linux/ipc/util.c
<<
>>
Prefs
   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        {
 126                int seq_limit = INT_MAX/SEQ_MULTIPLIER;
 127                if (seq_limit > USHRT_MAX)
 128                        ids->seq_max = USHRT_MAX;
 129                 else
 130                        ids->seq_max = seq_limit;
 131        }
 132
 133        idr_init(&ids->ipcs_idr);
 134}
 135
 136#ifdef CONFIG_PROC_FS
 137static const struct file_operations sysvipc_proc_fops;
 138/**
 139 *      ipc_init_proc_interface -  Create a proc interface for sysipc types using a seq_file interface.
 140 *      @path: Path in procfs
 141 *      @header: Banner to be printed at the beginning of the file.
 142 *      @ids: ipc id table to iterate.
 143 *      @show: show routine.
 144 */
 145void __init ipc_init_proc_interface(const char *path, const char *header,
 146                int ids, int (*show)(struct seq_file *, void *))
 147{
 148        struct proc_dir_entry *pde;
 149        struct ipc_proc_iface *iface;
 150
 151        iface = kmalloc(sizeof(*iface), GFP_KERNEL);
 152        if (!iface)
 153                return;
 154        iface->path     = path;
 155        iface->header   = header;
 156        iface->ids      = ids;
 157        iface->show     = show;
 158
 159        pde = proc_create_data(path,
 160                               S_IRUGO,        /* world readable */
 161                               NULL,           /* parent dir */
 162                               &sysvipc_proc_fops,
 163                               iface);
 164        if (!pde) {
 165                kfree(iface);
 166        }
 167}
 168#endif
 169
 170/**
 171 *      ipc_findkey     -       find a key in an ipc identifier set     
 172 *      @ids: Identifier set
 173 *      @key: The key to find
 174 *      
 175 *      Requires ipc_ids.rw_mutex locked.
 176 *      Returns the LOCKED pointer to the ipc structure if found or NULL
 177 *      if not.
 178 *      If key is found ipc points to the owning ipc structure
 179 */
 180 
 181static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 182{
 183        struct kern_ipc_perm *ipc;
 184        int next_id;
 185        int total;
 186
 187        for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
 188                ipc = idr_find(&ids->ipcs_idr, next_id);
 189
 190                if (ipc == NULL)
 191                        continue;
 192
 193                if (ipc->key != key) {
 194                        total++;
 195                        continue;
 196                }
 197
 198                ipc_lock_by_ptr(ipc);
 199                return ipc;
 200        }
 201
 202        return NULL;
 203}
 204
 205/**
 206 *      ipc_get_maxid   -       get the last assigned id
 207 *      @ids: IPC identifier set
 208 *
 209 *      Called with ipc_ids.rw_mutex held.
 210 */
 211
 212int ipc_get_maxid(struct ipc_ids *ids)
 213{
 214        struct kern_ipc_perm *ipc;
 215        int max_id = -1;
 216        int total, id;
 217
 218        if (ids->in_use == 0)
 219                return -1;
 220
 221        if (ids->in_use == IPCMNI)
 222                return IPCMNI - 1;
 223
 224        /* Look for the last assigned id */
 225        total = 0;
 226        for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
 227                ipc = idr_find(&ids->ipcs_idr, id);
 228                if (ipc != NULL) {
 229                        max_id = id;
 230                        total++;
 231                }
 232        }
 233        return max_id;
 234}
 235
 236/**
 237 *      ipc_addid       -       add an IPC identifier
 238 *      @ids: IPC identifier set
 239 *      @new: new IPC permission set
 240 *      @size: limit for the number of used ids
 241 *
 242 *      Add an entry 'new' to the IPC ids idr. The permissions object is
 243 *      initialised and the first free entry is set up and the id assigned
 244 *      is returned. The 'new' entry is returned in a locked state on success.
 245 *      On failure the entry is not locked and a negative err-code is returned.
 246 *
 247 *      Called with ipc_ids.rw_mutex held as a writer.
