util.c revision 3278a2c2
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		= FIELD_SIZEOF(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 file_operations sysvipc_proc_fops;
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_fops,
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
224		/* allocate the idx, with a NULL struct kern_ipc_perm */
225		idx = idr_alloc(&ids->ipcs_idr, NULL, 0, 0, GFP_NOWAIT);
226
227		if (idx >= 0) {
228			/*
229			 * idx got allocated successfully.
230			 * Now calculate the sequence number and set the
231			 * pointer for real.
232			 */
233			if (idx <= ids->last_idx) {
234				ids->seq++;
235				if (ids->seq >= ipcid_seq_max())
236					ids->seq = 0;
237			}
238			ids->last_idx = idx;
239
240			new->seq = ids->seq;
241			/* no need for smp_wmb(), this is done
242			 * inside idr_replace, as part of
243			 * rcu_assign_pointer
244			 */
245			idr_replace(&ids->ipcs_idr, new, idx);
246		}
247	} else {
248		new->seq = ipcid_to_seqx(next_id);
249		idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),
250				0, GFP_NOWAIT);
251	}
252	if (idx >= 0)
253		new->id = (new->seq << ipcmni_seq_shift()) + idx;
254	return idx;
255}
256
257/**
258 * ipc_addid - add an ipc identifier
259 * @ids: ipc identifier set
260 * @new: new ipc permission set
261 * @limit: limit for the number of used ids
262 *
263 * Add an entry 'new' to the ipc ids idr. The permissions object is
264 * initialised and the first free entry is set up and the index assigned
265 * is returned. The 'new' entry is returned in a locked state on success.
266 *
267 * On failure the entry is not locked and a negative err-code is returned.
268 * The caller must use ipc_rcu_putref() to free the identifier.
269 *
270 * Called with writer ipc_ids.rwsem held.
271 */
272int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
273{
274	kuid_t euid;
275	kgid_t egid;
276	int idx, err;
277
278	/* 1) Initialize the refcount so that ipc_rcu_putref works */
279	refcount_set(&new->refcount, 1);
280
281	if (limit > ipc_mni)
282		limit = ipc_mni;
283
284	if (ids->in_use >= limit)
285		return -ENOSPC;
286
287	idr_preload(GFP_KERNEL);
288
289	spin_lock_init(&new->lock);
290	rcu_read_lock();
291	spin_lock(&new->lock);
292
293	current_euid_egid(&euid, &egid);
294	new->cuid = new->uid = euid;
295	new->gid = new->cgid = egid;
296
297	new->deleted = false;
298
299	idx = ipc_idr_alloc(ids, new);
300	idr_preload_end();
301
302	if (idx >= 0 && new->key != IPC_PRIVATE) {
303		err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,
304					     ipc_kht_params);
305		if (err < 0) {
306			idr_remove(&ids->ipcs_idr, idx);
307			idx = err;
308		}
309	}
310	if (idx < 0) {
311		new->deleted = true;
312		spin_unlock(&new->lock);
313		rcu_read_unlock();
314		return idx;
315	}
316
317	ids->in_use++;
318	if (idx > ids->max_idx)
319		ids->max_idx = idx;
320	return idx;
321}
322
323/**
324 * ipcget_new -	create a new ipc object
325 * @ns: ipc namespace
326 * @ids: ipc identifier set
327 * @ops: the actual creation routine to call
328 * @params: its parameters
329 *
330 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
331 * when the key is IPC_PRIVATE.
332 */
333static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
334		const struct ipc_ops *ops, struct ipc_params *params)
335{
336	int err;
337
338	down_write(&ids->rwsem);
339	err = ops->getnew(ns, params);
340	up_write(&ids->rwsem);
341	return err;
342}
343
344/**
345 * ipc_check_perms - check security and permissions for an ipc object
346 * @ns: ipc namespace
347 * @ipcp: ipc permission set
348 * @ops: the actual security routine to call
349 * @params: its parameters
350 *
351 * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
352 * when the key is not IPC_PRIVATE and that key already exists in the
353 * ds IDR.
