linux/ipc/util.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * linux/ipc/util.c
   4 * Copyright (C) 1992 Krishna Balasubramanian
   5 *
   6 * Sep 1997 - Call suser() last after "normal" permission checks so we
   7 *            get BSD style process accounting right.
   8 *            Occurs in several places in the IPC code.
   9 *            Chris Evans, <chris@ferret.lmh.ox.ac.uk>
  10 * Nov 1999 - ipc helper functions, unified SMP locking
  11 *            Manfred Spraul <manfred@colorfullife.com>
  12 * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
  13 *            Mingming Cao <cmm@us.ibm.com>
  14 * Mar 2006 - support for audit of ipc object properties
  15 *            Dustin Kirkland <dustin.kirkland@us.ibm.com>
  16 * Jun 2006 - namespaces ssupport
  17 *            OpenVZ, SWsoft Inc.
  18 *            Pavel Emelianov <xemul@openvz.org>
  19 *
  20 * General sysv ipc locking scheme:
  21 *      rcu_read_lock()
  22 *          obtain the ipc object (kern_ipc_perm) by looking up the id in an idr
  23 *          tree.
  24 *          - perform initial checks (capabilities, auditing and permission,
  25 *            etc).
  26 *          - perform read-only operations, such as INFO command, that
  27 *            do not demand atomicity
  28 *            acquire the ipc lock (kern_ipc_perm.lock) through
  29 *            ipc_lock_object()
  30 *              - perform read-only operations that demand atomicity,
  31 *                such as STAT command.
  32 *              - perform data updates, such as SET, RMID commands and
  33 *                mechanism-specific operations (semop/semtimedop,
  34 *                msgsnd/msgrcv, shmat/shmdt).
  35 *          drop the ipc lock, through ipc_unlock_object().
  36 *      rcu_read_unlock()
  37 *
  38 *  The ids->rwsem must be taken when:
  39 *      - creating, removing and iterating the existing entries in ipc
  40 *        identifier sets.
  41 *      - iterating through files under /proc/sysvipc/
  42 *
  43 *  Note that sems have a special fast path that avoids kern_ipc_perm.lock -
  44 *  see sem_lock().
  45 */
  46
  47#include <linux/mm.h>
  48#include <linux/shm.h>
  49#include <linux/init.h>
  50#include <linux/msg.h>
  51#include <linux/vmalloc.h>
  52#include <linux/slab.h>
  53#include <linux/notifier.h>
  54#include <linux/capability.h>
  55#include <linux/highuid.h>
  56#include <linux/security.h>
  57#include <linux/rcupdate.h>
  58#include <linux/workqueue.h>
  59#include <linux/seq_file.h>
  60#include <linux/proc_fs.h>
  61#include <linux/audit.h>
  62#include <linux/nsproxy.h>
  63#include <linux/rwsem.h>
  64#include <linux/memory.h>
  65#include <linux/ipc_namespace.h>
  66#include <linux/rhashtable.h>
  67
  68#include <asm/unistd.h>
  69
  70#include "util.h"
  71
  72struct ipc_proc_iface {
  73        const char *path;
  74        const char *header;
  75        int ids;
  76        int (*show)(struct seq_file *, void *);
  77};
  78
  79/**
  80 * ipc_init - initialise ipc subsystem
  81 *
  82 * The various sysv ipc resources (semaphores, messages and shared
  83 * memory) are initialised.
  84 *
  85 * A callback routine is registered into the memory hotplug notifier
  86 * chain: since msgmni scales to lowmem this callback routine will be
  87 * called upon successful memory add / remove to recompute msmgni.
  88 */
  89static int __init ipc_init(void)
  90{
  91        proc_mkdir("sysvipc", NULL);
  92        sem_init();
  93        msg_init();
  94        shm_init();
  95
  96        return 0;
  97}
  98device_initcall(ipc_init);
  99
 100static const struct rhashtable_params ipc_kht_params = {
 101        .head_offset            = offsetof(struct kern_ipc_perm, khtnode),
 102        .key_offset             = offsetof(struct kern_ipc_perm, key),
 103        .key_len                = sizeof_field(struct kern_ipc_perm, key),
 104        .automatic_shrinking    = true,
 105};
 106
 107/**
 108 * ipc_init_ids - initialise ipc identifiers
 109 * @ids: ipc identifier set
 110 *
 111 * Set up the sequence range to use for the ipc identifier range (limited
 112 * below ipc_mni) then initialise the keys hashtable and ids idr.
