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/capability.h>
  27#include <linux/highuid.h>
  28#include <linux/security.h>
  29#include <linux/rcupdate.h>
  30#include <linux/workqueue.h>
  31#include <linux/seq_file.h>
  32#include <linux/proc_fs.h>
  33#include <linux/audit.h>
  34#include <linux/nsproxy.h>
  35#include <linux/rwsem.h>
  36#include <linux/memory.h>
  37#include <linux/ipc_namespace.h>
  38
  39#include <asm/unistd.h>
  40
  41#include "util.h"
  42
  43struct ipc_proc_iface {
  44        const char *path;
  45        const char *header;
  46        int ids;
  47        int (*show)(struct seq_file *, void *);
  48};
  49
  50#ifdef CONFIG_MEMORY_HOTPLUG
  51
  52static void ipc_memory_notifier(struct work_struct *work)
  53{
  54        ipcns_notify(IPCNS_MEMCHANGED);
  55}
  56
  57static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
  58
  59
  60static int ipc_memory_callback(struct notifier_block *self,
  61                                unsigned long action, void *arg)
  62{
  63        switch (action) {
  64        case MEM_ONLINE:    /* memory successfully brought online */
  65        case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
  66                /*
  67                 * This is done by invoking the ipcns notifier chain with the
  68                 * IPC_MEMCHANGED event.
  69                 * In order not to keep the lock on the hotplug memory chain
  70                 * for too long, queue a work item that will, when waken up,
  71                 * activate the ipcns notification chain.
  72                 * No need to keep several ipc work items on the queue.
  73                 */
  74                if (!work_pending(&ipc_memory_wq))
  75                        schedule_work(&ipc_memory_wq);
  76                break;
  77        case MEM_GOING_ONLINE:
  78        case MEM_GOING_OFFLINE:
  79        case MEM_CANCEL_ONLINE:
  80        case MEM_CANCEL_OFFLINE:
  81        default:
  82                break;
  83        }
  84
  85        return NOTIFY_OK;
  86}
  87
  88#endif /* CONFIG_MEMORY_HOTPLUG */
  89
  90/**
  91 *      ipc_init        -       initialise IPC subsystem
  92 *
  93 *      The various system5 IPC resources (semaphores, messages and shared
  94 *      memory) are initialised
  95 *      A callback routine is registered into the memory hotplug notifier
  96 *      chain: since msgmni scales to lowmem this callback routine will be
  97 *      called upon successful memory add / remove to recompute msmgni.
  98 */
  99 
 100static int __init ipc_init(void)
 101{
 102        sem_init();
 103        msg_init();
 104        shm_init();
 105        hotplug_memory_notifier(ipc_memory_callback, IPC_CALLBACK_PRI);
 106        register_ipcns_notifier(&init_ipc_ns);
 107        return 0;
 108}
 109__initcall(ipc_init);
 110
 111/**
 112 *      ipc_init_ids            -       initialise IPC identifiers
 113 *      @ids: Identifier set
 114 *
 115 *      Set up the sequence range to use for the ipc identifier range (limited
 116 *      below IPCMNI) then initialise the ids idr.
 117 */
 118 
 119void ipc_init_ids(struct ipc_ids *ids)
 120{
 121        init_rwsem(&ids->rw_mutex);
 122
 123        ids->in_use = 0;
 124        ids->seq = 0;
 125        ids->next_id = -1;
 126        {
 127                int seq_limit = INT_MAX/SEQ_MULTIPLIER;
 128                if (seq_limit > USHRT_MAX)
 129                        ids->seq_max = USHRT_MAX;
 130                 else
 131                        ids->seq_max = seq_limit;
 132        }
 133
 134        idr_init(&ids->ipcs_idr);
 135}
 136
 137#ifdef CONFIG_PROC_FS
 138static const struct file_operations sysvipc_proc_fops;
 139/**
 140 *      ipc_init_proc_interface -  Create a proc interface for sysipc types using a seq_file interface.
 141 *      @path: Path in procfs
 142 *      @header: Banner to be printed at the beginning of the file.
 143 *      @ids: ipc id table to iterate.
 144 *      @show: show routine.