354 *
355 * On success, the ipc id is returned.
356 *
357 * It is called with ipc_ids.rwsem and ipcp->lock held.
358 */
359static int ipc_check_perms(struct ipc_namespace *ns,
360			   struct kern_ipc_perm *ipcp,
361			   const struct ipc_ops *ops,
362			   struct ipc_params *params)
363{
364	int err;
365
366	if (ipcperms(ns, ipcp, params->flg))
367		err = -EACCES;
368	else {
369		err = ops->associate(ipcp, params->flg);
370		if (!err)
371			err = ipcp->id;
372	}
373
374	return err;
375}
376
377/**
378 * ipcget_public - get an ipc object or create a new one
379 * @ns: ipc namespace
380 * @ids: ipc identifier set
381 * @ops: the actual creation routine to call
382 * @params: its parameters
383 *
384 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
385 * when the key is not IPC_PRIVATE.
386 * It adds a new entry if the key is not found and does some permission
387 * / security checkings if the key is found.
388 *
389 * On success, the ipc id is returned.
390 */
391static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
392		const struct ipc_ops *ops, struct ipc_params *params)
393{
394	struct kern_ipc_perm *ipcp;
395	int flg = params->flg;
396	int err;
397
398	/*
399	 * Take the lock as a writer since we are potentially going to add
400	 * a new entry + read locks are not "upgradable"
401	 */
402	down_write(&ids->rwsem);
403	ipcp = ipc_findkey(ids, params->key);
404	if (ipcp == NULL) {
405		/* key not used */
406		if (!(flg & IPC_CREAT))
407			err = -ENOENT;
408		else
409			err = ops->getnew(ns, params);
410	} else {
411		/* ipc object has been locked by ipc_findkey() */
412
413		if (flg & IPC_CREAT && flg & IPC_EXCL)
414			err = -EEXIST;
415		else {
416			err = 0;
417			if (ops->more_checks)
418				err = ops->more_checks(ipcp, params);
419			if (!err)
420				/*
421				 * ipc_check_perms returns the IPC id on
422				 * success
423				 */
424				err = ipc_check_perms(ns, ipcp, ops, params);
425		}
426		ipc_unlock(ipcp);
427	}
428	up_write(&ids->rwsem);
429
430	return err;
431}
432
433/**
434 * ipc_kht_remove - remove an ipc from the key hashtable
435 * @ids: ipc identifier set
436 * @ipcp: ipc perm structure containing the key to remove
437 *
438 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
439 * before this function is called, and remain locked on the exit.
440 */
441static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
442{
443	if (ipcp->key != IPC_PRIVATE)
444		rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
445				       ipc_kht_params);
446}
447
448/**
449 * ipc_rmid - remove an ipc identifier
450 * @ids: ipc identifier set
451 * @ipcp: ipc perm structure containing the identifier to remove
452 *
453 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
454 * before this function is called, and remain locked on the exit.
455 */
456void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
457{
458	int idx = ipcid_to_idx(ipcp->id);
459
460	idr_remove(&ids->ipcs_idr, idx);
461	ipc_kht_remove(ids, ipcp);
462	ids->in_use--;
463	ipcp->deleted = true;
464
465	if (unlikely(idx == ids->max_idx)) {
466		do {
467			idx--;
468			if (idx == -1)
469				break;
470		} while (!idr_find(&ids->ipcs_idr, idx));
471		ids->max_idx = idx;
472	}
473}
474
475/**
476 * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE
477 * @ids: ipc identifier set
478 * @ipcp: ipc perm structure containing the key to modify
479 *
480 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
481 * before this function is called, and remain locked on the exit.
