util.c revision 600fe975
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/notifier.h>
27#include <linux/capability.h>
28#include <linux/highuid.h>
29#include <linux/security.h>
30#include <linux/rcupdate.h>
31#include <linux/workqueue.h>
32#include <linux/seq_file.h>
33#include <linux/proc_fs.h>
34#include <linux/audit.h>
35#include <linux/nsproxy.h>
36#include <linux/rwsem.h>
37#include <linux/memory.h>
38#include <linux/ipc_namespace.h>
39
40#include <asm/unistd.h>
41
42#include "util.h"
43
44struct ipc_proc_iface {
45	const char *path;
46	const char *header;
47	int ids;
48	int (*show)(struct seq_file *, void *);
49};
50
51static void ipc_memory_notifier(struct work_struct *work)
52{
53	ipcns_notify(IPCNS_MEMCHANGED);
54}
55
56static int ipc_memory_callback(struct notifier_block *self,
57				unsigned long action, void *arg)
58{
59	static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
60
61	switch (action) {
62	case MEM_ONLINE:    /* memory successfully brought online */
63	case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
64		/*
65		 * This is done by invoking the ipcns notifier chain with the
66		 * IPC_MEMCHANGED event.
67		 * In order not to keep the lock on the hotplug memory chain
68		 * for too long, queue a work item that will, when waken up,
69		 * activate the ipcns notification chain.
70		 * No need to keep several ipc work items on the queue.
71		 */
72		if (!work_pending(&ipc_memory_wq))
73			schedule_work(&ipc_memory_wq);
74		break;
75	case MEM_GOING_ONLINE:
76	case MEM_GOING_OFFLINE:
77	case MEM_CANCEL_ONLINE:
78	case MEM_CANCEL_OFFLINE:
79	default:
80		break;
81	}
82
83	return NOTIFY_OK;
84}
85
86static struct notifier_block ipc_memory_nb = {
87	.notifier_call = ipc_memory_callback,
88	.priority = IPC_CALLBACK_PRI,
89};
90
91/**
92 *	ipc_init	-	initialise IPC subsystem
93 *
94 *	The various system5 IPC resources (semaphores, messages and shared
95 *	memory) are initialised
96 *	A callback routine is registered into the memory hotplug notifier
97 *	chain: since msgmni scales to lowmem this callback routine will be
98 *	called upon successful memory add / remove to recompute msmgni.
99 */
100
101static int __init ipc_init(void)
102{
103	sem_init();
104	msg_init();
105	shm_init();
106	register_hotmemory_notifier(&ipc_memory_nb);
107	register_ipcns_notifier(&init_ipc_ns);
108	return 0;
109}
110__initcall(ipc_init);
111
112/**
113 *	ipc_init_ids		-	initialise IPC identifiers
114 *	@ids: Identifier set
115 *
116 *	Set up the sequence range to use for the ipc identifier range (limited
117 *	below IPCMNI) then initialise the ids idr.
118 */
119
120void ipc_init_ids(struct ipc_ids *ids)
121{
122	init_rwsem(&ids->rw_mutex);
123
124	ids->in_use = 0;
125	ids->seq = 0;
126	ids->next_id = -1;
127	{
128		int seq_limit = INT_MAX/SEQ_MULTIPLIER;
129		if (seq_limit > USHRT_MAX)
130			ids->seq_max = USHRT_MAX;
131		 else
132		 	ids->seq_max = seq_limit;
133	}
134
135	idr_init(&ids->ipcs_idr);
136}
137
138#ifdef CONFIG_PROC_FS
139static const struct file_operations sysvipc_proc_fops;
140/**
141 *	ipc_init_proc_interface	-  Create a proc interface for sysipc types using a seq_file interface.
142 *	@path: Path in procfs
143 *	@header: Banner to be printed at the beginning of the file.
144 *	@ids: ipc id table to iterate.
145 *	@show: show routine.
