util.c revision 0cfb6aee
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 * General sysv ipc locking scheme:
20 *	rcu_read_lock()
21 *          obtain the ipc object (kern_ipc_perm) by looking up the id in an idr
22 *	    tree.
23 *	    - perform initial checks (capabilities, auditing and permission,
24 *	      etc).
25 *	    - perform read-only operations, such as STAT, INFO commands.
26 *	      acquire the ipc lock (kern_ipc_perm.lock) through
27 *	      ipc_lock_object()
28 *		- perform data updates, such as SET, RMID commands and
29 *		  mechanism-specific operations (semop/semtimedop,
30 *		  msgsnd/msgrcv, shmat/shmdt).
31 *	    drop the ipc lock, through ipc_unlock_object().
32 *	rcu_read_unlock()
33 *
34 *  The ids->rwsem must be taken when:
35 *	- creating, removing and iterating the existing entries in ipc
36 *	  identifier sets.
37 *	- iterating through files under /proc/sysvipc/
38 *
39 *  Note that sems have a special fast path that avoids kern_ipc_perm.lock -
40 *  see sem_lock().
41 */
42
43#include <linux/mm.h>
44#include <linux/shm.h>
45#include <linux/init.h>
46#include <linux/msg.h>
47#include <linux/vmalloc.h>
48#include <linux/slab.h>
49#include <linux/notifier.h>
50#include <linux/capability.h>
51#include <linux/highuid.h>
52#include <linux/security.h>
53#include <linux/rcupdate.h>
54#include <linux/workqueue.h>
55#include <linux/seq_file.h>
56#include <linux/proc_fs.h>
57#include <linux/audit.h>
58#include <linux/nsproxy.h>
59#include <linux/rwsem.h>
60#include <linux/memory.h>
61#include <linux/ipc_namespace.h>
62
63#include <asm/unistd.h>
64
65#include "util.h"
66
67struct ipc_proc_iface {
68	const char *path;
69	const char *header;
70	int ids;
71	int (*show)(struct seq_file *, void *);
72};
73
74/**
75 * ipc_init - initialise ipc subsystem
76 *
77 * The various sysv ipc resources (semaphores, messages and shared
78 * memory) are initialised.
79 *
80 * A callback routine is registered into the memory hotplug notifier
81 * chain: since msgmni scales to lowmem this callback routine will be
82 * called upon successful memory add / remove to recompute msmgni.
83 */
84static int __init ipc_init(void)
85{
86	int err_sem, err_msg;
87
88	err_sem = sem_init();
89	WARN(err_sem, "ipc: sysv sem_init failed: %d\n", err_sem);
90	err_msg = msg_init();
91	WARN(err_msg, "ipc: sysv msg_init failed: %d\n", err_msg);
92	shm_init();
93
94	return err_msg ? err_msg : err_sem;
95}
96device_initcall(ipc_init);
97
98static const struct rhashtable_params ipc_kht_params = {
99	.head_offset		= offsetof(struct kern_ipc_perm, khtnode),
100	.key_offset		= offsetof(struct kern_ipc_perm, key),
101	.key_len		= FIELD_SIZEOF(struct kern_ipc_perm, key),
102	.locks_mul		= 1,
103	.automatic_shrinking	= true,
104};
105
106/**
107 * ipc_init_ids	- initialise ipc identifiers
108 * @ids: ipc identifier set
109 *
110 * Set up the sequence range to use for the ipc identifier range (limited
111 * below IPCMNI) then initialise the keys hashtable and ids idr.
112 */
113int ipc_init_ids(struct ipc_ids *ids)
114{
115	int err;
116	ids->in_use = 0;
117	ids->seq = 0;
118	ids->next_id = -1;
119	init_rwsem(&ids->rwsem);
120	err = rhashtable_init(&ids->key_ht, &ipc_kht_params);
121	if (err)
122		return err;
123	idr_init(&ids->ipcs_idr);
124	ids->tables_initialized = true;
125	return 0;
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 = NULL;
174
175	if (likely(ids->tables_initialized))
176		ipcp = rhashtable_lookup_fast(&ids->key_ht, &key,
177					      ipc_kht_params);
178
179	if (ipcp) {
180		rcu_read_lock();
181		ipc_lock_object(ipcp);
182		return ipcp;
183	}
184
185	return NULL;
186}
187
188/**
189 * ipc_get_maxid - get the last assigned id
190 * @ids: ipc identifier set
191 *
192 * Called with ipc_ids.rwsem held.