482 */
483void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
484{
485	ipc_kht_remove(ids, ipcp);
486	ipcp->key = IPC_PRIVATE;
487}
488
489bool ipc_rcu_getref(struct kern_ipc_perm *ptr)
490{
491	return refcount_inc_not_zero(&ptr->refcount);
492}
493
494void ipc_rcu_putref(struct kern_ipc_perm *ptr,
495			void (*func)(struct rcu_head *head))
496{
497	if (!refcount_dec_and_test(&ptr->refcount))
498		return;
499
500	call_rcu(&ptr->rcu, func);
501}
502
503/**
504 * ipcperms - check ipc permissions
505 * @ns: ipc namespace
506 * @ipcp: ipc permission set
507 * @flag: desired permission set
508 *
509 * Check user, group, other permissions for access
510 * to ipc resources. return 0 if allowed
511 *
512 * @flag will most probably be 0 or ``S_...UGO`` from <linux/stat.h>
513 */
514int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
515{
516	kuid_t euid = current_euid();
517	int requested_mode, granted_mode;
518
519	audit_ipc_obj(ipcp);
520	requested_mode = (flag >> 6) | (flag >> 3) | flag;
521	granted_mode = ipcp->mode;
522	if (uid_eq(euid, ipcp->cuid) ||
523	    uid_eq(euid, ipcp->uid))
524		granted_mode >>= 6;
525	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
526		granted_mode >>= 3;
527	/* is there some bit set in requested_mode but not in granted_mode? */
528	if ((requested_mode & ~granted_mode & 0007) &&
529	    !ns_capable(ns->user_ns, CAP_IPC_OWNER))
530		return -1;
531
532	return security_ipc_permission(ipcp, flag);
533}
534
535/*
536 * Functions to convert between the kern_ipc_perm structure and the
537 * old/new ipc_perm structures
538 */
539
540/**
541 * kernel_to_ipc64_perm	- convert kernel ipc permissions to user
542 * @in: kernel permissions
543 * @out: new style ipc permissions
544 *
545 * Turn the kernel object @in into a set of permissions descriptions
546 * for returning to userspace (@out).
547 */
548void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)
549{
550	out->key	= in->key;
551	out->uid	= from_kuid_munged(current_user_ns(), in->uid);
552	out->gid	= from_kgid_munged(current_user_ns(), in->gid);
553	out->cuid	= from_kuid_munged(current_user_ns(), in->cuid);
554	out->cgid	= from_kgid_munged(current_user_ns(), in->cgid);
555	out->mode	= in->mode;
556	out->seq	= in->seq;
557}
558
559/**
560 * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
561 * @in: new style ipc permissions
562 * @out: old style ipc permissions
563 *
564 * Turn the new style permissions object @in into a compatibility
565 * object and store it into the @out pointer.
566 */
567void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
568{
569	out->key	= in->key;
570	SET_UID(out->uid, in->uid);
571	SET_GID(out->gid, in->gid);
572	SET_UID(out->cuid, in->cuid);
573	SET_GID(out->cgid, in->cgid);
574	out->mode	= in->mode;
575	out->seq	= in->seq;
576}
577
578/**
579 * ipc_obtain_object_idr
580 * @ids: ipc identifier set
581 * @id: ipc id to look for
582 *
583 * Look for an id in the ipc ids idr and return associated ipc object.
584 *
585 * Call inside the RCU critical section.
586 * The ipc object is *not* locked on exit.
587 */
588struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
589{
590	struct kern_ipc_perm *out;
591	int idx = ipcid_to_idx(id);
592
593	out = idr_find(&ids->ipcs_idr, idx);
594	if (!out)
595		return ERR_PTR(-EINVAL);
596
597	return out;
598}
599
600/**
601 * ipc_obtain_object_check
602 * @ids: ipc identifier set
603 * @id: ipc id to look for
604 *
605 * Similar to ipc_obtain_object_idr() but also checks the ipc object
606 * sequence number.
607 *
608 * Call inside the RCU critical section.
609 * The ipc object is *not* locked on exit.