 145 */
 146void __init ipc_init_proc_interface(const char *path, const char *header,
 147                int ids, int (*show)(struct seq_file *, void *))
 148{
 149        struct proc_dir_entry *pde;
 150        struct ipc_proc_iface *iface;
 151
 152        iface = kmalloc(sizeof(*iface), GFP_KERNEL);
 153        if (!iface)
 154                return;
 155        iface->path     = path;
 156        iface->header   = header;
 157        iface->ids      = ids;
 158        iface->show     = show;
 159
 160        pde = proc_create_data(path,
 161                               S_IRUGO,        /* world readable */
 162                               NULL,           /* parent dir */
 163                               &sysvipc_proc_fops,
 164                               iface);
 165        if (!pde) {
 166                kfree(iface);
 167        }
 168}
 169#endif
 170
 171/**
 172 *      ipc_findkey     -       find a key in an ipc identifier set     
 173 *      @ids: Identifier set
 174 *      @key: The key to find
 175 *      
 176 *      Requires ipc_ids.rw_mutex locked.
 177 *      Returns the LOCKED pointer to the ipc structure if found or NULL
 178 *      if not.
 179 *      If key is found ipc points to the owning ipc structure
 180 */
 181 
 182static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 183{
 184        struct kern_ipc_perm *ipc;
 185        int next_id;
 186        int total;
 187
 188        for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
 189                ipc = idr_find(&ids->ipcs_idr, next_id);
 190
 191                if (ipc == NULL)
 192                        continue;
 193
 194                if (ipc->key != key) {
 195                        total++;
 196                        continue;
 197                }
 198
 199                ipc_lock_by_ptr(ipc);
 200                return ipc;
 201        }
 202
 203        return NULL;
 204}
 205
 206/**
 207 *      ipc_get_maxid   -       get the last assigned id
 208 *      @ids: IPC identifier set
 209 *
 210 *      Called with ipc_ids.rw_mutex held.
 211 */
 212
 213int ipc_get_maxid(struct ipc_ids *ids)
 214{
 215        struct kern_ipc_perm *ipc;
 216        int max_id = -1;
 217        int total, id;
 218
 219        if (ids->in_use == 0)
 220                return -1;
 221
 222        if (ids->in_use == IPCMNI)
 223                return IPCMNI - 1;
 224
 225        /* Look for the last assigned id */
 226        total = 0;
 227        for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
 228                ipc = idr_find(&ids->ipcs_idr, id);
 229                if (ipc != NULL) {
 230                        max_id = id;
 231                        total++;
 232                }
 233        }
 234        return max_id;
 235}
 236
 237/**
 238 *      ipc_addid       -       add an IPC identifier
 239 *      @ids: IPC identifier set
 240 *      @new: new IPC permission set
 241 *      @size: limit for the number of used ids
 242 *
 243 *      Add an entry 'new' to the IPC ids idr. The permissions object is
 244 *      initialised and the first free entry is set up and the id assigned
 245 *      is returned. The 'new' entry is returned in a locked state on success.
 246 *      On failure the entry is not locked and a negative err-code is returned.
 247 *
 248 *      Called with ipc_ids.rw_mutex held as a writer.
 249 */
 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, err;
 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        spin_lock_init(&new->lock);
 265        new->deleted = 0;
 266        rcu_read_lock();
 267        spin_lock(&new->lock);
 268
 269        err = idr_get_new_above(&ids->ipcs_idr, new,
 270                                (next_id < 0) ? 0 : ipcid_to_idx(next_id), &id);
 271        if (err) {
 272                spin_unlock(&new->lock);
 273                rcu_read_unlock();
 274                return err;
 275        }
 276
 277        ids->in_use++;
 278
 279        current_euid_egid(&euid, &egid);
 280        new->cuid = new->uid = euid;
 281        new->gid = new->cgid = egid;
 282
 283        if (next_id < 0) {
 284                new->seq = ids->seq++;
 285                if (ids->seq > ids->seq_max)
 286                        ids->seq = 0;
 287        } else {
 288                new->seq = ipcid_to_seqx(next_id);
 289                ids->next_id = -1;
 290        }
 291
 292        new->id = ipc_buildid(id, new->seq);
 293        return id;
 294}
 295
 296/**
 297 *      ipcget_new      -       create a new ipc object
 298 *      @ns: namespace
 299 *      @ids: IPC identifer set
 300 *      @ops: the actual creation routine to call
 301 *      @params: its parameters
 302 *
 303 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 304 *      when the key is IPC_PRIVATE.
