ipc/util.c

   1 /*
   2  * linux/ipc/util.c
   3  * Copyright (C) 1992 Krishna Balasubramanian
   4  *
   5  * Sep 1997 - Call suser() last after "normal" permission checks so we
   6  *            get BSD style process accounting right.
   7  *            Occurs in several places in the IPC code.
   8  *            Chris Evans, <chris@ferret.lmh.ox.ac.uk>
   9  * Nov 1999 - ipc helper functions, unified SMP locking
  10  *            Manfred Spraul <manfred@colorfullife.com>
  11  * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
  12  *            Mingming Cao <cmm@us.ibm.com>
  13  * Mar 2006 - support for audit of ipc object properties
  14  *            Dustin Kirkland <dustin.kirkland@us.ibm.com>
  15  * Jun 2006 - namespaces ssupport
  16  *            OpenVZ, SWsoft Inc.
  17  *            Pavel Emelianov <xemul@openvz.org>
  18  *
  19  * General sysv ipc locking scheme:
  20  *      rcu_read_lock()
  21  *          obtain the ipc object (kern_ipc_perm) by looking up the id in an idr
  22  *          tree.
  23  *          - perform initial checks (capabilities, auditing and permission,
  24  *            etc).
  25  *          - perform read-only operations, such as STAT, INFO commands.
  26  *            acquire the ipc lock (kern_ipc_perm.lock) through
  27  *            ipc_lock_object()
  28  *              - perform data updates, such as SET, RMID commands and
  29  *                mechanism-specific operations (semop/semtimedop,
  30  *                msgsnd/msgrcv, shmat/shmdt).
  31  *          drop the ipc lock, through ipc_unlock_object().
  32  *      rcu_read_unlock()
  33  *
  34  *  The ids->rwsem must be taken when:
  35  *      - creating, removing and iterating the existing entries in ipc
  36  *        identifier sets.
  37  *      - iterating through files under /proc/sysvipc/
  38  *
  39  *  Note that sems have a special fast path that avoids kern_ipc_perm.lock -
  40  *  see sem_lock().
  41  */
  42
  43 #include <linux/mm.h>
  44 #include <linux/shm.h>
  45 #include <linux/init.h>
  46 #include <linux/msg.h>
  47 #include <linux/vmalloc.h>
  48 #include <linux/slab.h>
  49 #include <linux/notifier.h>
  50 #include <linux/capability.h>
  51 #include <linux/highuid.h>
  52 #include <linux/security.h>
  53 #include <linux/rcupdate.h>
  54 #include <linux/workqueue.h>
  55 #include <linux/seq_file.h>
  56 #include <linux/proc_fs.h>
  57 #include <linux/audit.h>
  58 #include <linux/nsproxy.h>
  59 #include <linux/rwsem.h>
  60 #include <linux/memory.h>
  61 #include <linux/ipc_namespace.h>
  62
  63 #include <asm/unistd.h>
  64
  65 #include "util.h"
  66
  67 struct ipc_proc_iface {
  68         const char *path;
  69         const char *header;
  70         int ids;
  71         int (*show)(struct seq_file *, void *);
  72 };
  73
  74 static void ipc_memory_notifier(struct work_struct *work)
  75 {
  76         ipcns_notify(IPCNS_MEMCHANGED);
  77 }
  78
  79 static int ipc_memory_callback(struct notifier_block *self,
  80                                 unsigned long action, void *arg)
  81 {
  82         static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
  83
  84         switch (action) {
  85         case MEM_ONLINE:    /* memory successfully brought online */
  86         case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
  87                 /*
  88                  * This is done by invoking the ipcns notifier chain with the
  89                  * IPC_MEMCHANGED event.
  90                  * In order not to keep the lock on the hotplug memory chain
  91                  * for too long, queue a work item that will, when waken up,
  92                  * activate the ipcns notification chain.
  93                  */
  94                 schedule_work(&ipc_memory_wq);
  95                 break;
  96         case MEM_GOING_ONLINE:
  97         case MEM_GOING_OFFLINE:
  98         case MEM_CANCEL_ONLINE:
  99         case MEM_CANCEL_OFFLINE:
 100         default:
 101                 break;
 102         }
 103
 104         return NOTIFY_OK;
 105 }
 106
 107 static struct notifier_block ipc_memory_nb = {
 108         .notifier_call = ipc_memory_callback,
 109         .priority = IPC_CALLBACK_PRI,
 110 };
 111
 112 /**
 113  * ipc_init - initialise ipc subsystem
 114  *
 115  * The various sysv ipc resources (semaphores, messages and shared
 116  * memory) are initialised.
