util.c revision 99db46ea
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		int max_idx;
224
225		max_idx = max(ids->in_use*3/2, ipc_min_cycle);
226		max_idx = min(max_idx, ipc_mni);
227
228		/* allocate the idx, with a NULL struct kern_ipc_perm */
229		idx = idr_alloc_cyclic(&ids->ipcs_idr, NULL, 0, max_idx,
230					GFP_NOWAIT);
231
232		if (idx >= 0) {
233			/*
234			 * idx got allocated successfully.
235			 * Now calculate the sequence number and set the
236			 * pointer for real.
237			 */
238			if (idx <= ids->last_idx) {
239				ids->seq++;
240				if (ids->seq >= ipcid_seq_max())
241					ids->seq = 0;
242			}
243			ids->last_idx = idx;
244
245			new->seq = ids->seq;
246			/* no need for smp_wmb(), this is done
247			 * inside idr_replace, as part of
248			 * rcu_assign_pointer
249			 */
250			idr_replace(&ids->ipcs_idr, new, idx);
251		}
252	} else {
253		new->seq = ipcid_to_seqx(next_id);
254		idx = idr_alloc(&ids->ipcs_idr, new, ipcid_to_idx(next_id),
255				0, GFP_NOWAIT);
256	}
257	if (idx >= 0)
258		new->id = (new->seq << ipcmni_seq_shift()) + idx;
259	return idx;
260}
261
262/**
263 * ipc_addid - add an ipc identifier
264 * @ids: ipc identifier set
265 * @new: new ipc permission set
266 * @limit: limit for the number of used ids
267 *
268 * Add an entry 'new' to the ipc ids idr. The permissions object is
269 * initialised and the first free entry is set up and the index assigned
270 * is returned. The 'new' entry is returned in a locked state on success.
271 *
272 * On failure the entry is not locked and a negative err-code is returned.
273 * The caller must use ipc_rcu_putref() to free the identifier.
274 *
275 * Called with writer ipc_ids.rwsem held.
276 */
277int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
278{
279	kuid_t euid;
280	kgid_t egid;
281	int idx, err;
282
283	/* 1) Initialize the refcount so that ipc_rcu_putref works */
284	refcount_set(&new->refcount, 1);
285
286	if (limit > ipc_mni)
287		limit = ipc_mni;
288
289	if (ids->in_use >= limit)
290		return -ENOSPC;
291
292	idr_preload(GFP_KERNEL);
293
294	spin_lock_init(&new->lock);
295	rcu_read_lock();
296	spin_lock(&new->lock);
297
298	current_euid_egid(&euid, &egid);
299	new->cuid = new->uid = euid;
300	new->gid = new->cgid = egid;
301
302	new->deleted = false;
303
304	idx = ipc_idr_alloc(ids, new);
305	idr_preload_end();
306
307	if (idx >= 0 && new->key != IPC_PRIVATE) {
308		err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,
309					     ipc_kht_params);
310		if (err < 0) {
311			idr_remove(&ids->ipcs_idr, idx);
312			idx = err;
313		}
314	}
315	if (idx < 0) {
316		new->deleted = true;
317		spin_unlock(&new->lock);
318		rcu_read_unlock();
319		return idx;
320	}
321
322	ids->in_use++;
323	if (idx > ids->max_idx)
324		ids->max_idx = idx;
325	return idx;
326}
327
328/**
329 * ipcget_new -	create a new ipc object
330 * @ns: ipc namespace
331 * @ids: ipc identifier set
332 * @ops: the actual creation routine to call
333 * @params: its parameters
334 *
335 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
336 * when the key is IPC_PRIVATE.
337 */
338static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
339		const struct ipc_ops *ops, struct ipc_params *params)
340{
341	int err;
342
343	down_write(&ids->rwsem);
344	err = ops->getnew(ns, params);
345	up_write(&ids->rwsem);
346	return err;
347}
348
349/**
350 * ipc_check_perms - check security and permissions for an ipc object
351 * @ns: ipc namespace
352 * @ipcp: ipc permission set
353 * @ops: the actual security routine to call
354 * @params: its parameters
355 *
356 * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
357 * when the key is not IPC_PRIVATE and that key already exists in the
358 * ds IDR.
