util.c revision 27c331a1
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	.locks_mul		= 1,
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 IPCMNI) 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#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 */
197static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
198{
199	int idx, next_id = -1;
200
201#ifdef CONFIG_CHECKPOINT_RESTORE
202	next_id = ids->next_id;
203	ids->next_id = -1;
204#endif
205
206	/*
207	 * As soon as a new object is inserted into the idr,
208	 * ipc_obtain_object_idr() or ipc_obtain_object_check() can find it,
209	 * and the lockless preparations for ipc operations can start.
210	 * This means especially: permission checks, audit calls, allocation
211	 * of undo structures, ...
212	 *
213	 * Thus the object must be fully initialized, and if something fails,
214	 * then the full tear-down sequence must be followed.
215	 * (i.e.: set new->deleted, reduce refcount, call_rcu())
216	 */
217
218	if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */
219		new->seq = ids->seq++;
220		if (ids->seq > IPCID_SEQ_MAX)
221			ids->seq = 0;
222		idx = idr_alloc(&ids->ipcs_idr, new, 0, 0, GFP_NOWAIT);
223	} else {
224		new->seq = ipcid_to_seqx(next_id);
225		idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),
226				0, GFP_NOWAIT);
227	}
228	if (idx >= 0)
229		new->id = SEQ_MULTIPLIER * new->seq + idx;
230	return idx;
231}
232
233/**
234 * ipc_addid - add an ipc identifier
235 * @ids: ipc identifier set
236 * @new: new ipc permission set
237 * @limit: limit for the number of used ids
238 *
239 * Add an entry 'new' to the ipc ids idr. The permissions object is
240 * initialised and the first free entry is set up and the index assigned
241 * is returned. The 'new' entry is returned in a locked state on success.
242 *
243 * On failure the entry is not locked and a negative err-code is returned.
244 * The caller must use ipc_rcu_putref() to free the identifier.
245 *
246 * Called with writer ipc_ids.rwsem held.
247 */
248int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
249{
250	kuid_t euid;
251	kgid_t egid;
252	int idx, err;
253
254	/* 1) Initialize the refcount so that ipc_rcu_putref works */
255	refcount_set(&new->refcount, 1);
256
257	if (limit > IPCMNI)
258		limit = IPCMNI;
259
260	if (ids->in_use >= limit)
261		return -ENOSPC;
262
263	idr_preload(GFP_KERNEL);
264
265	spin_lock_init(&new->lock);
266	rcu_read_lock();
267	spin_lock(&new->lock);
268
269	current_euid_egid(&euid, &egid);
270	new->cuid = new->uid = euid;
271	new->gid = new->cgid = egid;
272
273	new->deleted = false;
274
275	idx = ipc_idr_alloc(ids, new);
276	idr_preload_end();
277
278	if (idx >= 0 && new->key != IPC_PRIVATE) {
279		err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,
280					     ipc_kht_params);
281		if (err < 0) {
282			idr_remove(&ids->ipcs_idr, idx);
283			idx = err;
284		}
285	}
286	if (idx < 0) {
287		new->deleted = true;
288		spin_unlock(&new->lock);
289		rcu_read_unlock();
290		return idx;
291	}
292
293	ids->in_use++;
294	if (idx > ids->max_idx)
295		ids->max_idx = idx;
296	return idx;
297}
298
299/**
300 * ipcget_new -	create a new ipc object
301 * @ns: ipc namespace
302 * @ids: ipc identifier set
303 * @ops: the actual creation routine to call
304 * @params: its parameters
305 *
306 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
307 * when the key is IPC_PRIVATE.
308 */
309static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
310		const struct ipc_ops *ops, struct ipc_params *params)
311{
312	int err;
313
314	down_write(&ids->rwsem);
315	err = ops->getnew(ns, params);
316	up_write(&ids->rwsem);
317	return err;
318}
319
320/**
321 * ipc_check_perms - check security and permissions for an ipc object
322 * @ns: ipc namespace
323 * @ipcp: ipc permission set
324 * @ops: the actual security routine to call
325 * @params: its parameters
326 *
327 * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
328 * when the key is not IPC_PRIVATE and that key already exists in the
329 * ds IDR.
