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#include <linux/log2.h>
68
69#include <asm/unistd.h>
70
71#include "util.h"
72
73struct ipc_proc_iface {
74	const char *path;
75	const char *header;
76	int ids;
77	int (*show)(struct seq_file *, void *);
78};
79
80/**
81 * ipc_init - initialise ipc subsystem
82 *
83 * The various sysv ipc resources (semaphores, messages and shared
84 * memory) are initialised.
85 *
86 * A callback routine is registered into the memory hotplug notifier
87 * chain: since msgmni scales to lowmem this callback routine will be
88 * called upon successful memory add / remove to recompute msmgni.
89 */
90static int __init ipc_init(void)
91{
92	proc_mkdir("sysvipc", NULL);
93	sem_init();
94	msg_init();
95	shm_init();
96
97	return 0;
98}
99device_initcall(ipc_init);
100
101static const struct rhashtable_params ipc_kht_params = {
102	.head_offset		= offsetof(struct kern_ipc_perm, khtnode),
103	.key_offset		= offsetof(struct kern_ipc_perm, key),
104	.key_len		= sizeof_field(struct kern_ipc_perm, key),
105	.automatic_shrinking	= true,
106};
107
108/**
109 * ipc_init_ids	- initialise ipc identifiers
110 * @ids: ipc identifier set
111 *
112 * Set up the sequence range to use for the ipc identifier range (limited
113 * below ipc_mni) then initialise the keys hashtable and ids idr.
114 */
115void ipc_init_ids(struct ipc_ids *ids)
116{
117	ids->in_use = 0;
118	ids->seq = 0;
119	init_rwsem(&ids->rwsem);
120	rhashtable_init(&ids->key_ht, &ipc_kht_params);
121	idr_init(&ids->ipcs_idr);
122	ids->max_idx = -1;
123	ids->last_idx = -1;
124#ifdef CONFIG_CHECKPOINT_RESTORE
125	ids->next_id = -1;
126#endif
127}
128
129#ifdef CONFIG_PROC_FS
130static const struct proc_ops sysvipc_proc_ops;
131/**
132 * ipc_init_proc_interface -  create a proc interface for sysipc types using a seq_file interface.
133 * @path: Path in procfs
134 * @header: Banner to be printed at the beginning of the file.
135 * @ids: ipc id table to iterate.
136 * @show: show routine.
137 */
138void __init ipc_init_proc_interface(const char *path, const char *header,
139		int ids, int (*show)(struct seq_file *, void *))
140{
141	struct proc_dir_entry *pde;
142	struct ipc_proc_iface *iface;
143
144	iface = kmalloc(sizeof(*iface), GFP_KERNEL);
145	if (!iface)
146		return;
147	iface->path	= path;
148	iface->header	= header;
149	iface->ids	= ids;
150	iface->show	= show;
151
152	pde = proc_create_data(path,
153			       S_IRUGO,        /* world readable */
154			       NULL,           /* parent dir */
155			       &sysvipc_proc_ops,
156			       iface);
157	if (!pde)
158		kfree(iface);
159}
160#endif
161
162/**
163 * ipc_findkey	- find a key in an ipc identifier set
164 * @ids: ipc identifier set
165 * @key: key to find
166 *
167 * Returns the locked pointer to the ipc structure if found or NULL
168 * otherwise. If key is found ipc points to the owning ipc structure
169 *
170 * Called with writer ipc_ids.rwsem held.
171 */
172static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
173{
174	struct kern_ipc_perm *ipcp;
175
176	ipcp = rhashtable_lookup_fast(&ids->key_ht, &key,
177					      ipc_kht_params);
178	if (!ipcp)
179		return NULL;
180
181	rcu_read_lock();
182	ipc_lock_object(ipcp);
183	return ipcp;
184}
185
186/*
187 * Insert new IPC object into idr tree, and set sequence number and id
188 * in the correct order.
189 * Especially:
190 * - the sequence number must be set before inserting the object into the idr,
191 *   because the sequence number is accessed without a lock.
192 * - the id can/must be set after inserting the object into the idr.
193 *   All accesses must be done after getting kern_ipc_perm.lock.
194 *
195 * The caller must own kern_ipc_perm.lock.of the new object.
196 * On error, the function returns a (negative) error code.
197 *
198 * To conserve sequence number space, especially with extended ipc_mni,
199 * the sequence number is incremented only when the returned ID is less than
200 * the last one.