 113 */
 114void ipc_init_ids(struct ipc_ids *ids)
 115{
 116        ids->in_use = 0;
 117        ids->seq = 0;
 118        init_rwsem(&ids->rwsem);
 119        rhashtable_init(&ids->key_ht, &ipc_kht_params);
 120        idr_init(&ids->ipcs_idr);
 121        ids->max_idx = -1;
 122        ids->last_idx = -1;
 123#ifdef CONFIG_CHECKPOINT_RESTORE
 124        ids->next_id = -1;
 125#endif
 126}
 127
 128#ifdef CONFIG_PROC_FS
 129static const struct proc_ops sysvipc_proc_ops;
 130/**
 131 * ipc_init_proc_interface -  create a proc interface for sysipc types using a seq_file interface.
 132 * @path: Path in procfs
 133 * @header: Banner to be printed at the beginning of the file.
 134 * @ids: ipc id table to iterate.
 135 * @show: show routine.
 136 */
 137void __init ipc_init_proc_interface(const char *path, const char *header,
 138                int ids, int (*show)(struct seq_file *, void *))
 139{
 140        struct proc_dir_entry *pde;
 141        struct ipc_proc_iface *iface;
 142
 143        iface = kmalloc(sizeof(*iface), GFP_KERNEL);
 144        if (!iface)
 145                return;
 146        iface->path     = path;
 147        iface->header   = header;
 148        iface->ids      = ids;
 149        iface->show     = show;
 150
 151        pde = proc_create_data(path,
 152                               S_IRUGO,        /* world readable */
 153                               NULL,           /* parent dir */
 154                               &sysvipc_proc_ops,
 155                               iface);
 156        if (!pde)
 157                kfree(iface);
 158}
 159#endif
 160
 161/**
 162 * ipc_findkey  - find a key in an ipc identifier set
 163 * @ids: ipc identifier set
 164 * @key: key to find
 165 *
 166 * Returns the locked pointer to the ipc structure if found or NULL
 167 * otherwise. If key is found ipc points to the owning ipc structure
 168 *
 169 * Called with writer ipc_ids.rwsem held.
 170 */
 171static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 172{
 173        struct kern_ipc_perm *ipcp;
 174
 175        ipcp = rhashtable_lookup_fast(&ids->key_ht, &key,
 176                                              ipc_kht_params);
 177        if (!ipcp)
 178                return NULL;
 179
 180        rcu_read_lock();
 181        ipc_lock_object(ipcp);
 182        return ipcp;
 183}
 184
 185/*
 186 * Insert new IPC object into idr tree, and set sequence number and id
 187 * in the correct order.
 188 * Especially:
 189 * - the sequence number must be set before inserting the object into the idr,
 190 *   because the sequence number is accessed without a lock.
 191 * - the id can/must be set after inserting the object into the idr.
 192 *   All accesses must be done after getting kern_ipc_perm.lock.
 193 *
 194 * The caller must own kern_ipc_perm.lock.of the new object.
 195 * On error, the function returns a (negative) error code.
 196 *
 197 * To conserve sequence number space, especially with extended ipc_mni,
 198 * the sequence number is incremented only when the returned ID is less than
 199 * the last one.
 200 */
 201static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
 202{
 203        int idx, next_id = -1;
 204
 205#ifdef CONFIG_CHECKPOINT_RESTORE
 206        next_id = ids->next_id;
 207        ids->next_id = -1;
 208#endif
 209
 210        /*
 211         * As soon as a new object is inserted into the idr,
 212         * ipc_obtain_object_idr() or ipc_obtain_object_check() can find it,
 213         * and the lockless preparations for ipc operations can start.
 214         * This means especially: permission checks, audit calls, allocation
 215         * of undo structures, ...
 216         *
 217         * Thus the object must be fully initialized, and if something fails,
 218         * then the full tear-down sequence must be followed.