330 *
331 * On success, the ipc id is returned.
332 *
333 * It is called with ipc_ids.rwsem and ipcp->lock held.
334 */
335static int ipc_check_perms(struct ipc_namespace *ns,
336			   struct kern_ipc_perm *ipcp,
337			   const struct ipc_ops *ops,
338			   struct ipc_params *params)
339{
340	int err;
341
342	if (ipcperms(ns, ipcp, params->flg))
343		err = -EACCES;
344	else {
345		err = ops->associate(ipcp, params->flg);
346		if (!err)
347			err = ipcp->id;
348	}
349
350	return err;
351}
352
353/**
354 * ipcget_public - get an ipc object or create a new one
355 * @ns: ipc namespace
356 * @ids: ipc identifier set
357 * @ops: the actual creation routine to call
358 * @params: its parameters
359 *
360 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
361 * when the key is not IPC_PRIVATE.
362 * It adds a new entry if the key is not found and does some permission
363 * / security checkings if the key is found.
364 *
365 * On success, the ipc id is returned.
366 */
367static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
368		const struct ipc_ops *ops, struct ipc_params *params)
369{
370	struct kern_ipc_perm *ipcp;
371	int flg = params->flg;
372	int err;
373
374	/*
375	 * Take the lock as a writer since we are potentially going to add
376	 * a new entry + read locks are not "upgradable"
377	 */
378	down_write(&ids->rwsem);
379	ipcp = ipc_findkey(ids, params->key);
380	if (ipcp == NULL) {
381		/* key not used */
382		if (!(flg & IPC_CREAT))
383			err = -ENOENT;
384		else
385			err = ops->getnew(ns, params);
386	} else {
387		/* ipc object has been locked by ipc_findkey() */
388
389		if (flg & IPC_CREAT && flg & IPC_EXCL)
390			err = -EEXIST;
391		else {
392			err = 0;
393			if (ops->more_checks)
394				err = ops->more_checks(ipcp, params);
395			if (!err)
396				/*
397				 * ipc_check_perms returns the IPC id on
398				 * success
399				 */
400				err = ipc_check_perms(ns, ipcp, ops, params);
401		}
402		ipc_unlock(ipcp);
403	}
404	up_write(&ids->rwsem);
405
406	return err;
407}
408
409/**
410 * ipc_kht_remove - remove an ipc from the key hashtable
411 * @ids: ipc identifier set
412 * @ipcp: ipc perm structure containing the key to remove
413 *
414 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
415 * before this function is called, and remain locked on the exit.
416 */
417static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
418{
419	if (ipcp->key != IPC_PRIVATE)
420		rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
421				       ipc_kht_params);
422}
423
424/**
425 * ipc_rmid - remove an ipc identifier
426 * @ids: ipc identifier set
427 * @ipcp: ipc perm structure containing the identifier to remove
428 *
429 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
430 * before this function is called, and remain locked on the exit.
431 */
432void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
433{
434	int idx = ipcid_to_idx(ipcp->id);
435
436	idr_remove(&ids->ipcs_idr, idx);
437	ipc_kht_remove(ids, ipcp);
438	ids->in_use--;
439	ipcp->deleted = true;
440
441	if (unlikely(idx == ids->max_idx)) {
442		do {
443			idx--;
444			if (idx == -1)
445				break;
446		} while (!idr_find(&ids->ipcs_idr, idx));
447		ids->max_idx = idx;
448	}
449}
450
451/**
452 * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE
453 * @ids: ipc identifier set
454 * @ipcp: ipc perm structure containing the key to modify
455 *
456 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
457 * before this function is called, and remain locked on the exit.
