Root/ipc/util.c

1/*
2 * linux/ipc/util.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 *
5 * Sep 1997 - Call suser() last after "normal" permission checks so we
6 * get BSD style process accounting right.
7 * Occurs in several places in the IPC code.
8 * Chris Evans, <chris@ferret.lmh.ox.ac.uk>
9 * Nov 1999 - ipc helper functions, unified SMP locking
10 * Manfred Spraul <manfred@colorfullife.com>
11 * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
12 * Mingming Cao <cmm@us.ibm.com>
13 * Mar 2006 - support for audit of ipc object properties
14 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
15 * Jun 2006 - namespaces ssupport
16 * OpenVZ, SWsoft Inc.
17 * Pavel Emelianov <xemul@openvz.org>
18 */
19
20#include <linux/mm.h>
21#include <linux/shm.h>
22#include <linux/init.h>
23#include <linux/msg.h>
24#include <linux/vmalloc.h>
25#include <linux/slab.h>
26#include <linux/capability.h>
27#include <linux/highuid.h>
28#include <linux/security.h>
29#include <linux/rcupdate.h>
30#include <linux/workqueue.h>
31#include <linux/seq_file.h>
32#include <linux/proc_fs.h>
33#include <linux/audit.h>
34#include <linux/nsproxy.h>
35#include <linux/rwsem.h>
36#include <linux/memory.h>
37#include <linux/ipc_namespace.h>
38
39#include <asm/unistd.h>
40
41#include "util.h"
42
43struct ipc_proc_iface {
44    const char *path;
45    const char *header;
46    int ids;
47    int (*show)(struct seq_file *, void *);
48};
49
50#ifdef CONFIG_MEMORY_HOTPLUG
51
52static void ipc_memory_notifier(struct work_struct *work)
53{
54    ipcns_notify(IPCNS_MEMCHANGED);
55}
56
57static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
58
59
60static int ipc_memory_callback(struct notifier_block *self,
61                unsigned long action, void *arg)
62{
63    switch (action) {
64    case MEM_ONLINE: /* memory successfully brought online */
65    case MEM_OFFLINE: /* or offline: it's time to recompute msgmni */
66        /*
67         * This is done by invoking the ipcns notifier chain with the
68         * IPC_MEMCHANGED event.
69         * In order not to keep the lock on the hotplug memory chain
70         * for too long, queue a work item that will, when waken up,
71         * activate the ipcns notification chain.
72         * No need to keep several ipc work items on the queue.
73         */
74        if (!work_pending(&ipc_memory_wq))
75            schedule_work(&ipc_memory_wq);
76        break;
77    case MEM_GOING_ONLINE:
78    case MEM_GOING_OFFLINE:
79    case MEM_CANCEL_ONLINE:
80    case MEM_CANCEL_OFFLINE:
81    default:
82        break;
83    }
84
85    return NOTIFY_OK;
86}
87
88#endif /* CONFIG_MEMORY_HOTPLUG */
89
90/**
91 * ipc_init - initialise IPC subsystem
92 *
93 * The various system5 IPC resources (semaphores, messages and shared
94 * memory) are initialised
95 * A callback routine is registered into the memory hotplug notifier
96 * chain: since msgmni scales to lowmem this callback routine will be
97 * called upon successful memory add / remove to recompute msmgni.
98 */
99 
100static int __init ipc_init(void)
101{
102    sem_init();
103    msg_init();
104    shm_init();
105    hotplug_memory_notifier(ipc_memory_callback, IPC_CALLBACK_PRI);
106    register_ipcns_notifier(&init_ipc_ns);
107    return 0;
108}
109__initcall(ipc_init);
110
111/**
112 * ipc_init_ids - initialise IPC identifiers
113 * @ids: Identifier set
114 *
115 * Set up the sequence range to use for the ipc identifier range (limited
116 * below IPCMNI) then initialise the ids idr.
