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 writer ipc_ids.rw_mutex held.
 250 */
 251int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 252{
 253        kuid_t euid;
 254        kgid_t egid;
 255        int id;
 256        int next_id = ids->next_id;
 257
 258        if (size > IPCMNI)
 259                size = IPCMNI;
 260
 261        if (ids->in_use >= size)
 262                return -ENOSPC;
 263
 264        idr_preload(GFP_KERNEL);
 265
 266        spin_lock_init(&new->lock);
 267        new->deleted = 0;
 268        rcu_read_lock();
 269        spin_lock(&new->lock);
 270
 271        id = idr_alloc(&ids->ipcs_idr, new,
 272                       (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
 273                       GFP_NOWAIT);
 274        idr_preload_end();
 275        if (id < 0) {
 276                spin_unlock(&new->lock);
 277                rcu_read_unlock();
 278                return id;
 279        }
 280
 281        ids->in_use++;
 282
 283        current_euid_egid(&euid, &egid);
 284        new->cuid = new->uid = euid;
 285        new->gid = new->cgid = egid;
 286
 287        if (next_id < 0) {
 288                new->seq = ids->seq++;
 289                if (ids->seq > ids->seq_max)
 290                        ids->seq = 0;
 291        } else {
 292                new->seq = ipcid_to_seqx(next_id);
 293                ids->next_id = -1;
 294        }
 295
 296        new->id = ipc_buildid(id, new->seq);
 297        return id;
 298}
 299
 300/**
 301 *      ipcget_new      -       create a new ipc object
 302 *      @ns: namespace
 303 *      @ids: IPC identifer set
 304 *      @ops: the actual creation routine to call
 305 *      @params: its parameters
 306 *
 307 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 308 *      when the key is IPC_PRIVATE.
 309 */
 310static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
 311                struct ipc_ops *ops, struct ipc_params *params)
 312{
 313        int err;
 314
 315        down_write(&ids->rw_mutex);
 316        err = ops->getnew(ns, params);
 317        up_write(&ids->rw_mutex);
 318        return err;
 319}
 320
 321/**
 322 *      ipc_check_perms -       check security and permissions for an IPC
 323 *      @ns: IPC namespace
 324 *      @ipcp: ipc permission set
 325 *      @ops: the actual security routine to call
 326 *      @params: its parameters
 327 *
 328 *      This routine is called by sys_msgget(), sys_semget() and sys_shmget()
 329 *      when the key is not IPC_PRIVATE and that key already exists in the
 330 *      ids IDR.
 331 *
 332 *      On success, the IPC id is returned.
 333 *
 334 *      It is called with ipc_ids.rw_mutex and ipcp->lock held.
 335 */
 336static int ipc_check_perms(struct ipc_namespace *ns,
 337                           struct kern_ipc_perm *ipcp,
 338                           struct ipc_ops *ops,
 339                           struct ipc_params *params)
 340{
 341        int err;
 342
 343        if (ipcperms(ns, ipcp, params->flg))
 344                err = -EACCES;
 345        else {
 346                err = ops->associate(ipcp, params->flg);
 347                if (!err)
 348                        err = ipcp->id;
 349        }
 350
 351        return err;
 352}
 353
 354/**
 355 *      ipcget_public   -       get an ipc object or create a new one
 356 *      @ns: namespace
 357 *      @ids: IPC identifer set
 358 *      @ops: the actual creation routine to call
 359 *      @params: its parameters
 360 *
 361 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 362 *      when the key is not IPC_PRIVATE.
 363 *      It adds a new entry if the key is not found and does some permission
 364 *      / security checkings if the key is found.
 365 *
 366 *      On success, the ipc id is returned.
 367 */
 368static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 369                struct ipc_ops *ops, struct ipc_params *params)
 370{
 371        struct kern_ipc_perm *ipcp;
 372        int flg = params->flg;
 373        int err;
 374
 375        /*
 376         * Take the lock as a writer since we are potentially going to add
 377         * a new entry + read locks are not "upgradable"
 378         */
 379        down_write(&ids->rw_mutex);
 380        ipcp = ipc_findkey(ids, params->key);
 381        if (ipcp == NULL) {
 382                /* key not used */
 383                if (!(flg & IPC_CREAT))
 384                        err = -ENOENT;
 385                else
 386                        err = ops->getnew(ns, params);
 387        } else {
 388                /* ipc object has been locked by ipc_findkey() */
 389
 390                if (flg & IPC_CREAT && flg & IPC_EXCL)
 391                        err = -EEXIST;
 392                else {
 393                        err = 0;
 394                        if (ops->more_checks)
 395                                err = ops->more_checks(ipcp, params);
 396                        if (!err)
 397                                /*
 398                                 * ipc_check_perms returns the IPC id on
 399                                 * success
 400                                 */
 401                                err = ipc_check_perms(ns, ipcp, ops, params);
 402                }
 403                ipc_unlock(ipcp);
 404        }
 405        up_write(&ids->rw_mutex);
 406
 407        return err;
 408}
 409
 410
 411/**
 412 *      ipc_rmid        -       remove an IPC identifier
 413 *      @ids: IPC identifier set
 414 *      @ipcp: ipc perm structure containing the identifier to remove
 415 *
 416 *      ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
 417 *      before this function is called, and remain locked on the exit.