193 */
194int ipc_get_maxid(struct ipc_ids *ids)
195{
196	struct kern_ipc_perm *ipc;
197	int max_id = -1;
198	int total, id;
199
200	if (ids->in_use == 0)
201		return -1;
202
203	if (ids->in_use == IPCMNI)
204		return IPCMNI - 1;
205
206	/* Look for the last assigned id */
207	total = 0;
208	for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
209		ipc = idr_find(&ids->ipcs_idr, id);
210		if (ipc != NULL) {
211			max_id = id;
212			total++;
213		}
214	}
215	return max_id;
216}
217
218/**
219 * ipc_addid - add an ipc identifier
220 * @ids: ipc identifier set
221 * @new: new ipc permission set
222 * @size: limit for the number of used ids
223 *
224 * Add an entry 'new' to the ipc ids idr. The permissions object is
225 * initialised and the first free entry is set up and the id assigned
226 * is returned. The 'new' entry is returned in a locked state on success.
227 * On failure the entry is not locked and a negative err-code is returned.
228 *
229 * Called with writer ipc_ids.rwsem held.
230 */
231int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int size)
232{
233	kuid_t euid;
234	kgid_t egid;
235	int id, err;
236	int next_id = ids->next_id;
237
238	if (size > IPCMNI)
239		size = IPCMNI;
240
241	if (!ids->tables_initialized || ids->in_use >= size)
242		return -ENOSPC;
243
244	idr_preload(GFP_KERNEL);
245
246	refcount_set(&new->refcount, 1);
247	spin_lock_init(&new->lock);
248	new->deleted = false;
249	rcu_read_lock();
250	spin_lock(&new->lock);
251
252	current_euid_egid(&euid, &egid);
253	new->cuid = new->uid = euid;
254	new->gid = new->cgid = egid;
255
256	id = idr_alloc(&ids->ipcs_idr, new,
257		       (next_id < 0) ? 0 : ipcid_to_idx(next_id), 0,
258		       GFP_NOWAIT);
259	idr_preload_end();
260
261	if (id >= 0 && new->key != IPC_PRIVATE) {
262		err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,
263					     ipc_kht_params);
264		if (err < 0) {
265			idr_remove(&ids->ipcs_idr, id);
266			id = err;
267		}
268	}
269	if (id < 0) {
270		spin_unlock(&new->lock);
271		rcu_read_unlock();
272		return id;
273	}
274
275	ids->in_use++;
276
277	if (next_id < 0) {
278		new->seq = ids->seq++;
279		if (ids->seq > IPCID_SEQ_MAX)
280			ids->seq = 0;
281	} else {
282		new->seq = ipcid_to_seqx(next_id);
283		ids->next_id = -1;
284	}
285
286	new->id = ipc_buildid(id, new->seq);
287	return id;
288}
289
290/**
291 * ipcget_new -	create a new ipc object
292 * @ns: ipc namespace
293 * @ids: ipc identifier set
294 * @ops: the actual creation routine to call
295 * @params: its parameters
296 *
297 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
298 * when the key is IPC_PRIVATE.
299 */
300static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
301		const struct ipc_ops *ops, struct ipc_params *params)
302{
303	int err;
304
305	down_write(&ids->rwsem);
306	err = ops->getnew(ns, params);
307	up_write(&ids->rwsem);
308	return err;
309}
310
311/**
312 * ipc_check_perms - check security and permissions for an ipc object
313 * @ns: ipc namespace
314 * @ipcp: ipc permission set
315 * @ops: the actual security routine to call
316 * @params: its parameters
317 *
318 * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
319 * when the key is not IPC_PRIVATE and that key already exists in the
320 * ds IDR.
321 *
322 * On success, the ipc id is returned.