 248 */
 249 
 250int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 251{
 252        uid_t euid;
 253        gid_t egid;
 254        int id, err;
 255
 256        if (size > IPCMNI)
 257                size = IPCMNI;
 258
 259        if (ids->in_use >= size)
 260                return -ENOSPC;
 261
 262        spin_lock_init(&new->lock);
 263        new->deleted = 0;
 264        rcu_read_lock();
 265        spin_lock(&new->lock);
 266
 267        err = idr_get_new(&ids->ipcs_idr, new, &id);
 268        if (err) {
 269                spin_unlock(&new->lock);
 270                rcu_read_unlock();
 271                return err;
 272        }
 273
 274        ids->in_use++;
 275
 276        current_euid_egid(&euid, &egid);
 277        new->cuid = new->uid = euid;
 278        new->gid = new->cgid = egid;
 279
 280        new->seq = ids->seq++;
 281        if(ids->seq > ids->seq_max)
 282                ids->seq = 0;
 283
 284        new->id = ipc_buildid(id, new->seq);
 285        return id;
 286}
 287
 288/**
 289 *      ipcget_new      -       create a new ipc object
 290 *      @ns: namespace
 291 *      @ids: IPC identifer set
 292 *      @ops: the actual creation routine to call
 293 *      @params: its parameters
 294 *
 295 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 296 *      when the key is IPC_PRIVATE.
 297 */
 298static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
 299                struct ipc_ops *ops, struct ipc_params *params)
 300{
 301        int err;
 302retry:
 303        err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
 304
 305        if (!err)
 306                return -ENOMEM;
 307
 308        down_write(&ids->rw_mutex);
 309        err = ops->getnew(ns, params);
 310        up_write(&ids->rw_mutex);
 311
 312        if (err == -EAGAIN)
 313                goto retry;
 314
 315        return err;
 316}
 317
 318/**
 319 *      ipc_check_perms -       check security and permissions for an IPC
 320 *      @ns: IPC namespace
 321 *      @ipcp: ipc permission set
 322 *      @ops: the actual security routine to call
 323 *      @params: its parameters
 324 *
 325 *      This routine is called by sys_msgget(), sys_semget() and sys_shmget()
 326 *      when the key is not IPC_PRIVATE and that key already exists in the
 327 *      ids IDR.
 328 *
 329 *      On success, the IPC id is returned.
 330 *
 331 *      It is called with ipc_ids.rw_mutex and ipcp->lock held.
 332 */
 333static int ipc_check_perms(struct ipc_namespace *ns,
 334                           struct kern_ipc_perm *ipcp,
 335                           struct ipc_ops *ops,
 336                           struct ipc_params *params)
 337{
 338        int err;
 339
 340        if (ipcperms(ns, ipcp, params->flg))
 341                err = -EACCES;
 342        else {
 343                err = ops->associate(ipcp, params->flg);
 344                if (!err)
 345                        err = ipcp->id;
 346        }
 347
 348        return err;
 349}
 350
 351/**
 352 *      ipcget_public   -       get an ipc object or create a new one
 353 *      @ns: namespace
 354 *      @ids: IPC identifer set
 355 *      @ops: the actual creation routine to call
 356 *      @params: its parameters
 357 *
 358 *      This routine is called by sys_msgget, sys_semget() and sys_shmget()
 359 *      when the key is not IPC_PRIVATE.
 360 *      It adds a new entry if the key is not found and does some permission
 361 *      / security checkings if the key is found.
 362 *
 363 *      On success, the ipc id is returned.
 364 */
 365static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 366                struct ipc_ops *ops, struct ipc_params *params)
 367{
 368        struct kern_ipc_perm *ipcp;
 369        int flg = params->flg;
 370        int err;
 371retry:
 372        err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
 373
 374        /*
 375         * Take the lock as a writer since we are potentially going to add
 376         * a new entry + read locks are not "upgradable"
 377         */
 378        down_write(&ids->rw_mutex);
 379        ipcp = ipc_findkey(ids, params->key);
 380        if (ipcp == NULL) {
 381                /* key not used */
 382                if (!(flg & IPC_CREAT))
 383                        err = -ENOENT;
 384                else if (!err)
 385                        err = -ENOMEM;
 386                else
 387                        err = ops->getnew(ns, params);
 388        } else {
 389                /* ipc object has been locked by ipc_findkey() */
 390
 391                if (flg & IPC_CREAT && flg & IPC_EXCL)
 392                        err = -EEXIST;
 393                else {
 394                        err = 0;
 395                        if (ops->more_checks)
 396                                err = ops->more_checks(ipcp, params);
 397                        if (!err)
 398                                /*
 399                                 * ipc_check_perms returns the IPC id on
 400                                 * success
 401                                 */
 402                                err = ipc_check_perms(ns, ipcp, ops, params);
 403                }
 404                ipc_unlock(ipcp);
 405        }
 406        up_write(&ids->rw_mutex);
 407
 408        if (err == -EAGAIN)
 409                goto retry;
 410
 411        return err;
 412}
 413
 414
 415/**
 416 *      ipc_rmid        -       remove an IPC identifier
 417 *      @ids: IPC identifier set
 418 *      @ipcp: ipc perm structure containing the identifier to remove
 419 *
 420 *      ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
 421 *      before this function is called, and remain locked on the exit.
