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 * @ns: IPC namespace
321 * @ipcp: ipc permission set
322 * @ops: the actual security routine to call
323 * @params: its parameters
324 *
325 * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
326 * when the key is not IPC_PRIVATE and that key already exists in the
327 * ids IDR.
328 *
329 * On success, the IPC id is returned.
330 *
331 * It is called with ipc_ids.rw_mutex and ipcp->lock held.
332 */
333static int ipc_check_perms(struct ipc_namespace *ns,
334               struct kern_ipc_perm *ipcp,
335               struct ipc_ops *ops,
336               struct ipc_params *params)
337{
338    int err;
339
340    if (ipcperms(ns, ipcp, params->flg))
341        err = -EACCES;
342    else {
343        err = ops->associate(ipcp, params->flg);
344        if (!err)
345            err = ipcp->id;
346    }
347
348    return err;
349}
350
351/**
352 * ipcget_public - get an ipc object or create a new one
353 * @ns: namespace
354 * @ids: IPC identifer set
355 * @ops: the actual creation routine to call
356 * @params: its parameters
357 *
358 * This routine is called by sys_msgget, sys_semget() and sys_shmget()
359 * when the key is not IPC_PRIVATE.
360 * It adds a new entry if the key is not found and does some permission
361 * / security checkings if the key is found.
362 *
363 * On success, the ipc id is returned.
364 */
365static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
366        struct ipc_ops *ops, struct ipc_params *params)
367{
368    struct kern_ipc_perm *ipcp;
369    int flg = params->flg;
370    int err;
371retry:
372    err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL);
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->rw_mutex);
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 if (!err)
385            err = -ENOMEM;
386        else
387            err = ops->getnew(ns, params);
388    } else {
389        /* ipc object has been locked by ipc_findkey() */
390
391        if (flg & IPC_CREAT && flg & IPC_EXCL)
392            err = -EEXIST;
393        else {
394            err = 0;
395            if (ops->more_checks)
396                err = ops->more_checks(ipcp, params);
397            if (!err)
398                /*
399                 * ipc_check_perms returns the IPC id on
400                 * success
401                 */
402                err = ipc_check_perms(ns, ipcp, ops, params);
403        }
404        ipc_unlock(ipcp);
405    }
406    up_write(&ids->rw_mutex);
407
408    if (err == -EAGAIN)
409        goto retry;
410
411    return err;
412}
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.rw_mutex (as a writer) and the spinlock for this ID are held
421 * before this function is called, and remain locked on the exit.
422 */
423 
424void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
425{
426    int lid = ipcid_to_idx(ipcp->id);
427
428    idr_remove(&ids->ipcs_idr, lid);
429
430    ids->in_use--;
431
432    ipcp->deleted = 1;
433
434    return;
435}
436
437/**
438 * ipc_alloc - allocate ipc space
439 * @size: size desired
440 *
441 * Allocate memory from the appropriate pools and return a pointer to it.
442 * NULL is returned if the allocation fails
443 */
444 
445void* ipc_alloc(int size)
446{
447    void* out;
448    if(size > PAGE_SIZE)
449        out = vmalloc(size);
450    else
451        out = kmalloc(size, GFP_KERNEL);
452    return out;
453}
454
455/**
456 * ipc_free - free ipc space
457 * @ptr: pointer returned by ipc_alloc
458 * @size: size of block
459 *
460 * Free a block created with ipc_alloc(). The caller must know the size
461 * used in the allocation call.
462 */
463
464void ipc_free(void* ptr, int size)
465{
466    if(size > PAGE_SIZE)
467        vfree(ptr);
468    else
469        kfree(ptr);
470}
471
472/*
473 * rcu allocations:
474 * There are three headers that are prepended to the actual allocation:
475 * - during use: ipc_rcu_hdr.
476 * - during the rcu grace period: ipc_rcu_grace.
477 * - [only if vmalloc]: ipc_rcu_sched.
478 * Their lifetime doesn't overlap, thus the headers share the same memory.
479 * Unlike a normal union, they are right-aligned, thus some container_of
480 * forward/backward casting is necessary:
481 */
482struct ipc_rcu_hdr
483{
484    int refcount;
485    int is_vmalloc;
486    void *data[0];
487};
488
489
490struct ipc_rcu_grace
491{
492    struct rcu_head rcu;
493    /* "void *" makes sure alignment of following data is sane. */
494    void *data[0];
495};
496
497struct ipc_rcu_sched
498{
499    struct work_struct work;
500    /* "void *" makes sure alignment of following data is sane. */
501    void *data[0];
502};
503
504#define HDRLEN_KMALLOC (sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
505                    sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
506#define HDRLEN_VMALLOC (sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
507                    sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
508
509static inline int rcu_use_vmalloc(int size)
510{
511    /* Too big for a single page? */
512    if (HDRLEN_KMALLOC + size > PAGE_SIZE)
513        return 1;
514    return 0;
515}
516
517/**
518 * ipc_rcu_alloc - allocate ipc and rcu space
519 * @size: size desired
520 *
521 * Allocate memory for the rcu header structure + the object.