323 *
324 * It is called with ipc_ids.rwsem and ipcp->lock held.
325 */
326static int ipc_check_perms(struct ipc_namespace *ns,
327			   struct kern_ipc_perm *ipcp,
328			   const struct ipc_ops *ops,
329			   struct ipc_params *params)
330{
331	int err;
332
333	if (ipcperms(ns, ipcp, params->flg))
334		err = -EACCES;
335	else {
336		err = ops->associate(ipcp, params->flg);
337		if (!err)
338			err = ipcp->id;
339	}
340
341	return err;
342}
343
344/**
345 * ipcget_public - get an ipc object or create a new one
346 * @ns: ipc namespace
347 * @ids: ipc identifier set
348 * @ops: the actual creation routine to call
349 * @params: its parameters
350 *
351 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
352 * when the key is not IPC_PRIVATE.
353 * It adds a new entry if the key is not found and does some permission
354 * / security checkings if the key is found.
355 *
356 * On success, the ipc id is returned.
357 */
358static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
359		const struct ipc_ops *ops, struct ipc_params *params)
360{
361	struct kern_ipc_perm *ipcp;
362	int flg = params->flg;
363	int err;
364
365	/*
366	 * Take the lock as a writer since we are potentially going to add
367	 * a new entry + read locks are not "upgradable"
368	 */
369	down_write(&ids->rwsem);
370	ipcp = ipc_findkey(ids, params->key);
371	if (ipcp == NULL) {
372		/* key not used */
373		if (!(flg & IPC_CREAT))
374			err = -ENOENT;
375		else
376			err = ops->getnew(ns, params);
377	} else {
378		/* ipc object has been locked by ipc_findkey() */
379
380		if (flg & IPC_CREAT && flg & IPC_EXCL)
381			err = -EEXIST;
382		else {
383			err = 0;
384			if (ops->more_checks)
385				err = ops->more_checks(ipcp, params);
386			if (!err)
387				/*
388				 * ipc_check_perms returns the IPC id on
389				 * success
390				 */
391				err = ipc_check_perms(ns, ipcp, ops, params);
392		}
393		ipc_unlock(ipcp);
394	}
395	up_write(&ids->rwsem);
396
397	return err;
398}
399
400/**
401 * ipc_kht_remove - remove an ipc from the key hashtable
402 * @ids: ipc identifier set
403 * @ipcp: ipc perm structure containing the key to remove
404 *
405 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
406 * before this function is called, and remain locked on the exit.
407 */
408static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
409{
410	if (ipcp->key != IPC_PRIVATE)
411		rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
412				       ipc_kht_params);
413}
414
415/**
416 * ipc_rmid - remove an ipc identifier
417 * @ids: ipc identifier set
418 * @ipcp: ipc perm structure containing the identifier to remove
419 *
420 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
421 * before this function is called, and remain locked on the exit.
422 */
423void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
424{
425	int lid = ipcid_to_idx(ipcp->id);
426
427	idr_remove(&ids->ipcs_idr, lid);
428	ipc_kht_remove(ids, ipcp);
429	ids->in_use--;
430	ipcp->deleted = true;
431}
432
433/**
434 * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE
435 * @ids: ipc identifier set
436 * @ipcp: ipc perm structure containing the key to modify
437 *
438 * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
439 * before this function is called, and remain locked on the exit.
