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 *      rcu_read_lock()
  21 *          obtain the ipc object (kern_ipc_perm) by looking up the id in an idr
  22 *          tree.
  23 *          - perform initial checks (capabilities, auditing and permission,
  24 *            etc).
  25 *          - perform read-only operations, such as STAT, INFO commands.
  26 *            acquire the ipc lock (kern_ipc_perm.lock) through
  27 *            ipc_lock_object()
  28 *              - perform data updates, such as SET, RMID commands and
  29 *                mechanism-specific operations (semop/semtimedop,
  30 *                msgsnd/msgrcv, shmat/shmdt).
  31 *          drop the ipc lock, through ipc_unlock_object().
  32 *      rcu_read_unlock()
  33 *
  34 *  The ids->rwsem must be taken when:
  35 *      - creating, removing and iterating the existing entries in ipc
  36 *        identifier sets.
  37 *      - iterating through files under /proc/sysvipc/
  38 *
  39 *  Note that sems have a special fast path that avoids kern_ipc_perm.lock -
  40 *  see sem_lock().
  41 */
  42
  43#include <linux/mm.h>
  44#include <linux/shm.h>
  45#include <linux/init.h>
  46#include <linux/msg.h>
  47#include <linux/vmalloc.h>
  48#include <linux/slab.h>
  49#include <linux/notifier.h>
  50#include <linux/capability.h>
  51#include <linux/highuid.h>
  52#include <linux/security.h>
  53#include <linux/rcupdate.h>
  54#include <linux/workqueue.h>
  55#include <linux/seq_file.h>
  56#include <linux/proc_fs.h>
  57#include <linux/audit.h>
  58#include <linux/nsproxy.h>
  59#include <linux/rwsem.h>
  60#include <linux/memory.h>
  61#include <linux/ipc_namespace.h>
  62
  63#include <asm/unistd.h>
  64
  65#include "util.h"
  66
  67struct ipc_proc_iface {
  68        const char *path;
  69        const char *header;
  70        int ids;
  71        int (*show)(struct seq_file *, void *);
  72};
  73
  74static void ipc_memory_notifier(struct work_struct *work)
  75{
  76        ipcns_notify(IPCNS_MEMCHANGED);
  77}
  78
  79static int ipc_memory_callback(struct notifier_block *self,
  80                                unsigned long action, void *arg)
  81{
  82        static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
  83
  84        switch (action) {
  85        case MEM_ONLINE:    /* memory successfully brought online */
  86        case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
  87                /*
  88                 * This is done by invoking the ipcns notifier chain with the
  89                 * IPC_MEMCHANGED event.
  90                 * In order not to keep the lock on the hotplug memory chain
  91                 * for too long, queue a work item that will, when waken up,
  92                 * activate the ipcns notification chain.
  93                 * No need to keep several ipc work items on the queue.
  94                 */
  95                if (!work_pending(&ipc_memory_wq))
  96                        schedule_work(&ipc_memory_wq);
  97                break;
  98        case MEM_GOING_ONLINE:
  99        case MEM_GOING_OFFLINE:
 100        case MEM_CANCEL_ONLINE:
 101        case MEM_CANCEL_OFFLINE:
 102        default:
 103                break;
 104        }
 105
 106        return NOTIFY_OK;
 107}
 108
 109static struct notifier_block ipc_memory_nb = {
 110        .notifier_call = ipc_memory_callback,
 111        .priority = IPC_CALLBACK_PRI,
 112};
 113
 114/**
 115 *      ipc_init        -       initialise IPC subsystem
 116 *
 117 *      The various system5 IPC resources (semaphores, messages and shared
 118 *      memory) are initialised
 119 *      A callback routine is registered into the memory hotplug notifier
 120 *      chain: since msgmni scales to lowmem this callback routine will be
 121 *      called upon successful memory add / remove to recompute msmgni.
