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

Archive Download this file



interactive