440 */
441void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
442{
443	ipc_kht_remove(ids, ipcp);
444	ipcp->key = IPC_PRIVATE;
445}
446
447int ipc_rcu_getref(struct kern_ipc_perm *ptr)
448{
449	return refcount_inc_not_zero(&ptr->refcount);
450}
451
452void ipc_rcu_putref(struct kern_ipc_perm *ptr,
453			void (*func)(struct rcu_head *head))
454{
455	if (!refcount_dec_and_test(&ptr->refcount))
456		return;
457
458	call_rcu(&ptr->rcu, func);
459}
460
461/**
462 * ipcperms - check ipc permissions
463 * @ns: ipc namespace
464 * @ipcp: ipc permission set
465 * @flag: desired permission set
466 *
467 * Check user, group, other permissions for access
468 * to ipc resources. return 0 if allowed
469 *
470 * @flag will most probably be 0 or ``S_...UGO`` from <linux/stat.h>
471 */
472int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
473{
474	kuid_t euid = current_euid();
475	int requested_mode, granted_mode;
476
477	audit_ipc_obj(ipcp);
478	requested_mode = (flag >> 6) | (flag >> 3) | flag;
479	granted_mode = ipcp->mode;
480	if (uid_eq(euid, ipcp->cuid) ||
481	    uid_eq(euid, ipcp->uid))
482		granted_mode >>= 6;
483	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
484		granted_mode >>= 3;
485	/* is there some bit set in requested_mode but not in granted_mode? */
486	if ((requested_mode & ~granted_mode & 0007) &&
487	    !ns_capable(ns->user_ns, CAP_IPC_OWNER))
488		return -1;
489
490	return security_ipc_permission(ipcp, flag);
491}
492
493/*
494 * Functions to convert between the kern_ipc_perm structure and the
495 * old/new ipc_perm structures
496 */
497
498/**
499 * kernel_to_ipc64_perm	- convert kernel ipc permissions to user
500 * @in: kernel permissions
501 * @out: new style ipc permissions
502 *
503 * Turn the kernel object @in into a set of permissions descriptions
504 * for returning to userspace (@out).
505 */
506void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)
507{
508	out->key	= in->key;
509	out->uid	= from_kuid_munged(current_user_ns(), in->uid);
510	out->gid	= from_kgid_munged(current_user_ns(), in->gid);
511	out->cuid	= from_kuid_munged(current_user_ns(), in->cuid);
512	out->cgid	= from_kgid_munged(current_user_ns(), in->cgid);
513	out->mode	= in->mode;
514	out->seq	= in->seq;
515}
516
517/**
518 * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
519 * @in: new style ipc permissions
520 * @out: old style ipc permissions
521 *
522 * Turn the new style permissions object @in into a compatibility
523 * object and store it into the @out pointer.
524 */
525void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
526{
527	out->key	= in->key;
528	SET_UID(out->uid, in->uid);
529	SET_GID(out->gid, in->gid);
530	SET_UID(out->cuid, in->cuid);
531	SET_GID(out->cgid, in->cgid);
532	out->mode	= in->mode;
533	out->seq	= in->seq;
534}
535
536/**
537 * ipc_obtain_object_idr
538 * @ids: ipc identifier set
539 * @id: ipc id to look for
540 *
541 * Look for an id in the ipc ids idr and return associated ipc object.
542 *
543 * Call inside the RCU critical section.
544 * The ipc object is *not* locked on exit.
545 */
546struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
547{
548	struct kern_ipc_perm *out;
549	int lid = ipcid_to_idx(id);
550
551	if (unlikely(!ids->tables_initialized))
552		return ERR_PTR(-EINVAL);
553
554	out = idr_find(&ids->ipcs_idr, lid);
555	if (!out)
556		return ERR_PTR(-EINVAL);
557
558	return out;
559}
560
561/**
562 * ipc_lock - lock an ipc structure without rwsem held
563 * @ids: ipc identifier set
564 * @id: ipc id to look for
565 *
566 * Look for an id in the ipc ids idr and lock the associated ipc object.
567 *
568 * The ipc object is locked on successful exit.
569 */
570struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
571{
572	struct kern_ipc_perm *out;
573
574	rcu_read_lock();
575	out = ipc_obtain_object_idr(ids, id);
576	if (IS_ERR(out))
577		goto err;
578
579	spin_lock(&out->lock);
580
581	/*
582	 * ipc_rmid() may have already freed the ID while ipc_lock()
583	 * was spinning: here verify that the structure is still valid.
584	 * Upon races with RMID, return -EIDRM, thus indicating that
585	 * the ID points to a removed identifier.
586	 */
587	if (ipc_valid_object(out))
588		return out;
589
590	spin_unlock(&out->lock);
591	out = ERR_PTR(-EIDRM);
592err:
593	rcu_read_unlock();
594	return out;
595}
596
597/**
598 * ipc_obtain_object_check
599 * @ids: ipc identifier set
600 * @id: ipc id to look for
601 *
602 * Similar to ipc_obtain_object_idr() but also checks
603 * the ipc object reference counter.