 117  *
 118  * A callback routine is registered into the memory hotplug notifier
 119  * chain: since msgmni scales to lowmem this callback routine will be
 120  * called upon successful memory add / remove to recompute msmgni.
 121  */
 122 static int __init ipc_init(void)
 123 {
 124         sem_init();
 125         msg_init();
 126         shm_init();
 127         register_hotmemory_notifier(&ipc_memory_nb);
 128         register_ipcns_notifier(&init_ipc_ns);
 129         return 0;
 130 }
 131 device_initcall(ipc_init);
 132
 133 /**
 134  * ipc_init_ids - initialise ipc identifiers
 135  * @ids: ipc identifier set
 136  *
 137  * Set up the sequence range to use for the ipc identifier range (limited
 138  * below IPCMNI) then initialise the ids idr.
 139  */
 140 void ipc_init_ids(struct ipc_ids *ids)
 141 {
 142         ids->in_use = 0;
 143         ids->seq = 0;
 144         ids->next_id = -1;
 145         init_rwsem(&ids->rwsem);
 146         idr_init(&ids->ipcs_idr);
 147 }
 148
 149 #ifdef CONFIG_PROC_FS
 150 static const struct file_operations sysvipc_proc_fops;
 151 /**
 152  * ipc_init_proc_interface -  create a proc interface for sysipc types using a seq_file interface.
 153  * @path: Path in procfs
 154  * @header: Banner to be printed at the beginning of the file.
 155  * @ids: ipc id table to iterate.
 156  * @show: show routine.
 157  */
 158 void __init ipc_init_proc_interface(const char *path, const char *header,
 159                 int ids, int (*show)(struct seq_file *, void *))
 160 {
 161         struct proc_dir_entry *pde;
 162         struct ipc_proc_iface *iface;
 163
 164         iface = kmalloc(sizeof(*iface), GFP_KERNEL);
 165         if (!iface)
 166                 return;
 167         iface->path     = path;
 168         iface->header   = header;
 169         iface->ids      = ids;
 170         iface->show     = show;
 171
 172         pde = proc_create_data(path,
 173                                S_IRUGO,        /* world readable */
 174                                NULL,           /* parent dir */
 175                                &sysvipc_proc_fops,
 176                                iface);
 177         if (!pde)
 178                 kfree(iface);
 179 }
 180 #endif
 181
 182 /**
 183  * ipc_findkey  - find a key in an ipc identifier set
 184  * @ids: ipc identifier set
 185  * @key: key to find
 186  *
 187  * Returns the locked pointer to the ipc structure if found or NULL
 188  * otherwise. If key is found ipc points to the owning ipc structure
 189  *
 190  * Called with ipc_ids.rwsem held.
 191  */
 192 static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
 193 {
 194         struct kern_ipc_perm *ipc;
 195         int next_id;
 196         int total;
 197
 198         for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
 199                 ipc = idr_find(&ids->ipcs_idr, next_id);
 200
 201                 if (ipc == NULL)
 202                         continue;
 203
 204                 if (ipc->key != key) {
 205                         total++;
 206                         continue;
 207                 }
 208
 209                 rcu_read_lock();
 210                 ipc_lock_object(ipc);
 211                 return ipc;
 212         }
 213
 214         return NULL;
 215 }
 216
 217 /**
 218  * ipc_get_maxid - get the last assigned id
 219  * @ids: ipc identifier set
 220  *
 221  * Called with ipc_ids.rwsem held.
 222  */
 223 int ipc_get_maxid(struct ipc_ids *ids)
 224 {
 225         struct kern_ipc_perm *ipc;
 226         int max_id = -1;
 227         int total, id;
 228
 229         if (ids->in_use == 0)
 230                 return -1;
 231
 232         if (ids->in_use == IPCMNI)
 233                 return IPCMNI - 1;
 234
 235         /* Look for the last assigned id */
 236         total = 0;
 237         for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
 238                 ipc = idr_find(&ids->ipcs_idr, id);
 239                 if (ipc != NULL) {
 240                         max_id = id;
 241                         total++;
 242                 }
 243         }
 244         return max_id;
 245 }
 246
 247 /**
 248  * ipc_addid - add an ipc identifier
 249  * @ids: ipc identifier set
 250  * @new: new ipc permission set
 251  * @size: limit for the number of used ids
 252  *
 253  * Add an entry 'new' to the ipc ids idr. The permissions object is
 254  * initialised and the first free entry is set up and the id assigned
 255  * is returned. The 'new' entry is returned in a locked state on success.