 219         * (i.e.: set new->deleted, reduce refcount, call_rcu())
 220         */
 221
 222        if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */
 223                int max_idx;
 224
 225                max_idx = max(ids->in_use*3/2, ipc_min_cycle);
 226                max_idx = min(max_idx, ipc_mni);
 227
 228                /* allocate the idx, with a NULL struct kern_ipc_perm */
 229                idx = idr_alloc_cyclic(&ids->ipcs_idr, NULL, 0, max_idx,
 230                                        GFP_NOWAIT);
 231
 232                if (idx >= 0) {
 233                        /*
 234                         * idx got allocated successfully.
 235                         * Now calculate the sequence number and set the
 236                         * pointer for real.
 237                         */
 238                        if (idx <= ids->last_idx) {
 239                                ids->seq++;
 240                                if (ids->seq >= ipcid_seq_max())
 241                                        ids->seq = 0;
 242                        }
 243                        ids->last_idx = idx;
 244
 245                        new->seq = ids->seq;
 246                        /* no need for smp_wmb(), this is done
 247                         * inside idr_replace, as part of
 248                         * rcu_assign_pointer
 249                         */
 250                        idr_replace(&ids->ipcs_idr, new, idx);
 251                }
 252        } else {
 253                new->seq = ipcid_to_seqx(next_id);
 254                idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),
 255                                0, GFP_NOWAIT);
 256        }
 257        if (idx >= 0)
 258                new->id = (new->seq << ipcmni_seq_shift()) + idx;
 259        return idx;
 260}
 261
 262/**
 263 * ipc_addid - add an ipc identifier
 264 * @ids: ipc identifier set
 265 * @new: new ipc permission set
 266 * @limit: 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 index assigned
 270 * is returned. The 'new' entry is returned in a locked state on success.
 271 *
 272 * On failure the entry is not locked and a negative err-code is returned.
 273 * The caller must use ipc_rcu_putref() to free the identifier.
 274 *
 275 * Called with writer ipc_ids.rwsem held.
 276 */
 277int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
 278{
 279        kuid_t euid;
 280        kgid_t egid;
 281        int idx, err;
 282
 283        /* 1) Initialize the refcount so that ipc_rcu_putref works */
 284        refcount_set(&new->refcount, 1);
 285
 286        if (limit > ipc_mni)
 287                limit = ipc_mni;
 288
 289        if (ids->in_use >= limit)
 290                return -ENOSPC;
 291
 292        idr_preload(GFP_KERNEL);
 293
 294        spin_lock_init(&new->lock);
 295        rcu_read_lock();
 296        spin_lock(&new->lock);
 297
 298        current_euid_egid(&euid, &egid);
 299        new->cuid = new->uid = euid;
 300        new->gid = new->cgid = egid;
 301
 302        new->deleted = false;
 303
 304        idx = ipc_idr_alloc(ids, new);
 305        idr_preload_end();
 306
 307        if (idx >= 0 && new->key != IPC_PRIVATE) {
 308                err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,
 309                                             ipc_kht_params);
 310                if (err < 0) {
 311                        idr_remove(&ids->ipcs_idr, idx);
 312                        idx = err;
 313                }
 314        }
 315        if (idx < 0) {
 316                new->deleted = true;
 317                spin_unlock(&new->lock);
 318                rcu_read_unlock();
 319                return idx;
 320        }
 321
 322        ids->in_use++;
 323        if (idx > ids->max_idx)
 324                ids->max_idx = idx;
 325        return idx;
 326}
 327
 328/**
 329 * ipcget_new - create a new ipc object
 330 * @ns: ipc namespace
 331 * @ids: ipc identifier set
 332 * @ops: the actual creation routine to call
 333 * @params: its parameters
 334 *
 335 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
 336 * when the key is IPC_PRIVATE.
 337 */
 338static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
 339                const struct ipc_ops *ops, struct ipc_params *params)
 340{
 341        int err;
 342
 343        down_write(&ids->rwsem);
 344        err = ops->getnew(ns, params);
 345        up_write(&ids->rwsem);
 346        return err;
 347}
 348
 349/**
 350 * ipc_check_perms - check security and permissions for an ipc object
 351 * @ns: ipc namespace
 352 * @ipcp: ipc permission set
 353 * @ops: the actual security routine to call
 354 * @params: its parameters
 355 *
 356 * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
 357 * when the key is not IPC_PRIVATE and that key already exists in the
 358 * ds IDR.
 359 *
 360 * On success, the ipc id is returned.