 122 */
 123 
 124static int __init ipc_init(void)
 125{
 126        sem_init();
 127        msg_init();
 128        shm_init();
 129        register_hotmemory_notifier(&ipc_memory_nb);
 130        register_ipcns_notifier(&init_ipc_ns);
 131        return 0;
 132}
 133__initcall(ipc_init);
 134
 135/**
 136 *      ipc_init_ids            -       initialise IPC identifiers
 137 *      @ids: Identifier set
 138 *
 139 *      Set up the sequence range to use for the ipc identifier range (limited
 140 *      below IPCMNI) then initialise the ids idr.
 141 */
 142 
 143void ipc_init_ids(struct ipc_ids *ids)
 144{
 145        init_rwsem(&ids->rwsem);
 146
 147        ids->in_use = 0;
 148        ids->seq = 0;
 149        ids->next_id = -1;
 150        {
 151                int seq_limit = INT_MAX/SEQ_MULTIPLIER;
 152                if (seq_limit > USHRT_MAX)
 153                        ids->seq_max = USHRT_MAX;
 154                 else
 155                        ids->seq_max = seq_limit;
 156        }
 157
 158        idr_init(&ids->ipcs_idr);
 159}
 160
 161#ifdef CONFIG_PROC_FS
 162static const struct file_operations sysvipc_proc_fops;
 163/**
 164 *      ipc_init_proc_interface -  Create a proc interface for sysipc types using a seq_file interface.
 165 *      @path: Path in procfs
 166 *      @header: Banner to be printed at the beginning of the file.
 167 *      @ids: ipc id table to iterate.
 168 *      @show: show routine.
 169 */
 170void __init ipc_init_proc_interface(const char *path, const char *header,
 171                int ids, int (*show)(struct seq_file *, void *))
 172{
 173        struct proc_dir_entry *pde;
 174        struct ipc_proc_iface *iface;
 175
 176        iface = kmalloc(sizeof(*iface), GFP_KERNEL);
 177        if (!iface)
 178                return;
 179        iface->path     = path;
 180        iface->header   = header;
 181        iface->ids      = ids;
 182        iface->show     = show;
 183
 184        pde = proc_create_data(path,
 185                               S_IRUGO,        /* world readable */
 186                               NULL,           /* parent dir */
 187                               &sysvipc_proc_fops,
 188                               iface);
 189        if (!pde) {
 190                kfree(iface);
 191        }
 192}
 193#endif
 194
 195/**
 196 *      ipc_findkey     -       find a key in an ipc identifier set     
 197 *      @ids: Identifier set
 198 *      @key: The key to find
 199 *      
 200 *      Requires ipc_ids.rwsem locked.
 201 *      Returns the LOCKED pointer to the ipc structure if found or NULL
 202 *      if not.
 203 *      If key is found ipc points to the owning ipc structure
 204 */
 205 
 206static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 207{
 208        struct kern_ipc_perm *ipc;
 209        int next_id;
 210        int total;
 211
 212        for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
 213                ipc = idr_find(&ids->ipcs_idr, next_id);
 214
 215                if (ipc == NULL)
 216                        continue;
 217
 218                if (ipc->key != key) {
 219                        total++;
 220                        continue;
 221                }
 222
 223                rcu_read_lock();
 224                ipc_lock_object(ipc);
 225                return ipc;
 226        }
 227
 228        return NULL;
 229}
 230
 231/**
 232 *      ipc_get_maxid   -       get the last assigned id
 233 *      @ids: IPC identifier set
 234 *
 235 *      Called with ipc_ids.rwsem held.
 236 */
 237
 238int ipc_get_maxid(struct ipc_ids *ids)
 239{
 240        struct kern_ipc_perm *ipc;
 241        int max_id = -1;
 242        int total, id;
 243
 244        if (ids->in_use == 0)
 245                return -1;
 246
 247        if (ids->in_use == IPCMNI)
 248                return IPCMNI - 1;
 249
 250        /* Look for the last assigned id */
 251        total = 0;
 252        for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
 253                ipc = idr_find(&ids->ipcs_idr, id);
 254                if (ipc != NULL) {
 255                        max_id = id;
 256                        total++;
 257                }
 258        }
 259        return max_id;
 260}
 261
 262/**
 263 *      ipc_addid       -       add an IPC identifier
 264 *      @ids: IPC identifier set
 265 *      @new: new IPC permission set
 266 *      @size: limit for the number of used ids
 267 *
 268 *      Add an entry 'new' to the IPC ids idr. The permissions object is
 269 *      initialised and the first free entry is set up and the id assigned
 270 *      is returned. The 'new' entry is returned in a locked state on success.