146 */
147void __init ipc_init_proc_interface(const char *path, const char *header,
148		int ids, int (*show)(struct seq_file *, void *))
149{
150	struct proc_dir_entry *pde;
151	struct ipc_proc_iface *iface;
152
153	iface = kmalloc(sizeof(*iface), GFP_KERNEL);
154	if (!iface)
155		return;
156	iface->path	= path;
157	iface->header	= header;
158	iface->ids	= ids;
159	iface->show	= show;
160
161	pde = proc_create_data(path,
162			       S_IRUGO,        /* world readable */
163			       NULL,           /* parent dir */
164			       &sysvipc_proc_fops,
165			       iface);
166	if (!pde) {
167		kfree(iface);
168	}
169}
170#endif
171
172/**
173 *	ipc_findkey	-	find a key in an ipc identifier set
174 *	@ids: Identifier set
175 *	@key: The key to find
176 *
177 *	Requires ipc_ids.rw_mutex locked.
178 *	Returns the LOCKED pointer to the ipc structure if found or NULL
179 *	if not.
180 *	If key is found ipc points to the owning ipc structure
181 */
182
183static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
184{
185	struct kern_ipc_perm *ipc;
186	int next_id;
187	int total;
188
189	for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
190		ipc = idr_find(&ids->ipcs_idr, next_id);
191
192		if (ipc == NULL)
193			continue;
194
195		if (ipc->key != key) {
196			total++;
197			continue;
198		}
199
200		ipc_lock_by_ptr(ipc);
201		return ipc;
202	}
203
204	return NULL;
205}
206
207/**
208 *	ipc_get_maxid 	-	get the last assigned id
209 *	@ids: IPC identifier set
210 *
211 *	Called with ipc_ids.rw_mutex held.
212 */
213
214int ipc_get_maxid(struct ipc_ids *ids)
215{
216	struct kern_ipc_perm *ipc;
217	int max_id = -1;
218	int total, id;
219
220	if (ids->in_use == 0)
221		return -1;
222
223	if (ids->in_use == IPCMNI)
224		return IPCMNI - 1;
225
226	/* Look for the last assigned id */
227	total = 0;
228	for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
229		ipc = idr_find(&ids->ipcs_idr, id);
230		if (ipc != NULL) {
231			max_id = id;
232			total++;
233		}
234	}
235	return max_id;
236}
237
238/**
239 *	ipc_addid 	-	add an IPC identifier
240 *	@ids: IPC identifier set
241 *	@new: new IPC permission set
242 *	@size: limit for the number of used ids
243 *
244 *	Add an entry 'new' to the IPC ids idr. The permissions object is
245 *	initialised and the first free entry is set up and the id assigned
246 *	is returned. The 'new' entry is returned in a locked state on success.
247 *	On failure the entry is not locked and a negative err-code is returned.
248 *
249 *	Called with ipc_ids.rw_mutex held as a writer.
250 */
251
252int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
253{
254	kuid_t euid;
255	kgid_t egid;
256	int id;
257	int next_id = ids->next_id;
258
259	if (size > IPCMNI)
260		size = IPCMNI;
261
262	if (ids->in_use >= size)
263		return -ENOSPC;
264
265	idr_preload(GFP_KERNEL);
266
267	spin_lock_init(&new->lock);
268	new->deleted = 0;
269	rcu_read_lock();
270	spin_lock(&new->lock);
271
272	id = idr_alloc(&ids->ipcs_idr, new,
273		       (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
274		       GFP_NOWAIT);
275	idr_preload_end();
276	if (id < 0) {
277		spin_unlock(&new->lock);
278		rcu_read_unlock();
279		return id;
280	}
281
282	ids->in_use++;
283
284	current_euid_egid(&euid, &egid);
285	new->cuid = new->uid = euid;
286	new->gid = new->cgid = egid;
287
288	if (next_id < 0) {
289		new->seq = ids->seq++;
290		if (ids->seq > ids->seq_max)
291			ids->seq = 0;
292	} else {
293		new->seq = ipcid_to_seqx(next_id);
294		ids->next_id = -1;
295	}
296
297	new->id = ipc_buildid(id, new->seq);
298	return id;
299}
300
301/**
302 *	ipcget_new	-	create a new ipc object
303 *	@ns: namespace
304 *	@ids: IPC identifer set
305 *	@ops: the actual creation routine to call
306 *	@params: its parameters
307 *
308 *	This routine is called by sys_msgget, sys_semget() and sys_shmget()
309 *	when the key is IPC_PRIVATE.