 422 */
 423 
 424void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 425{
 426        int lid = ipcid_to_idx(ipcp->id);
 427
 428        idr_remove(&ids->ipcs_idr, lid);
 429
 430        ids->in_use--;
 431
 432        ipcp->deleted = 1;
 433
 434        return;
 435}
 436
 437/**
 438 *      ipc_alloc       -       allocate ipc space
 439 *      @size: size desired
 440 *
 441 *      Allocate memory from the appropriate pools and return a pointer to it.
 442 *      NULL is returned if the allocation fails
 443 */
 444 
 445void* ipc_alloc(int size)
 446{
 447        void* out;
 448        if(size > PAGE_SIZE)
 449                out = vmalloc(size);
 450        else
 451                out = kmalloc(size, GFP_KERNEL);
 452        return out;
 453}
 454
 455/**
 456 *      ipc_free        -       free ipc space
 457 *      @ptr: pointer returned by ipc_alloc
 458 *      @size: size of block
 459 *
 460 *      Free a block created with ipc_alloc(). The caller must know the size
 461 *      used in the allocation call.
 462 */
 463
 464void ipc_free(void* ptr, int size)
 465{
 466        if(size > PAGE_SIZE)
 467                vfree(ptr);
 468        else
 469                kfree(ptr);
 470}
 471
 472/*
 473 * rcu allocations:
 474 * There are three headers that are prepended to the actual allocation:
 475 * - during use: ipc_rcu_hdr.
 476 * - during the rcu grace period: ipc_rcu_grace.
 477 * - [only if vmalloc]: ipc_rcu_sched.
 478 * Their lifetime doesn't overlap, thus the headers share the same memory.
 479 * Unlike a normal union, they are right-aligned, thus some container_of
 480 * forward/backward casting is necessary:
 481 */
 482struct ipc_rcu_hdr
 483{
 484        int refcount;
 485        int is_vmalloc;
 486        void *data[0];
 487};
 488
 489
 490struct ipc_rcu_grace
 491{
 492        struct rcu_head rcu;
 493        /* "void *" makes sure alignment of following data is sane. */
 494        void *data[0];
 495};
 496
 497struct ipc_rcu_sched
 498{
 499        struct work_struct work;
 500        /* "void *" makes sure alignment of following data is sane. */
 501        void *data[0];
 502};
 503
 504#define HDRLEN_KMALLOC          (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
 505                                        sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
 506#define HDRLEN_VMALLOC          (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
 507                                        sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
 508
 509static inline int rcu_use_vmalloc(int size)
 510{
 511        /* Too big for a single page? */
 512        if (HDRLEN_KMALLOC + size > PAGE_SIZE)
 513                return 1;
 514        return 0;
 515}
 516
 517/**
 518 *      ipc_rcu_alloc   -       allocate ipc and rcu space 
 519 *      @size: size desired
 520 *
 521 *      Allocate memory for the rcu header structure +  the object.
 522 *      Returns the pointer to the object.
 523 *      NULL is returned if the allocation fails. 
 524 */
 525 
 526void* ipc_rcu_alloc(int size)
 527{
 528        void* out;
 529        /* 
 530         * We prepend the allocation with the rcu struct, and
 531         * workqueue if necessary (for vmalloc). 
 532         */
 533        if (rcu_use_vmalloc(size)) {
 534                out = vmalloc(HDRLEN_VMALLOC + size);
 535                if (out) {
 536                        out += HDRLEN_VMALLOC;
 537                        container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
 538                        container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
 539                }
 540        } else {
 541                out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
 542                if (out) {
 543                        out += HDRLEN_KMALLOC;
 544                        container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
 545                        container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
 546                }
 547        }
 548
 549        return out;
 550}
 551
 552void ipc_rcu_getref(void *ptr)
 553{
 554        container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
 555}
 556
 557static void ipc_do_vfree(struct work_struct *work)
 558{
 559        vfree(container_of(work, struct ipc_rcu_sched, work));
 560}
 561
 562/**
 563 * ipc_schedule_free - free ipc + rcu space
 564 * @head: RCU callback structure for queued work
 565 * 
 566 * Since RCU callback function is called in bh,
 567 * we need to defer the vfree to schedule_work().