 361 *
 362 * It is called with ipc_ids.rwsem and ipcp->lock held.
 363 */
 364static int ipc_check_perms(struct ipc_namespace *ns,
 365                           struct kern_ipc_perm *ipcp,
 366                           const struct ipc_ops *ops,
 367                           struct ipc_params *params)
 368{
 369        int err;
 370
 371        if (ipcperms(ns, ipcp, params->flg))
 372                err = -EACCES;
 373        else {
 374                err = ops->associate(ipcp, params->flg);
 375                if (!err)
 376                        err = ipcp->id;
 377        }
 378
 379        return err;
 380}
 381
 382/**
 383 * ipcget_public - get an ipc object or create a new one
 384 * @ns: ipc namespace
 385 * @ids: ipc identifier set
 386 * @ops: the actual creation routine to call
 387 * @params: its parameters
 388 *
 389 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
 390 * when the key is not IPC_PRIVATE.
 391 * It adds a new entry if the key is not found and does some permission
 392 * / security checkings if the key is found.
 393 *
 394 * On success, the ipc id is returned.
 395 */
 396static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 397                const struct ipc_ops *ops, struct ipc_params *params)
 398{
 399        struct kern_ipc_perm *ipcp;
 400        int flg = params->flg;
 401        int err;
 402
 403        /*
 404         * Take the lock as a writer since we are potentially going to add
 405         * a new entry + read locks are not "upgradable"
 406         */
 407        down_write(&ids->rwsem);
 408        ipcp = ipc_findkey(ids, params->key);
 409        if (ipcp == NULL) {
 410                /* key not used */
 411                if (!(flg & IPC_CREAT))
 412                        err = -ENOENT;
 413                else
 414                        err = ops->getnew(ns, params);
 415        } else {
 416                /* ipc object has been locked by ipc_findkey() */
 417
 418                if (flg & IPC_CREAT && flg & IPC_EXCL)
 419                        err = -EEXIST;
 420                else {
 421                        err = 0;
 422                        if (ops->more_checks)
 423                                err = ops->more_checks(ipcp, params);
 424                        if (!err)
 425                                /*
 426                                 * ipc_check_perms returns the IPC id on
 427                                 * success
 428                                 */
 429                                err = ipc_check_perms(ns, ipcp, ops, params);
 430                }
 431                ipc_unlock(ipcp);
 432        }
 433        up_write(&ids->rwsem);
 434
 435        return err;
 436}
 437
 438/**
 439 * ipc_kht_remove - remove an ipc from the key hashtable
 440 * @ids: ipc identifier set
 441 * @ipcp: ipc perm structure containing the key to remove
 442 *
 443 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
 444 * before this function is called, and remain locked on the exit.
 445 */
 446static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 447{
 448        if (ipcp->key != IPC_PRIVATE)
 449                rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
 450                                       ipc_kht_params);
 451}
 452
 453/**
 454 * ipc_rmid - remove an ipc identifier
 455 * @ids: ipc identifier set
 456 * @ipcp: ipc perm structure containing the identifier to remove
 457 *
 458 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
 459 * before this function is called, and remain locked on the exit.
 460 */
 461void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 462{
 463        int idx = ipcid_to_idx(ipcp->id);
 464
 465        idr_remove(&ids->ipcs_idr, idx);
 466        ipc_kht_remove(ids, ipcp);
 467        ids->in_use--;
 468        ipcp->deleted = true;
 469
 470        if (unlikely(idx == ids->max_idx)) {
 471                do {
 472                        idx--;
 473                        if (idx == -1)
 474                                break;
 475                } while (!idr_find(&ids->ipcs_idr, idx));
 476                ids->max_idx = idx;
 477        }
 478}
 479
 480/**
 481 * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE
 482 * @ids: ipc identifier set
 483 * @ipcp: ipc perm structure containing the key to modify
 484 *
 485 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
 486 * before this function is called, and remain locked on the exit.