310 */
311static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
312		struct ipc_ops *ops, struct ipc_params *params)
313{
314	int err;
315
316	down_write(&ids->rw_mutex);
317	err = ops->getnew(ns, params);
318	up_write(&ids->rw_mutex);
319	return err;
320}
321
322/**
323 *	ipc_check_perms	-	check security and permissions for an IPC
324 *	@ns: IPC namespace
325 *	@ipcp: ipc permission set
326 *	@ops: the actual security routine to call
327 *	@params: its parameters
328 *
329 *	This routine is called by sys_msgget(), sys_semget() and sys_shmget()
330 *      when the key is not IPC_PRIVATE and that key already exists in the
331 *      ids IDR.
332 *
333 *	On success, the IPC id is returned.
334 *
335 *	It is called with ipc_ids.rw_mutex and ipcp->lock held.
336 */
337static int ipc_check_perms(struct ipc_namespace *ns,
338			   struct kern_ipc_perm *ipcp,
339			   struct ipc_ops *ops,
340			   struct ipc_params *params)
341{
342	int err;
343
344	if (ipcperms(ns, ipcp, params->flg))
345		err = -EACCES;
346	else {
347		err = ops->associate(ipcp, params->flg);
348		if (!err)
349			err = ipcp->id;
350	}
351
352	return err;
353}
354
355/**
356 *	ipcget_public	-	get an ipc object or create a new one
357 *	@ns: namespace
358 *	@ids: IPC identifer set
359 *	@ops: the actual creation routine to call
360 *	@params: its parameters
361 *
362 *	This routine is called by sys_msgget, sys_semget() and sys_shmget()
363 *	when the key is not IPC_PRIVATE.
364 *	It adds a new entry if the key is not found and does some permission
365 *      / security checkings if the key is found.
366 *
367 *	On success, the ipc id is returned.
368 */
369static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
370		struct ipc_ops *ops, struct ipc_params *params)
371{
372	struct kern_ipc_perm *ipcp;
373	int flg = params->flg;
374	int err;
375
376	/*
377	 * Take the lock as a writer since we are potentially going to add
378	 * a new entry + read locks are not "upgradable"
379	 */
380	down_write(&ids->rw_mutex);
381	ipcp = ipc_findkey(ids, params->key);
382	if (ipcp == NULL) {
383		/* key not used */
384		if (!(flg & IPC_CREAT))
385			err = -ENOENT;
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	return err;
409}
410
411
412/**
413 *	ipc_rmid	-	remove an IPC identifier
414 *	@ids: IPC identifier set
415 *	@ipcp: ipc perm structure containing the identifier to remove
416 *
417 *	ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
418 *	before this function is called, and remain locked on the exit.
419 */
420
421void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
422{
423	int lid = ipcid_to_idx(ipcp->id);
424
425	idr_remove(&ids->ipcs_idr, lid);
426
427	ids->in_use--;
428
429	ipcp->deleted = 1;
430
431	return;
432}
433
434/**
435 *	ipc_alloc	-	allocate ipc space
436 *	@size: size desired
437 *
438 *	Allocate memory from the appropriate pools and return a pointer to it.
439 *	NULL is returned if the allocation fails
440 */
441
442void *ipc_alloc(int size)
443{
444	void *out;
445	if(size > PAGE_SIZE)
446		out = vmalloc(size);
447	else
448		out = kmalloc(size, GFP_KERNEL);
449	return out;
450}
451
452/**
453 *	ipc_free        -       free ipc space
454 *	@ptr: pointer returned by ipc_alloc
455 *	@size: size of block
456 *
457 *	Free a block created with ipc_alloc(). The caller must know the size
458 *	used in the allocation call.