201 */
202static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
203{
204	int idx, next_id = -1;
205
206#ifdef CONFIG_CHECKPOINT_RESTORE
207	next_id = ids->next_id;
208	ids->next_id = -1;
209#endif
210
211	/*
212	 * As soon as a new object is inserted into the idr,
213	 * ipc_obtain_object_idr() or ipc_obtain_object_check() can find it,
214	 * and the lockless preparations for ipc operations can start.
215	 * This means especially: permission checks, audit calls, allocation
216	 * of undo structures, ...
217	 *
218	 * Thus the object must be fully initialized, and if something fails,
219	 * then the full tear-down sequence must be followed.
220	 * (i.e.: set new->deleted, reduce refcount, call_rcu())
221	 */
222
223	if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */
224		int max_idx;
225
226		max_idx = max(ids->in_use*3/2, ipc_min_cycle);
227		max_idx = min(max_idx, ipc_mni);
228
229		/* allocate the idx, with a NULL struct kern_ipc_perm */
230		idx = idr_alloc_cyclic(&ids->ipcs_idr, NULL, 0, max_idx,
231					GFP_NOWAIT);
232
233		if (idx >= 0) {
234			/*
235			 * idx got allocated successfully.
236			 * Now calculate the sequence number and set the
237			 * pointer for real.
238			 */
239			if (idx <= ids->last_idx) {
240				ids->seq++;
241				if (ids->seq >= ipcid_seq_max())
242					ids->seq = 0;
243			}
244			ids->last_idx = idx;
245
246			new->seq = ids->seq;
247			/* no need for smp_wmb(), this is done
248			 * inside idr_replace, as part of
249			 * rcu_assign_pointer
250			 */
251			idr_replace(&ids->ipcs_idr, new, idx);
252		}
253	} else {
254		new->seq = ipcid_to_seqx(next_id);
255		idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),
256				0, GFP_NOWAIT);
257	}
258	if (idx >= 0)
259		new->id = (new->seq << ipcmni_seq_shift()) + idx;
260	return idx;
261}
262
263/**
264 * ipc_addid - add an ipc identifier
265 * @ids: ipc identifier set
266 * @new: new ipc permission set
267 * @limit: limit for the number of used ids
268 *
269 * Add an entry 'new' to the ipc ids idr. The permissions object is
270 * initialised and the first free entry is set up and the index assigned
271 * is returned. The 'new' entry is returned in a locked state on success.
272 *
273 * On failure the entry is not locked and a negative err-code is returned.
274 * The caller must use ipc_rcu_putref() to free the identifier.
275 *
276 * Called with writer ipc_ids.rwsem held.
277 */
278int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
279{
280	kuid_t euid;
281	kgid_t egid;
282	int idx, err;
283
284	/* 1) Initialize the refcount so that ipc_rcu_putref works */
285	refcount_set(&new->refcount, 1);
286
287	if (limit > ipc_mni)
288		limit = ipc_mni;
289
290	if (ids->in_use >= limit)
291		return -ENOSPC;
292
293	idr_preload(GFP_KERNEL);
294
295	spin_lock_init(&new->lock);
296	rcu_read_lock();
297	spin_lock(&new->lock);
298
299	current_euid_egid(&euid, &egid);
300	new->cuid = new->uid = euid;
301	new->gid = new->cgid = egid;
302
303	new->deleted = false;
304
305	idx = ipc_idr_alloc(ids, new);
306	idr_preload_end();
307
308	if (idx >= 0 && new->key != IPC_PRIVATE) {
309		err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,
310					     ipc_kht_params);
311		if (err < 0) {
312			idr_remove(&ids->ipcs_idr, idx);
313			idx = err;
314		}
315	}
316	if (idx < 0) {
317		new->deleted = true;
318		spin_unlock(&new->lock);
319		rcu_read_unlock();
320		return idx;
321	}
322
323	ids->in_use++;
324	if (idx > ids->max_idx)
325		ids->max_idx = idx;
326	return idx;
327}
328
329/**
330 * ipcget_new -	create a new ipc object
331 * @ns: ipc namespace
332 * @ids: ipc identifier set
333 * @ops: the actual creation routine to call
334 * @params: its parameters
335 *
336 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
337 * when the key is IPC_PRIVATE.