 568 */
 569static void ipc_schedule_free(struct rcu_head *head)
 570{
 571        struct ipc_rcu_grace *grace;
 572        struct ipc_rcu_sched *sched;
 573
 574        grace = container_of(head, struct ipc_rcu_grace, rcu);
 575        sched = container_of(&(grace->data[0]), struct ipc_rcu_sched,
 576                                data[0]);
 577
 578        INIT_WORK(&sched->work, ipc_do_vfree);
 579        schedule_work(&sched->work);
 580}
 581
 582void ipc_rcu_putref(void *ptr)
 583{
 584        if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
 585                return;
 586
 587        if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
 588                call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
 589                                ipc_schedule_free);
 590        } else {
 591                kfree_rcu(container_of(ptr, struct ipc_rcu_grace, data), rcu);
 592        }
 593}
 594
 595/**
 596 *      ipcperms        -       check IPC permissions
 597 *      @ns: IPC namespace
 598 *      @ipcp: IPC permission set
 599 *      @flag: desired permission set.
 600 *
 601 *      Check user, group, other permissions for access
 602 *      to ipc resources. return 0 if allowed
 603 *
 604 *      @flag will most probably be 0 or S_...UGO from <linux/stat.h>
 605 */
 606 
 607int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
 608{
 609        uid_t euid = current_euid();
 610        int requested_mode, granted_mode;
 611
 612        audit_ipc_obj(ipcp);
 613        requested_mode = (flag >> 6) | (flag >> 3) | flag;
 614        granted_mode = ipcp->mode;
 615        if (euid == ipcp->cuid ||
 616            euid == ipcp->uid)
 617                granted_mode >>= 6;
 618        else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 619                granted_mode >>= 3;
 620        /* is there some bit set in requested_mode but not in granted_mode? */
 621        if ((requested_mode & ~granted_mode & 0007) && 
 622            !ns_capable(ns->user_ns, CAP_IPC_OWNER))
 623                return -1;
 624
 625        return security_ipc_permission(ipcp, flag);
 626}
 627
 628/*
 629 * Functions to convert between the kern_ipc_perm structure and the
 630 * old/new ipc_perm structures
 631 */
 632
 633/**
 634 *      kernel_to_ipc64_perm    -       convert kernel ipc permissions to user
 635 *      @in: kernel permissions
 636 *      @out: new style IPC permissions
 637 *
 638 *      Turn the kernel object @in into a set of permissions descriptions
 639 *      for returning to userspace (@out).
 640 */
 641 
 642
 643void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
 644{
 645        out->key        = in->key;
 646        out->uid        = in->uid;
 647        out->gid        = in->gid;
 648        out->cuid       = in->cuid;
 649        out->cgid       = in->cgid;
 650        out->mode       = in->mode;
 651        out->seq        = in->seq;
 652}
 653
 654/**
 655 *      ipc64_perm_to_ipc_perm  -       convert new ipc permissions to old
 656 *      @in: new style IPC permissions
 657 *      @out: old style IPC permissions
 658 *
 659 *      Turn the new style permissions object @in into a compatibility
 660 *      object and store it into the @out pointer.
 661 */
 662 
 663void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
 664{
 665        out->key        = in->key;
 666        SET_UID(out->uid, in->uid);
 667        SET_GID(out->gid, in->gid);
 668        SET_UID(out->cuid, in->cuid);
 669        SET_GID(out->cgid, in->cgid);
 670        out->mode       = in->mode;
 671        out->seq        = in->seq;
 672}
 673
 674/**
 675 * ipc_lock - Lock an ipc structure without rw_mutex held
 676 * @ids: IPC identifier set
 677 * @id: ipc id to look for
 678 *
 679 * Look for an id in the ipc ids idr and lock the associated ipc object.
 680 *
 681 * The ipc object is locked on exit.