117 */
118 
119void ipc_init_ids(struct ipc_ids *ids)
120{
121    init_rwsem(&ids->rw_mutex);
122
123    ids->in_use = 0;
124    ids->seq = 0;
125    {
126        int seq_limit = INT_MAX/SEQ_MULTIPLIER;
127        if (seq_limit > USHRT_MAX)
128            ids->seq_max = USHRT_MAX;
129         else
130             ids->seq_max = seq_limit;
131    }
132
133    idr_init(&ids->ipcs_idr);
134}
135
136#ifdef CONFIG_PROC_FS
137static const struct file_operations sysvipc_proc_fops;
138/**
139 * ipc_init_proc_interface - Create a proc interface for sysipc types using a seq_file interface.
140 * @path: Path in procfs
141 * @header: Banner to be printed at the beginning of the file.
142 * @ids: ipc id table to iterate.
143 * @show: show routine.
144 */
145void __init ipc_init_proc_interface(const char *path, const char *header,
146        int ids, int (*show)(struct seq_file *, void *))
147{
148    struct proc_dir_entry *pde;
149    struct ipc_proc_iface *iface;
150
151    iface = kmalloc(sizeof(*iface), GFP_KERNEL);
152    if (!iface)
153        return;
154    iface->path = path;
155    iface->header = header;
156    iface->ids = ids;
157    iface->show = show;
158
159    pde = proc_create_data(path,
160                   S_IRUGO, /* world readable */
161                   NULL, /* parent dir */
162                   &sysvipc_proc_fops,
163                   iface);
164    if (!pde) {
165        kfree(iface);
166    }
167}
168#endif
169
170/**
171 * ipc_findkey - find a key in an ipc identifier set
172 * @ids: Identifier set
173 * @key: The key to find
174 *
175 * Requires ipc_ids.rw_mutex locked.
176 * Returns the LOCKED pointer to the ipc structure if found or NULL
177 * if not.
178 * If key is found ipc points to the owning ipc structure
179 */
180 
181static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
182{
183    struct kern_ipc_perm *ipc;
184    int next_id;
185    int total;
186
187    for (total = 0, next_id = 0; total < ids->in_use; next_id++) {
188        ipc = idr_find(&ids->ipcs_idr, next_id);
189
190        if (ipc == NULL)
191            continue;
192
193        if (ipc->key != key) {
194            total++;
195            continue;
196        }
197
198        ipc_lock_by_ptr(ipc);
199        return ipc;
200    }
201
202    return NULL;
203}
204
205/**
206 * ipc_get_maxid - get the last assigned id
207 * @ids: IPC identifier set
208 *
209 * Called with ipc_ids.rw_mutex held.
210 */
211
212int ipc_get_maxid(struct ipc_ids *ids)
213{
214    struct kern_ipc_perm *ipc;
215    int max_id = -1;
216    int total, id;
217
218    if (ids->in_use == 0)
219        return -1;
220
221    if (ids->in_use == IPCMNI)
222        return IPCMNI - 1;
223
224    /* Look for the last assigned id */
225    total = 0;
226    for (id = 0; id < IPCMNI && total < ids->in_use; id++) {
227        ipc = idr_find(&ids->ipcs_idr, id);
228        if (ipc != NULL) {
229            max_id = id;
230            total++;
231        }
232    }
233    return max_id;
234}
235
236/**
237 * ipc_addid - add an IPC identifier
238 * @ids: IPC identifier set
239 * @new: new IPC permission set
240 * @size: limit for the number of used ids
241 *
242 * Add an entry 'new' to the IPC ids idr. The permissions object is
243 * initialised and the first free entry is set up and the id assigned
244 * is returned. The 'new' entry is returned in a locked state on success.
245 * On failure the entry is not locked and a negative err-code is returned.
246 *
247 * Called with ipc_ids.rw_mutex held as a writer.