459 */
460
461void ipc_free(void* ptr, int size)
462{
463	if(size > PAGE_SIZE)
464		vfree(ptr);
465	else
466		kfree(ptr);
467}
468
469struct ipc_rcu {
470	struct rcu_head rcu;
471	atomic_t refcount;
472	/* "void *" makes sure alignment of following data is sane. */
473	void *data[0];
474};
475
476/**
477 *	ipc_rcu_alloc	-	allocate ipc and rcu space
478 *	@size: size desired
479 *
480 *	Allocate memory for the rcu header structure +  the object.
481 *	Returns the pointer to the object or NULL upon failure.
482 */
483void *ipc_rcu_alloc(int size)
484{
485	/*
486	 * We prepend the allocation with the rcu struct
487	 */
488	struct ipc_rcu *out = ipc_alloc(sizeof(struct ipc_rcu) + size);
489	if (unlikely(!out))
490		return NULL;
491	atomic_set(&out->refcount, 1);
492	return out->data;
493}
494
495int ipc_rcu_getref(void *ptr)
496{
497	return atomic_inc_not_zero(&container_of(ptr, struct ipc_rcu, data)->refcount);
498}
499
500/**
501 * ipc_schedule_free - free ipc + rcu space
502 * @head: RCU callback structure for queued work
503 */
504static void ipc_schedule_free(struct rcu_head *head)
505{
506	vfree(container_of(head, struct ipc_rcu, rcu));
507}
508
509void ipc_rcu_putref(void *ptr)
510{
511	struct ipc_rcu *p = container_of(ptr, struct ipc_rcu, data);
512
513	if (!atomic_dec_and_test(&p->refcount))
514		return;
515
516	if (is_vmalloc_addr(ptr)) {
517		call_rcu(&p->rcu, ipc_schedule_free);
518	} else {
519		kfree_rcu(p, rcu);
520	}
521}
522
523/**
524 *	ipcperms	-	check IPC permissions
525 *	@ns: IPC namespace
526 *	@ipcp: IPC permission set
527 *	@flag: desired permission set.
528 *
529 *	Check user, group, other permissions for access
530 *	to ipc resources. return 0 if allowed
531 *
532 * 	@flag will most probably be 0 or S_...UGO from <linux/stat.h>
533 */
534
535int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
536{
537	kuid_t euid = current_euid();
538	int requested_mode, granted_mode;
539
540	audit_ipc_obj(ipcp);
541	requested_mode = (flag >> 6) | (flag >> 3) | flag;
542	granted_mode = ipcp->mode;
543	if (uid_eq(euid, ipcp->cuid) ||
544	    uid_eq(euid, ipcp->uid))
545		granted_mode >>= 6;
546	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
547		granted_mode >>= 3;
548	/* is there some bit set in requested_mode but not in granted_mode? */
549	if ((requested_mode & ~granted_mode & 0007) &&
550	    !ns_capable(ns->user_ns, CAP_IPC_OWNER))
551		return -1;
552
553	return security_ipc_permission(ipcp, flag);
554}
555
556/*
557 * Functions to convert between the kern_ipc_perm structure and the
558 * old/new ipc_perm structures
559 */
560
561/**
562 *	kernel_to_ipc64_perm	-	convert kernel ipc permissions to user
563 *	@in: kernel permissions
564 *	@out: new style IPC permissions
565 *
566 *	Turn the kernel object @in into a set of permissions descriptions
567 *	for returning to userspace (@out).