522 * Returns the pointer to the object.
523 * NULL is returned if the allocation fails.
524 */
525 
526void* ipc_rcu_alloc(int size)
527{
528    void* out;
529    /*
530     * We prepend the allocation with the rcu struct, and
531     * workqueue if necessary (for vmalloc).
532     */
533    if (rcu_use_vmalloc(size)) {
534        out = vmalloc(HDRLEN_VMALLOC + size);
535        if (out) {
536            out += HDRLEN_VMALLOC;
537            container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
538            container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
539        }
540    } else {
541        out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
542        if (out) {
543            out += HDRLEN_KMALLOC;
544            container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
545            container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
546        }
547    }
548
549    return out;
550}
551
552void ipc_rcu_getref(void *ptr)
553{
554    container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
555}
556
557static void ipc_do_vfree(struct work_struct *work)
558{
559    vfree(container_of(work, struct ipc_rcu_sched, work));
560}
561
562/**
563 * ipc_schedule_free - free ipc + rcu space
564 * @head: RCU callback structure for queued work
565 *
566 * Since RCU callback function is called in bh,
567 * we need to defer the vfree to schedule_work().
568 */
569static void ipc_schedule_free(struct rcu_head *head)
570{
571    struct ipc_rcu_grace *grace;
572    struct ipc_rcu_sched *sched;
573
574    grace = container_of(head, struct ipc_rcu_grace, rcu);
575    sched = container_of(&(grace->data[0]), struct ipc_rcu_sched,
576                data[0]);
577
578    INIT_WORK(&sched->work, ipc_do_vfree);
579    schedule_work(&sched->work);
580}
581
582/**
583 * ipc_immediate_free - free ipc + rcu space
584 * @head: RCU callback structure that contains pointer to be freed
585 *
586 * Free from the RCU callback context.
587 */
588static void ipc_immediate_free(struct rcu_head *head)
589{
590    struct ipc_rcu_grace *free =
591        container_of(head, struct ipc_rcu_grace, rcu);
592    kfree(free);
593}
594
595void ipc_rcu_putref(void *ptr)
596{
597    if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
598        return;
599
600    if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
601        call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
602                ipc_schedule_free);
603    } else {
604        call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
605                ipc_immediate_free);
606    }
607}
608
609/**
610 * ipcperms - check IPC permissions
611 * @ns: IPC namespace
612 * @ipcp: IPC permission set
613 * @flag: desired permission set.
614 *
615 * Check user, group, other permissions for access
616 * to ipc resources. return 0 if allowed
617 *
618 * @flag will most probably be 0 or S_...UGO from <linux/stat.h>
619 */
620 
621int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
622{
623    uid_t euid = current_euid();
624    int requested_mode, granted_mode;
625
626    audit_ipc_obj(ipcp);
627    requested_mode = (flag >> 6) | (flag >> 3) | flag;
628    granted_mode = ipcp->mode;
629    if (euid == ipcp->cuid ||
630        euid == ipcp->uid)
631        granted_mode >>= 6;
632    else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
633        granted_mode >>= 3;
634    /* is there some bit set in requested_mode but not in granted_mode? */
635    if ((requested_mode & ~granted_mode & 0007) &&
636        !ns_capable(ns->user_ns, CAP_IPC_OWNER))
637        return -1;
638
639    return security_ipc_permission(ipcp, flag);
640}
641
642/*
643 * Functions to convert between the kern_ipc_perm structure and the
644 * old/new ipc_perm structures
645 */
646
647/**
648 * kernel_to_ipc64_perm - convert kernel ipc permissions to user
649 * @in: kernel permissions
650 * @out: new style IPC permissions
651 *
652 * Turn the kernel object @in into a set of permissions descriptions
653 * for returning to userspace (@out).
654 */
655 
656
657void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
658{
659    out->key = in->key;
660    out->uid = in->uid;
661    out->gid = in->gid;
662    out->cuid = in->cuid;
663    out->cgid = in->cgid;
664    out->mode = in->mode;
665    out->seq = in->seq;
666}
667
668/**
669 * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
670 * @in: new style IPC permissions
671 * @out: old style IPC permissions
672 *
673 * Turn the new style permissions object @in into a compatibility
674 * object and store it into the @out pointer.