248 */
249 
250int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
251{
252    uid_t euid;
253    gid_t egid;
254    int id, err;
255
256    if (size > IPCMNI)
257        size = IPCMNI;
258
259    if (ids->in_use >= size)
260        return -ENOSPC;
261
262    spin_lock_init(&new->lock);
263    new->deleted = 0;
264    rcu_read_lock();
265    spin_lock(&new->lock);
266
267    err = idr_get_new(&ids->ipcs_idr, new, &id);
268    if (err) {
269        spin_unlock(&new->lock);
270        rcu_read_unlock();
271        return err;
272    }
273
274    ids->in_use++;
275
276    current_euid_egid(&euid, &egid);
277    new->cuid = new->uid = euid;
278    new->gid = new->cgid = egid;
279
280    new->seq = ids->seq++;
281    if(ids->seq > ids->seq_max)
282        ids->seq = 0;
283
284    new->id = ipc_buildid(id, new->seq);
285    return id;
286}
287
288/**
289 * ipcget_new - create a new ipc object
290 * @ns: namespace
291 * @ids: IPC identifer set
292 * @ops: the actual creation routine to call
293 * @params: its parameters
294 *
295 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
296 * when the key is IPC_PRIVATE.
297 */
298static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
299        struct ipc_ops *ops, struct ipc_params *params)
300{
301    int err;
302retry:
303    err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
304
305    if (!err)
306        return -ENOMEM;
307
308    down_write(&ids->rw_mutex);
309    err = ops->getnew(ns, params);
310    up_write(&ids->rw_mutex);
311
312    if (err == -EAGAIN)
313        goto retry;
314
315    return err;
316}
317
318/**
319 * ipc_check_perms - check security and permissions for an IPC
320 * @ipcp: ipc permission set
321 * @ops: the actual security routine to call
322 * @params: its parameters
323 *
324 * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
325 * when the key is not IPC_PRIVATE and that key already exists in the
326 * ids IDR.
327 *
328 * On success, the IPC id is returned.
329 *
330 * It is called with ipc_ids.rw_mutex and ipcp->lock held.
331 */
332static int ipc_check_perms(struct kern_ipc_perm *ipcp, struct ipc_ops *ops,
333            struct ipc_params *params)
334{
335    int err;
336
337    if (ipcperms(ipcp, params->flg))
338        err = -EACCES;
339    else {
340        err = ops->associate(ipcp, params->flg);
341        if (!err)
342            err = ipcp->id;
343    }
344
345    return err;
346}
347
348/**
349 * ipcget_public - get an ipc object or create a new one
350 * @ns: namespace
351 * @ids: IPC identifer set
352 * @ops: the actual creation routine to call
353 * @params: its parameters
354 *
355 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
356 * when the key is not IPC_PRIVATE.
357 * It adds a new entry if the key is not found and does some permission
358 * / security checkings if the key is found.
359 *
360 * On success, the ipc id is returned.
361 */
362static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
363        struct ipc_ops *ops, struct ipc_params *params)
364{
365    struct kern_ipc_perm *ipcp;
366    int flg = params->flg;
367    int err;
368retry:
369    err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
370
371    /*
372     * Take the lock as a writer since we are potentially going to add
373     * a new entry + read locks are not "upgradable"
374     */
375    down_write(&ids->rw_mutex);
376    ipcp = ipc_findkey(ids, params->key);
377    if (ipcp == NULL) {
378        /* key not used */
379        if (!(flg & IPC_CREAT))
380            err = -ENOENT;
381        else if (!err)
382            err = -ENOMEM;
383        else
384            err = ops->getnew(ns, params);
385    } else {
386        /* ipc object has been locked by ipc_findkey() */
387
388        if (flg & IPC_CREAT && flg & IPC_EXCL)
389            err = -EEXIST;
390        else {
391            err = 0;
392            if (ops->more_checks)
393                err = ops->more_checks(ipcp, params);
394            if (!err)
395                /*
396                 * ipc_check_perms returns the IPC id on
397                 * success
398                 */
399                err = ipc_check_perms(ipcp, ops, params);
400        }
401        ipc_unlock(ipcp);
402    }
403    up_write(&ids->rw_mutex);
404
405    if (err == -EAGAIN)
406        goto retry;
407
408    return err;
409}
410
411
412/**
413 * ipc_rmid - remove an IPC identifier
414 * @ids: IPC identifier set
415 * @ipcp: ipc perm structure containing the identifier to remove
416 *
417 * ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held
418 * before this function is called, and remain locked on the exit.