568 */
569
570
571void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
572{
573	out->key	= in->key;
574	out->uid	= from_kuid_munged(current_user_ns(), in->uid);
575	out->gid	= from_kgid_munged(current_user_ns(), in->gid);
576	out->cuid	= from_kuid_munged(current_user_ns(), in->cuid);
577	out->cgid	= from_kgid_munged(current_user_ns(), in->cgid);
578	out->mode	= in->mode;
579	out->seq	= in->seq;
580}
581
582/**
583 *	ipc64_perm_to_ipc_perm	-	convert new ipc permissions to old
584 *	@in: new style IPC permissions
585 *	@out: old style IPC permissions
586 *
587 *	Turn the new style permissions object @in into a compatibility
588 *	object and store it into the @out pointer.
589 */
590
591void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
592{
593	out->key	= in->key;
594	SET_UID(out->uid, in->uid);
595	SET_GID(out->gid, in->gid);
596	SET_UID(out->cuid, in->cuid);
597	SET_GID(out->cgid, in->cgid);
598	out->mode	= in->mode;
599	out->seq	= in->seq;
600}
601
602/**
603 * ipc_obtain_object
604 * @ids: ipc identifier set
605 * @id: ipc id to look for
606 *
607 * Look for an id in the ipc ids idr and return associated ipc object.
608 *
609 * Call inside the RCU critical section.
610 * The ipc object is *not* locked on exit.
611 */
612struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id)
613{
614	struct kern_ipc_perm *out;
615	int lid = ipcid_to_idx(id);
616
617	out = idr_find(&ids->ipcs_idr, lid);
618	if (!out)
619		return ERR_PTR(-EINVAL);
620
621	return out;
622}
623
624/**
625 * ipc_lock - Lock an ipc structure without rw_mutex held
626 * @ids: IPC identifier set
627 * @id: ipc id to look for
628 *
629 * Look for an id in the ipc ids idr and lock the associated ipc object.
630 *
631 * The ipc object is locked on successful exit.
632 */
633struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
634{
635	struct kern_ipc_perm *out;
636
637	rcu_read_lock();
638	out = ipc_obtain_object(ids, id);
639	if (IS_ERR(out))
640		goto err1;
641
642	spin_lock(&out->lock);
643
644	/* ipc_rmid() may have already freed the ID while ipc_lock
645	 * was spinning: here verify that the structure is still valid
646	 */
647	if (!out->deleted)
648		return out;
649
650	spin_unlock(&out->lock);
651	out = ERR_PTR(-EINVAL);
652err1:
653	rcu_read_unlock();
654	return out;
655}
656
657/**
658 * ipc_obtain_object_check
659 * @ids: ipc identifier set
660 * @id: ipc id to look for
661 *
662 * Similar to ipc_obtain_object() but also checks
663 * the ipc object reference counter.
664 *
665 * Call inside the RCU critical section.
666 * The ipc object is *not* locked on exit.
667 */
668struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
669{
670	struct kern_ipc_perm *out = ipc_obtain_object(ids, id);
671
672	if (IS_ERR(out))
673		goto out;
674
675	if (ipc_checkid(out, id))
676		return ERR_PTR(-EIDRM);
677out:
678	return out;
679}
680
681struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
682{
683	struct kern_ipc_perm *out;
684
685	out = ipc_lock(ids, id);
686	if (IS_ERR(out))
687		return out;
688
689	if (ipc_checkid(out, id)) {
690		ipc_unlock(out);
691		return ERR_PTR(-EIDRM);
692	}
693
694	return out;
695}
696
697/**
698 * ipcget - Common sys_*get() code
699 * @ns : namsepace
700 * @ids : IPC identifier set
701 * @ops : operations to be called on ipc object creation, permission checks
702 *        and further checks
703 * @params : the parameters needed by the previous operations.
704 *
705 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
706 */
707int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
708			struct ipc_ops *ops, struct ipc_params *params)
709{
710	if (params->key == IPC_PRIVATE)
711		return ipcget_new(ns, ids, ops, params);
712	else
713		return ipcget_public(ns, ids, ops, params);
714}
715
716/**
717 * ipc_update_perm - update the permissions of an IPC.
718 * @in:  the permission given as input.