 305 */
 306static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
 307                struct ipc_ops *ops, struct ipc_params *params)
 308{
 309        int err;
 310retry:
 311        err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
 312
 313        if (!err)
 314                return -ENOMEM;
 315
 316        down_write(&ids->rw_mutex);
 317        err = ops->getnew(ns, params);
 318        up_write(&ids->rw_mutex);
 319
 320        if (err == -EAGAIN)
 321                goto retry;
 322
 323        return err;
 324}
 325
 326/**
 327 *      ipc_check_perms -       check security and permissions for an IPC
 328 *      @ns: IPC namespace
 329 *      @ipcp: ipc permission set
 330 *      @ops: the actual security routine to call
 331 *      @params: its parameters
 332 *
 333 *      This routine is called by sys_msgget(), sys_semget() and sys_shmget()
 334 *      when the key is not IPC_PRIVATE and that key already exists in the
 335 *      ids IDR.
 336 *
 337 *      On success, the IPC id is returned.
 338 *
 339 *      It is called with ipc_ids.rw_mutex and ipcp->lock held.
 340 */
 341static int ipc_check_perms(struct ipc_namespace *ns,
 342                           struct kern_ipc_perm *ipcp,
 343                           struct ipc_ops *ops,
 344                           struct ipc_params *params)
 345{
 346        int err;
 347
 348        if (ipcperms(ns, ipcp, params->flg))
 349                err = -EACCES;
 350        else {
 351                err = ops->associate(ipcp, params->flg);
 352                if (!err)
 353                        err = ipcp->id;
 354        }
 355
 356        return err;
 357}
 358
 359/**
 360 *      ipcget_public   -       get an ipc object or create a new one
 361 *      @ns: namespace
 362 *      @ids: IPC identifer set
 363 *      @ops: the actual creation routine to call
 364 *      @params: its parameters
 365 *
 366 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 367 *      when the key is not IPC_PRIVATE.
 368 *      It adds a new entry if the key is not found and does some permission
 369 *      / security checkings if the key is found.
 370 *
 371 *      On success, the ipc id is returned.
 372 */
 373static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 374                struct ipc_ops *ops, struct ipc_params *params)
 375{
 376        struct kern_ipc_perm *ipcp;
 377        int flg = params->flg;
 378        int err;
 379retry:
 380        err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
 381
 382        /*
 383         * Take the lock as a writer since we are potentially going to add
 384         * a new entry + read locks are not "upgradable"
 385         */
 386        down_write(&ids->rw_mutex);
 387        ipcp = ipc_findkey(ids, params->key);
 388        if (ipcp == NULL) {
 389                /* key not used */
 390                if (!(flg & IPC_CREAT))
 391                        err = -ENOENT;
 392                else if (!err)
 393                        err = -ENOMEM;
 394                else
 395                        err = ops->getnew(ns, params);
 396        } else {
 397                /* ipc object has been locked by ipc_findkey() */
 398
 399                if (flg & IPC_CREAT && flg & IPC_EXCL)
 400                        err = -EEXIST;
 401                else {
 402                        err = 0;
 403                        if (ops->more_checks)
 404                                err = ops->more_checks(ipcp, params);
 405                        if (!err)
 406                                /*
 407                                 * ipc_check_perms returns the IPC id on
 408                                 * success
 409                                 */
 410                                err = ipc_check_perms(ns, ipcp, ops, params);
 411                }
 412                ipc_unlock(ipcp);
 413        }
 414        up_write(&ids->rw_mutex);
 415
 416        if (err == -EAGAIN)
 417                goto retry;
 418
 419        return err;
 420}
 421
 422
 423/**
 424 *      ipc_rmid        -       remove an IPC identifier
 425 *      @ids: IPC identifier set
 426 *      @ipcp: ipc perm structure containing the identifier to remove
 427 *
 428 *      ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
 429 *      before this function is called, and remain locked on the exit.
 430 */
 431 
 432void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 433{
 434        int lid = ipcid_to_idx(ipcp->id);
 435
 436        idr_remove(&ids->ipcs_idr, lid);
 437
 438        ids->in_use--;
 439
 440        ipcp->deleted = 1;
 441
 442        return;
 443}
 444
 445/**
 446 *      ipc_alloc       -       allocate ipc space
 447 *      @size: size desired
 448 *
 449 *      Allocate memory from the appropriate pools and return a pointer to it.