 682 */
 683
 684struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
 685{
 686        struct kern_ipc_perm *out;
 687        int lid = ipcid_to_idx(id);
 688
 689        rcu_read_lock();
 690        out = idr_find(&ids->ipcs_idr, lid);
 691        if (out == NULL) {
 692                rcu_read_unlock();
 693                return ERR_PTR(-EINVAL);
 694        }
 695
 696        spin_lock(&out->lock);
 697        
 698        /* ipc_rmid() may have already freed the ID while ipc_lock
 699         * was spinning: here verify that the structure is still valid
 700         */
 701        if (out->deleted) {
 702                spin_unlock(&out->lock);
 703                rcu_read_unlock();
 704                return ERR_PTR(-EINVAL);
 705        }
 706
 707        return out;
 708}
 709
 710struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
 711{
 712        struct kern_ipc_perm *out;
 713
 714        out = ipc_lock(ids, id);
 715        if (IS_ERR(out))
 716                return out;
 717
 718        if (ipc_checkid(out, id)) {
 719                ipc_unlock(out);
 720                return ERR_PTR(-EIDRM);
 721        }
 722
 723        return out;
 724}
 725
 726/**
 727 * ipcget - Common sys_*get() code
 728 * @ns : namsepace
 729 * @ids : IPC identifier set
 730 * @ops : operations to be called on ipc object creation, permission checks
 731 *        and further checks
 732 * @params : the parameters needed by the previous operations.
 733 *
 734 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
 735 */
 736int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
 737                        struct ipc_ops *ops, struct ipc_params *params)
 738{
 739        if (params->key == IPC_PRIVATE)
 740                return ipcget_new(ns, ids, ops, params);
 741        else
 742                return ipcget_public(ns, ids, ops, params);
 743}
 744
 745/**
 746 * ipc_update_perm - update the permissions of an IPC.
 747 * @in:  the permission given as input.
 748 * @out: the permission of the ipc to set.
 749 */
 750void ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 751{
 752        out->uid = in->uid;
 753        out->gid = in->gid;
 754        out->mode = (out->mode & ~S_IRWXUGO)
 755                | (in->mode & S_IRWXUGO);
 756}
 757
 758/**
 759 * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
 760 * @ns:  the ipc namespace
 761 * @ids:  the table of ids where to look for the ipc
 762 * @id:   the id of the ipc to retrieve
 763 * @cmd:  the cmd to check
 764 * @perm: the permission to set
 765 * @extra_perm: one extra permission parameter used by msq
 766 *
 767 * This function does some common audit and permissions check for some IPC_XXX
 768 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
 769 * It must be called without any lock held and
 770 *  - retrieves the ipc with the given id in the given table.
 771 *  - performs some audit and permission check, depending on the given cmd
 772 *  - returns the ipc with both ipc and rw_mutex locks held in case of success
 773 *    or an err-code without any lock held otherwise.
 774 */
 775struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
 776                                      struct ipc_ids *ids, int id, int cmd,
 777                                      struct ipc64_perm *perm, int extra_perm)
 778{
 779        struct kern_ipc_perm *ipcp;
 780        uid_t euid;
 781        int err;
 782
 783        down_write(&ids->rw_mutex);
 784        ipcp = ipc_lock_check(ids, id);
 785        if (IS_ERR(ipcp)) {
 786                err = PTR_ERR(ipcp);
 787                goto out_up;
 788        }
 789
 790        audit_ipc_obj(ipcp);
 791        if (cmd == IPC_SET)
 792                audit_ipc_set_perm(extra_perm, perm->uid,
 793                                         perm->gid, perm->mode);
 794
 795        euid = current_euid();
 796        if (euid == ipcp->cuid || euid == ipcp->uid  ||
 797            ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 798                return ipcp;
 799
 800        err = -EPERM;
 801        ipc_unlock(ipcp);
 802out_up:
 803        up_write(&ids->rw_mutex);
 804        return ERR_PTR(err);
 805}
 806
 807#ifdef __ARCH_WANT_IPC_PARSE_VERSION
 808
 809
 810/**
 811 *      ipc_parse_version       -       IPC call version
 812 *      @cmd: pointer to command
 813 *
 814 *      Return IPC_64 for new style IPC and IPC_OLD for old style IPC. 
 815 *      The @cmd value is turned from an encoding command and version into
 816 *      just the command code.
 817 */
 818 
 819int ipc_parse_version (int *cmd)
 820{
 821        if (*cmd & IPC_64) {
 822                *cmd ^= IPC_64;
 823                return IPC_64;
 824        } else {
 825                return IPC_OLD;
 826        }
 827}
 828
 829#endif /* __ARCH_WANT_IPC_PARSE_VERSION */
 830
 831#ifdef CONFIG_PROC_FS
 832struct ipc_proc_iter {
 833        struct ipc_namespace *ns;
 834        struct ipc_proc_iface *iface;
 835};
 836
 837/*
 838 * This routine locks the ipc structure found at least at position pos.