719 * @out: the permission of the ipc to set.
720 */
721int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
722{
723	kuid_t uid = make_kuid(current_user_ns(), in->uid);
724	kgid_t gid = make_kgid(current_user_ns(), in->gid);
725	if (!uid_valid(uid) || !gid_valid(gid))
726		return -EINVAL;
727
728	out->uid = uid;
729	out->gid = gid;
730	out->mode = (out->mode & ~S_IRWXUGO)
731		| (in->mode & S_IRWXUGO);
732
733	return 0;
734}
735
736/**
737 * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
738 * @ns:  the ipc namespace
739 * @ids:  the table of ids where to look for the ipc
740 * @id:   the id of the ipc to retrieve
741 * @cmd:  the cmd to check
742 * @perm: the permission to set
743 * @extra_perm: one extra permission parameter used by msq
744 *
745 * This function does some common audit and permissions check for some IPC_XXX
746 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
747 * It must be called without any lock held and
748 *  - retrieves the ipc with the given id in the given table.
749 *  - performs some audit and permission check, depending on the given cmd
750 *  - returns the ipc with both ipc and rw_mutex locks held in case of success
751 *    or an err-code without any lock held otherwise.
752 */
753struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
754				      struct ipc_ids *ids, int id, int cmd,
755				      struct ipc64_perm *perm, int extra_perm)
756{
757	struct kern_ipc_perm *ipcp;
758
759	ipcp = ipcctl_pre_down_nolock(ns, ids, id, cmd, perm, extra_perm);
760	if (IS_ERR(ipcp))
761		goto out;
762
763	spin_lock(&ipcp->lock);
764out:
765	return ipcp;
766}
767
768struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
769					     struct ipc_ids *ids, int id, int cmd,
770					     struct ipc64_perm *perm, int extra_perm)
771{
772	kuid_t euid;
773	int err = -EPERM;
774	struct kern_ipc_perm *ipcp;
775
776	down_write(&ids->rw_mutex);
777	rcu_read_lock();
778
779	ipcp = ipc_obtain_object_check(ids, id);
780	if (IS_ERR(ipcp)) {
781		err = PTR_ERR(ipcp);
782		goto out_up;
783	}
784
785	audit_ipc_obj(ipcp);
786	if (cmd == IPC_SET)
787		audit_ipc_set_perm(extra_perm, perm->uid,
788				   perm->gid, perm->mode);
789
790	euid = current_euid();
791	if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
792	    ns_capable(ns->user_ns, CAP_SYS_ADMIN))
793		return ipcp;
794
795out_up:
796	/*
797	 * Unsuccessful lookup, unlock and return
798	 * the corresponding error.
799	 */
800	rcu_read_unlock();
801	up_write(&ids->rw_mutex);
802
803	return ERR_PTR(err);
804}
805
806#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
807
808
809/**
810 *	ipc_parse_version	-	IPC call version
811 *	@cmd: pointer to command
812 *
813 *	Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
814 *	The @cmd value is turned from an encoding command and version into
815 *	just the command code.
816 */
817
818int ipc_parse_version (int *cmd)
819{
820	if (*cmd & IPC_64) {
821		*cmd ^= IPC_64;
822		return IPC_64;
823	} else {
824		return IPC_OLD;
825	}
826}
827
828#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
829
830#ifdef CONFIG_PROC_FS
831struct ipc_proc_iter {
832	struct ipc_namespace *ns;
833	struct ipc_proc_iface *iface;
834};
835
836/*
837 * This routine locks the ipc structure found at least at position pos.