675 */
676 
677void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
678{
679    out->key = in->key;
680    SET_UID(out->uid, in->uid);
681    SET_GID(out->gid, in->gid);
682    SET_UID(out->cuid, in->cuid);
683    SET_GID(out->cgid, in->cgid);
684    out->mode = in->mode;
685    out->seq = in->seq;
686}
687
688/**
689 * ipc_lock - Lock an ipc structure without rw_mutex held
690 * @ids: IPC identifier set
691 * @id: ipc id to look for
692 *
693 * Look for an id in the ipc ids idr and lock the associated ipc object.
694 *
695 * The ipc object is locked on exit.
696 */
697
698struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
699{
700    struct kern_ipc_perm *out;
701    int lid = ipcid_to_idx(id);
702
703    rcu_read_lock();
704    out = idr_find(&ids->ipcs_idr, lid);
705    if (out == NULL) {
706        rcu_read_unlock();
707        return ERR_PTR(-EINVAL);
708    }
709
710    spin_lock(&out->lock);
711    
712    /* ipc_rmid() may have already freed the ID while ipc_lock
713     * was spinning: here verify that the structure is still valid
714     */
715    if (out->deleted) {
716        spin_unlock(&out->lock);
717        rcu_read_unlock();
718        return ERR_PTR(-EINVAL);
719    }
720
721    return out;
722}
723
724struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id)
725{
726    struct kern_ipc_perm *out;
727
728    out = ipc_lock(ids, id);
729    if (IS_ERR(out))
730        return out;
731
732    if (ipc_checkid(out, id)) {
733        ipc_unlock(out);
734        return ERR_PTR(-EIDRM);
735    }
736
737    return out;
738}
739
740/**
741 * ipcget - Common sys_*get() code
742 * @ns : namsepace
743 * @ids : IPC identifier set
744 * @ops : operations to be called on ipc object creation, permission checks
745 * and further checks
746 * @params : the parameters needed by the previous operations.
747 *
748 * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
749 */
750int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
751            struct ipc_ops *ops, struct ipc_params *params)
752{
753    if (params->key == IPC_PRIVATE)
754        return ipcget_new(ns, ids, ops, params);
755    else
756        return ipcget_public(ns, ids, ops, params);
757}
758
759/**
760 * ipc_update_perm - update the permissions of an IPC.
761 * @in: the permission given as input.
762 * @out: the permission of the ipc to set.
763 */
764void ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
765{
766    out->uid = in->uid;
767    out->gid = in->gid;
768    out->mode = (out->mode & ~S_IRWXUGO)
769        | (in->mode & S_IRWXUGO);
770}
771
772/**
773 * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd
774 * @ns: the ipc namespace
775 * @ids: the table of ids where to look for the ipc
776 * @id: the id of the ipc to retrieve
777 * @cmd: the cmd to check
778 * @perm: the permission to set
779 * @extra_perm: one extra permission parameter used by msq
780 *
781 * This function does some common audit and permissions check for some IPC_XXX
782 * cmd and is called from semctl_down, shmctl_down and msgctl_down.
783 * It must be called without any lock held and
784 * - retrieves the ipc with the given id in the given table.
785 * - performs some audit and permission check, depending on the given cmd
786 * - returns the ipc with both ipc and rw_mutex locks held in case of success
787 * or an err-code without any lock held otherwise.
788 */
789struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns,
790                      struct ipc_ids *ids, int id, int cmd,
791                      struct ipc64_perm *perm, int extra_perm)
792{
793    struct kern_ipc_perm *ipcp;
794    uid_t euid;
795    int err;
796
797    down_write(&ids->rw_mutex);
798    ipcp = ipc_lock_check(ids, id);
799    if (IS_ERR(ipcp)) {
800        err = PTR_ERR(ipcp);
801        goto out_up;
802    }
803
804    audit_ipc_obj(ipcp);
805    if (cmd == IPC_SET)
806        audit_ipc_set_perm(extra_perm, perm->uid,
807                     perm->gid, perm->mode);
808
809    euid = current_euid();
810    if (euid == ipcp->cuid || euid == ipcp->uid ||
811        ns_capable(ns->user_ns, CAP_SYS_ADMIN))
812        return ipcp;
813
814    err = -EPERM;
815    ipc_unlock(ipcp);
816out_up:
817    up_write(&ids->rw_mutex);
818    return ERR_PTR(err);
819}
820
821#ifdef __ARCH_WANT_IPC_PARSE_VERSION
822
823
824/**
825 * ipc_parse_version - IPC call version
826 * @cmd: pointer to command
827 *
828 * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
829 * The @cmd value is turned from an encoding command and version into
830 * just the command code.