 487 */
 488void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 489{
 490        ipc_kht_remove(ids, ipcp);
 491        ipcp->key = IPC_PRIVATE;
 492}
 493
 494bool ipc_rcu_getref(struct kern_ipc_perm *ptr)
 495{
 496        return refcount_inc_not_zero(&ptr->refcount);
 497}
 498
 499void ipc_rcu_putref(struct kern_ipc_perm *ptr,
 500                        void (*func)(struct rcu_head *head))
 501{
 502        if (!refcount_dec_and_test(&ptr->refcount))
 503                return;
 504
 505        call_rcu(&ptr->rcu, func);
 506}
 507
 508/**
 509 * ipcperms - check ipc permissions
 510 * @ns: ipc namespace
 511 * @ipcp: ipc permission set
 512 * @flag: desired permission set
 513 *
 514 * Check user, group, other permissions for access
 515 * to ipc resources. return 0 if allowed
 516 *
 517 * @flag will most probably be 0 or ``S_...UGO`` from <linux/stat.h>
 518 */
 519int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
 520{
 521        kuid_t euid = current_euid();
 522        int requested_mode, granted_mode;
 523
 524        audit_ipc_obj(ipcp);
 525        requested_mode = (flag >> 6) | (flag >> 3) | flag;
 526        granted_mode = ipcp->mode;
 527        if (uid_eq(euid, ipcp->cuid) ||
 528            uid_eq(euid, ipcp->uid))
 529                granted_mode >>= 6;
 530        else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 531                granted_mode >>= 3;
 532        /* is there some bit set in requested_mode but not in granted_mode? */
 533        if ((requested_mode & ~granted_mode & 0007) &&
 534            !ns_capable(ns->user_ns, CAP_IPC_OWNER))
 535                return -1;
 536
 537        return security_ipc_permission(ipcp, flag);
 538}
 539
 540/*
 541 * Functions to convert between the kern_ipc_perm structure and the
 542 * old/new ipc_perm structures
 543 */
 544
 545/**
 546 * kernel_to_ipc64_perm - convert kernel ipc permissions to user
 547 * @in: kernel permissions
 548 * @out: new style ipc permissions
 549 *
 550 * Turn the kernel object @in into a set of permissions descriptions
 551 * for returning to userspace (@out).
 552 */
 553void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)
 554{
 555        out->key        = in->key;
 556        out->uid        = from_kuid_munged(current_user_ns(), in->uid);
 557        out->gid        = from_kgid_munged(current_user_ns(), in->gid);
 558        out->cuid       = from_kuid_munged(current_user_ns(), in->cuid);
 559        out->cgid       = from_kgid_munged(current_user_ns(), in->cgid);
 560        out->mode       = in->mode;
 561        out->seq        = in->seq;
 562}
 563
 564/**
 565 * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
 566 * @in: new style ipc permissions
 567 * @out: old style ipc permissions
 568 *
 569 * Turn the new style permissions object @in into a compatibility
 570 * object and store it into the @out pointer.
 571 */
 572void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
 573{
 574        out->key        = in->key;
 575        SET_UID(out->uid, in->uid);
 576        SET_GID(out->gid, in->gid);
 577        SET_UID(out->cuid, in->cuid);
 578        SET_GID(out->cgid, in->cgid);
 579        out->mode       = in->mode;
 580        out->seq        = in->seq;
 581}
 582
 583/**
 584 * ipc_obtain_object_idr
 585 * @ids: ipc identifier set
 586 * @id: ipc id to look for
 587 *
 588 * Look for an id in the ipc ids idr and return associated ipc object.
 589 *
 590 * Call inside the RCU critical section.
 591 * The ipc object is *not* locked on exit.
 592 */
 593struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
 594{
 595        struct kern_ipc_perm *out;
 596        int idx = ipcid_to_idx(id);
 597
 598        out = idr_find(&ids->ipcs_idr, idx);
 599        if (!out)
 600                return ERR_PTR(-EINVAL);
 601
 602        return out;
 603}
 604
 605/**
 606 * ipc_obtain_object_check
 607 * @ids: ipc identifier set
 608 * @id: ipc id to look for
 609 *
 610 * Similar to ipc_obtain_object_idr() but also checks the ipc object
 611 * sequence number.
 612 *
 613 * Call inside the RCU critical section.
 614 * The ipc object is *not* locked on exit.
 615 */
 616struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
 617{
 618        struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id);
 619
 620        if (IS_ERR(out))
 621                goto out;
 622
 623        if (ipc_checkid(out, id))
 624                return ERR_PTR(-EINVAL);
 625out:
 626        return out;
 627}
 628
 629/**
 630 * ipcget - Common sys_*get() code
 631 * @ns: namespace
 632 * @ids: ipc identifier set
 633 * @ops: operations to be called on ipc object creation, permission checks
 634 *       and further checks
 635 * @params: the parameters needed by the previous operations.