458 */
459void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
460{
461	ipc_kht_remove(ids, ipcp);
462	ipcp->key = IPC_PRIVATE;
463}
464
465int ipc_rcu_getref(struct kern_ipc_perm *ptr)
466{
467	return refcount_inc_not_zero(&ptr->refcount);
468}
469
470void ipc_rcu_putref(struct kern_ipc_perm *ptr,
471			void (*func)(struct rcu_head *head))
472{
473	if (!refcount_dec_and_test(&ptr->refcount))
474		return;
475
476	call_rcu(&ptr->rcu, func);
477}
478
479/**
480 * ipcperms - check ipc permissions
481 * @ns: ipc namespace
482 * @ipcp: ipc permission set
483 * @flag: desired permission set
484 *
485 * Check user, group, other permissions for access
486 * to ipc resources. return 0 if allowed
487 *
488 * @flag will most probably be 0 or ``S_...UGO`` from <linux/stat.h>
489 */
490int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
491{
492	kuid_t euid = current_euid();
493	int requested_mode, granted_mode;
494
495	audit_ipc_obj(ipcp);
496	requested_mode = (flag >> 6) | (flag >> 3) | flag;
497	granted_mode = ipcp->mode;
498	if (uid_eq(euid, ipcp->cuid) ||
499	    uid_eq(euid, ipcp->uid))
500		granted_mode >>= 6;
501	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
502		granted_mode >>= 3;
503	/* is there some bit set in requested_mode but not in granted_mode? */
504	if ((requested_mode & ~granted_mode & 0007) &&
505	    !ns_capable(ns->user_ns, CAP_IPC_OWNER))
506		return -1;
507
508	return security_ipc_permission(ipcp, flag);
509}
510
511/*
512 * Functions to convert between the kern_ipc_perm structure and the
513 * old/new ipc_perm structures
514 */
515
516/**
517 * kernel_to_ipc64_perm	- convert kernel ipc permissions to user
518 * @in: kernel permissions
519 * @out: new style ipc permissions
520 *
521 * Turn the kernel object @in into a set of permissions descriptions
522 * for returning to userspace (@out).
523 */
524void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)
525{
526	out->key	= in->key;
527	out->uid	= from_kuid_munged(current_user_ns(), in->uid);
528	out->gid	= from_kgid_munged(current_user_ns(), in->gid);
529	out->cuid	= from_kuid_munged(current_user_ns(), in->cuid);
530	out->cgid	= from_kgid_munged(current_user_ns(), in->cgid);
531	out->mode	= in->mode;
532	out->seq	= in->seq;
533}
534
535/**
536 * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
537 * @in: new style ipc permissions
538 * @out: old style ipc permissions
539 *
540 * Turn the new style permissions object @in into a compatibility
541 * object and store it into the @out pointer.
542 */
543void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
544{
545	out->key	= in->key;
546	SET_UID(out->uid, in->uid);
547	SET_GID(out->gid, in->gid);
548	SET_UID(out->cuid, in->cuid);
549	SET_GID(out->cgid, in->cgid);
550	out->mode	= in->mode;
551	out->seq	= in->seq;
552}
553
554/**
555 * ipc_obtain_object_idr
556 * @ids: ipc identifier set
557 * @id: ipc id to look for
558 *
559 * Look for an id in the ipc ids idr and return associated ipc object.
560 *
561 * Call inside the RCU critical section.
562 * The ipc object is *not* locked on exit.
563 */
564struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
565{
566	struct kern_ipc_perm *out;
567	int idx = ipcid_to_idx(id);
568
569	out = idr_find(&ids->ipcs_idr, idx);
570	if (!out)
571		return ERR_PTR(-EINVAL);
572
573	return out;
574}
575
576/**
577 * ipc_obtain_object_check
578 * @ids: ipc identifier set
579 * @id: ipc id to look for
580 *
581 * Similar to ipc_obtain_object_idr() but also checks the ipc object
582 * sequence number.
583 *
584 * Call inside the RCU critical section.
585 * The ipc object is *not* locked on exit.