419 */
420 
421void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
422{
423    int lid = ipcid_to_idx(ipcp->id);
424
425    idr_remove(&ids->ipcs_idr, lid);
426
427    ids->in_use--;
428
429    ipcp->deleted = 1;
430
431    return;
432}
433
434/**
435 * ipc_alloc - allocate ipc space
436 * @size: size desired
437 *
438 * Allocate memory from the appropriate pools and return a pointer to it.
439 * NULL is returned if the allocation fails
440 */
441 
442void* ipc_alloc(int size)
443{
444    void* out;
445    if(size > PAGE_SIZE)
446        out = vmalloc(size);
447    else
448        out = kmalloc(size, GFP_KERNEL);
449    return out;
450}
451
452/**
453 * ipc_free - free ipc space
454 * @ptr: pointer returned by ipc_alloc
455 * @size: size of block
456 *
457 * Free a block created with ipc_alloc(). The caller must know the size
458 * used in the allocation call.
459 */
460
461void ipc_free(void* ptr, int size)
462{
463    if(size > PAGE_SIZE)
464        vfree(ptr);
465    else
466        kfree(ptr);
467}
468
469/*
470 * rcu allocations:
471 * There are three headers that are prepended to the actual allocation:
472 * - during use: ipc_rcu_hdr.
473 * - during the rcu grace period: ipc_rcu_grace.
474 * - [only if vmalloc]: ipc_rcu_sched.
475 * Their lifetime doesn't overlap, thus the headers share the same memory.
476 * Unlike a normal union, they are right-aligned, thus some container_of
477 * forward/backward casting is necessary:
478 */
479struct ipc_rcu_hdr
480{
481    int refcount;
482    int is_vmalloc;
483    void *data[0];
484};
485
486
487struct ipc_rcu_grace
488{
489    struct rcu_head rcu;
490    /* "void *" makes sure alignment of following data is sane. */
491    void *data[0];
492};
493
494struct ipc_rcu_sched
495{
496    struct work_struct work;
497    /* "void *" makes sure alignment of following data is sane. */
498    void *data[0];
499};
500
501#define HDRLEN_KMALLOC (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
502                    sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
503#define HDRLEN_VMALLOC (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
504                    sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
505
506static inline int rcu_use_vmalloc(int size)
507{
508    /* Too big for a single page? */
509    if (HDRLEN_KMALLOC + size > PAGE_SIZE)
510        return 1;
511    return 0;
512}
513
514/**
515 * ipc_rcu_alloc - allocate ipc and rcu space
516 * @size: size desired
517 *
518 * Allocate memory for the rcu header structure + the object.
519 * Returns the pointer to the object.
520 * NULL is returned if the allocation fails.
521 */
522 
523void* ipc_rcu_alloc(int size)
524{
525    void* out;
526    /*
527     * We prepend the allocation with the rcu struct, and
528     * workqueue if necessary (for vmalloc).
529     */
530    if (rcu_use_vmalloc(size)) {
531        out = vmalloc(HDRLEN_VMALLOC + size);
532        if (out) {
533            out += HDRLEN_VMALLOC;
534            container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
535            container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
536        }
537    } else {
538        out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
539        if (out) {
540            out += HDRLEN_KMALLOC;
541            container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
542            container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
543        }
544    }
545
546    return out;
547}
548
549void ipc_rcu_getref(void *ptr)
550{
551    container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
552}
553
554static void ipc_do_vfree(struct work_struct *work)
555{
556    vfree(container_of(work, struct ipc_rcu_sched, work));
557}
558
559/**
560 * ipc_schedule_free - free ipc + rcu space
561 * @head: RCU callback structure for queued work
562 *
563 * Since RCU callback function is called in bh,
564 * we need to defer the vfree to schedule_work().
565 */
566static void ipc_schedule_free(struct rcu_head *head)
567{
568    struct ipc_rcu_grace *grace;
569    struct ipc_rcu_sched *sched;
570
571    grace = container_of(head, struct ipc_rcu_grace, rcu);
572    sched = container_of(&(grace->data[0]), struct ipc_rcu_sched,
573                data[0]);
574
575    INIT_WORK(&sched->work, ipc_do_vfree);
576    schedule_work(&sched->work);
577}
578
579/**
580 * ipc_immediate_free - free ipc + rcu space
581 * @head: RCU callback structure that contains pointer to be freed
582 *
583 * Free from the RCU callback context.