610 */
611struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
612{
613	struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id);
614
615	if (IS_ERR(out))
616		goto out;
617
618	if (ipc_checkid(out, id))
619		return ERR_PTR(-EINVAL);
620out:
621	return out;
622}
623
624/**
625 * ipcget - Common sys_*get() code
626 * @ns: namespace
627 * @ids: ipc identifier set
628 * @ops: operations to be called on ipc object creation, permission checks
629 *       and further checks
630 * @params: the parameters needed by the previous operations.
631 *
632 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
633 */
634int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
635			const struct ipc_ops *ops, struct ipc_params *params)
636{
637	if (params->key == IPC_PRIVATE)
638		return ipcget_new(ns, ids, ops, params);
639	else
640		return ipcget_public(ns, ids, ops, params);
641}
642
643/**
644 * ipc_update_perm - update the permissions of an ipc object
645 * @in:  the permission given as input.
646 * @out: the permission of the ipc to set.
647 */
648int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
649{
650	kuid_t uid = make_kuid(current_user_ns(), in->uid);
651	kgid_t gid = make_kgid(current_user_ns(), in->gid);
652	if (!uid_valid(uid) || !gid_valid(gid))
653		return -EINVAL;
654
655	out->uid = uid;
656	out->gid = gid;
657	out->mode = (out->mode & ~S_IRWXUGO)
658		| (in->mode & S_IRWXUGO);
659
660	return 0;
661}
662
663/**
664 * ipcctl_obtain_check - retrieve an ipc object and check permissions
665 * @ns:  ipc namespace
666 * @ids:  the table of ids where to look for the ipc
667 * @id:   the id of the ipc to retrieve
668 * @cmd:  the cmd to check
669 * @perm: the permission to set
670 * @extra_perm: one extra permission parameter used by msq
671 *
672 * This function does some common audit and permissions check for some IPC_XXX
673 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
674 *
675 * It:
676 *   - retrieves the ipc object with the given id in the given table.
677 *   - performs some audit and permission check, depending on the given cmd
678 *   - returns a pointer to the ipc object or otherwise, the corresponding
679 *     error.
680 *
681 * Call holding the both the rwsem and the rcu read lock.
682 */
683struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,
684					struct ipc_ids *ids, int id, int cmd,
685					struct ipc64_perm *perm, int extra_perm)
686{
687	kuid_t euid;
688	int err = -EPERM;
689	struct kern_ipc_perm *ipcp;
690
691	ipcp = ipc_obtain_object_check(ids, id);
692	if (IS_ERR(ipcp)) {
693		err = PTR_ERR(ipcp);
694		goto err;
695	}
696
697	audit_ipc_obj(ipcp);
698	if (cmd == IPC_SET)
699		audit_ipc_set_perm(extra_perm, perm->uid,
700				   perm->gid, perm->mode);
701
702	euid = current_euid();
703	if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
704	    ns_capable(ns->user_ns, CAP_SYS_ADMIN))
705		return ipcp; /* successful lookup */
706err:
707	return ERR_PTR(err);
708}
709
710#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
711
712
713/**
714 * ipc_parse_version - ipc call version
715 * @cmd: pointer to command
716 *
717 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
718 * The @cmd value is turned from an encoding command and version into
719 * just the command code.
720 */
721int ipc_parse_version(int *cmd)
722{
723	if (*cmd & IPC_64) {
724		*cmd ^= IPC_64;
725		return IPC_64;
726	} else {
727		return IPC_OLD;
728	}
729}
730
731#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
732
733#ifdef CONFIG_PROC_FS
734struct ipc_proc_iter {
735	struct ipc_namespace *ns;
736	struct pid_namespace *pid_ns;
737	struct ipc_proc_iface *iface;
738};
739
740struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s)
741{
742	struct ipc_proc_iter *iter = s->private;
743	return iter->pid_ns;
744}
745
746/*
747 * This routine locks the ipc structure found at least at position pos.