586 */
587struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
588{
589	struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id);
590
591	if (IS_ERR(out))
592		goto out;
593
594	if (ipc_checkid(out, id))
595		return ERR_PTR(-EINVAL);
596out:
597	return out;
598}
599
600/**
601 * ipcget - Common sys_*get() code
602 * @ns: namespace
603 * @ids: ipc identifier set
604 * @ops: operations to be called on ipc object creation, permission checks
605 *       and further checks
606 * @params: the parameters needed by the previous operations.
607 *
608 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
609 */
610int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
611			const struct ipc_ops *ops, struct ipc_params *params)
612{
613	if (params->key == IPC_PRIVATE)
614		return ipcget_new(ns, ids, ops, params);
615	else
616		return ipcget_public(ns, ids, ops, params);
617}
618
619/**
620 * ipc_update_perm - update the permissions of an ipc object
621 * @in:  the permission given as input.
622 * @out: the permission of the ipc to set.
623 */
624int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
625{
626	kuid_t uid = make_kuid(current_user_ns(), in->uid);
627	kgid_t gid = make_kgid(current_user_ns(), in->gid);
628	if (!uid_valid(uid) || !gid_valid(gid))
629		return -EINVAL;
630
631	out->uid = uid;
632	out->gid = gid;
633	out->mode = (out->mode & ~S_IRWXUGO)
634		| (in->mode & S_IRWXUGO);
635
636	return 0;
637}
638
639/**
640 * ipcctl_obtain_check - retrieve an ipc object and check permissions
641 * @ns:  ipc namespace
642 * @ids:  the table of ids where to look for the ipc
643 * @id:   the id of the ipc to retrieve
644 * @cmd:  the cmd to check
645 * @perm: the permission to set
646 * @extra_perm: one extra permission parameter used by msq
647 *
648 * This function does some common audit and permissions check for some IPC_XXX
649 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
650 *
651 * It:
652 *   - retrieves the ipc object with the given id in the given table.
653 *   - performs some audit and permission check, depending on the given cmd
654 *   - returns a pointer to the ipc object or otherwise, the corresponding
655 *     error.
656 *
657 * Call holding the both the rwsem and the rcu read lock.
658 */
659struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,
660					struct ipc_ids *ids, int id, int cmd,
661					struct ipc64_perm *perm, int extra_perm)
662{
663	kuid_t euid;
664	int err = -EPERM;
665	struct kern_ipc_perm *ipcp;
666
667	ipcp = ipc_obtain_object_check(ids, id);
668	if (IS_ERR(ipcp)) {
669		err = PTR_ERR(ipcp);
670		goto err;
671	}
672
673	audit_ipc_obj(ipcp);
674	if (cmd == IPC_SET)
675		audit_ipc_set_perm(extra_perm, perm->uid,
676				   perm->gid, perm->mode);
677
678	euid = current_euid();
679	if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
680	    ns_capable(ns->user_ns, CAP_SYS_ADMIN))
681		return ipcp; /* successful lookup */
682err:
683	return ERR_PTR(err);
684}
685
686#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
687
688
689/**
690 * ipc_parse_version - ipc call version
691 * @cmd: pointer to command
692 *
693 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
694 * The @cmd value is turned from an encoding command and version into
695 * just the command code.
696 */
697int ipc_parse_version(int *cmd)
698{
699	if (*cmd & IPC_64) {
700		*cmd ^= IPC_64;
701		return IPC_64;
702	} else {
703		return IPC_OLD;
704	}
705}
706
707#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
708
709#ifdef CONFIG_PROC_FS
710struct ipc_proc_iter {
711	struct ipc_namespace *ns;
712	struct pid_namespace *pid_ns;
713	struct ipc_proc_iface *iface;
714};
715
716struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s)
717{
718	struct ipc_proc_iter *iter = s->private;
719	return iter->pid_ns;
720}
721
722/*
723 * This routine locks the ipc structure found at least at position pos.