604 *
605 * Call inside the RCU critical section.
606 * The ipc object is *not* locked on exit.
607 */
608struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
609{
610	struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id);
611
612	if (IS_ERR(out))
613		goto out;
614
615	if (ipc_checkid(out, id))
616		return ERR_PTR(-EINVAL);
617out:
618	return out;
619}
620
621/**
622 * ipcget - Common sys_*get() code
623 * @ns: namespace
624 * @ids: ipc identifier set
625 * @ops: operations to be called on ipc object creation, permission checks
626 *       and further checks
627 * @params: the parameters needed by the previous operations.
628 *
629 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
630 */
631int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
632			const struct ipc_ops *ops, struct ipc_params *params)
633{
634	if (params->key == IPC_PRIVATE)
635		return ipcget_new(ns, ids, ops, params);
636	else
637		return ipcget_public(ns, ids, ops, params);
638}
639
640/**
641 * ipc_update_perm - update the permissions of an ipc object
642 * @in:  the permission given as input.
643 * @out: the permission of the ipc to set.
644 */
645int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
646{
647	kuid_t uid = make_kuid(current_user_ns(), in->uid);
648	kgid_t gid = make_kgid(current_user_ns(), in->gid);
649	if (!uid_valid(uid) || !gid_valid(gid))
650		return -EINVAL;
651
652	out->uid = uid;
653	out->gid = gid;
654	out->mode = (out->mode & ~S_IRWXUGO)
655		| (in->mode & S_IRWXUGO);
656
657	return 0;
658}
659
660/**
661 * ipcctl_pre_down_nolock - retrieve an ipc and check permissions for some IPC_XXX cmd
662 * @ns:  ipc namespace
663 * @ids:  the table of ids where to look for the ipc
664 * @id:   the id of the ipc to retrieve
665 * @cmd:  the cmd to check
666 * @perm: the permission to set
667 * @extra_perm: one extra permission parameter used by msq
668 *
669 * This function does some common audit and permissions check for some IPC_XXX
670 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
671 * It must be called without any lock held and:
672 *
673 *   - retrieves the ipc with the given id in the given table.
674 *   - performs some audit and permission check, depending on the given cmd
675 *   - returns a pointer to the ipc object or otherwise, the corresponding
676 *     error.
677 *
678 * Call holding the both the rwsem and the rcu read lock.
679 */
680struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
681					struct ipc_ids *ids, int id, int cmd,
682					struct ipc64_perm *perm, int extra_perm)
683{
684	kuid_t euid;
685	int err = -EPERM;
686	struct kern_ipc_perm *ipcp;
687
688	ipcp = ipc_obtain_object_check(ids, id);
689	if (IS_ERR(ipcp)) {
690		err = PTR_ERR(ipcp);
691		goto err;
692	}
693
694	audit_ipc_obj(ipcp);
695	if (cmd == IPC_SET)
696		audit_ipc_set_perm(extra_perm, perm->uid,
697				   perm->gid, perm->mode);
698
699	euid = current_euid();
700	if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
701	    ns_capable(ns->user_ns, CAP_SYS_ADMIN))
702		return ipcp; /* successful lookup */
703err:
704	return ERR_PTR(err);
705}
706
707#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
708
709
710/**
711 * ipc_parse_version - ipc call version
712 * @cmd: pointer to command
713 *
714 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
715 * The @cmd value is turned from an encoding command and version into
716 * just the command code.
717 */
718int ipc_parse_version(int *cmd)
719{
720	if (*cmd & IPC_64) {
721		*cmd ^= IPC_64;
722		return IPC_64;
723	} else {
724		return IPC_OLD;
725	}
726}
727
728#endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
729
730#ifdef CONFIG_PROC_FS
731struct ipc_proc_iter {
732	struct ipc_namespace *ns;
733	struct ipc_proc_iface *iface;
734};
735
736/*
737 * This routine locks the ipc structure found at least at position pos.