584 */
585static void ipc_immediate_free(struct rcu_head *head)
586{
587    struct ipc_rcu_grace *free =
588        container_of(head, struct ipc_rcu_grace, rcu);
589    kfree(free);
590}
591
592void ipc_rcu_putref(void *ptr)
593{
594    if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
595        return;
596
597    if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
598        call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
599                ipc_schedule_free);
600    } else {
601        call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
602                ipc_immediate_free);
603    }
604}
605
606/**
607 * ipcperms - check IPC permissions
608 * @ipcp: IPC permission set
609 * @flag: desired permission set.
610 *
611 * Check user, group, other permissions for access
612 * to ipc resources. return 0 if allowed
613 */
614 
615int ipcperms (struct kern_ipc_perm *ipcp, short flag)
616{ /* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
617    uid_t euid = current_euid();
618    int requested_mode, granted_mode;
619
620    audit_ipc_obj(ipcp);
621    requested_mode = (flag >> 6) | (flag >> 3) | flag;
622    granted_mode = ipcp->mode;
623    if (euid == ipcp->cuid ||
624        euid == ipcp->uid)
625        granted_mode >>= 6;
626    else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
627        granted_mode >>= 3;
628    /* is there some bit set in requested_mode but not in granted_mode? */
629    if ((requested_mode & ~granted_mode & 0007) &&
630        !capable(CAP_IPC_OWNER))
631        return -1;
632
633    return security_ipc_permission(ipcp, flag);
634}
635
636/*
637 * Functions to convert between the kern_ipc_perm structure and the
638 * old/new ipc_perm structures
639 */
640
641/**
642 * kernel_to_ipc64_perm - convert kernel ipc permissions to user
643 * @in: kernel permissions
644 * @out: new style IPC permissions
645 *
646 * Turn the kernel object @in into a set of permissions descriptions
647 * for returning to userspace (@out).
648 */
649 
650
651void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
652{
653    out->key = in->key;
654    out->uid = in->uid;
655    out->gid = in->gid;
656    out->cuid = in->cuid;
657    out->cgid = in->cgid;
658    out->mode = in->mode;
659    out->seq = in->seq;
660}
661
662/**
663 * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
664 * @in: new style IPC permissions
665 * @out: old style IPC permissions
666 *
667 * Turn the new style permissions object @in into a compatibility
668 * object and store it into the @out pointer.
669 */
670 
671void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
672{
673    out->key = in->key;
674    SET_UID(out->uid, in->uid);
675    SET_GID(out->gid, in->gid);
676    SET_UID(out->cuid, in->cuid);
677    SET_GID(out->cgid, in->cgid);
678    out->mode = in->mode;
679    out->seq = in->seq;
680}
681
682/**
683 * ipc_lock - Lock an ipc structure without rw_mutex held
684 * @ids: IPC identifier set
685 * @id: ipc id to look for
686 *
687 * Look for an id in the ipc ids idr and lock the associated ipc object.
688 *
689 * The ipc object is locked on exit.
690 */
691
692struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
693{
694    struct kern_ipc_perm *out;
695    int lid = ipcid_to_idx(id);
696
697    rcu_read_lock();
698    out = idr_find(&ids->ipcs_idr, lid);
699    if (out == NULL) {
700        rcu_read_unlock();
701        return ERR_PTR(-EINVAL);
702    }
703
704    spin_lock(&out->lock);
705    
706    /* ipc_rmid() may have already freed the ID while ipc_lock
707     * was spinning: here verify that the structure is still valid
708     */
709    if (out->deleted) {
710        spin_unlock(&out->lock);
711        rcu_read_unlock();
712        return ERR_PTR(-EINVAL);
713    }
714
715    return out;
716}
717
718struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
719{
720    struct kern_ipc_perm *out;
721
722    out = ipc_lock(ids, id);
723    if (IS_ERR(out))
724        return out;
725
726    if (ipc_checkid(out, id)) {
727        ipc_unlock(out);
728        return ERR_PTR(-EIDRM);
729    }
730
731    return out;
732}
733
734/**
735 * ipcget - Common sys_*get() code
736 * @ns : namsepace
737 * @ids : IPC identifier set
738 * @ops : operations to be called on ipc object creation, permission checks
739 * and further checks
740 * @params : the parameters needed by the previous operations.