359 *
360 * On success, the ipc id is returned.
361 *
362 * It is called with ipc_ids.rwsem and ipcp->lock held.
363 */
364static int ipc_check_perms(struct ipc_namespace *ns,
365			   struct kern_ipc_perm *ipcp,
366			   const struct ipc_ops *ops,
367			   struct ipc_params *params)
368{
369	int err;
370
371	if (ipcperms(ns, ipcp, params->flg))
372		err = -EACCES;
373	else {
374		err = ops->associate(ipcp, params->flg);
375		if (!err)
376			err = ipcp->id;
377	}
378
379	return err;
380}
381
382/**
383 * ipcget_public - get an ipc object or create a new one
384 * @ns: ipc namespace
385 * @ids: ipc identifier set
386 * @ops: the actual creation routine to call
387 * @params: its parameters
388 *
389 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
390 * when the key is not IPC_PRIVATE.
391 * It adds a new entry if the key is not found and does some permission
392 * / security checkings if the key is found.
393 *
394 * On success, the ipc id is returned.
395 */
396static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
397		const struct ipc_ops *ops, struct ipc_params *params)
398{
399	struct kern_ipc_perm *ipcp;
400	int flg = params->flg;
401	int err;
402
403	/*
404	 * Take the lock as a writer since we are potentially going to add
405	 * a new entry + read locks are not "upgradable"
406	 */
407	down_write(&ids->rwsem);
408	ipcp = ipc_findkey(ids, params->key);
409	if (ipcp == NULL) {
410		/* key not used */
411		if (!(flg & IPC_CREAT))
412			err = -ENOENT;
413		else
414			err = ops->getnew(ns, params);
415	} else {
416		/* ipc object has been locked by ipc_findkey() */
417
418		if (flg & IPC_CREAT && flg & IPC_EXCL)
419			err = -EEXIST;
420		else {
421			err = 0;
422			if (ops->more_checks)
423				err = ops->more_checks(ipcp, params);
424			if (!err)
425				/*
426				 * ipc_check_perms returns the IPC id on
427				 * success
428				 */
429				err = ipc_check_perms(ns, ipcp, ops, params);
430		}
431		ipc_unlock(ipcp);
432	}
433	up_write(&ids->rwsem);
434
435	return err;
436}
437
438/**
439 * ipc_kht_remove - remove an ipc from the key hashtable
440 * @ids: ipc identifier set
441 * @ipcp: ipc perm structure containing the key to remove
442 *
443 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
444 * before this function is called, and remain locked on the exit.
445 */
446static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
447{
448	if (ipcp->key != IPC_PRIVATE)
449		rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
450				       ipc_kht_params);
451}
452
453/**
454 * ipc_rmid - remove an ipc identifier
455 * @ids: ipc identifier set
456 * @ipcp: ipc perm structure containing the identifier to remove
457 *
458 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
459 * before this function is called, and remain locked on the exit.
460 */
461void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
462{
463	int idx = ipcid_to_idx(ipcp->id);
464
465	idr_remove(&ids->ipcs_idr, idx);
466	ipc_kht_remove(ids, ipcp);
467	ids->in_use--;
468	ipcp->deleted = true;
469
470	if (unlikely(idx == ids->max_idx)) {
471		do {
472			idx--;
473			if (idx == -1)
474				break;
475		} while (!idr_find(&ids->ipcs_idr, idx));
476		ids->max_idx = idx;
477	}
478}
479
480/**
481 * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE
482 * @ids: ipc identifier set
483 * @ipcp: ipc perm structure containing the key to modify
484 *
485 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
486 * before this function is called, and remain locked on the exit.