 271 *      On failure the entry is not locked and a negative err-code is returned.
 272 *
 273 *      Called with writer ipc_ids.rwsem held.
 274 */
 275int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 276{
 277        kuid_t euid;
 278        kgid_t egid;
 279        int id;
 280        int next_id = ids->next_id;
 281
 282        if (size > IPCMNI)
 283                size = IPCMNI;
 284
 285        if (ids->in_use >= size)
 286                return -ENOSPC;
 287
 288        idr_preload(GFP_KERNEL);
 289
 290        spin_lock_init(&new->lock);
 291        new->deleted = 0;
 292        rcu_read_lock();
 293        spin_lock(&new->lock);
 294
 295        id = idr_alloc(&ids->ipcs_idr, new,
 296                       (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
 297                       GFP_NOWAIT);
 298        idr_preload_end();
 299        if (id < 0) {
 300                spin_unlock(&new->lock);
 301                rcu_read_unlock();
 302                return id;
 303        }
 304
 305        ids->in_use++;
 306
 307        current_euid_egid(&euid, &egid);
 308        new->cuid = new->uid = euid;
 309        new->gid = new->cgid = egid;
 310
 311        if (next_id < 0) {
 312                new->seq = ids->seq++;
 313                if (ids->seq > ids->seq_max)
 314                        ids->seq = 0;
 315        } else {
 316                new->seq = ipcid_to_seqx(next_id);
 317                ids->next_id = -1;
 318        }
 319
 320        new->id = ipc_buildid(id, new->seq);
 321        return id;
 322}
 323
 324/**
 325 *      ipcget_new      -       create a new ipc object
 326 *      @ns: namespace
 327 *      @ids: IPC identifer set
 328 *      @ops: the actual creation routine to call
 329 *      @params: its parameters
 330 *
 331 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 332 *      when the key is IPC_PRIVATE.
 333 */
 334static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
 335                struct ipc_ops *ops, struct ipc_params *params)
 336{
 337        int err;
 338
 339        down_write(&ids->rwsem);
 340        err = ops->getnew(ns, params);
 341        up_write(&ids->rwsem);
 342        return err;
 343}
 344
 345/**
 346 *      ipc_check_perms -       check security and permissions for an IPC
 347 *      @ns: IPC namespace
 348 *      @ipcp: ipc permission set
 349 *      @ops: the actual security routine to call
 350 *      @params: its parameters
 351 *
 352 *      This routine is called by sys_msgget(), sys_semget() and sys_shmget()
 353 *      when the key is not IPC_PRIVATE and that key already exists in the
 354 *      ids IDR.
 355 *
 356 *      On success, the IPC id is returned.
 357 *
 358 *      It is called with ipc_ids.rwsem and ipcp->lock held.
 359 */
 360static int ipc_check_perms(struct ipc_namespace *ns,
 361                           struct kern_ipc_perm *ipcp,
 362                           struct ipc_ops *ops,
 363                           struct ipc_params *params)
 364{
 365        int err;
 366
 367        if (ipcperms(ns, ipcp, params->flg))
 368                err = -EACCES;
 369        else {
 370                err = ops->associate(ipcp, params->flg);
 371                if (!err)
 372                        err = ipcp->id;
 373        }
 374
 375        return err;
 376}
 377
 378/**
 379 *      ipcget_public   -       get an ipc object or create a new one
 380 *      @ns: namespace
 381 *      @ids: IPC identifer set
 382 *      @ops: the actual creation routine to call
 383 *      @params: its parameters
 384 *
 385 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 386 *      when the key is not IPC_PRIVATE.
 387 *      It adds a new entry if the key is not found and does some permission
 388 *      / security checkings if the key is found.