 256  * On failure the entry is not locked and a negative err-code is returned.
 257  *
 258  * Called with writer ipc_ids.rwsem held.
 259  */
 260 int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size)
 261 {
 262         kuid_t euid;
 263         kgid_t egid;
 264         int id;
 265         int next_id = ids->next_id;
 266
 267         if (size > IPCMNI)
 268                 size = IPCMNI;
 269
 270         if (ids->in_use >= size)
 271                 return -ENOSPC;
 272
 273         idr_preload(GFP_KERNEL);
 274
 275         spin_lock_init(&new->lock);
 276         new->deleted = false;
 277         rcu_read_lock();
 278         spin_lock(&new->lock);
 279
 280         id = idr_alloc(&ids->ipcs_idr, new,
 281                        (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
 282                        GFP_NOWAIT);
 283         idr_preload_end();
 284         if (id < 0) {
 285                 spin_unlock(&new->lock);
 286                 rcu_read_unlock();
 287                 return id;
 288         }
 289
 290         ids->in_use++;
 291
 292         current_euid_egid(&euid, &egid);
 293         new->cuid = new->uid = euid;
 294         new->gid = new->cgid = egid;
 295
 296         if (next_id < 0) {
 297                 new->seq = ids->seq++;
 298                 if (ids->seq > IPCID_SEQ_MAX)
 299                         ids->seq = 0;
 300         } else {
 301                 new->seq = ipcid_to_seqx(next_id);
 302                 ids->next_id = -1;
 303         }
 304
 305         new->id = ipc_buildid(id, new->seq);
 306         return id;
 307 }
 308
 309 /**
 310  * ipcget_new - create a new ipc object
 311  * @ns: ipc namespace
 312  * @ids: ipc identifer set
 313  * @ops: the actual creation routine to call
 314  * @params: its parameters
 315  *
 316  * This routine is called by sys_msgget, sys_semget() and sys_shmget()
 317  * when the key is IPC_PRIVATE.
 318  */
 319 static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
 320                 const struct ipc_ops *ops, struct ipc_params *params)
 321 {
 322         int err;
 323
 324         down_write(&ids->rwsem);
 325         err = ops->getnew(ns, params);
 326         up_write(&ids->rwsem);
 327         return err;
 328 }
 329
 330 /**
 331  * ipc_check_perms - check security and permissions for an ipc object
 332  * @ns: ipc namespace
 333  * @ipcp: ipc permission set
 334  * @ops: the actual security routine to call
 335  * @params: its parameters
 336  *
 337  * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
 338  * when the key is not IPC_PRIVATE and that key already exists in the
 339  * ds IDR.
 340  *
 341  * On success, the ipc id is returned.
 342  *
 343  * It is called with ipc_ids.rwsem and ipcp->lock held.
 344  */
 345 static int ipc_check_perms(struct ipc_namespace *ns,
 346                            struct kern_ipc_perm *ipcp,
 347                            const struct ipc_ops *ops,
 348                            struct ipc_params *params)
 349 {
 350         int err;
 351
 352         if (ipcperms(ns, ipcp, params->flg))
 353                 err = -EACCES;
 354         else {
 355                 err = ops->associate(ipcp, params->flg);
 356                 if (!err)
 357                         err = ipcp->id;
 358         }
 359
 360         return err;
 361 }
 362
 363 /**
 364  * ipcget_public - get an ipc object or create a new one
 365  * @ns: ipc namespace
 366  * @ids: ipc identifer set
 367  * @ops: the actual creation routine to call
 368  * @params: its parameters
 369  *
 370  * This routine is called by sys_msgget, sys_semget() and sys_shmget()
 371  * when the key is not IPC_PRIVATE.
 372  * It adds a new entry if the key is not found and does some permission
 373  * / security checkings if the key is found.