487 */
488void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
489{
490	ipc_kht_remove(ids, ipcp);
491	ipcp->key = IPC_PRIVATE;
492}
493
494bool ipc_rcu_getref(struct kern_ipc_perm *ptr)
495{
496	return refcount_inc_not_zero(&ptr->refcount);
497}
498
499void ipc_rcu_putref(struct kern_ipc_perm *ptr,
500			void (*func)(struct rcu_head *head))
501{
502	if (!refcount_dec_and_test(&ptr->refcount))
503		return;
504
505	call_rcu(&ptr->rcu, func);
506}
507
508/**
509 * ipcperms - check ipc permissions
510 * @ns: ipc namespace
511 * @ipcp: ipc permission set
512 * @flag: desired permission set
513 *
514 * Check user, group, other permissions for access
515 * to ipc resources. return 0 if allowed
516 *
517 * @flag will most probably be 0 or ``S_...UGO`` from <linux/stat.h>
518 */
519int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
520{
521	kuid_t euid = current_euid();
522	int requested_mode, granted_mode;
523
524	audit_ipc_obj(ipcp);
525	requested_mode = (flag >> 6) | (flag >> 3) | flag;
526	granted_mode = ipcp->mode;
527	if (uid_eq(euid, ipcp->cuid) ||
528	    uid_eq(euid, ipcp->uid))
529		granted_mode >>= 6;
530	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
531		granted_mode >>= 3;
532	/* is there some bit set in requested_mode but not in granted_mode? */
533	if ((requested_mode & ~granted_mode & 0007) &&
534	    !ns_capable(ns->user_ns, CAP_IPC_OWNER))
535		return -1;
536
537	return security_ipc_permission(ipcp, flag);
538}
539
540/*
541 * Functions to convert between the kern_ipc_perm structure and the
542 * old/new ipc_perm structures
543 */
544
545/**
546 * kernel_to_ipc64_perm	- convert kernel ipc permissions to user
547 * @in: kernel permissions
548 * @out: new style ipc permissions
549 *
550 * Turn the kernel object @in into a set of permissions descriptions
551 * for returning to userspace (@out).
552 */
553void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)
554{
555	out->key	= in->key;
556	out->uid	= from_kuid_munged(current_user_ns(), in->uid);
557	out->gid	= from_kgid_munged(current_user_ns(), in->gid);
558	out->cuid	= from_kuid_munged(current_user_ns(), in->cuid);
559	out->cgid	= from_kgid_munged(current_user_ns(), in->cgid);
560	out->mode	= in->mode;
561	out->seq	= in->seq;
562}
563
564/**
565 * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
566 * @in: new style ipc permissions
567 * @out: old style ipc permissions
568 *
569 * Turn the new style permissions object @in into a compatibility
570 * object and store it into the @out pointer.
571 */
572void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
573{
574	out->key	= in->key;
575	SET_UID(out->uid, in->uid);
576	SET_GID(out->gid, in->gid);
577	SET_UID(out->cuid, in->cuid);
578	SET_GID(out->cgid, in->cgid);
579	out->mode	= in->mode;
580	out->seq	= in->seq;
581}
582
583/**
584 * ipc_obtain_object_idr
585 * @ids: ipc identifier set
586 * @id: ipc id to look for
587 *
588 * Look for an id in the ipc ids idr and return associated ipc object.
589 *
590 * Call inside the RCU critical section.
591 * The ipc object is *not* locked on exit.
592 */
593struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
594{
595	struct kern_ipc_perm *out;
596	int idx = ipcid_to_idx(id);
597
598	out = idr_find(&ids->ipcs_idr, idx);
599	if (!out)
600		return ERR_PTR(-EINVAL);
601
602	return out;
603}
604
605/**
606 * ipc_obtain_object_check
607 * @ids: ipc identifier set
608 * @id: ipc id to look for
609 *
610 * Similar to ipc_obtain_object_idr() but also checks the ipc object
611 * sequence number.
612 *
613 * Call inside the RCU critical section.
614 * The ipc object is *not* locked on exit.