338 */
339static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
340		const struct ipc_ops *ops, struct ipc_params *params)
341{
342	int err;
343
344	down_write(&ids->rwsem);
345	err = ops->getnew(ns, params);
346	up_write(&ids->rwsem);
347	return err;
348}
349
350/**
351 * ipc_check_perms - check security and permissions for an ipc object
352 * @ns: ipc namespace
353 * @ipcp: ipc permission set
354 * @ops: the actual security routine to call
355 * @params: its parameters
356 *
357 * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
358 * when the key is not IPC_PRIVATE and that key already exists in the
359 * ds IDR.
360 *
361 * On success, the ipc id is returned.
362 *
363 * It is called with ipc_ids.rwsem and ipcp->lock held.
364 */
365static int ipc_check_perms(struct ipc_namespace *ns,
366			   struct kern_ipc_perm *ipcp,
367			   const struct ipc_ops *ops,
368			   struct ipc_params *params)
369{
370	int err;
371
372	if (ipcperms(ns, ipcp, params->flg))
373		err = -EACCES;
374	else {
375		err = ops->associate(ipcp, params->flg);
376		if (!err)
377			err = ipcp->id;
378	}
379
380	return err;
381}
382
383/**
384 * ipcget_public - get an ipc object or create a new one
385 * @ns: ipc namespace
386 * @ids: ipc identifier set
387 * @ops: the actual creation routine to call
388 * @params: its parameters
389 *
390 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
391 * when the key is not IPC_PRIVATE.
392 * It adds a new entry if the key is not found and does some permission
393 * / security checkings if the key is found.
394 *
395 * On success, the ipc id is returned.
396 */
397static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
398		const struct ipc_ops *ops, struct ipc_params *params)
399{
400	struct kern_ipc_perm *ipcp;
401	int flg = params->flg;
402	int err;
403
404	/*
405	 * Take the lock as a writer since we are potentially going to add
406	 * a new entry + read locks are not "upgradable"
407	 */
408	down_write(&ids->rwsem);
409	ipcp = ipc_findkey(ids, params->key);
410	if (ipcp == NULL) {
411		/* key not used */
412		if (!(flg & IPC_CREAT))
413			err = -ENOENT;
414		else
415			err = ops->getnew(ns, params);
416	} else {
417		/* ipc object has been locked by ipc_findkey() */
418
419		if (flg & IPC_CREAT && flg & IPC_EXCL)
420			err = -EEXIST;
421		else {
422			err = 0;
423			if (ops->more_checks)
424				err = ops->more_checks(ipcp, params);
425			if (!err)
426				/*
427				 * ipc_check_perms returns the IPC id on
428				 * success
429				 */
430				err = ipc_check_perms(ns, ipcp, ops, params);
431		}
432		ipc_unlock(ipcp);
433	}
434	up_write(&ids->rwsem);
435
436	return err;
437}
438
439/**
440 * ipc_kht_remove - remove an ipc from the key hashtable
441 * @ids: ipc identifier set
442 * @ipcp: ipc perm structure containing the key to remove
443 *
444 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
445 * before this function is called, and remain locked on the exit.
446 */
447static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
448{
449	if (ipcp->key != IPC_PRIVATE)
450		rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
451				       ipc_kht_params);
452}
453
454/**
455 * ipc_search_maxidx - search for the highest assigned index
456 * @ids: ipc identifier set
457 * @limit: known upper limit for highest assigned index
458 *
459 * The function determines the highest assigned index in @ids. It is intended
460 * to be called when ids->max_idx needs to be updated.
461 * Updating ids->max_idx is necessary when the current highest index ipc
462 * object is deleted.
463 * If no ipc object is allocated, then -1 is returned.
464 *
465 * ipc_ids.rwsem needs to be held by the caller.
466 */
467static int ipc_search_maxidx(struct ipc_ids *ids, int limit)
468{
469	int tmpidx;
470	int i;
471	int retval;
472
473	i = ilog2(limit+1);
474
475	retval = 0;
476	for (; i >= 0; i--) {
477		tmpidx = retval | (1<<i);
478		/*
479		 * "0" is a possible index value, thus search using
480		 * e.g. 15,7,3,1,0 instead of 16,8,4,2,1.