748 */
749static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
750					      loff_t *new_pos)
751{
752	struct kern_ipc_perm *ipc;
753	int total, id;
754
755	total = 0;
756	for (id = 0; id < pos && total < ids->in_use; id++) {
757		ipc = idr_find(&ids->ipcs_idr, id);
758		if (ipc != NULL)
759			total++;
760	}
761
762	if (total >= ids->in_use)
763		return NULL;
764
765	for (; pos < ipc_mni; pos++) {
766		ipc = idr_find(&ids->ipcs_idr, pos);
767		if (ipc != NULL) {
768			*new_pos = pos + 1;
769			rcu_read_lock();
770			ipc_lock_object(ipc);
771			return ipc;
772		}
773	}
774
775	/* Out of range - return NULL to terminate iteration */
776	return NULL;
777}
778
779static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
780{
781	struct ipc_proc_iter *iter = s->private;
782	struct ipc_proc_iface *iface = iter->iface;
783	struct kern_ipc_perm *ipc = it;
784
785	/* If we had an ipc id locked before, unlock it */
786	if (ipc && ipc != SEQ_START_TOKEN)
787		ipc_unlock(ipc);
788
789	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
790}
791
792/*
793 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
794 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
795 */
796static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
797{
798	struct ipc_proc_iter *iter = s->private;
799	struct ipc_proc_iface *iface = iter->iface;
800	struct ipc_ids *ids;
801
802	ids = &iter->ns->ids[iface->ids];
803
804	/*
805	 * Take the lock - this will be released by the corresponding
806	 * call to stop().
807	 */
808	down_read(&ids->rwsem);
809
810	/* pos < 0 is invalid */
811	if (*pos < 0)
812		return NULL;
813
814	/* pos == 0 means header */
815	if (*pos == 0)
816		return SEQ_START_TOKEN;
817
818	/* Find the (pos-1)th ipc */
819	return sysvipc_find_ipc(ids, *pos - 1, pos);
820}
821
822static void sysvipc_proc_stop(struct seq_file *s, void *it)
823{
824	struct kern_ipc_perm *ipc = it;
825	struct ipc_proc_iter *iter = s->private;
826	struct ipc_proc_iface *iface = iter->iface;
827	struct ipc_ids *ids;
828
829	/* If we had a locked structure, release it */
830	if (ipc && ipc != SEQ_START_TOKEN)
831		ipc_unlock(ipc);
832
833	ids = &iter->ns->ids[iface->ids];
834	/* Release the lock we took in start() */
835	up_read(&ids->rwsem);
836}
837
838static int sysvipc_proc_show(struct seq_file *s, void *it)
839{
840	struct ipc_proc_iter *iter = s->private;
841	struct ipc_proc_iface *iface = iter->iface;
842
843	if (it == SEQ_START_TOKEN) {
844		seq_puts(s, iface->header);
845		return 0;
846	}
847
848	return iface->show(s, it);
849}
850
851static const struct seq_operations sysvipc_proc_seqops = {
852	.start = sysvipc_proc_start,
853	.stop  = sysvipc_proc_stop,
854	.next  = sysvipc_proc_next,
855	.show  = sysvipc_proc_show,
856};
857
858static int sysvipc_proc_open(struct inode *inode, struct file *file)
859{
860	struct ipc_proc_iter *iter;
861
862	iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter));
863	if (!iter)
864		return -ENOMEM;
865
866	iter->iface = PDE_DATA(inode);
867	iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
868	iter->pid_ns = get_pid_ns(task_active_pid_ns(current));
869
870	return 0;
871}
872
873static int sysvipc_proc_release(struct inode *inode, struct file *file)
874{
875	struct seq_file *seq = file->private_data;
876	struct ipc_proc_iter *iter = seq->private;
877	put_ipc_ns(iter->ns);
878	put_pid_ns(iter->pid_ns);
879	return seq_release_private(inode, file);
880}
881
882static const struct file_operations sysvipc_proc_fops = {
883	.open    = sysvipc_proc_open,
884	.read    = seq_read,
885	.llseek  = seq_lseek,
886	.release = sysvipc_proc_release,
887};
888#endif /* CONFIG_PROC_FS */
889