 374  *
 375  * On success, the ipc id is returned.
 376  */
 377 static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
 378                 const struct ipc_ops *ops, struct ipc_params *params)
 379 {
 380         struct kern_ipc_perm *ipcp;
 381         int flg = params->flg;
 382         int err;
 383
 384         /*
 385          * Take the lock as a writer since we are potentially going to add
 386          * a new entry + read locks are not "upgradable"
 387          */
 388         down_write(&ids->rwsem);
 389         ipcp = ipc_findkey(ids, params->key);
 390         if (ipcp == NULL) {
 391                 /* key not used */
 392                 if (!(flg & IPC_CREAT))
 393                         err = -ENOENT;
 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->rwsem);
 415
 416         return err;
 417 }
 418
 419
 420 /**
 421  * ipc_rmid - remove an ipc identifier
 422  * @ids: ipc identifier set
 423  * @ipcp: ipc perm structure containing the identifier to remove
 424  *
 425  * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
 426  * before this function is called, and remain locked on the exit.
 427  */
 428 void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
 429 {
 430         int lid = ipcid_to_idx(ipcp->id);
 431
 432         idr_remove(&ids->ipcs_idr, lid);
 433         ids->in_use--;
 434         ipcp->deleted = true;
 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 void *ipc_alloc(int size)
 445 {
 446         void *out;
 447         if (size > PAGE_SIZE)
 448                 out = vmalloc(size);
 449         else
 450                 out = kmalloc(size, GFP_KERNEL);
 451         return out;
 452 }
 453
 454 /**
 455  * ipc_free - free ipc space
 456  * @ptr: pointer returned by ipc_alloc
 457  * @size: size of block
 458  *
 459  * Free a block created with ipc_alloc(). The caller must know the size
 460  * used in the allocation call.
 461  */
 462 void ipc_free(void *ptr, int size)
 463 {
 464         if (size > PAGE_SIZE)
 465                 vfree(ptr);
 466         else
 467                 kfree(ptr);
 468 }
 469
 470 /**
 471  * ipc_rcu_alloc - allocate ipc and rcu space
 472  * @size: size desired
 473  *
 474  * Allocate memory for the rcu header structure +  the object.
 475  * Returns the pointer to the object or NULL upon failure.
 476  */
 477 void *ipc_rcu_alloc(int size)
 478 {
 479         /*
 480          * We prepend the allocation with the rcu struct
 481          */
 482         struct ipc_rcu *out = ipc_alloc(sizeof(struct ipc_rcu) + size);
 483         if (unlikely(!out))
 484                 return NULL;
 485         atomic_set(&out->refcount, 1);
 486         return out + 1;
 487 }
 488
 489 int ipc_rcu_getref(void *ptr)
 490 {
 491         struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;
 492
 493         return atomic_inc_not_zero(&p->refcount);
 494 }
 495
 496 void ipc_rcu_putref(void *ptr, void (*func)(struct rcu_head *head))
 497 {
 498         struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1;
 499
 500         if (!atomic_dec_and_test(&p->refcount))
 501                 return;
 502
 503         call_rcu(&p->rcu, func);
 504 }
 505
 506 void ipc_rcu_free(struct rcu_head *head)
 507 {
 508         struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
 509
 510         if (is_vmalloc_addr(p))
 511                 vfree(p);
 512         else
 513                 kfree(p);
 514 }
 515
 516 /**
 517  * ipcperms - check ipc permissions
 518  * @ns: ipc namespace
 519  * @ipcp: ipc permission set
 520  * @flag: desired permission set
 521  *
 522  * Check user, group, other permissions for access
 523  * to ipc resources. return 0 if allowed
 524  *
 525  * @flag will most probably be 0 or S_...UGO from <linux/stat.h>
 526  */
 527 int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
 528 {
 529         kuid_t euid = current_euid();
 530         int requested_mode, granted_mode;
 531
 532         audit_ipc_obj(ipcp);
 533         requested_mode = (flag >> 6) | (flag >> 3) | flag;
 534         granted_mode = ipcp->mode;
 535         if (uid_eq(euid, ipcp->cuid) ||
 536             uid_eq(euid, ipcp->uid))
 537                 granted_mode >>= 6;
 538         else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
 539                 granted_mode >>= 3;
 540         /* is there some bit set in requested_mode but not in granted_mode? */
 541         if ((requested_mode & ~granted_mode & 0007) &&
 542             !ns_capable(ns->user_ns, CAP_IPC_OWNER))
 543                 return -1;
 544
 545         return security_ipc_permission(ipcp, flag);
 546 }
 547
 548 /*
 549  * Functions to convert between the kern_ipc_perm structure and the
 550  * old/new ipc_perm structures
 551  */
 552
 553 /**
 554  * kernel_to_ipc64_perm - convert kernel ipc permissions to user
 555  * @in: kernel permissions
 556  * @out: new style ipc permissions
 557  *
 558  * Turn the kernel object @in into a set of permissions descriptions
 559  * for returning to userspace (@out).