738 */
739static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
740					      loff_t *new_pos)
741{
742	struct kern_ipc_perm *ipc;
743	int total, id;
744
745	total = 0;
746	for (id = 0; id < pos && total < ids->in_use; id++) {
747		ipc = idr_find(&ids->ipcs_idr, id);
748		if (ipc != NULL)
749			total++;
750	}
751
752	if (total >= ids->in_use)
753		return NULL;
754
755	for (; pos < IPCMNI; pos++) {
756		ipc = idr_find(&ids->ipcs_idr, pos);
757		if (ipc != NULL) {
758			*new_pos = pos + 1;
759			rcu_read_lock();
760			ipc_lock_object(ipc);
761			return ipc;
762		}
763	}
764
765	/* Out of range - return NULL to terminate iteration */
766	return NULL;
767}
768
769static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
770{
771	struct ipc_proc_iter *iter = s->private;
772	struct ipc_proc_iface *iface = iter->iface;
773	struct kern_ipc_perm *ipc = it;
774
775	/* If we had an ipc id locked before, unlock it */
776	if (ipc && ipc != SEQ_START_TOKEN)
777		ipc_unlock(ipc);
778
779	return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
780}
781
782/*
783 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
784 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
785 */
786static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
787{
788	struct ipc_proc_iter *iter = s->private;
789	struct ipc_proc_iface *iface = iter->iface;
790	struct ipc_ids *ids;
791
792	ids = &iter->ns->ids[iface->ids];
793
794	/*
795	 * Take the lock - this will be released by the corresponding
796	 * call to stop().
797	 */
798	down_read(&ids->rwsem);
799
800	/* pos < 0 is invalid */
801	if (*pos < 0)
802		return NULL;
803
804	/* pos == 0 means header */
805	if (*pos == 0)
806		return SEQ_START_TOKEN;
807
808	/* Find the (pos-1)th ipc */
809	return sysvipc_find_ipc(ids, *pos - 1, pos);
810}
811
812static void sysvipc_proc_stop(struct seq_file *s, void *it)
813{
814	struct kern_ipc_perm *ipc = it;
815	struct ipc_proc_iter *iter = s->private;
816	struct ipc_proc_iface *iface = iter->iface;
817	struct ipc_ids *ids;
818
819	/* If we had a locked structure, release it */
820	if (ipc && ipc != SEQ_START_TOKEN)
821		ipc_unlock(ipc);
822
823	ids = &iter->ns->ids[iface->ids];
824	/* Release the lock we took in start() */
825	up_read(&ids->rwsem);
826}
827
828static int sysvipc_proc_show(struct seq_file *s, void *it)
829{
830	struct ipc_proc_iter *iter = s->private;
831	struct ipc_proc_iface *iface = iter->iface;
832
833	if (it == SEQ_START_TOKEN) {
834		seq_puts(s, iface->header);
835		return 0;
836	}
837
838	return iface->show(s, it);
839}
840
841static const struct seq_operations sysvipc_proc_seqops = {
842	.start = sysvipc_proc_start,
843	.stop  = sysvipc_proc_stop,
844	.next  = sysvipc_proc_next,
845	.show  = sysvipc_proc_show,
846};
847
848static int sysvipc_proc_open(struct inode *inode, struct file *file)
849{
850	struct ipc_proc_iter *iter;
851
852	iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter));
853	if (!iter)
854		return -ENOMEM;
855
856	iter->iface = PDE_DATA(inode);
857	iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
858
859	return 0;
860}
861
862static int sysvipc_proc_release(struct inode *inode, struct file *file)
863{
864	struct seq_file *seq = file->private_data;
865	struct ipc_proc_iter *iter = seq->private;
866	put_ipc_ns(iter->ns);
867	return seq_release_private(inode, file);
868}
869
870static const struct file_operations sysvipc_proc_fops = {
871	.open    = sysvipc_proc_open,
872	.read    = seq_read,
873	.llseek  = seq_lseek,
874	.release = sysvipc_proc_release,
875};
876#endif /* CONFIG_PROC_FS */
877