 418 */
 419 
 420void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 421{
 422        int lid = ipcid_to_idx(ipcp->id);
 423
 424        idr_remove(&ids->ipcs_idr, lid);
 425
 426        ids->in_use--;
 427
 428        ipcp->deleted = 1;
 429
 430        return;
 431}
 432
 433/**
 434 *      ipc_alloc       -       allocate ipc space
 435 *      @size: size desired
 436 *
 437 *      Allocate memory from the appropriate pools and return a pointer to it.
 438 *      NULL is returned if the allocation fails
 439 */
 440 
 441void *ipc_alloc(int size)
 442{
 443        void *out;
 444        if(size > PAGE_SIZE)
 445                out = vmalloc(size);
 446        else
 447                out = kmalloc(size, GFP_KERNEL);
 448        return out;
 449}
 450
 451/**
 452 *      ipc_free        -       free ipc space
 453 *      @ptr: pointer returned by ipc_alloc
 454 *      @size: size of block
 455 *
 456 *      Free a block created with ipc_alloc(). The caller must know the size
 457 *      used in the allocation call.
 458 */
 459
 460void ipc_free(void* ptr, int size)
 461{
 462        if(size > PAGE_SIZE)
 463                vfree(ptr);
 464        else
 465                kfree(ptr);
 466}
 467
 468struct ipc_rcu {
 469        struct rcu_head rcu;
 470        atomic_t refcount;
 471} ____cacheline_aligned_in_smp;
 472
 473/**
 474 *      ipc_rcu_alloc   -       allocate ipc and rcu space 
 475 *      @size: size desired
 476 *
 477 *      Allocate memory for the rcu header structure +  the object.
 478 *      Returns the pointer to the object or NULL upon failure.
 479 */
 480void *ipc_rcu_alloc(int size)
 481{
 482        /*
 483         * We prepend the allocation with the rcu struct
 484         */
 485        struct ipc_rcu *out = ipc_alloc(sizeof(struct ipc_rcu) + size);
 486        if (unlikely(!out))
 487                return NULL;
 488        atomic_set(&out->refcount, 1);
 489        return out + 1;
 490}
 491
 492int ipc_rcu_getref(void *ptr)
 493{
 494        struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;
 495
 496        return atomic_inc_not_zero(&p->refcount);
 497}
 498
 499/**
 500 * ipc_schedule_free - free ipc + rcu space
 501 * @head: RCU callback structure for queued work
 502 */
 503static void ipc_schedule_free(struct rcu_head *head)
 504{
 505        vfree(container_of(head, struct ipc_rcu, rcu));
 506}
 507
 508void ipc_rcu_putref(void *ptr)
 509{
 510        struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;
 511
 512        if (!atomic_dec_and_test(&p->refcount))
 513                return;
 514
 515        if (is_vmalloc_addr(ptr)) {
 516                call_rcu(&p->rcu, ipc_schedule_free);
 517        } else {
 518                kfree_rcu(p, rcu);
 519        }
 520}
 521
 522/**
 523 *      ipcperms        -       check IPC permissions
 524 *      @ns: IPC namespace
 525 *      @ipcp: IPC permission set
 526 *      @flag: desired permission set.