 450 *      NULL is returned if the allocation fails
 451 */
 452 
 453void* ipc_alloc(int size)
 454{
 455        void* out;
 456        if(size > PAGE_SIZE)
 457                out = vmalloc(size);
 458        else
 459                out = kmalloc(size, GFP_KERNEL);
 460        return out;
 461}
 462
 463/**
 464 *      ipc_free        -       free ipc space
 465 *      @ptr: pointer returned by ipc_alloc
 466 *      @size: size of block
 467 *
 468 *      Free a block created with ipc_alloc(). The caller must know the size
 469 *      used in the allocation call.
 470 */
 471
 472void ipc_free(void* ptr, int size)
 473{
 474        if(size > PAGE_SIZE)
 475                vfree(ptr);
 476        else
 477                kfree(ptr);
 478}
 479
 480/*
 481 * rcu allocations:
 482 * There are three headers that are prepended to the actual allocation:
 483 * - during use: ipc_rcu_hdr.
 484 * - during the rcu grace period: ipc_rcu_grace.
 485 * - [only if vmalloc]: ipc_rcu_sched.
 486 * Their lifetime doesn't overlap, thus the headers share the same memory.
 487 * Unlike a normal union, they are right-aligned, thus some container_of
 488 * forward/backward casting is necessary:
 489 */
 490struct ipc_rcu_hdr
 491{
 492        int refcount;
 493        int is_vmalloc;
 494        void *data[0];
 495};
 496
 497
 498struct ipc_rcu_grace
 499{
 500        struct rcu_head rcu;
 501        /* "void *" makes sure alignment of following data is sane. */
 502        void *data[0];
 503};
 504
 505struct ipc_rcu_sched
 506{
 507        struct work_struct work;
 508        /* "void *" makes sure alignment of following data is sane. */
 509        void *data[0];
 510};
 511
 512#define HDRLEN_KMALLOC          (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
 513                                        sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
 514#define HDRLEN_VMALLOC          (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
 515                                        sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
 516
 517static inline int rcu_use_vmalloc(int size)
 518{
 519        /* Too big for a single page? */
 520        if (HDRLEN_KMALLOC + size > PAGE_SIZE)
 521                return 1;
 522        return 0;
 523}
 524
 525/**
 526 *      ipc_rcu_alloc   -       allocate ipc and rcu space 
 527 *      @size: size desired
 528 *
 529 *      Allocate memory for the rcu header structure +  the object.
 530 *      Returns the pointer to the object.
 531 *      NULL is returned if the allocation fails. 
 532 */
 533 
 534void* ipc_rcu_alloc(int size)
 535{
 536        void* out;
 537        /* 
 538         * We prepend the allocation with the rcu struct, and
 539         * workqueue if necessary (for vmalloc). 
 540         */
 541        if (rcu_use_vmalloc(size)) {
 542                out = vmalloc(HDRLEN_VMALLOC + size);
 543                if (out) {
 544                        out += HDRLEN_VMALLOC;
 545                        container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
 546                        container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
 547                }
 548        } else {
 549                out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
 550                if (out) {
 551                        out += HDRLEN_KMALLOC;
 552                        container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
 553                        container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
 554                }
 555        }
 556
 557        return out;
 558}
 559
 560void ipc_rcu_getref(void *ptr)
 561{
 562        container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
 563}
 564
 565static void ipc_do_vfree(struct work_struct *work)
 566{
 567        vfree(container_of(work, struct ipc_rcu_sched, work));
 568}
 569
 570/**
 571 * ipc_schedule_free - free ipc + rcu space
 572 * @head: RCU callback structure for queued work
 573 * 
 574 * Since RCU callback function is called in bh,
 575 * we need to defer the vfree to schedule_work().
 576 */
 577static void ipc_schedule_free(struct rcu_head *head)
 578{
 579        struct ipc_rcu_grace *grace;
 580        struct ipc_rcu_sched *sched;
 581
 582        grace = container_of(head, struct ipc_rcu_grace, rcu);
 583        sched = container_of(&(grace->data[0]), struct ipc_rcu_sched,
 584                                data[0]);
 585
 586        INIT_WORK(&sched->work, ipc_do_vfree);
 587        schedule_work(&sched->work);
 588}
 589
 590void ipc_rcu_putref(void *ptr)
 591{
 592        if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
 593                return;
 594
 595        if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
 596                call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
 597                                ipc_schedule_free);
 598        } else {
 599                kfree_rcu(container_of(ptr, struct ipc_rcu_grace, data), rcu);
 600        }
 601}
 602
 603/**
 604 *      ipcperms        -       check IPC permissions
 605 *      @ns: IPC namespace
 606 *      @ipcp: IPC permission set
 607 *      @flag: desired permission set.