 389 *
 390 *      On success, the ipc id is returned.
 391 */
 392static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 393                struct ipc_ops *ops, struct ipc_params *params)
 394{
 395        struct kern_ipc_perm *ipcp;
 396        int flg = params->flg;
 397        int err;
 398
 399        /*
 400         * Take the lock as a writer since we are potentially going to add
 401         * a new entry + read locks are not "upgradable"
 402         */
 403        down_write(&ids->rwsem);
 404        ipcp = ipc_findkey(ids, params->key);
 405        if (ipcp == NULL) {
 406                /* key not used */
 407                if (!(flg & IPC_CREAT))
 408                        err = -ENOENT;
 409                else
 410                        err = ops->getnew(ns, params);
 411        } else {
 412                /* ipc object has been locked by ipc_findkey() */
 413
 414                if (flg & IPC_CREAT && flg & IPC_EXCL)
 415                        err = -EEXIST;
 416                else {
 417                        err = 0;
 418                        if (ops->more_checks)
 419                                err = ops->more_checks(ipcp, params);
 420                        if (!err)
 421                                /*
 422                                 * ipc_check_perms returns the IPC id on
 423                                 * success
 424                                 */
 425                                err = ipc_check_perms(ns, ipcp, ops, params);
 426                }
 427                ipc_unlock(ipcp);
 428        }
 429        up_write(&ids->rwsem);
 430
 431        return err;
 432}
 433
 434
 435/**
 436 *      ipc_rmid        -       remove an IPC identifier
 437 *      @ids: IPC identifier set
 438 *      @ipcp: ipc perm structure containing the identifier to remove
 439 *
 440 *      ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
 441 *      before this function is called, and remain locked on the exit.
 442 */
 443 
 444void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 445{
 446        int lid = ipcid_to_idx(ipcp->id);
 447
 448        idr_remove(&ids->ipcs_idr, lid);
 449
 450        ids->in_use--;
 451
 452        ipcp->deleted = 1;
 453
 454        return;
 455}
 456
 457/**
 458 *      ipc_alloc       -       allocate ipc space
 459 *      @size: size desired
 460 *
 461 *      Allocate memory from the appropriate pools and return a pointer to it.
 462 *      NULL is returned if the allocation fails
 463 */
 464 
 465void *ipc_alloc(int size)
 466{
 467        void *out;
 468        if(size > PAGE_SIZE)
 469                out = vmalloc(size);
 470        else
 471                out = kmalloc(size, GFP_KERNEL);
 472        return out;
 473}
 474
 475/**
 476 *      ipc_free        -       free ipc space
 477 *      @ptr: pointer returned by ipc_alloc
 478 *      @size: size of block
 479 *
 480 *      Free a block created with ipc_alloc(). The caller must know the size
 481 *      used in the allocation call.
 482 */
 483
 484void ipc_free(void* ptr, int size)
 485{
 486        if(size > PAGE_SIZE)
 487                vfree(ptr);
 488        else
 489                kfree(ptr);
 490}
 491
 492/**
 493 *      ipc_rcu_alloc   -       allocate ipc and rcu space 
 494 *      @size: size desired
 495 *
 496 *      Allocate memory for the rcu header structure +  the object.
 497 *      Returns the pointer to the object or NULL upon failure.
 498 */
 499void *ipc_rcu_alloc(int size)
 500{
 501        /*
 502         * We prepend the allocation with the rcu struct
 503         */
 504        struct ipc_rcu *out = ipc_alloc(sizeof(struct ipc_rcu) + size);
 505        if (unlikely(!out))
 506                return NULL;
 507        atomic_set(&out->refcount, 1);
 508        return out + 1;
 509}
 510
 511int ipc_rcu_getref(void *ptr)
 512{
 513        struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;
 514
 515        return atomic_inc_not_zero(&p->refcount);
 516}
 517
 518void ipc_rcu_putref(void *ptr, void (*func)(struct rcu_head *head))
 519{
 520        struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;
 521
 522        if (!atomic_dec_and_test(&p->refcount))
 523                return;
 524
 525        call_rcu(&p->rcu, func);
 526}
 527
 528void ipc_rcu_free(struct rcu_head *head)
 529{
 530        struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
 531
 532        if (is_vmalloc_addr(p))
 533                vfree(p);
 534        else
 535                kfree(p);
 536}
 537
 538/**
 539 *      ipcperms        -       check IPC permissions
 540 *      @ns: IPC namespace
 541 *      @ipcp: IPC permission set
 542 *      @flag: desired permission set.