 527 *
 528 *      Check user, group, other permissions for access
 529 *      to ipc resources. return 0 if allowed
 530 *
 531 *      @flag will most probably be 0 or S_...UGO from <linux/stat.h>
 532 */
 533 
 534int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
 535{
 536        kuid_t euid = current_euid();
 537        int requested_mode, granted_mode;
 538
 539        audit_ipc_obj(ipcp);
 540        requested_mode = (flag >> 6) | (flag >> 3) | flag;
 541        granted_mode = ipcp->mode;
 542        if (uid_eq(euid, ipcp->cuid) ||
 543            uid_eq(euid, ipcp->uid))
 544                granted_mode >>= 6;
 545        else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 546                granted_mode >>= 3;
 547        /* is there some bit set in requested_mode but not in granted_mode? */
 548        if ((requested_mode & ~granted_mode & 0007) && 
 549            !ns_capable(ns->user_ns, CAP_IPC_OWNER))
 550                return -1;
 551
 552        return security_ipc_permission(ipcp, flag);
 553}
 554
 555/*
 556 * Functions to convert between the kern_ipc_perm structure and the
 557 * old/new ipc_perm structures
 558 */
 559
 560/**
 561 *      kernel_to_ipc64_perm    -       convert kernel ipc permissions to user
 562 *      @in: kernel permissions
 563 *      @out: new style IPC permissions
 564 *
 565 *      Turn the kernel object @in into a set of permissions descriptions
 566 *      for returning to userspace (@out).
 567 */
 568 
 569
 570void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
 571{
 572        out->key        = in->key;
 573        out->uid        = from_kuid_munged(current_user_ns(), in->uid);
 574        out->gid        = from_kgid_munged(current_user_ns(), in->gid);
 575        out->cuid       = from_kuid_munged(current_user_ns(), in->cuid);
 576        out->cgid       = from_kgid_munged(current_user_ns(), in->cgid);
 577        out->mode       = in->mode;
 578        out->seq        = in->seq;
 579}
 580
 581/**
 582 *      ipc64_perm_to_ipc_perm  -       convert new ipc permissions to old
 583 *      @in: new style IPC permissions
 584 *      @out: old style IPC permissions
 585 *
 586 *      Turn the new style permissions object @in into a compatibility
 587 *      object and store it into the @out pointer.
 588 */
 589 
 590void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
 591{
 592        out->key        = in->key;
 593        SET_UID(out->uid, in->uid);
 594        SET_GID(out->gid, in->gid);
 595        SET_UID(out->cuid, in->cuid);
 596        SET_GID(out->cgid, in->cgid);
 597        out->mode       = in->mode;
 598        out->seq        = in->seq;
 599}
 600
 601/**
 602 * ipc_obtain_object
 603 * @ids: ipc identifier set
 604 * @id: ipc id to look for
 605 *
 606 * Look for an id in the ipc ids idr and return associated ipc object.
 607 *
 608 * Call inside the RCU critical section.
 609 * The ipc object is *not* locked on exit.
 610 */
 611struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id)
 612{
 613        struct kern_ipc_perm *out;
 614        int lid = ipcid_to_idx(id);
 615
 616        out = idr_find(&ids->ipcs_idr, lid);
 617        if (!out)
 618                return ERR_PTR(-EINVAL);
 619
 620        return out;
 621}
 622
 623/**
 624 * ipc_lock - Lock an ipc structure without rw_mutex held
 625 * @ids: IPC identifier set
 626 * @id: ipc id to look for
 627 *
 628 * Look for an id in the ipc ids idr and lock the associated ipc object.
 629 *
 630 * The ipc object is locked on successful exit.
 631 */
 632struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
 633{
 634        struct kern_ipc_perm *out;
 635
 636        rcu_read_lock();
 637        out = ipc_obtain_object(ids, id);
 638        if (IS_ERR(out))
 639                goto err1;
 640
 641        spin_lock(&out->lock);
 642
 643        /* ipc_rmid() may have already freed the ID while ipc_lock
 644         * was spinning: here verify that the structure is still valid
 645         */
 646        if (!out->deleted)
 647                return out;
 648
 649        spin_unlock(&out->lock);
 650        out = ERR_PTR(-EINVAL);
 651err1:
 652        rcu_read_unlock();
 653        return out;
 654}
 655
 656/**
 657 * ipc_obtain_object_check
 658 * @ids: ipc identifier set
 659 * @id: ipc id to look for
 660 *
 661 * Similar to ipc_obtain_object() but also checks
 662 * the ipc object reference counter.
 663 *
 664 * Call inside the RCU critical section.
 665 * The ipc object is *not* locked on exit.
 666 */
 667struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
 668{
 669        struct kern_ipc_perm *out = ipc_obtain_object(ids, id);
 670
 671        if (IS_ERR(out))
 672                goto out;
 673
 674        if (ipc_checkid(out, id))
 675                return ERR_PTR(-EIDRM);
 676out:
 677        return out;
 678}
 679
 680struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
 681{
 682        struct kern_ipc_perm *out;
 683
 684        out = ipc_lock(ids, id);
 685        if (IS_ERR(out))
 686                return out;
 687
 688        if (ipc_checkid(out, id)) {
 689                ipc_unlock(out);
 690                return ERR_PTR(-EIDRM);
 691        }
 692
 693        return out;
 694}
 695
 696/**
 697 * ipcget - Common sys_*get() code
 698 * @ns : namsepace
 699 * @ids : IPC identifier set
 700 * @ops : operations to be called on ipc object creation, permission checks
 701 *        and further checks
 702 * @params : the parameters needed by the previous operations.