 608 *
 609 *      Check user, group, other permissions for access
 610 *      to ipc resources. return 0 if allowed
 611 *
 612 *      @flag will most probably be 0 or S_...UGO from <linux/stat.h>
 613 */
 614 
 615int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
 616{
 617        kuid_t euid = current_euid();
 618        int requested_mode, granted_mode;
 619
 620        audit_ipc_obj(ipcp);
 621        requested_mode = (flag >> 6) | (flag >> 3) | flag;
 622        granted_mode = ipcp->mode;
 623        if (uid_eq(euid, ipcp->cuid) ||
 624            uid_eq(euid, ipcp->uid))
 625                granted_mode >>= 6;
 626        else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 627                granted_mode >>= 3;
 628        /* is there some bit set in requested_mode but not in granted_mode? */
 629        if ((requested_mode & ~granted_mode & 0007) && 
 630            !ns_capable(ns->user_ns, CAP_IPC_OWNER))
 631                return -1;
 632
 633        return security_ipc_permission(ipcp, flag);
 634}
 635
 636/*
 637 * Functions to convert between the kern_ipc_perm structure and the
 638 * old/new ipc_perm structures
 639 */
 640
 641/**
 642 *      kernel_to_ipc64_perm    -       convert kernel ipc permissions to user
 643 *      @in: kernel permissions
 644 *      @out: new style IPC permissions
 645 *
 646 *      Turn the kernel object @in into a set of permissions descriptions
 647 *      for returning to userspace (@out).
 648 */
 649 
 650
 651void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
 652{
 653        out->key        = in->key;
 654        out->uid        = from_kuid_munged(current_user_ns(), in->uid);
 655        out->gid        = from_kgid_munged(current_user_ns(), in->gid);
 656        out->cuid       = from_kuid_munged(current_user_ns(), in->cuid);
 657        out->cgid       = from_kgid_munged(current_user_ns(), in->cgid);
 658        out->mode       = in->mode;
 659        out->seq        = in->seq;
 660}
 661
 662/**
 663 *      ipc64_perm_to_ipc_perm  -       convert new ipc permissions to old
 664 *      @in: new style IPC permissions
 665 *      @out: old style IPC permissions
 666 *
 667 *      Turn the new style permissions object @in into a compatibility
 668 *      object and store it into the @out pointer.
 669 */
 670 
 671void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
 672{
 673        out->key        = in->key;
 674        SET_UID(out->uid, in->uid);
 675        SET_GID(out->gid, in->gid);
 676        SET_UID(out->cuid, in->cuid);
 677        SET_GID(out->cgid, in->cgid);
 678        out->mode       = in->mode;
 679        out->seq        = in->seq;
 680}
 681
 682/**
 683 * ipc_lock - Lock an ipc structure without rw_mutex held
 684 * @ids: IPC identifier set
 685 * @id: ipc id to look for
 686 *
 687 * Look for an id in the ipc ids idr and lock the associated ipc object.
 688 *
 689 * The ipc object is locked on exit.
 690 */
 691
 692struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
 693{
 694        struct kern_ipc_perm *out;
 695        int lid = ipcid_to_idx(id);
 696
 697        rcu_read_lock();
 698        out = idr_find(&ids->ipcs_idr, lid);
 699        if (out == NULL) {
 700                rcu_read_unlock();
 701                return ERR_PTR(-EINVAL);
 702        }
 703
 704        spin_lock(&out->lock);
 705        
 706        /* ipc_rmid() may have already freed the ID while ipc_lock
 707         * was spinning: here verify that the structure is still valid
 708         */
 709        if (out->deleted) {
 710                spin_unlock(&out->lock);
 711                rcu_read_unlock();
 712                return ERR_PTR(-EINVAL);
 713        }
 714
 715        return out;
 716}
 717
 718struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
 719{
 720        struct kern_ipc_perm *out;
 721
 722        out = ipc_lock(ids, id);
 723        if (IS_ERR(out))
 724                return out;
 725
 726        if (ipc_checkid(out, id)) {
 727                ipc_unlock(out);
 728                return ERR_PTR(-EIDRM);
 729        }
 730
 731        return out;
 732}
 733
 734/**
 735 * ipcget - Common sys_*get() code
 736 * @ns : namsepace
 737 * @ids : IPC identifier set
 738 * @ops : operations to be called on ipc object creation, permission checks
 739 *        and further checks
 740 * @params : the parameters needed by the previous operations.