 560  */
 561 void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)
 562 {
 563         out->key        = in->key;
 564         out->uid        = from_kuid_munged(current_user_ns(), in->uid);
 565         out->gid        = from_kgid_munged(current_user_ns(), in->gid);
 566         out->cuid       = from_kuid_munged(current_user_ns(), in->cuid);
 567         out->cgid       = from_kgid_munged(current_user_ns(), in->cgid);
 568         out->mode       = in->mode;
 569         out->seq        = in->seq;
 570 }
 571
 572 /**
 573  * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
 574  * @in: new style ipc permissions
 575  * @out: old style ipc permissions
 576  *
 577  * Turn the new style permissions object @in into a compatibility
 578  * object and store it into the @out pointer.
 579  */
 580 void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
 581 {
 582         out->key        = in->key;
 583         SET_UID(out->uid, in->uid);
 584         SET_GID(out->gid, in->gid);
 585         SET_UID(out->cuid, in->cuid);
 586         SET_GID(out->cgid, in->cgid);
 587         out->mode       = in->mode;
 588         out->seq        = in->seq;
 589 }
 590
 591 /**
 592  * ipc_obtain_object
 593  * @ids: ipc identifier set
 594  * @id: ipc id to look for
 595  *
 596  * Look for an id in the ipc ids idr and return associated ipc object.
 597  *
 598  * Call inside the RCU critical section.
 599  * The ipc object is *not* locked on exit.
 600  */
 601 struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id)
 602 {
 603         struct kern_ipc_perm *out;
 604         int lid = ipcid_to_idx(id);
 605
 606         out = idr_find(&ids->ipcs_idr, lid);
 607         if (!out)
 608                 return ERR_PTR(-EINVAL);
 609
 610         return out;
 611 }
 612
 613 /**
 614  * ipc_lock - lock an ipc structure without rwsem held
 615  * @ids: ipc identifier set
 616  * @id: ipc id to look for
 617  *
 618  * Look for an id in the ipc ids idr and lock the associated ipc object.
 619  *
 620  * The ipc object is locked on successful exit.
 621  */
 622 struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
 623 {
 624         struct kern_ipc_perm *out;
 625
 626         rcu_read_lock();
 627         out = ipc_obtain_object(ids, id);
 628         if (IS_ERR(out))
 629                 goto err1;
 630
 631         spin_lock(&out->lock);
 632
 633         /* ipc_rmid() may have already freed the ID while ipc_lock
 634          * was spinning: here verify that the structure is still valid
 635          */
 636         if (ipc_valid_object(out))
 637                 return out;
 638
 639         spin_unlock(&out->lock);
 640         out = ERR_PTR(-EINVAL);
 641 err1:
 642         rcu_read_unlock();
 643         return out;
 644 }
 645
 646 /**
 647  * ipc_obtain_object_check
 648  * @ids: ipc identifier set
 649  * @id: ipc id to look for
 650  *
 651  * Similar to ipc_obtain_object() but also checks
 652  * the ipc object reference counter.
 653  *
 654  * Call inside the RCU critical section.
 655  * The ipc object is *not* locked on exit.
 656  */
 657 struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
 658 {
 659         struct kern_ipc_perm *out = ipc_obtain_object(ids, id);
 660
 661         if (IS_ERR(out))
 662                 goto out;
 663
 664         if (ipc_checkid(out, id))
 665                 return ERR_PTR(-EIDRM);
 666 out:
 667         return out;
 668 }
 669
 670 /**
 671  * ipcget - Common sys_*get() code
 672  * @ns: namsepace
 673  * @ids: ipc identifier set
 674  * @ops: operations to be called on ipc object creation, permission checks
 675  *       and further checks
 676  * @params: the parameters needed by the previous operations.