741 *
742 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
743 */
744int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
745            struct ipc_ops *ops, struct ipc_params *params)
746{
747    if (params->key == IPC_PRIVATE)
748        return ipcget_new(ns, ids, ops, params);
749    else
750        return ipcget_public(ns, ids, ops, params);
751}
752
753/**
754 * ipc_update_perm - update the permissions of an IPC.
755 * @in: the permission given as input.
756 * @out: the permission of the ipc to set.
757 */
758void ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
759{
760    out->uid = in->uid;
761    out->gid = in->gid;
762    out->mode = (out->mode & ~S_IRWXUGO)
763        | (in->mode & S_IRWXUGO);
764}
765
766/**
767 * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
768 * @ids: the table of ids where to look for the ipc
769 * @id: the id of the ipc to retrieve
770 * @cmd: the cmd to check
771 * @perm: the permission to set
772 * @extra_perm: one extra permission parameter used by msq
773 *
774 * This function does some common audit and permissions check for some IPC_XXX
775 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
776 * It must be called without any lock held and
777 * - retrieves the ipc with the given id in the given table.
778 * - performs some audit and permission check, depending on the given cmd
779 * - returns the ipc with both ipc and rw_mutex locks held in case of success
780 * or an err-code without any lock held otherwise.
781 */
782struct kern_ipc_perm *ipcctl_pre_down(struct ipc_ids *ids, int id, int cmd,
783                      struct ipc64_perm *perm, int extra_perm)
784{
785    struct kern_ipc_perm *ipcp;
786    uid_t euid;
787    int err;
788
789    down_write(&ids->rw_mutex);
790    ipcp = ipc_lock_check(ids, id);
791    if (IS_ERR(ipcp)) {
792        err = PTR_ERR(ipcp);
793        goto out_up;
794    }
795
796    audit_ipc_obj(ipcp);
797    if (cmd == IPC_SET)
798        audit_ipc_set_perm(extra_perm, perm->uid,
799                     perm->gid, perm->mode);
800
801    euid = current_euid();
802    if (euid == ipcp->cuid ||
803        euid == ipcp->uid || capable(CAP_SYS_ADMIN))
804        return ipcp;
805
806    err = -EPERM;
807    ipc_unlock(ipcp);
808out_up:
809    up_write(&ids->rw_mutex);
810    return ERR_PTR(err);
811}
812
813#ifdef __ARCH_WANT_IPC_PARSE_VERSION
814
815
816/**
817 * ipc_parse_version - IPC call version
818 * @cmd: pointer to command
819 *
820 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
821 * The @cmd value is turned from an encoding command and version into
822 * just the command code.
823 */
824 
825int ipc_parse_version (int *cmd)
826{
827    if (*cmd & IPC_64) {
828        *cmd ^= IPC_64;
829        return IPC_64;
830    } else {
831        return IPC_OLD;
832    }
833}
834
835#endif /* __ARCH_WANT_IPC_PARSE_VERSION */
836
837#ifdef CONFIG_PROC_FS
838struct ipc_proc_iter {
839    struct ipc_namespace *ns;
840    struct ipc_proc_iface *iface;
841};
842
843/*
844 * This routine locks the ipc structure found at least at position pos.