481		 */
482		tmpidx = tmpidx-1;
483		if (idr_get_next(&ids->ipcs_idr, &tmpidx))
484			retval |= (1<<i);
485	}
486	return retval - 1;
487}
488
489/**
490 * ipc_rmid - remove an ipc identifier
491 * @ids: ipc identifier set
492 * @ipcp: ipc perm structure containing the identifier to remove
493 *
494 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
495 * before this function is called, and remain locked on the exit.
496 */
497void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
498{
499	int idx = ipcid_to_idx(ipcp->id);
500
501	idr_remove(&ids->ipcs_idr, idx);
502	ipc_kht_remove(ids, ipcp);
503	ids->in_use--;
504	ipcp->deleted = true;
505
506	if (unlikely(idx == ids->max_idx)) {
507		idx = ids->max_idx-1;
508		if (idx >= 0)
509			idx = ipc_search_maxidx(ids, idx);
510		ids->max_idx = idx;
511	}
512}
513
514/**
515 * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE
516 * @ids: ipc identifier set
517 * @ipcp: ipc perm structure containing the key to modify
518 *
519 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
520 * before this function is called, and remain locked on the exit.
521 */
522void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
523{
524	ipc_kht_remove(ids, ipcp);
525	ipcp->key = IPC_PRIVATE;
526}
527
528bool ipc_rcu_getref(struct kern_ipc_perm *ptr)
529{
530	return refcount_inc_not_zero(&ptr->refcount);
531}
532
533void ipc_rcu_putref(struct kern_ipc_perm *ptr,
534			void (*func)(struct rcu_head *head))
535{
536	if (!refcount_dec_and_test(&ptr->refcount))
537		return;
538
539	call_rcu(&ptr->rcu, func);
540}
541
542/**
543 * ipcperms - check ipc permissions
544 * @ns: ipc namespace
545 * @ipcp: ipc permission set
546 * @flag: desired permission set
547 *
548 * Check user, group, other permissions for access
549 * to ipc resources. return 0 if allowed
550 *
551 * @flag will most probably be 0 or ``S_...UGO`` from <linux/stat.h>
552 */
553int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
554{
555	kuid_t euid = current_euid();
556	int requested_mode, granted_mode;
557
558	audit_ipc_obj(ipcp);
559	requested_mode = (flag >> 6) | (flag >> 3) | flag;
560	granted_mode = ipcp->mode;
561	if (uid_eq(euid, ipcp->cuid) ||
562	    uid_eq(euid, ipcp->uid))
563		granted_mode >>= 6;
564	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
565		granted_mode >>= 3;
566	/* is there some bit set in requested_mode but not in granted_mode? */
567	if ((requested_mode & ~granted_mode & 0007) &&
568	    !ns_capable(ns->user_ns, CAP_IPC_OWNER))
569		return -1;
570
571	return security_ipc_permission(ipcp, flag);
572}
573
574/*
575 * Functions to convert between the kern_ipc_perm structure and the
576 * old/new ipc_perm structures
577 */
578
579/**
580 * kernel_to_ipc64_perm	- convert kernel ipc permissions to user
581 * @in: kernel permissions
582 * @out: new style ipc permissions
583 *
584 * Turn the kernel object @in into a set of permissions descriptions
585 * for returning to userspace (@out).
586 */
587void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)
588{
589	out->key	= in->key;
590	out->uid	= from_kuid_munged(current_user_ns(), in->uid);
591	out->gid	= from_kgid_munged(current_user_ns(), in->gid);
592	out->cuid	= from_kuid_munged(current_user_ns(), in->cuid);
593	out->cgid	= from_kgid_munged(current_user_ns(), in->cgid);
594	out->mode	= in->mode;
595	out->seq	= in->seq;
596}
597
598/**
599 * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
600 * @in: new style ipc permissions
601 * @out: old style ipc permissions
602 *
603 * Turn the new style permissions object @in into a compatibility
604 * object and store it into the @out pointer.
605 */
606void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
607{
608	out->key	= in->key;
609	SET_UID(out->uid, in->uid);
610	SET_GID(out->gid, in->gid);
611	SET_UID(out->cuid, in->cuid);
612	SET_GID(out->cgid, in->cgid);
613	out->mode	= in->mode;
614	out->seq	= in->seq;
615}
616
617/**
618 * ipc_obtain_object_idr
619 * @ids: ipc identifier set
620 * @id: ipc id to look for
621 *
622 * Look for an id in the ipc ids idr and return associated ipc object.