 839 */
 840static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 841                                              loff_t *new_pos)
 842{
 843        struct kern_ipc_perm *ipc;
 844        int total, id;
 845
 846        total = 0;
 847        for (id = 0; id < pos && total < ids->in_use; id++) {
 848                ipc = idr_find(&ids->ipcs_idr, id);
 849                if (ipc != NULL)
 850                        total++;
 851        }
 852
 853        if (total >= ids->in_use)
 854                return NULL;
 855
 856        for ( ; pos < IPCMNI; pos++) {
 857                ipc = idr_find(&ids->ipcs_idr, pos);
 858                if (ipc != NULL) {
 859                        *new_pos = pos + 1;
 860                        ipc_lock_by_ptr(ipc);
 861                        return ipc;
 862                }
 863        }
 864
 865        /* Out of range - return NULL to terminate iteration */
 866        return NULL;
 867}
 868
 869static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 870{
 871        struct ipc_proc_iter *iter = s->private;
 872        struct ipc_proc_iface *iface = iter->iface;
 873        struct kern_ipc_perm *ipc = it;
 874
 875        /* If we had an ipc id locked before, unlock it */
 876        if (ipc && ipc != SEQ_START_TOKEN)
 877                ipc_unlock(ipc);
 878
 879        return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 880}
 881
 882/*
 883 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
 884 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
 885 */
 886static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 887{
 888        struct ipc_proc_iter *iter = s->private;
 889        struct ipc_proc_iface *iface = iter->iface;
 890        struct ipc_ids *ids;
 891
 892        ids = &iter->ns->ids[iface->ids];
 893
 894        /*
 895         * Take the lock - this will be released by the corresponding
 896         * call to stop().
 897         */
 898        down_read(&ids->rw_mutex);
 899
 900        /* pos < 0 is invalid */
 901        if (*pos < 0)
 902                return NULL;
 903
 904        /* pos == 0 means header */
 905        if (*pos == 0)
 906                return SEQ_START_TOKEN;
 907
 908        /* Find the (pos-1)th ipc */
 909        return sysvipc_find_ipc(ids, *pos - 1, pos);
 910}
 911
 912static void sysvipc_proc_stop(struct seq_file *s, void *it)
 913{
 914        struct kern_ipc_perm *ipc = it;
 915        struct ipc_proc_iter *iter = s->private;
 916        struct ipc_proc_iface *iface = iter->iface;
 917        struct ipc_ids *ids;
 918
 919        /* If we had a locked structure, release it */
 920        if (ipc && ipc != SEQ_START_TOKEN)
 921                ipc_unlock(ipc);
 922
 923        ids = &iter->ns->ids[iface->ids];
 924        /* Release the lock we took in start() */
 925        up_read(&ids->rw_mutex);
 926}
 927
 928static int sysvipc_proc_show(struct seq_file *s, void *it)
 929{
 930        struct ipc_proc_iter *iter = s->private;
 931        struct ipc_proc_iface *iface = iter->iface;
 932
 933        if (it == SEQ_START_TOKEN)
 934                return seq_puts(s, iface->header);
 935
 936        return iface->show(s, it);
 937}
 938
 939static const struct seq_operations sysvipc_proc_seqops = {
 940        .start = sysvipc_proc_start,
 941        .stop  = sysvipc_proc_stop,
 942        .next  = sysvipc_proc_next,
 943        .show  = sysvipc_proc_show,
 944};
 945
 946static int sysvipc_proc_open(struct inode *inode, struct file *file)
 947{
 948        int ret;
 949        struct seq_file *seq;
 950        struct ipc_proc_iter *iter;
 951
 952        ret = -ENOMEM;
 953        iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 954        if (!iter)
 955                goto out;
 956
 957        ret = seq_open(file, &sysvipc_proc_seqops);
 958        if (ret)
 959                goto out_kfree;
 960
 961        seq = file->private_data;
 962        seq->private = iter;
 963
 964        iter->iface = PDE(inode)->data;
 965        iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 966out:
 967        return ret;
 968out_kfree:
 969        kfree(iter);
 970        goto out;
 971}
 972
 973static int sysvipc_proc_release(struct inode *inode, struct file *file)
 974{
 975        struct seq_file *seq = file->private_data;
 976        struct ipc_proc_iter *iter = seq->private;
 977        put_ipc_ns(iter->ns);
 978        return seq_release_private(inode, file);
 979}
 980
 981static const struct file_operations sysvipc_proc_fops = {
 982        .open    = sysvipc_proc_open,
 983        .read    = seq_read,
 984        .llseek  = seq_lseek,
 985        .release = sysvipc_proc_release,
 986};
 987#endif /* CONFIG_PROC_FS */
 988
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.