838 */
839static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
840					      loff_t *new_pos)
841{
842	struct kern_ipc_perm *ipc;
843	int total, id;
844
845	total = 0;
846	for (id = 0; id < pos && total < ids->in_use; id++) {
847		ipc = idr_find(&ids->ipcs_idr, id);
848		if (ipc != NULL)
849			total++;
850	}
851
852	if (total >= ids->in_use)
853		return NULL;
854
855	for ( ; pos < IPCMNI; pos++) {
856		ipc = idr_find(&ids->ipcs_idr, pos);
857		if (ipc != NULL) {
858			*new_pos = pos + 1;
859			ipc_lock_by_ptr(ipc);
860			return ipc;
861		}
862	}
863
864	/* Out of range - return NULL to terminate iteration */
865	return NULL;
866}
867
868static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
869{
870	struct ipc_proc_iter *iter = s->private;
871	struct ipc_proc_iface *iface = iter->iface;
872	struct kern_ipc_perm *ipc = it;
873
874	/* If we had an ipc id locked before, unlock it */
875	if (ipc && ipc != SEQ_START_TOKEN)
876		ipc_unlock(ipc);
877
878	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
879}
880
881/*
882 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
883 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
884 */
885static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
886{
887	struct ipc_proc_iter *iter = s->private;
888	struct ipc_proc_iface *iface = iter->iface;
889	struct ipc_ids *ids;
890
891	ids = &iter->ns->ids[iface->ids];
892
893	/*
894	 * Take the lock - this will be released by the corresponding
895	 * call to stop().
896	 */
897	down_read(&ids->rw_mutex);
898
899	/* pos < 0 is invalid */
900	if (*pos < 0)
901		return NULL;
902
903	/* pos == 0 means header */
904	if (*pos == 0)
905		return SEQ_START_TOKEN;
906
907	/* Find the (pos-1)th ipc */
908	return sysvipc_find_ipc(ids, *pos - 1, pos);
909}
910
911static void sysvipc_proc_stop(struct seq_file *s, void *it)
912{
913	struct kern_ipc_perm *ipc = it;
914	struct ipc_proc_iter *iter = s->private;
915	struct ipc_proc_iface *iface = iter->iface;
916	struct ipc_ids *ids;
917
918	/* If we had a locked structure, release it */
919	if (ipc && ipc != SEQ_START_TOKEN)
920		ipc_unlock(ipc);
921
922	ids = &iter->ns->ids[iface->ids];
923	/* Release the lock we took in start() */
924	up_read(&ids->rw_mutex);
925}
926
927static int sysvipc_proc_show(struct seq_file *s, void *it)
928{
929	struct ipc_proc_iter *iter = s->private;
930	struct ipc_proc_iface *iface = iter->iface;
931
932	if (it == SEQ_START_TOKEN)
933		return seq_puts(s, iface->header);
934
935	return iface->show(s, it);
936}
937
938static const struct seq_operations sysvipc_proc_seqops = {
939	.start = sysvipc_proc_start,
940	.stop  = sysvipc_proc_stop,
941	.next  = sysvipc_proc_next,
942	.show  = sysvipc_proc_show,
943};
944
945static int sysvipc_proc_open(struct inode *inode, struct file *file)
946{
947	int ret;
948	struct seq_file *seq;
949	struct ipc_proc_iter *iter;
950
951	ret = -ENOMEM;
952	iter = kmalloc(sizeof(*iter), GFP_KERNEL);
953	if (!iter)
954		goto out;
955
956	ret = seq_open(file, &sysvipc_proc_seqops);
957	if (ret)
958		goto out_kfree;
959
960	seq = file->private_data;
961	seq->private = iter;
962
963	iter->iface = PDE_DATA(inode);
964	iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
965out:
966	return ret;
967out_kfree:
968	kfree(iter);
969	goto out;
970}
971
972static int sysvipc_proc_release(struct inode *inode, struct file *file)
973{
974	struct seq_file *seq = file->private_data;
975	struct ipc_proc_iter *iter = seq->private;
976	put_ipc_ns(iter->ns);
977	return seq_release_private(inode, file);
978}
979
980static const struct file_operations sysvipc_proc_fops = {
981	.open    = sysvipc_proc_open,
982	.read    = seq_read,
983	.llseek  = seq_lseek,
984	.release = sysvipc_proc_release,
985};
986#endif /* CONFIG_PROC_FS */
987