623 *
624 * Call inside the RCU critical section.
625 * The ipc object is *not* locked on exit.
626 */
627struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
628{
629	struct kern_ipc_perm *out;
630	int idx = ipcid_to_idx(id);
631
632	out = idr_find(&ids->ipcs_idr, idx);
633	if (!out)
634		return ERR_PTR(-EINVAL);
635
636	return out;
637}
638
639/**
640 * ipc_obtain_object_check
641 * @ids: ipc identifier set
642 * @id: ipc id to look for
643 *
644 * Similar to ipc_obtain_object_idr() but also checks the ipc object
645 * sequence number.
646 *
647 * Call inside the RCU critical section.
648 * The ipc object is *not* locked on exit.
649 */
650struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
651{
652	struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id);
653
654	if (IS_ERR(out))
655		goto out;
656
657	if (ipc_checkid(out, id))
658		return ERR_PTR(-EINVAL);
659out:
660	return out;
661}
662
663/**
664 * ipcget - Common sys_*get() code
665 * @ns: namespace
666 * @ids: ipc identifier set
667 * @ops: operations to be called on ipc object creation, permission checks
668 *       and further checks
669 * @params: the parameters needed by the previous operations.
670 *
671 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
672 */
673int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
674			const struct ipc_ops *ops, struct ipc_params *params)
675{
676	if (params->key == IPC_PRIVATE)
677		return ipcget_new(ns, ids, ops, params);
678	else
679		return ipcget_public(ns, ids, ops, params);
680}
681
682/**
683 * ipc_update_perm - update the permissions of an ipc object
684 * @in:  the permission given as input.
685 * @out: the permission of the ipc to set.
686 */
687int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
688{
689	kuid_t uid = make_kuid(current_user_ns(), in->uid);
690	kgid_t gid = make_kgid(current_user_ns(), in->gid);
691	if (!uid_valid(uid) || !gid_valid(gid))
692		return -EINVAL;
693
694	out->uid = uid;
695	out->gid = gid;
696	out->mode = (out->mode & ~S_IRWXUGO)
697		| (in->mode & S_IRWXUGO);
698
699	return 0;
700}
701
702/**
703 * ipcctl_obtain_check - retrieve an ipc object and check permissions
704 * @ns:  ipc namespace
705 * @ids:  the table of ids where to look for the ipc
706 * @id:   the id of the ipc to retrieve
707 * @cmd:  the cmd to check
708 * @perm: the permission to set
709 * @extra_perm: one extra permission parameter used by msq
710 *
711 * This function does some common audit and permissions check for some IPC_XXX
712 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
713 *
714 * It:
715 *   - retrieves the ipc object with the given id in the given table.
716 *   - performs some audit and permission check, depending on the given cmd
717 *   - returns a pointer to the ipc object or otherwise, the corresponding
718 *     error.
719 *
720 * Call holding the both the rwsem and the rcu read lock.
721 */
722struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,
723					struct ipc_ids *ids, int id, int cmd,
724					struct ipc64_perm *perm, int extra_perm)
725{
726	kuid_t euid;
727	int err = -EPERM;
728	struct kern_ipc_perm *ipcp;
729
730	ipcp = ipc_obtain_object_check(ids, id);
731	if (IS_ERR(ipcp)) {
732		err = PTR_ERR(ipcp);
733		goto err;
734	}
735
736	audit_ipc_obj(ipcp);
737	if (cmd == IPC_SET)
738		audit_ipc_set_perm(extra_perm, perm->uid,
739				   perm->gid, perm->mode);
740
741	euid = current_euid();
742	if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
743	    ns_capable(ns->user_ns, CAP_SYS_ADMIN))
744		return ipcp; /* successful lookup */
745err:
746	return ERR_PTR(err);
747}
748
749#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
750
751
752/**
753 * ipc_parse_version - ipc call version
754 * @cmd: pointer to command
755 *
756 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
757 * The @cmd value is turned from an encoding command and version into
758 * just the command code.
759 */
760int ipc_parse_version(int *cmd)
761{
762	if (*cmd & IPC_64) {
763		*cmd ^= IPC_64;
764		return IPC_64;
765	} else {
766		return IPC_OLD;
767	}
768}
769
770#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
771
772#ifdef CONFIG_PROC_FS
773struct ipc_proc_iter {
774	struct ipc_namespace *ns;
775	struct pid_namespace *pid_ns;
776	struct ipc_proc_iface *iface;
777};
778
779struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s)
780{
781	struct ipc_proc_iter *iter = s->private;
782	return iter->pid_ns;
783}
784
785/*
786 * This routine locks the ipc structure found at least at position pos.