615 */
616struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
617{
618	struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id);
619
620	if (IS_ERR(out))
621		goto out;
622
623	if (ipc_checkid(out, id))
624		return ERR_PTR(-EINVAL);
625out:
626	return out;
627}
628
629/**
630 * ipcget - Common sys_*get() code
631 * @ns: namespace
632 * @ids: ipc identifier set
633 * @ops: operations to be called on ipc object creation, permission checks
634 *       and further checks
635 * @params: the parameters needed by the previous operations.
636 *
637 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
638 */
639int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
640			const struct ipc_ops *ops, struct ipc_params *params)
641{
642	if (params->key == IPC_PRIVATE)
643		return ipcget_new(ns, ids, ops, params);
644	else
645		return ipcget_public(ns, ids, ops, params);
646}
647
648/**
649 * ipc_update_perm - update the permissions of an ipc object
650 * @in:  the permission given as input.
651 * @out: the permission of the ipc to set.
652 */
653int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
654{
655	kuid_t uid = make_kuid(current_user_ns(), in->uid);
656	kgid_t gid = make_kgid(current_user_ns(), in->gid);
657	if (!uid_valid(uid) || !gid_valid(gid))
658		return -EINVAL;
659
660	out->uid = uid;
661	out->gid = gid;
662	out->mode = (out->mode & ~S_IRWXUGO)
663		| (in->mode & S_IRWXUGO);
664
665	return 0;
666}
667
668/**
669 * ipcctl_obtain_check - retrieve an ipc object and check permissions
670 * @ns:  ipc namespace
671 * @ids:  the table of ids where to look for the ipc
672 * @id:   the id of the ipc to retrieve
673 * @cmd:  the cmd to check
674 * @perm: the permission to set
675 * @extra_perm: one extra permission parameter used by msq
676 *
677 * This function does some common audit and permissions check for some IPC_XXX
678 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
679 *
680 * It:
681 *   - retrieves the ipc object with the given id in the given table.
682 *   - performs some audit and permission check, depending on the given cmd
683 *   - returns a pointer to the ipc object or otherwise, the corresponding
684 *     error.
685 *
686 * Call holding the both the rwsem and the rcu read lock.
687 */
688struct kern_ipc_perm *ipcctl_obtain_check(struct ipc_namespace *ns,
689					struct ipc_ids *ids, int id, int cmd,
690					struct ipc64_perm *perm, int extra_perm)
691{
692	kuid_t euid;
693	int err = -EPERM;
694	struct kern_ipc_perm *ipcp;
695
696	ipcp = ipc_obtain_object_check(ids, id);
697	if (IS_ERR(ipcp)) {
698		err = PTR_ERR(ipcp);
699		goto err;
700	}
701
702	audit_ipc_obj(ipcp);
703	if (cmd == IPC_SET)
704		audit_ipc_set_perm(extra_perm, perm->uid,
705				   perm->gid, perm->mode);
706
707	euid = current_euid();
708	if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
709	    ns_capable(ns->user_ns, CAP_SYS_ADMIN))
710		return ipcp; /* successful lookup */
711err:
712	return ERR_PTR(err);
713}
714
715#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
716
717
718/**
719 * ipc_parse_version - ipc call version
720 * @cmd: pointer to command
721 *
722 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
723 * The @cmd value is turned from an encoding command and version into
724 * just the command code.
725 */
726int ipc_parse_version(int *cmd)
727{
728	if (*cmd & IPC_64) {
729		*cmd ^= IPC_64;
730		return IPC_64;
731	} else {
732		return IPC_OLD;
733	}
734}
735
736#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
737
738#ifdef CONFIG_PROC_FS
739struct ipc_proc_iter {
740	struct ipc_namespace *ns;
741	struct pid_namespace *pid_ns;
742	struct ipc_proc_iface *iface;
743};
744
745struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s)
746{
747	struct ipc_proc_iter *iter = s->private;
748	return iter->pid_ns;
749}
750
751/*
752 * This routine locks the ipc structure found at least at position pos.