 703 *
 704 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
 705 */
 706int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
 707                        struct ipc_ops *ops, struct ipc_params *params)
 708{
 709        if (params->key == IPC_PRIVATE)
 710                return ipcget_new(ns, ids, ops, params);
 711        else
 712                return ipcget_public(ns, ids, ops, params);
 713}
 714
 715/**
 716 * ipc_update_perm - update the permissions of an IPC.
 717 * @in:  the permission given as input.
 718 * @out: the permission of the ipc to set.
 719 */
 720int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 721{
 722        kuid_t uid = make_kuid(current_user_ns(), in->uid);
 723        kgid_t gid = make_kgid(current_user_ns(), in->gid);
 724        if (!uid_valid(uid) || !gid_valid(gid))
 725                return -EINVAL;
 726
 727        out->uid = uid;
 728        out->gid = gid;
 729        out->mode = (out->mode & ~S_IRWXUGO)
 730                | (in->mode & S_IRWXUGO);
 731
 732        return 0;
 733}
 734
 735/**
 736 * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
 737 * @ns:  the ipc namespace
 738 * @ids:  the table of ids where to look for the ipc
 739 * @id:   the id of the ipc to retrieve
 740 * @cmd:  the cmd to check
 741 * @perm: the permission to set
 742 * @extra_perm: one extra permission parameter used by msq
 743 *
 744 * This function does some common audit and permissions check for some IPC_XXX
 745 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
 746 * It must be called without any lock held and
 747 *  - retrieves the ipc with the given id in the given table.
 748 *  - performs some audit and permission check, depending on the given cmd
 749 *  - returns the ipc with the ipc lock held in case of success
 750 *    or an err-code without any lock held otherwise.
 751 *
 752 * Call holding the both the rw_mutex and the rcu read lock.
 753 */
 754struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
 755                                      struct ipc_ids *ids, int id, int cmd,
 756                                      struct ipc64_perm *perm, int extra_perm)
 757{
 758        struct kern_ipc_perm *ipcp;
 759
 760        ipcp = ipcctl_pre_down_nolock(ns, ids, id, cmd, perm, extra_perm);
 761        if (IS_ERR(ipcp))
 762                goto out;
 763
 764        spin_lock(&ipcp->lock);
 765out:
 766        return ipcp;
 767}
 768
 769struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
 770                                             struct ipc_ids *ids, int id, int cmd,
 771                                             struct ipc64_perm *perm, int extra_perm)
 772{
 773        kuid_t euid;
 774        int err = -EPERM;
 775        struct kern_ipc_perm *ipcp;
 776
 777        ipcp = ipc_obtain_object_check(ids, id);
 778        if (IS_ERR(ipcp)) {
 779                err = PTR_ERR(ipcp);
 780                goto err;
 781        }
 782
 783        audit_ipc_obj(ipcp);
 784        if (cmd == IPC_SET)
 785                audit_ipc_set_perm(extra_perm, perm->uid,
 786                                   perm->gid, perm->mode);
 787
 788        euid = current_euid();
 789        if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
 790            ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 791                return ipcp; /* successful lookup */
 792err:
 793        return ERR_PTR(err);
 794}
 795
 796#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
 797
 798
 799/**
 800 *      ipc_parse_version       -       IPC call version
 801 *      @cmd: pointer to command
 802 *
 803 *      Return IPC_64 for new style IPC and IPC_OLD for old style IPC. 
 804 *      The @cmd value is turned from an encoding command and version into
 805 *      just the command code.
 806 */
 807 
 808int ipc_parse_version (int *cmd)
 809{
 810        if (*cmd & IPC_64) {
 811                *cmd ^= IPC_64;
 812                return IPC_64;
 813        } else {
 814                return IPC_OLD;
 815        }
 816}
 817
 818#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
 819
 820#ifdef CONFIG_PROC_FS
 821struct ipc_proc_iter {
 822        struct ipc_namespace *ns;
 823        struct ipc_proc_iface *iface;
 824};
 825
 826/*
 827 * This routine locks the ipc structure found at least at position pos.