 636 *
 637 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
 638 */
 639int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
 640                        const struct ipc_ops *ops, struct ipc_params *params)
 641{
 642        if (params->key == IPC_PRIVATE)
 643                return ipcget_new(ns, ids, ops, params);
 644        else
 645                return ipcget_public(ns, ids, ops, params);
 646}
 647
 648/**
 649 * ipc_update_perm - update the permissions of an ipc object
 650 * @in:  the permission given as input.
 651 * @out: the permission of the ipc to set.
 652 */
 653int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 654{
 655        kuid_t uid = make_kuid(current_user_ns(), in->uid);
 656        kgid_t gid = make_kgid(current_user_ns(), in->gid);
 657        if (!uid_valid(uid) || !gid_valid(gid))
 658                return -EINVAL;
 659
 660        out->uid = uid;
 661        out->gid = gid;
 662        out->mode = (out->mode & ~S_IRWXUGO)
 663                | (in->mode & S_IRWXUGO);
 664
 665        return 0;
 666}
 667
 668/**
 669 * ipcctl_obtain_check - retrieve an ipc object and check permissions
 670 * @ns:  ipc namespace
 671 * @ids:  the table of ids where to look for the ipc
 672 * @id:   the id of the ipc to retrieve
 673 * @cmd:  the cmd to check
 674 * @perm: the permission to set
 675 * @extra_perm: one extra permission parameter used by msq
 676 *
 677 * This function does some common audit and permissions check for some IPC_XXX
 678 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
 679 *
 680 * It:
 681 *   - retrieves the ipc object with the given id in the given table.
 682 *   - performs some audit and permission check, depending on the given cmd
 683 *   - returns a pointer to the ipc object or otherwise, the corresponding
 684 *     error.
 685 *
 686 * Call holding the both the rwsem and the rcu read lock.
 687 */
 688struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,
 689                                        struct ipc_ids *ids, int id, int cmd,
 690                                        struct ipc64_perm *perm, int extra_perm)
 691{
 692        kuid_t euid;
 693        int err = -EPERM;
 694        struct kern_ipc_perm *ipcp;
 695
 696        ipcp = ipc_obtain_object_check(ids, id);
 697        if (IS_ERR(ipcp)) {
 698                err = PTR_ERR(ipcp);
 699                goto err;
 700        }
 701
 702        audit_ipc_obj(ipcp);
 703        if (cmd == IPC_SET)
 704                audit_ipc_set_perm(extra_perm, perm->uid,
 705                                   perm->gid, perm->mode);
 706
 707        euid = current_euid();
 708        if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
 709            ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 710                return ipcp; /* successful lookup */
 711err:
 712        return ERR_PTR(err);
 713}
 714
 715#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
 716
 717
 718/**
 719 * ipc_parse_version - ipc call version
 720 * @cmd: pointer to command
 721 *
 722 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
 723 * The @cmd value is turned from an encoding command and version into
 724 * just the command code.
 725 */
 726int ipc_parse_version(int *cmd)
 727{
 728        if (*cmd & IPC_64) {
 729                *cmd ^= IPC_64;
 730                return IPC_64;
 731        } else {
 732                return IPC_OLD;
 733        }
 734}
 735
 736#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
 737
 738#ifdef CONFIG_PROC_FS
 739struct ipc_proc_iter {
 740        struct ipc_namespace *ns;
 741        struct pid_namespace *pid_ns;
 742        struct ipc_proc_iface *iface;
 743};
 744
 745struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s)
 746{
 747        struct ipc_proc_iter *iter = s->private;
 748        return iter->pid_ns;
 749}
 750
 751/*
 752 * This routine locks the ipc structure found at least at position pos.