 543 *
 544 *      Check user, group, other permissions for access
 545 *      to ipc resources. return 0 if allowed
 546 *
 547 *      @flag will most probably be 0 or S_...UGO from <linux/stat.h>
 548 */
 549 
 550int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
 551{
 552        kuid_t euid = current_euid();
 553        int requested_mode, granted_mode;
 554
 555        audit_ipc_obj(ipcp);
 556        requested_mode = (flag >> 6) | (flag >> 3) | flag;
 557        granted_mode = ipcp->mode;
 558        if (uid_eq(euid, ipcp->cuid) ||
 559            uid_eq(euid, ipcp->uid))
 560                granted_mode >>= 6;
 561        else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 562                granted_mode >>= 3;
 563        /* is there some bit set in requested_mode but not in granted_mode? */
 564        if ((requested_mode & ~granted_mode & 0007) && 
 565            !ns_capable(ns->user_ns, CAP_IPC_OWNER))
 566                return -1;
 567
 568        return security_ipc_permission(ipcp, flag);
 569}
 570
 571/*
 572 * Functions to convert between the kern_ipc_perm structure and the
 573 * old/new ipc_perm structures
 574 */
 575
 576/**
 577 *      kernel_to_ipc64_perm    -       convert kernel ipc permissions to user
 578 *      @in: kernel permissions
 579 *      @out: new style IPC permissions
 580 *
 581 *      Turn the kernel object @in into a set of permissions descriptions
 582 *      for returning to userspace (@out).
 583 */
 584 
 585
 586void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
 587{
 588        out->key        = in->key;
 589        out->uid        = from_kuid_munged(current_user_ns(), in->uid);
 590        out->gid        = from_kgid_munged(current_user_ns(), in->gid);
 591        out->cuid       = from_kuid_munged(current_user_ns(), in->cuid);
 592        out->cgid       = from_kgid_munged(current_user_ns(), in->cgid);
 593        out->mode       = in->mode;
 594        out->seq        = in->seq;
 595}
 596
 597/**
 598 *      ipc64_perm_to_ipc_perm  -       convert new ipc permissions to old
 599 *      @in: new style IPC permissions
 600 *      @out: old style IPC permissions
 601 *
 602 *      Turn the new style permissions object @in into a compatibility
 603 *      object and store it into the @out pointer.
 604 */
 605 
 606void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
 607{
 608        out->key        = in->key;
 609        SET_UID(out->uid, in->uid);
 610        SET_GID(out->gid, in->gid);
 611        SET_UID(out->cuid, in->cuid);
 612        SET_GID(out->cgid, in->cgid);
 613        out->mode       = in->mode;
 614        out->seq        = in->seq;
 615}
 616
 617/**
 618 * ipc_obtain_object
 619 * @ids: ipc identifier set
 620 * @id: ipc id to look for
 621 *
 622 * Look for an id in the ipc ids idr and return associated ipc object.
 623 *
 624 * Call inside the RCU critical section.
 625 * The ipc object is *not* locked on exit.
 626 */
 627struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id)
 628{
 629        struct kern_ipc_perm *out;
 630        int lid = ipcid_to_idx(id);
 631
 632        out = idr_find(&ids->ipcs_idr, lid);
 633        if (!out)
 634                return ERR_PTR(-EINVAL);
 635
 636        return out;
 637}
 638
 639/**
 640 * ipc_lock - Lock an ipc structure without rwsem held
 641 * @ids: IPC identifier set
 642 * @id: ipc id to look for
 643 *
 644 * Look for an id in the ipc ids idr and lock the associated ipc object.