753 */
754static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
755					      loff_t *new_pos)
756{
757	struct kern_ipc_perm *ipc;
758	int total, id;
759
760	total = 0;
761	for (id = 0; id < pos && total < ids->in_use; id++) {
762		ipc = idr_find(&ids->ipcs_idr, id);
763		if (ipc != NULL)
764			total++;
765	}
766
767	if (total >= ids->in_use)
768		return NULL;
769
770	for (; pos < ipc_mni; pos++) {
771		ipc = idr_find(&ids->ipcs_idr, pos);
772		if (ipc != NULL) {
773			*new_pos = pos + 1;
774			rcu_read_lock();
775			ipc_lock_object(ipc);
776			return ipc;
777		}
778	}
779
780	/* Out of range - return NULL to terminate iteration */
781	return NULL;
782}
783
784static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
785{
786	struct ipc_proc_iter *iter = s->private;
787	struct ipc_proc_iface *iface = iter->iface;
788	struct kern_ipc_perm *ipc = it;
789
790	/* If we had an ipc id locked before, unlock it */
791	if (ipc && ipc != SEQ_START_TOKEN)
792		ipc_unlock(ipc);
793
794	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
795}
796
797/*
798 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
799 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
800 */
801static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
802{
803	struct ipc_proc_iter *iter = s->private;
804	struct ipc_proc_iface *iface = iter->iface;
805	struct ipc_ids *ids;
806
807	ids = &iter->ns->ids[iface->ids];
808
809	/*
810	 * Take the lock - this will be released by the corresponding
811	 * call to stop().
812	 */
813	down_read(&ids->rwsem);
814
815	/* pos < 0 is invalid */
816	if (*pos < 0)
817		return NULL;
818
819	/* pos == 0 means header */
820	if (*pos == 0)
821		return SEQ_START_TOKEN;
822
823	/* Find the (pos-1)th ipc */
824	return sysvipc_find_ipc(ids, *pos - 1, pos);
825}
826
827static void sysvipc_proc_stop(struct seq_file *s, void *it)
828{
829	struct kern_ipc_perm *ipc = it;
830	struct ipc_proc_iter *iter = s->private;
831	struct ipc_proc_iface *iface = iter->iface;
832	struct ipc_ids *ids;
833
834	/* If we had a locked structure, release it */
835	if (ipc && ipc != SEQ_START_TOKEN)
836		ipc_unlock(ipc);
837
838	ids = &iter->ns->ids[iface->ids];
839	/* Release the lock we took in start() */
840	up_read(&ids->rwsem);
841}
842
843static int sysvipc_proc_show(struct seq_file *s, void *it)
844{
845	struct ipc_proc_iter *iter = s->private;
846	struct ipc_proc_iface *iface = iter->iface;
847
848	if (it == SEQ_START_TOKEN) {
849		seq_puts(s, iface->header);
850		return 0;
851	}
852
853	return iface->show(s, it);
854}
855
856static const struct seq_operations sysvipc_proc_seqops = {
857	.start = sysvipc_proc_start,
858	.stop  = sysvipc_proc_stop,
859	.next  = sysvipc_proc_next,
860	.show  = sysvipc_proc_show,
861};
862
863static int sysvipc_proc_open(struct inode *inode, struct file *file)
864{
865	struct ipc_proc_iter *iter;
866
867	iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter));
868	if (!iter)
869		return -ENOMEM;
870
871	iter->iface = PDE_DATA(inode);
872	iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
873	iter->pid_ns = get_pid_ns(task_active_pid_ns(current));
874
875	return 0;
876}
877
878static int sysvipc_proc_release(struct inode *inode, struct file *file)
879{
880	struct seq_file *seq = file->private_data;
881	struct ipc_proc_iter *iter = seq->private;
882	put_ipc_ns(iter->ns);
883	put_pid_ns(iter->pid_ns);
884	return seq_release_private(inode, file);
885}
886
887static const struct file_operations sysvipc_proc_fops = {
888	.open    = sysvipc_proc_open,
889	.read    = seq_read,
890	.llseek  = seq_lseek,
891	.release = sysvipc_proc_release,
892};
893#endif /* CONFIG_PROC_FS */
894