 753 */
 754static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 755                                              loff_t *new_pos)
 756{
 757        struct kern_ipc_perm *ipc;
 758        int total, id;
 759
 760        total = 0;
 761        for (id = 0; id < pos && total < ids->in_use; id++) {
 762                ipc = idr_find(&ids->ipcs_idr, id);
 763                if (ipc != NULL)
 764                        total++;
 765        }
 766
 767        ipc = NULL;
 768        if (total >= ids->in_use)
 769                goto out;
 770
 771        for (; pos < ipc_mni; pos++) {
 772                ipc = idr_find(&ids->ipcs_idr, pos);
 773                if (ipc != NULL) {
 774                        rcu_read_lock();
 775                        ipc_lock_object(ipc);
 776                        break;
 777                }
 778        }
 779out:
 780        *new_pos = pos + 1;
 781        return ipc;
 782}
 783
 784static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 785{
 786        struct ipc_proc_iter *iter = s->private;
 787        struct ipc_proc_iface *iface = iter->iface;
 788        struct kern_ipc_perm *ipc = it;
 789
 790        /* If we had an ipc id locked before, unlock it */
 791        if (ipc && ipc != SEQ_START_TOKEN)
 792                ipc_unlock(ipc);
 793
 794        return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 795}
 796
 797/*
 798 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
 799 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
 800 */
 801static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 802{
 803        struct ipc_proc_iter *iter = s->private;
 804        struct ipc_proc_iface *iface = iter->iface;
 805        struct ipc_ids *ids;
 806
 807        ids = &iter->ns->ids[iface->ids];
 808
 809        /*
 810         * Take the lock - this will be released by the corresponding
 811         * call to stop().
 812         */
 813        down_read(&ids->rwsem);
 814
 815        /* pos < 0 is invalid */
 816        if (*pos < 0)
 817                return NULL;
 818
 819        /* pos == 0 means header */
 820        if (*pos == 0)
 821                return SEQ_START_TOKEN;
 822
 823        /* Find the (pos-1)th ipc */
 824        return sysvipc_find_ipc(ids, *pos - 1, pos);
 825}
 826
 827static void sysvipc_proc_stop(struct seq_file *s, void *it)
 828{
 829        struct kern_ipc_perm *ipc = it;
 830        struct ipc_proc_iter *iter = s->private;
 831        struct ipc_proc_iface *iface = iter->iface;
 832        struct ipc_ids *ids;
 833
 834        /* If we had a locked structure, release it */
 835        if (ipc && ipc != SEQ_START_TOKEN)
 836                ipc_unlock(ipc);
 837
 838        ids = &iter->ns->ids[iface->ids];
 839        /* Release the lock we took in start() */
 840        up_read(&ids->rwsem);
 841}
 842
 843static int sysvipc_proc_show(struct seq_file *s, void *it)
 844{
 845        struct ipc_proc_iter *iter = s->private;
 846        struct ipc_proc_iface *iface = iter->iface;
 847
 848        if (it == SEQ_START_TOKEN) {
 849                seq_puts(s, iface->header);
 850                return 0;
 851        }
 852
 853        return iface->show(s, it);
 854}
 855
 856static const struct seq_operations sysvipc_proc_seqops = {
 857        .start = sysvipc_proc_start,
 858        .stop  = sysvipc_proc_stop,
 859        .next  = sysvipc_proc_next,
 860        .show  = sysvipc_proc_show,
 861};
 862
 863static int sysvipc_proc_open(struct inode *inode, struct file *file)
 864{
 865        struct ipc_proc_iter *iter;
 866
 867        iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter));
 868        if (!iter)
 869                return -ENOMEM;
 870
 871        iter->iface = PDE_DATA(inode);
 872        iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 873        iter->pid_ns = get_pid_ns(task_active_pid_ns(current));
 874
 875        return 0;
 876}
 877
 878static int sysvipc_proc_release(struct inode *inode, struct file *file)
 879{
 880        struct seq_file *seq = file->private_data;
 881        struct ipc_proc_iter *iter = seq->private;
 882        put_ipc_ns(iter->ns);
 883        put_pid_ns(iter->pid_ns);
 884        return seq_release_private(inode, file);
 885}
 886
 887static const struct proc_ops sysvipc_proc_ops = {
 888        .proc_flags     = PROC_ENTRY_PERMANENT,
 889        .proc_open      = sysvipc_proc_open,
 890        .proc_read      = seq_read,
 891        .proc_lseek     = seq_lseek,
 892        .proc_release   = sysvipc_proc_release,
 893};
 894#endif /* CONFIG_PROC_FS */
 895