 828 */
 829static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 830                                              loff_t *new_pos)
 831{
 832        struct kern_ipc_perm *ipc;
 833        int total, id;
 834
 835        total = 0;
 836        for (id = 0; id < pos && total < ids->in_use; id++) {
 837                ipc = idr_find(&ids->ipcs_idr, id);
 838                if (ipc != NULL)
 839                        total++;
 840        }
 841
 842        if (total >= ids->in_use)
 843                return NULL;
 844
 845        for ( ; pos < IPCMNI; pos++) {
 846                ipc = idr_find(&ids->ipcs_idr, pos);
 847                if (ipc != NULL) {
 848                        *new_pos = pos + 1;
 849                        ipc_lock_by_ptr(ipc);
 850                        return ipc;
 851                }
 852        }
 853
 854        /* Out of range - return NULL to terminate iteration */
 855        return NULL;
 856}
 857
 858static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 859{
 860        struct ipc_proc_iter *iter = s->private;
 861        struct ipc_proc_iface *iface = iter->iface;
 862        struct kern_ipc_perm *ipc = it;
 863
 864        /* If we had an ipc id locked before, unlock it */
 865        if (ipc && ipc != SEQ_START_TOKEN)
 866                ipc_unlock(ipc);
 867
 868        return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 869}
 870
 871/*
 872 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
 873 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
 874 */
 875static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 876{
 877        struct ipc_proc_iter *iter = s->private;
 878        struct ipc_proc_iface *iface = iter->iface;
 879        struct ipc_ids *ids;
 880
 881        ids = &iter->ns->ids[iface->ids];
 882
 883        /*
 884         * Take the lock - this will be released by the corresponding
 885         * call to stop().
 886         */
 887        down_read(&ids->rw_mutex);
 888
 889        /* pos < 0 is invalid */
 890        if (*pos < 0)
 891                return NULL;
 892
 893        /* pos == 0 means header */
 894        if (*pos == 0)
 895                return SEQ_START_TOKEN;
 896
 897        /* Find the (pos-1)th ipc */
 898        return sysvipc_find_ipc(ids, *pos - 1, pos);
 899}
 900
 901static void sysvipc_proc_stop(struct seq_file *s, void *it)
 902{
 903        struct kern_ipc_perm *ipc = it;
 904        struct ipc_proc_iter *iter = s->private;
 905        struct ipc_proc_iface *iface = iter->iface;
 906        struct ipc_ids *ids;
 907
 908        /* If we had a locked structure, release it */
 909        if (ipc && ipc != SEQ_START_TOKEN)
 910                ipc_unlock(ipc);
 911
 912        ids = &iter->ns->ids[iface->ids];
 913        /* Release the lock we took in start() */
 914        up_read(&ids->rw_mutex);
 915}
 916
 917static int sysvipc_proc_show(struct seq_file *s, void *it)
 918{
 919        struct ipc_proc_iter *iter = s->private;
 920        struct ipc_proc_iface *iface = iter->iface;
 921
 922        if (it == SEQ_START_TOKEN)
 923                return seq_puts(s, iface->header);
 924
 925        return iface->show(s, it);
 926}
 927
 928static const struct seq_operations sysvipc_proc_seqops = {
 929        .start = sysvipc_proc_start,
 930        .stop  = sysvipc_proc_stop,
 931        .next  = sysvipc_proc_next,
 932        .show  = sysvipc_proc_show,
 933};
 934
 935static int sysvipc_proc_open(struct inode *inode, struct file *file)
 936{
 937        int ret;
 938        struct seq_file *seq;
 939        struct ipc_proc_iter *iter;
 940
 941        ret = -ENOMEM;
 942        iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 943        if (!iter)
 944                goto out;
 945
 946        ret = seq_open(file, &sysvipc_proc_seqops);
 947        if (ret)
 948                goto out_kfree;
 949
 950        seq = file->private_data;
 951        seq->private = iter;
 952
 953        iter->iface = PDE_DATA(inode);
 954        iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 955out:
 956        return ret;
 957out_kfree:
 958        kfree(iter);
 959        goto out;
 960}
 961
 962static int sysvipc_proc_release(struct inode *inode, struct file *file)
 963{
 964        struct seq_file *seq = file->private_data;
 965        struct ipc_proc_iter *iter = seq->private;
 966        put_ipc_ns(iter->ns);
 967        return seq_release_private(inode, file);
 968}
 969
 970static const struct file_operations sysvipc_proc_fops = {
 971        .open    = sysvipc_proc_open,
 972        .read    = seq_read,
 973        .llseek  = seq_lseek,
 974        .release = sysvipc_proc_release,
 975};
 976#endif /* CONFIG_PROC_FS */
 977
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