 645 *
 646 * The ipc object is locked on successful exit.
 647 */
 648struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
 649{
 650        struct kern_ipc_perm *out;
 651
 652        rcu_read_lock();
 653        out = ipc_obtain_object(ids, id);
 654        if (IS_ERR(out))
 655                goto err1;
 656
 657        spin_lock(&out->lock);
 658
 659        /* ipc_rmid() may have already freed the ID while ipc_lock
 660         * was spinning: here verify that the structure is still valid
 661         */
 662        if (!out->deleted)
 663                return out;
 664
 665        spin_unlock(&out->lock);
 666        out = ERR_PTR(-EINVAL);
 667err1:
 668        rcu_read_unlock();
 669        return out;
 670}
 671
 672/**
 673 * ipc_obtain_object_check
 674 * @ids: ipc identifier set
 675 * @id: ipc id to look for
 676 *
 677 * Similar to ipc_obtain_object() but also checks
 678 * the ipc object reference counter.
 679 *
 680 * Call inside the RCU critical section.
 681 * The ipc object is *not* locked on exit.
 682 */
 683struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
 684{
 685        struct kern_ipc_perm *out = ipc_obtain_object(ids, id);
 686
 687        if (IS_ERR(out))
 688                goto out;
 689
 690        if (ipc_checkid(out, id))
 691                return ERR_PTR(-EIDRM);
 692out:
 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_nolock - 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 a pointer to the ipc object or otherwise, the corresponding error.
 750 *
 751 * Call holding the both the rwsem and the rcu read lock.
 752 */
 753struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
 754                                        struct ipc_ids *ids, int id, int cmd,
 755                                        struct ipc64_perm *perm, int extra_perm)
 756{
 757        kuid_t euid;
 758        int err = -EPERM;
 759        struct kern_ipc_perm *ipcp;
 760
 761        ipcp = ipc_obtain_object_check(ids, id);
 762        if (IS_ERR(ipcp)) {
 763                err = PTR_ERR(ipcp);
 764                goto err;
 765        }
 766
 767        audit_ipc_obj(ipcp);
 768        if (cmd == IPC_SET)
 769                audit_ipc_set_perm(extra_perm, perm->uid,
 770                                   perm->gid, perm->mode);
 771
 772        euid = current_euid();
 773        if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
 774            ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 775                return ipcp; /* successful lookup */
 776err:
 777        return ERR_PTR(err);
 778}
 779
 780#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
 781
 782
 783/**
 784 *      ipc_parse_version       -       IPC call version
 785 *      @cmd: pointer to command
 786 *
 787 *      Return IPC_64 for new style IPC and IPC_OLD for old style IPC. 
 788 *      The @cmd value is turned from an encoding command and version into
 789 *      just the command code.
 790 */
 791 
 792int ipc_parse_version (int *cmd)
 793{
 794        if (*cmd & IPC_64) {
 795                *cmd ^= IPC_64;
 796                return IPC_64;
 797        } else {
 798                return IPC_OLD;
 799        }
 800}
 801
 802#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
 803
 804#ifdef CONFIG_PROC_FS
 805struct ipc_proc_iter {
 806        struct ipc_namespace *ns;
 807        struct ipc_proc_iface *iface;
 808};
 809
 810/*
 811 * This routine locks the ipc structure found at least at position pos.
