ipc_set_perm(extra_perm, perm->uid,
 788                                   perm->gid, perm->mode);
 789
 790        euid = current_euid();
 791        if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
 792            ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 793                return ipcp;
 794
 795out_up:
 796        /*
 797         * Unsuccessful lookup, unlock and return
 798         * the corresponding error.
 799         */
 800        rcu_read_unlock();
 801        up_write(&ids->rw_mutex);
 802
 803        return ERR_PTR(err);
 804}
 805
 806#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
 807
 808
 809/**
 810 *      ipc_parse_version       -       IPC call version
 811 *      @cmd: pointer to command
 812 *
 813 *      Return IPC_64 for new style IPC and IPC_OLD for old style IPC. 
 814 *      The @cmd value is turned from an encoding command and version into
 815 *      just the command code.
 816 */
 817 
 818int ipc_parse_version (int *cmd)
 819{
 820        if (*cmd & IPC_64) {
 821                *cmd ^= IPC_64;
 822                return IPC_64;
 823        } else {
 824                return IPC_OLD;
 825        }
 826}
 827
 828#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
 829
 830#ifdef CONFIG_PROC_FS
 831struct ipc_proc_iter {
 832        struct ipc_namespace *ns;
 833        struct ipc_proc_iface *iface;
 834};
 835
 836/*
 837 * This routine locks the ipc structure found at least at position pos.
 838 */
 839static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 840                                              loff_t *new_pos)
 841{
 842        struct kern_ipc_perm *ipc;
 843        int total, id;
 844
 845        total = 0;
 846        for (id = 0; id < pos && total < ids->in_use; id++) {
 847                ipc = idr_find(&ids->ipcs_idr, id);
 848                if (ipc != NULL)
 849                        total++;
 850        }
 851
 852        if (total >= ids->in_use)
 853                return NULL;
 854
 855        for ( ; pos < IPCMNI; pos++) {
 856                ipc = idr_find(&ids->ipcs_idr, pos);
 857                if (ipc != NULL) {
 858                        *new_pos = pos + 1;
 859                        ipc_lock_by_ptr(ipc);
 860                        return ipc;
 861                }
 862        }
 863
 864        /* Out of range - return NULL to terminate iteration */
 865        return NULL;
 866}
 867
 868static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 869{
 870        struct ipc_proc_iter *iter = s->private;
 871        struct ipc_proc_iface *iface = iter->iface;
 872        struct kern_ipc_perm *ipc = it;
 873
 874        /* If we had an ipc id locked before, unlock it */
 875        if (ipc && ipc != SEQ_START_TOKEN)
 876                ipc_unlock(ipc);
 877
 878        return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 879}
 880
 881/*
 882 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
 883 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
 884 */
 885static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 886{
 887        struct ipc_proc_iter *iter = s->private;
 888        struct ipc_proc_iface *iface = iter->iface;
 889        struct ipc_ids *ids;
 890
 891        ids = &iter->ns->ids[iface->ids];
 892
 893        /*
 894         * Take the lock - this will be released by the corresponding
 895         * call to stop().
 896         */
 897        down_read(&ids->rw_mutex);
 898
 899        /* pos < 0 is invalid */
 900        if (*pos < 0)
 901                return NULL;
 902
 903        /* pos == 0 means header */
 904        if (*pos == 0)
 905                return SEQ_START_TOKEN;
 906
 907        /* Find the (pos-1)th ipc */
 908        return sysvipc_find_ipc(ids, *pos - 1, pos);
 909}
 910
 911static void sysvipc_proc_stop(struct seq_file *s, void *it)
 912{
 913        struct kern_ipc_perm *ipc = it;
 914        struct ipc_proc_iter *iter = s->private;
 915        struct ipc_proc_iface *iface = iter->iface;
 916        struct ipc_ids *ids;
 917
 918        /* If we had a locked structure, release it */
 919        if (ipc && ipc != SEQ_START_TOKEN)
 920                ipc_unlock(ipc);
 921
 922        ids = &iter->ns->ids[iface->ids];
 923        /* Release the lock we took in start() */
 924        up_read(&ids->rw_mutex);
 925}
 926
 927static int sysvipc_proc_show(struct seq_file *s, void *it)
 928{
 929        struct ipc_proc_iter *iter = s->private;
 930        struct ipc_proc_iface *iface = iter->iface;
 931
 932        if (it == SEQ_START_TOKEN)
 933                return seq_puts(s, iface->header);
 934
 935        return iface->show(s, it);
 936}
 937
 938static const struct seq_operations sysvipc_proc_seqops = {
 939        .start = sysvipc_proc_start,
 940        .stop  = sysvipc_proc_stop,
 941        .next  = sysvipc_proc_next,
 942        .show  = sysvipc_proc_show,
 943};
 944
 945static int sysvipc_proc_open(struct inode *inode, struct file *file)
 946{
 947        int ret;
 948        struct seq_file *seq;
 949        struct ipc_proc_iter *iter;
 950
 951        ret = -ENOMEM;
 952        iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 953        if (!iter)
 954                goto out;
 955
 956        ret = seq_open(file, &sysvipc_proc_seqops);
 957        if (ret)
 958                goto out_kfree;
 959
 960        seq = file->private_data;
 961        seq->private = iter;
 962
 963        iter->iface = PDE_DATA(inode);
 964        iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 965out:
 966        return ret;
 967out_kfree:
 968        kfree(iter);
 969        goto out;
 970}
 971
 972static int sysvipc_proc_release(struct inode *inode, struct file *file)
 973{
 974        struct seq_file *seq = file->private_data;
 975        struct ipc_proc_iter *iter = seq->private;
 976        put_ipc_ns(iter->ns);
 977        return seq_release_private(inode, file);
 978}
 979
 980static const struct file_operations sysvipc_proc_fops = {
 981        .open    = sysvipc_proc_open,
 982        .read    = seq_read,
 983        .llseek  = seq_lseek,
 984        .release = sysvipc_proc_release,
 985};
 986#endif /* CONFIG_PROC_FS */
 987
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