 677  *
 678  * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
 679  */
 680 int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
 681                         const struct ipc_ops *ops, struct ipc_params *params)
 682 {
 683         if (params->key == IPC_PRIVATE)
 684                 return ipcget_new(ns, ids, ops, params);
 685         else
 686                 return ipcget_public(ns, ids, ops, params);
 687 }
 688
 689 /**
 690  * ipc_update_perm - update the permissions of an ipc object
 691  * @in:  the permission given as input.
 692  * @out: the permission of the ipc to set.
 693  */
 694 int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
 695 {
 696         kuid_t uid = make_kuid(current_user_ns(), in->uid);
 697         kgid_t gid = make_kgid(current_user_ns(), in->gid);
 698         if (!uid_valid(uid) || !gid_valid(gid))
 699                 return -EINVAL;
 700
 701         out->uid = uid;
 702         out->gid = gid;
 703         out->mode = (out->mode & ~S_IRWXUGO)
 704                 | (in->mode & S_IRWXUGO);
 705
 706         return 0;
 707 }
 708
 709 /**
 710  * ipcctl_pre_down_nolock - retrieve an ipc and check permissions for some IPC_XXX cmd
 711  * @ns:  ipc namespace
 712  * @ids:  the table of ids where to look for the ipc
 713  * @id:   the id of the ipc to retrieve
 714  * @cmd:  the cmd to check
 715  * @perm: the permission to set
 716  * @extra_perm: one extra permission parameter used by msq
 717  *
 718  * This function does some common audit and permissions check for some IPC_XXX
 719  * cmd and is called from semctl_down, shmctl_down and msgctl_down.
 720  * It must be called without any lock held and
 721  *  - retrieves the ipc with the given id in the given table.
 722  *  - performs some audit and permission check, depending on the given cmd
 723  *  - returns a pointer to the ipc object or otherwise, the corresponding error.
 724  *
 725  * Call holding the both the rwsem and the rcu read lock.
 726  */
 727 struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
 728                                         struct ipc_ids *ids, int id, int cmd,
 729                                         struct ipc64_perm *perm, int extra_perm)
 730 {
 731         kuid_t euid;
 732         int err = -EPERM;
 733         struct kern_ipc_perm *ipcp;
 734
 735         ipcp = ipc_obtain_object_check(ids, id);
 736         if (IS_ERR(ipcp)) {
 737                 err = PTR_ERR(ipcp);
 738                 goto err;
 739         }
 740
 741         audit_ipc_obj(ipcp);
 742         if (cmd == IPC_SET)
 743                 audit_ipc_set_perm(extra_perm, perm->uid,
 744                                    perm->gid, perm->mode);
 745
 746         euid = current_euid();
 747         if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
 748             ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 749                 return ipcp; /* successful lookup */
 750 err:
 751         return ERR_PTR(err);
 752 }
 753
 754 #ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
 755
 756
 757 /**
 758  * ipc_parse_version - ipc call version
 759  * @cmd: pointer to command
 760  *
 761  * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
 762  * The @cmd value is turned from an encoding command and version into
 763  * just the command code.
 764  */
 765 int ipc_parse_version(int *cmd)
 766 {
 767         if (*cmd & IPC_64) {
 768                 *cmd ^= IPC_64;
 769                 return IPC_64;
 770         } else {
 771                 return IPC_OLD;
 772         }
 773 }
 774
 775 #endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
 776
 777 #ifdef CONFIG_PROC_FS
 778 struct ipc_proc_iter {
 779         struct ipc_namespace *ns;
 780         struct ipc_proc_iface *iface;
 781 };
 782
 783 /*
 784  * This routine locks the ipc structure found at least at position pos.