 812 */
 813static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 814                                              loff_t *new_pos)
 815{
 816        struct kern_ipc_perm *ipc;
 817        int total, id;
 818
 819        total = 0;
 820        for (id = 0; id < pos && total < ids->in_use; id++) {
 821                ipc = idr_find(&ids->ipcs_idr, id);
 822                if (ipc != NULL)
 823                        total++;
 824        }
 825
 826        if (total >= ids->in_use)
 827                return NULL;
 828
 829        for ( ; pos < IPCMNI; pos++) {
 830                ipc = idr_find(&ids->ipcs_idr, pos);
 831                if (ipc != NULL) {
 832                        *new_pos = pos + 1;
 833                        rcu_read_lock();
 834                        ipc_lock_object(ipc);
 835                        return ipc;
 836                }
 837        }
 838
 839        /* Out of range - return NULL to terminate iteration */
 840        return NULL;
 841}
 842
 843static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 844{
 845        struct ipc_proc_iter *iter = s->private;
 846        struct ipc_proc_iface *iface = iter->iface;
 847        struct kern_ipc_perm *ipc = it;
 848
 849        /* If we had an ipc id locked before, unlock it */
 850        if (ipc && ipc != SEQ_START_TOKEN)
 851                ipc_unlock(ipc);
 852
 853        return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 854}
 855
 856/*
 857 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
 858 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
 859 */
 860static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 861{
 862        struct ipc_proc_iter *iter = s->private;
 863        struct ipc_proc_iface *iface = iter->iface;
 864        struct ipc_ids *ids;
 865
 866        ids = &iter->ns->ids[iface->ids];
 867
 868        /*
 869         * Take the lock - this will be released by the corresponding
 870         * call to stop().
 871         */
 872        down_read(&ids->rwsem);
 873
 874        /* pos < 0 is invalid */
 875        if (*pos < 0)
 876                return NULL;
 877
 878        /* pos == 0 means header */
 879        if (*pos == 0)
 880                return SEQ_START_TOKEN;
 881
 882        /* Find the (pos-1)th ipc */
 883        return sysvipc_find_ipc(ids, *pos - 1, pos);
 884}
 885
 886static void sysvipc_proc_stop(struct seq_file *s, void *it)
 887{
 888        struct kern_ipc_perm *ipc = it;
 889        struct ipc_proc_iter *iter = s->private;
 890        struct ipc_proc_iface *iface = iter->iface;
 891        struct ipc_ids *ids;
 892
 893        /* If we had a locked structure, release it */
 894        if (ipc && ipc != SEQ_START_TOKEN)
 895                ipc_unlock(ipc);
 896
 897        ids = &iter->ns->ids[iface->ids];
 898        /* Release the lock we took in start() */
 899        up_read(&ids->rwsem);
 900}
 901
 902static int sysvipc_proc_show(struct seq_file *s, void *it)
 903{
 904        struct ipc_proc_iter *iter = s->private;
 905        struct ipc_proc_iface *iface = iter->iface;
 906
 907        if (it == SEQ_START_TOKEN)
 908                return seq_puts(s, iface->header);
 909
 910        return iface->show(s, it);
 911}
 912
 913static const struct seq_operations sysvipc_proc_seqops = {
 914        .start = sysvipc_proc_start,
 915        .stop  = sysvipc_proc_stop,
 916        .next  = sysvipc_proc_next,
 917        .show  = sysvipc_proc_show,
 918};
 919
 920static int sysvipc_proc_open(struct inode *inode, struct file *file)
 921{
 922        int ret;
 923        struct seq_file *seq;
 924        struct ipc_proc_iter *iter;
 925
 926        ret = -ENOMEM;
 927        iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 928        if (!iter)
 929                goto out;
 930
 931        ret = seq_open(file, &sysvipc_proc_seqops);
 932        if (ret)
 933                goto out_kfree;
 934
 935        seq = file->private_data;
 936        seq->private = iter;
 937
 938        iter->iface = PDE_DATA(inode);
 939        iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 940out:
 941        return ret;
 942out_kfree:
 943        kfree(iter);
 944        goto out;
 945}
 946
 947static int sysvipc_proc_release(struct inode *inode, struct file *file)
 948{
 949        struct seq_file *seq = file->private_data;
 950        struct ipc_proc_iter *iter = seq->private;
 951        put_ipc_ns(iter->ns);
 952        return seq_release_private(inode, file);
 953}
 954
 955static const struct file_operations sysvipc_proc_fops = {
 956        .open    = sysvipc_proc_open,
 957        .read    = seq_read,
 958        .llseek  = seq_lseek,
 959        .release = sysvipc_proc_release,
 960};
 961#endif /* CONFIG_PROC_FS */
 962
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