724 */
725static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
726					      loff_t *new_pos)
727{
728	struct kern_ipc_perm *ipc;
729	int total, id;
730
731	total = 0;
732	for (id = 0; id < pos && total < ids->in_use; id++) {
733		ipc = idr_find(&ids->ipcs_idr, id);
734		if (ipc != NULL)
735			total++;
736	}
737
738	if (total >= ids->in_use)
739		return NULL;
740
741	for (; pos < IPCMNI; pos++) {
742		ipc = idr_find(&ids->ipcs_idr, pos);
743		if (ipc != NULL) {
744			*new_pos = pos + 1;
745			rcu_read_lock();
746			ipc_lock_object(ipc);
747			return ipc;
748		}
749	}
750
751	/* Out of range - return NULL to terminate iteration */
752	return NULL;
753}
754
755static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
756{
757	struct ipc_proc_iter *iter = s->private;
758	struct ipc_proc_iface *iface = iter->iface;
759	struct kern_ipc_perm *ipc = it;
760
761	/* If we had an ipc id locked before, unlock it */
762	if (ipc && ipc != SEQ_START_TOKEN)
763		ipc_unlock(ipc);
764
765	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
766}
767
768/*
769 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
770 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
771 */
772static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
773{
774	struct ipc_proc_iter *iter = s->private;
775	struct ipc_proc_iface *iface = iter->iface;
776	struct ipc_ids *ids;
777
778	ids = &iter->ns->ids[iface->ids];
779
780	/*
781	 * Take the lock - this will be released by the corresponding
782	 * call to stop().
783	 */
784	down_read(&ids->rwsem);
785
786	/* pos < 0 is invalid */
787	if (*pos < 0)
788		return NULL;
789
790	/* pos == 0 means header */
791	if (*pos == 0)
792		return SEQ_START_TOKEN;
793
794	/* Find the (pos-1)th ipc */
795	return sysvipc_find_ipc(ids, *pos - 1, pos);
796}
797
798static void sysvipc_proc_stop(struct seq_file *s, void *it)
799{
800	struct kern_ipc_perm *ipc = it;
801	struct ipc_proc_iter *iter = s->private;
802	struct ipc_proc_iface *iface = iter->iface;
803	struct ipc_ids *ids;
804
805	/* If we had a locked structure, release it */
806	if (ipc && ipc != SEQ_START_TOKEN)
807		ipc_unlock(ipc);
808
809	ids = &iter->ns->ids[iface->ids];
810	/* Release the lock we took in start() */
811	up_read(&ids->rwsem);
812}
813
814static int sysvipc_proc_show(struct seq_file *s, void *it)
815{
816	struct ipc_proc_iter *iter = s->private;
817	struct ipc_proc_iface *iface = iter->iface;
818
819	if (it == SEQ_START_TOKEN) {
820		seq_puts(s, iface->header);
821		return 0;
822	}
823
824	return iface->show(s, it);
825}
826
827static const struct seq_operations sysvipc_proc_seqops = {
828	.start = sysvipc_proc_start,
829	.stop  = sysvipc_proc_stop,
830	.next  = sysvipc_proc_next,
831	.show  = sysvipc_proc_show,
832};
833
834static int sysvipc_proc_open(struct inode *inode, struct file *file)
835{
836	struct ipc_proc_iter *iter;
837
838	iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter));
839	if (!iter)
840		return -ENOMEM;
841
842	iter->iface = PDE_DATA(inode);
843	iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
844	iter->pid_ns = get_pid_ns(task_active_pid_ns(current));
845
846	return 0;
847}
848
849static int sysvipc_proc_release(struct inode *inode, struct file *file)
850{
851	struct seq_file *seq = file->private_data;
852	struct ipc_proc_iter *iter = seq->private;
853	put_ipc_ns(iter->ns);
854	put_pid_ns(iter->pid_ns);
855	return seq_release_private(inode, file);
856}
857
858static const struct file_operations sysvipc_proc_fops = {
859	.open    = sysvipc_proc_open,
860	.read    = seq_read,
861	.llseek  = seq_lseek,
862	.release = sysvipc_proc_release,
863};
864#endif /* CONFIG_PROC_FS */
865