845 */
846static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
847                          loff_t *new_pos)
848{
849    struct kern_ipc_perm *ipc;
850    int total, id;
851
852    total = 0;
853    for (id = 0; id < pos && total < ids->in_use; id++) {
854        ipc = idr_find(&ids->ipcs_idr, id);
855        if (ipc != NULL)
856            total++;
857    }
858
859    if (total >= ids->in_use)
860        return NULL;
861
862    for ( ; pos < IPCMNI; pos++) {
863        ipc = idr_find(&ids->ipcs_idr, pos);
864        if (ipc != NULL) {
865            *new_pos = pos + 1;
866            ipc_lock_by_ptr(ipc);
867            return ipc;
868        }
869    }
870
871    /* Out of range - return NULL to terminate iteration */
872    return NULL;
873}
874
875static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
876{
877    struct ipc_proc_iter *iter = s->private;
878    struct ipc_proc_iface *iface = iter->iface;
879    struct kern_ipc_perm *ipc = it;
880
881    /* If we had an ipc id locked before, unlock it */
882    if (ipc && ipc != SEQ_START_TOKEN)
883        ipc_unlock(ipc);
884
885    return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
886}
887
888/*
889 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
890 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
891 */
892static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
893{
894    struct ipc_proc_iter *iter = s->private;
895    struct ipc_proc_iface *iface = iter->iface;
896    struct ipc_ids *ids;
897
898    ids = &iter->ns->ids[iface->ids];
899
900    /*
901     * Take the lock - this will be released by the corresponding
902     * call to stop().
903     */
904    down_read(&ids->rw_mutex);
905
906    /* pos < 0 is invalid */
907    if (*pos < 0)
908        return NULL;
909
910    /* pos == 0 means header */
911    if (*pos == 0)
912        return SEQ_START_TOKEN;
913
914    /* Find the (pos-1)th ipc */
915    return sysvipc_find_ipc(ids, *pos - 1, pos);
916}
917
918static void sysvipc_proc_stop(struct seq_file *s, void *it)
919{
920    struct kern_ipc_perm *ipc = it;
921    struct ipc_proc_iter *iter = s->private;
922    struct ipc_proc_iface *iface = iter->iface;
923    struct ipc_ids *ids;
924
925    /* If we had a locked structure, release it */
926    if (ipc && ipc != SEQ_START_TOKEN)
927        ipc_unlock(ipc);
928
929    ids = &iter->ns->ids[iface->ids];
930    /* Release the lock we took in start() */
931    up_read(&ids->rw_mutex);
932}
933
934static int sysvipc_proc_show(struct seq_file *s, void *it)
935{
936    struct ipc_proc_iter *iter = s->private;
937    struct ipc_proc_iface *iface = iter->iface;
938
939    if (it == SEQ_START_TOKEN)
940        return seq_puts(s, iface->header);
941
942    return iface->show(s, it);
943}
944
945static const struct seq_operations sysvipc_proc_seqops = {
946    .start = sysvipc_proc_start,
947    .stop = sysvipc_proc_stop,
948    .next = sysvipc_proc_next,
949    .show = sysvipc_proc_show,
950};
951
952static int sysvipc_proc_open(struct inode *inode, struct file *file)
953{
954    int ret;
955    struct seq_file *seq;
956    struct ipc_proc_iter *iter;
957
958    ret = -ENOMEM;
959    iter = kmalloc(sizeof(*iter), GFP_KERNEL);
960    if (!iter)
961        goto out;
962
963    ret = seq_open(file, &sysvipc_proc_seqops);
964    if (ret)
965        goto out_kfree;
966
967    seq = file->private_data;
968    seq->private = iter;
969
970    iter->iface = PDE(inode)->data;
971    iter->ns = get_ipc_ns(current->nsproxy->ipc_ns);
972out:
973    return ret;
974out_kfree:
975    kfree(iter);
976    goto out;
977}
978
979static int sysvipc_proc_release(struct inode *inode, struct file *file)
980{
981    struct seq_file *seq = file->private_data;
982    struct ipc_proc_iter *iter = seq->private;
983    put_ipc_ns(iter->ns);
984    return seq_release_private(inode, file);
985}
986
987static const struct file_operations sysvipc_proc_fops = {
988    .open = sysvipc_proc_open,
989    .read = seq_read,
990    .llseek = seq_lseek,
991    .release = sysvipc_proc_release,
992};
993#endif /* CONFIG_PROC_FS */
994

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