787 */
788static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
789					      loff_t *new_pos)
790{
791	struct kern_ipc_perm *ipc = NULL;
792	int max_idx = ipc_get_maxidx(ids);
793
794	if (max_idx == -1 || pos > max_idx)
795		goto out;
796
797	for (; pos <= max_idx; pos++) {
798		ipc = idr_find(&ids->ipcs_idr, pos);
799		if (ipc != NULL) {
800			rcu_read_lock();
801			ipc_lock_object(ipc);
802			break;
803		}
804	}
805out:
806	*new_pos = pos + 1;
807	return ipc;
808}
809
810static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
811{
812	struct ipc_proc_iter *iter = s->private;
813	struct ipc_proc_iface *iface = iter->iface;
814	struct kern_ipc_perm *ipc = it;
815
816	/* If we had an ipc id locked before, unlock it */
817	if (ipc && ipc != SEQ_START_TOKEN)
818		ipc_unlock(ipc);
819
820	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
821}
822
823/*
824 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
825 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
826 */
827static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
828{
829	struct ipc_proc_iter *iter = s->private;
830	struct ipc_proc_iface *iface = iter->iface;
831	struct ipc_ids *ids;
832
833	ids = &iter->ns->ids[iface->ids];
834
835	/*
836	 * Take the lock - this will be released by the corresponding
837	 * call to stop().
838	 */
839	down_read(&ids->rwsem);
840
841	/* pos < 0 is invalid */
842	if (*pos < 0)
843		return NULL;
844
845	/* pos == 0 means header */
846	if (*pos == 0)
847		return SEQ_START_TOKEN;
848
849	/* Find the (pos-1)th ipc */
850	return sysvipc_find_ipc(ids, *pos - 1, pos);
851}
852
853static void sysvipc_proc_stop(struct seq_file *s, void *it)
854{
855	struct kern_ipc_perm *ipc = it;
856	struct ipc_proc_iter *iter = s->private;
857	struct ipc_proc_iface *iface = iter->iface;
858	struct ipc_ids *ids;
859
860	/* If we had a locked structure, release it */
861	if (ipc && ipc != SEQ_START_TOKEN)
862		ipc_unlock(ipc);
863
864	ids = &iter->ns->ids[iface->ids];
865	/* Release the lock we took in start() */
866	up_read(&ids->rwsem);
867}
868
869static int sysvipc_proc_show(struct seq_file *s, void *it)
870{
871	struct ipc_proc_iter *iter = s->private;
872	struct ipc_proc_iface *iface = iter->iface;
873
874	if (it == SEQ_START_TOKEN) {
875		seq_puts(s, iface->header);
876		return 0;
877	}
878
879	return iface->show(s, it);
880}
881
882static const struct seq_operations sysvipc_proc_seqops = {
883	.start = sysvipc_proc_start,
884	.stop  = sysvipc_proc_stop,
885	.next  = sysvipc_proc_next,
886	.show  = sysvipc_proc_show,
887};
888
889static int sysvipc_proc_open(struct inode *inode, struct file *file)
890{
891	struct ipc_proc_iter *iter;
892
893	iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter));
894	if (!iter)
895		return -ENOMEM;
896
897	iter->iface = PDE_DATA(inode);
898	iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
899	iter->pid_ns = get_pid_ns(task_active_pid_ns(current));
900
901	return 0;
902}
903
904static int sysvipc_proc_release(struct inode *inode, struct file *file)
905{
906	struct seq_file *seq = file->private_data;
907	struct ipc_proc_iter *iter = seq->private;
908	put_ipc_ns(iter->ns);
909	put_pid_ns(iter->pid_ns);
910	return seq_release_private(inode, file);
911}
912
913static const struct proc_ops sysvipc_proc_ops = {
914	.proc_flags	= PROC_ENTRY_PERMANENT,
915	.proc_open	= sysvipc_proc_open,
916	.proc_read	= seq_read,
917	.proc_lseek	= seq_lseek,
918	.proc_release	= sysvipc_proc_release,
919};
920#endif /* CONFIG_PROC_FS */
921