Root/ipc/util.c

Source at commit fbf123cd4cc0c097fe9a99c90109ebb2a5e94a50 created 7 years 11 months ago.
By Lars-Peter Clausen, dma: jz4740: Dequeue descriptor from active list before completing it
1/*
2 * linux/ipc/util.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 *
5 * Sep 1997 - Call suser() last after "normal" permission checks so we
6 * get BSD style process accounting right.
7 * Occurs in several places in the IPC code.
8 * Chris Evans, <chris@ferret.lmh.ox.ac.uk>
9 * Nov 1999 - ipc helper functions, unified SMP locking
10 * Manfred Spraul <manfred@colorfullife.com>
11 * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
12 * Mingming Cao <cmm@us.ibm.com>
13 * Mar 2006 - support for audit of ipc object properties
14 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
15 * Jun 2006 - namespaces ssupport
16 * OpenVZ, SWsoft Inc.
17 * Pavel Emelianov <xemul@openvz.org>
18 *
19 * General sysv ipc locking scheme:
20 * rcu_read_lock()
21 * obtain the ipc object (kern_ipc_perm) by looking up the id in an idr
22 * tree.
23 * - perform initial checks (capabilities, auditing and permission,
24 * etc).
25 * - perform read-only operations, such as STAT, INFO commands.
26 * acquire the ipc lock (kern_ipc_perm.lock) through
27 * ipc_lock_object()
28 * - perform data updates, such as SET, RMID commands and
29 * mechanism-specific operations (semop/semtimedop,
30 * msgsnd/msgrcv, shmat/shmdt).
31 * drop the ipc lock, through ipc_unlock_object().
32 * rcu_read_unlock()
33 *
34 * The ids->rwsem must be taken when:
35 * - creating, removing and iterating the existing entries in ipc
36 * identifier sets.
37 * - iterating through files under /proc/sysvipc/
38 *
39 * Note that sems have a special fast path that avoids kern_ipc_perm.lock -
40 * see sem_lock().
41 */
42
43#include <linux/mm.h>
44#include <linux/shm.h>
45#include <linux/init.h>
46#include <linux/msg.h>
47#include <linux/vmalloc.h>
48#include <linux/slab.h>
49#include <linux/notifier.h>
50#include <linux/capability.h>
51#include <linux/highuid.h>
52#include <linux/security.h>
53#include <linux/rcupdate.h>
54#include <linux/workqueue.h>
55#include <linux/seq_file.h>
56#include <linux/proc_fs.h>
57#include <linux/audit.h>
58#include <linux/nsproxy.h>
59#include <linux/rwsem.h>
60#include <linux/memory.h>
61#include <linux/ipc_namespace.h>
62
63#include <asm/unistd.h>
64
65#include "util.h"
66
67struct ipc_proc_iface {
68    const char *path;
69    const char *header;
70    int ids;
71    int (*show)(struct seq_file *, void *);
72};
73
74static void ipc_memory_notifier(struct work_struct *work)
75{
76    ipcns_notify(IPCNS_MEMCHANGED);
77}
78
79static int ipc_memory_callback(struct notifier_block *self,
80                unsigned long action, void *arg)
81{
82    static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
83
84    switch (action) {
85    case MEM_ONLINE: /* memory successfully brought online */
86    case MEM_OFFLINE: /* or offline: it's time to recompute msgmni */
87        /*
88         * This is done by invoking the ipcns notifier chain with the
89         * IPC_MEMCHANGED event.
90         * In order not to keep the lock on the hotplug memory chain
91         * for too long, queue a work item that will, when waken up,
92         * activate the ipcns notification chain.
93         */
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
107static 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 */
122static 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}
131device_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 */
140void 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
150static 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 */
158void __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 */
192static 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 */
223int 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 */
260int 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 */
319static 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 */
345static 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 */
377static 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 */
428void 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 */
444void *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 */
462void 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 */
477void *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
489int 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
496void 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
506void 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 */
527int 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 */
561void 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 */
580void 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 */
601struct 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 */
622struct 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);
641err1:
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 */
657struct 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);
666out:
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 */
680int 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 */
694int 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 */
727struct 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 */
750err:
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 */
765int 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
778struct 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 */
786static 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
816static 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 */
833static 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
859static 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
875static 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
886static 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
893static 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);
915out:
916    return ret;
917}
918
919static 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
927static 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 */
934

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