 741 *
 742 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
 743 */
 744int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
 745                        struct ipc_ops *ops, struct ipc_params *params)
 746{
 747        if (params->key == IPC_PRIVATE)
 748                return ipcget_new(ns, ids, ops, params);
 749        else
 750                return ipcget_public(ns, ids, ops, params);
 751}
 752
 753/**
 754 * ipc_update_perm - update the permissions of an IPC.
 755 * @in:  the permission given as input.
 756 * @out: the permission of the ipc to set.
 757 */
 758int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 759{
 760        kuid_t uid = make_kuid(current_user_ns(), in->uid);
 761        kgid_t gid = make_kgid(current_user_ns(), in->gid);
 762        if (!uid_valid(uid) || !gid_valid(gid))
 763                return -EINVAL;
 764
 765        out->uid = uid;
 766        out->gid = gid;
 767        out->mode = (out->mode & ~S_IRWXUGO)
 768                | (in->mode & S_IRWXUGO);
 769
 770        return 0;
 771}
 772
 773/**
 774 * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
 775 * @ns:  the ipc namespace
 776 * @ids:  the table of ids where to look for the ipc
 777 * @id:   the id of the ipc to retrieve
 778 * @cmd:  the cmd to check
 779 * @perm: the permission to set
 780 * @extra_perm: one extra permission parameter used by msq
 781 *
 782 * This function does some common audit and permissions check for some IPC_XXX
 783 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
 784 * It must be called without any lock held and
 785 *  - retrieves the ipc with the given id in the given table.
 786 *  - performs some audit and permission check, depending on the given cmd
 787 *  - returns the ipc with both ipc and rw_mutex locks held in case of success
 788 *    or an err-code without any lock held otherwise.
 789 */
 790struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
 791                                      struct ipc_ids *ids, int id, int cmd,
 792                                      struct ipc64_perm *perm, int extra_perm)
 793{
 794        struct kern_ipc_perm *ipcp;
 795        kuid_t euid;
 796        int err;
 797
 798        down_write(&ids->rw_mutex);
 799        ipcp = ipc_lock_check(ids, id);
 800        if (IS_ERR(ipcp)) {
 801                err = PTR_ERR(ipcp);
 802                goto out_up;
 803        }
 804
 805        audit_ipc_obj(ipcp);
 806        if (cmd == IPC_SET)
 807                audit_ipc_set_perm(extra_perm, perm->uid,
 808                                         perm->gid, perm->mode);
 809
 810        euid = current_euid();
 811        if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
 812            ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 813                return ipcp;
 814
 815        err = -EPERM;
 816        ipc_unlock(ipcp);
 817out_up:
 818        up_write(&ids->rw_mutex);
 819        return ERR_PTR(err);
 820}
 821
 822#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
 823
 824
 825/**
 826 *      ipc_parse_version       -       IPC call version
 827 *      @cmd: pointer to command
 828 *
 829 *      Return IPC_64 for new style IPC and IPC_OLD for old style IPC. 
 830 *      The @cmd value is turned from an encoding command and version into
 831 *      just the command code.
 832 */
 833 
 834int ipc_parse_version (int *cmd)
 835{
 836        if (*cmd & IPC_64) {
 837                *cmd ^= IPC_64;
 838                return IPC_64;
 839        } else {
 840                return IPC_OLD;
 841        }
 842}
 843
 844#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
 845
 846#ifdef CONFIG_PROC_FS
 847struct ipc_proc_iter {
 848        struct ipc_namespace *ns;
 849        struct ipc_proc_iface *iface;
 850};
 851
 852/*
 853 * This routine locks the ipc structure found at least at position pos.