831 */
832 
833int ipc_parse_version (int *cmd)
834{
835    if (*cmd & IPC_64) {
836        *cmd ^= IPC_64;
837        return IPC_64;
838    } else {
839        return IPC_OLD;
840    }
841}
842
843#endif /* __ARCH_WANT_IPC_PARSE_VERSION */
844
845#ifdef CONFIG_PROC_FS
846struct ipc_proc_iter {
847    struct ipc_namespace *ns;
848    struct ipc_proc_iface *iface;
849};
850
851/*
852 * This routine locks the ipc structure found at least at position pos.
853 */
854static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
855                          loff_t *new_pos)
856{
857    struct kern_ipc_perm *ipc;
858    int total, id;
859
860    total = 0;
861    for (id = 0; id < pos && total < ids->in_use; id++) {
862        ipc = idr_find(&ids->ipcs_idr, id);
863        if (ipc != NULL)
864            total++;
865    }
866
867    if (total >= ids->in_use)
868        return NULL;
869
870    for ( ; pos < IPCMNI; pos++) {
871        ipc = idr_find(&ids->ipcs_idr, pos);
872        if (ipc != NULL) {
873            *new_pos = pos + 1;
874            ipc_lock_by_ptr(ipc);
875            return ipc;
876        }
877    }
878
879    /* Out of range - return NULL to terminate iteration */
880    return NULL;
881}
882
883static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
884{
885    struct ipc_proc_iter *iter = s->private;
886    struct ipc_proc_iface *iface = iter->iface;
887    struct kern_ipc_perm *ipc = it;
888
889    /* If we had an ipc id locked before, unlock it */
890    if (ipc && ipc != SEQ_START_TOKEN)
891        ipc_unlock(ipc);
892
893    return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
894}
895
896/*
897 * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
898 * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
899 */
900static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
901{
902    struct ipc_proc_iter *iter = s->private;
903    struct ipc_proc_iface *iface = iter->iface;
904    struct ipc_ids *ids;
905
906    ids = &iter->ns->ids[iface->ids];
907
908    /*
909     * Take the lock - this will be released by the corresponding
910     * call to stop().
911     */
912    down_read(&ids->rw_mutex);
913
914    /* pos < 0 is invalid */
915    if (*pos < 0)
916        return NULL;
917
918    /* pos == 0 means header */
919    if (*pos == 0)
920        return SEQ_START_TOKEN;
921
922    /* Find the (pos-1)th ipc */
923    return sysvipc_find_ipc(ids, *pos - 1, pos);
924}
925
926static void sysvipc_proc_stop(struct seq_file *s, void *it)
927{
928    struct kern_ipc_perm *ipc = it;
929    struct ipc_proc_iter *iter = s->private;
930    struct ipc_proc_iface *iface = iter->iface;
931    struct ipc_ids *ids;
932
933    /* If we had a locked structure, release it */
934    if (ipc && ipc != SEQ_START_TOKEN)
935        ipc_unlock(ipc);
936
937    ids = &iter->ns->ids[iface->ids];
938    /* Release the lock we took in start() */
939    up_read(&ids->rw_mutex);
940}
941
942static int sysvipc_proc_show(struct seq_file *s, void *it)
943{
944    struct ipc_proc_iter *iter = s->private;
945    struct ipc_proc_iface *iface = iter->iface;
946
947    if (it == SEQ_START_TOKEN)
948        return seq_puts(s, iface->header);
949
950    return iface->show(s, it);
951}
952
953static const struct seq_operations sysvipc_proc_seqops = {
954    .start = sysvipc_proc_start,
955    .stop = sysvipc_proc_stop,
956    .next = sysvipc_proc_next,
957    .show = sysvipc_proc_show,
958};
959
960static int sysvipc_proc_open(struct inode *inode, struct file *file)
961{
962    int ret;
963    struct seq_file *seq;
964    struct ipc_proc_iter *iter;
965
966    ret = -ENOMEM;
967    iter = kmalloc(sizeof(*iter), GFP_KERNEL);
968    if (!iter)
969        goto out;
970
971    ret = seq_open(file, &sysvipc_proc_seqops);
972    if (ret)
973        goto out_kfree;
974
975    seq = file->private_data;
976    seq->private = iter;
977
978    iter->iface = PDE(inode)->data;
979    iter->ns = get_ipc_ns(current->nsproxy->ipc_ns);
980out:
981    return ret;
982out_kfree:
983    kfree(iter);
984    goto out;
985}
986
987static int sysvipc_proc_release(struct inode *inode, struct file *file)
988{
989    struct seq_file *seq = file->private_data;
990    struct ipc_proc_iter *iter = seq->private;
991    put_ipc_ns(iter->ns);
992    return seq_release_private(inode, file);
993}
994
995static const struct file_operations sysvipc_proc_fops = {
996    .open = sysvipc_proc_open,
997    .read = seq_read,
998    .llseek = seq_lseek,
999    .release = sysvipc_proc_release,
1000};
1001#endif /* CONFIG_PROC_FS */
1002

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