 785  */
 786 static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
 787                                               loff_t *new_pos)
 788 {
 789         struct kern_ipc_perm *ipc;
 790         int total, id;
 791
 792         total = 0;
 793         for (id = 0; id < pos && total < ids->in_use; id++) {
 794                 ipc = idr_find(&ids->ipcs_idr, id);
 795                 if (ipc != NULL)
 796                         total++;
 797         }
 798
 799         if (total >= ids->in_use)
 800                 return NULL;
 801
 802         for (; pos < IPCMNI; pos++) {
 803                 ipc = idr_find(&ids->ipcs_idr, pos);
 804                 if (ipc != NULL) {
 805                         *new_pos = pos + 1;
 806                         rcu_read_lock();
 807                         ipc_lock_object(ipc);
 808                         return ipc;
 809                 }
 810         }
 811
 812         /* Out of range - return NULL to terminate iteration */
 813         return NULL;
 814 }
 815
 816 static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
 817 {
 818         struct ipc_proc_iter *iter = s->private;
 819         struct ipc_proc_iface *iface = iter->iface;
 820         struct kern_ipc_perm *ipc = it;
 821
 822         /* If we had an ipc id locked before, unlock it */
 823         if (ipc && ipc != SEQ_START_TOKEN)
 824                 ipc_unlock(ipc);
 825
 826         return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
 827 }
 828
 829 /*
 830  * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
 831  * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
 832  */
 833 static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
 834 {
 835         struct ipc_proc_iter *iter = s->private;
 836         struct ipc_proc_iface *iface = iter->iface;
 837         struct ipc_ids *ids;
 838
 839         ids = &iter->ns->ids[iface->ids];
 840
 841         /*
 842          * Take the lock - this will be released by the corresponding
 843          * call to stop().
 844          */
 845         down_read(&ids->rwsem);
 846
 847         /* pos < 0 is invalid */
 848         if (*pos < 0)
 849                 return NULL;
 850
 851         /* pos == 0 means header */
 852         if (*pos == 0)
 853                 return SEQ_START_TOKEN;
 854
 855         /* Find the (pos-1)th ipc */
 856         return sysvipc_find_ipc(ids, *pos - 1, pos);
 857 }
 858
 859 static void sysvipc_proc_stop(struct seq_file *s, void *it)
 860 {
 861         struct kern_ipc_perm *ipc = it;
 862         struct ipc_proc_iter *iter = s->private;
 863         struct ipc_proc_iface *iface = iter->iface;
 864         struct ipc_ids *ids;
 865
 866         /* If we had a locked structure, release it */
 867         if (ipc && ipc != SEQ_START_TOKEN)
 868                 ipc_unlock(ipc);
 869
 870         ids = &iter->ns->ids[iface->ids];
 871         /* Release the lock we took in start() */
 872         up_read(&ids->rwsem);
 873 }
 874
 875 static int sysvipc_proc_show(struct seq_file *s, void *it)
 876 {
 877         struct ipc_proc_iter *iter = s->private;
 878         struct ipc_proc_iface *iface = iter->iface;
 879
 880         if (it == SEQ_START_TOKEN)
 881                 return seq_puts(s, iface->header);
 882
 883         return iface->show(s, it);
 884 }
 885
 886 static const struct seq_operations sysvipc_proc_seqops = {
 887         .start = sysvipc_proc_start,
 888         .stop  = sysvipc_proc_stop,
 889         .next  = sysvipc_proc_next,
 890         .show  = sysvipc_proc_show,
 891 };
 892
 893 static int sysvipc_proc_open(struct inode *inode, struct file *file)
 894 {
 895         int ret;
 896         struct seq_file *seq;
 897         struct ipc_proc_iter *iter;
 898
 899         ret = -ENOMEM;
 900         iter = kmalloc(sizeof(*iter), GFP_KERNEL);
 901         if (!iter)
 902                 goto out;
 903
 904         ret = seq_open(file, &sysvipc_proc_seqops);
 905         if (ret) {
 906                 kfree(iter);
 907                 goto out;
 908         }
 909
 910         seq = file->private_data;
 911         seq->private = iter;
 912
 913         iter->iface = PDE_DATA(inode);
 914         iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
 915 out:
 916         return ret;
 917 }
 918
 919 static int sysvipc_proc_release(struct inode *inode, struct file *file)
 920 {
 921         struct seq_file *seq = file->private_data;
 922         struct ipc_proc_iter *iter = seq->private;
 923         put_ipc_ns(iter->ns);
 924         return seq_release_private(inode, file);
 925 }
 926
 927 static const struct file_operations sysvipc_proc_fops = {
 928         .open    = sysvipc_proc_open,
 929         .read    = seq_read,
 930         .llseek  = seq_lseek,
 931         .release = sysvipc_proc_release,
 932 };
 933 #endif /* CONFIG_PROC_FS */