 854 */
 855static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 856                                              loff_t *new_pos)
 857{
 858        struct kern_ipc_perm *ipc;
 859        int total, id;
 860
 861        total = 0;
 862        for (id = 0; id < pos && total < ids->in_use; id++) {
 863                ipc = idr_find(&ids->ipcs_idr, id);
 864                if (ipc != NULL)
 865                        total++;
 866        }
 867
 868        if (total >= ids->in_use)
 869                return NULL;
 870
 871        for ( ; pos < IPCMNI; pos++) {
 872                ipc = idr_find(&ids->ipcs_idr, pos);
 873                if (ipc != NULL) {
 874                        *new_pos = pos + 1;
 875                        ipc_lock_by_ptr(ipc);
 876                        return ipc;
 877                }
 878        }
 879
 880        /* Out of range - return NULL to terminate iteration */
 881        return NULL;
 882}
 883
 884static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 885{
 886        struct ipc_proc_iter *iter = s->private;
 887        struct ipc_proc_iface *iface = iter->iface;
 888        struct kern_ipc_perm *ipc = it;
 889
 890        /* If we had an ipc id locked before, unlock it */
 891        if (ipc && ipc != SEQ_START_TOKEN)
 892                ipc_unlock(ipc);
 893
 894        return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 895}
 896
 897/*
 898 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
 899 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
 900 */
 901static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 902{
 903        struct ipc_proc_iter *iter = s->private;
 904        struct ipc_proc_iface *iface = iter->iface;
 905        struct ipc_ids *ids;
 906
 907        ids = &iter->ns->ids[iface->ids];
 908
 909        /*
 910         * Take the lock - this will be released by the corresponding
 911         * call to stop().
 912         */
 913        down_read(&ids->rw_mutex);
 914
 915        /* pos < 0 is invalid */
 916        if (*pos < 0)
 917                return NULL;
 918
 919        /* pos == 0 means header */
 920        if (*pos == 0)
 921                return SEQ_START_TOKEN;
 922
 923        /* Find the (pos-1)th ipc */
 924        return sysvipc_find_ipc(ids, *pos - 1, pos);
 925}
 926
 927static void sysvipc_proc_stop(struct seq_file *s, void *it)
 928{
 929        struct kern_ipc_perm *ipc = it;
 930        struct ipc_proc_iter *iter = s->private;
 931        struct ipc_proc_iface *iface = iter->iface;
 932        struct ipc_ids *ids;
 933
 934        /* If we had a locked structure, release it */
 935        if (ipc && ipc != SEQ_START_TOKEN)
 936                ipc_unlock(ipc);
 937
 938        ids = &iter->ns->ids[iface->ids];
 939        /* Release the lock we took in start() */
 940        up_read(&ids->rw_mutex);
 941}
 942
 943static int sysvipc_proc_show(struct seq_file *s, void *it)
 944{
 945        struct ipc_proc_iter *iter = s->private;
 946        struct ipc_proc_iface *iface = iter->iface;
 947
 948        if (it == SEQ_START_TOKEN)
 949                return seq_puts(s, iface->header);
 950
 951        return iface->show(s, it);
 952}
 953
 954static const struct seq_operations sysvipc_proc_seqops = {
 955        .start = sysvipc_proc_start,
 956        .stop  = sysvipc_proc_stop,
 957        .next  = sysvipc_proc_next,
 958        .show  = sysvipc_proc_show,
 959};
 960
 961static int sysvipc_proc_open(struct inode *inode, struct file *file)
 962{
 963        int ret;
 964        struct seq_file *seq;
 965        struct ipc_proc_iter *iter;
 966
 967        ret = -ENOMEM;
 968        iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 969        if (!iter)
 970                goto out;
 971
 972        ret = seq_open(file, &sysvipc_proc_seqops);
 973        if (ret)
 974                goto out_kfree;
 975
 976        seq = file->private_data;
 977        seq->private = iter;
 978
 979        iter->iface = PDE(inode)->data;
 980        iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 981out:
 982        return ret;
 983out_kfree:
 984        kfree(iter);
 985        goto out;
 986}
 987
 988static int sysvipc_proc_release(struct inode *inode, struct file *file)
 989{
 990        struct seq_file *seq = file->private_data;
 991        struct ipc_proc_iter *iter = seq->private;
 992        put_ipc_ns(iter->ns);
 993        return seq_release_private(inode, file);
 994}
 995
 996static const struct file_operations sysvipc_proc_fops = {
 997        .open    = sysvipc_proc_open,
 998        .read    = seq_read,
 999        .llseek  = seq_lseek,
1000        .release = sysvipc_proc_release,
1001};
1002#endif /* CONFIG_PROC_FS */
1003
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