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Linux/ipc/util.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * linux/ipc/util.c
  4  * Copyright (C) 1992 Krishna Balasubramanian
  5  *
  6  * Sep 1997 - Call suser() last after "normal" permission checks so we
  7  *            get BSD style process accounting right.
  8  *            Occurs in several places in the IPC code.
  9  *            Chris Evans, <chris@ferret.lmh.ox.ac.uk>
 10  * Nov 1999 - ipc helper functions, unified SMP locking
 11  *            Manfred Spraul <manfred@colorfullife.com>
 12  * Oct 2002 - One lock per IPC id. RCU ipc_free for lock-free grow_ary().
 13  *            Mingming Cao <cmm@us.ibm.com>
 14  * Mar 2006 - support for audit of ipc object properties
 15  *            Dustin Kirkland <dustin.kirkland@us.ibm.com>
 16  * Jun 2006 - namespaces ssupport
 17  *            OpenVZ, SWsoft Inc.
 18  *            Pavel Emelianov <xemul@openvz.org>
 19  *
 20  * General sysv ipc locking scheme:
 21  *      rcu_read_lock()
 22  *          obtain the ipc object (kern_ipc_perm) by looking up the id in an idr
 23  *          tree.
 24  *          - perform initial checks (capabilities, auditing and permission,
 25  *            etc).
 26  *          - perform read-only operations, such as INFO command, that
 27  *            do not demand atomicity
 28  *            acquire the ipc lock (kern_ipc_perm.lock) through
 29  *            ipc_lock_object()
 30  *              - perform read-only operations that demand atomicity,
 31  *                such as STAT command.
 32  *              - perform data updates, such as SET, RMID commands and
 33  *                mechanism-specific operations (semop/semtimedop,
 34  *                msgsnd/msgrcv, shmat/shmdt).
 35  *          drop the ipc lock, through ipc_unlock_object().
 36  *      rcu_read_unlock()
 37  *
 38  *  The ids->rwsem must be taken when:
 39  *      - creating, removing and iterating the existing entries in ipc
 40  *        identifier sets.
 41  *      - iterating through files under /proc/sysvipc/
 42  *
 43  *  Note that sems have a special fast path that avoids kern_ipc_perm.lock -
 44  *  see sem_lock().
 45  */
 46 
 47 #include <linux/mm.h>
 48 #include <linux/shm.h>
 49 #include <linux/init.h>
 50 #include <linux/msg.h>
 51 #include <linux/vmalloc.h>
 52 #include <linux/slab.h>
 53 #include <linux/notifier.h>
 54 #include <linux/capability.h>
 55 #include <linux/highuid.h>
 56 #include <linux/security.h>
 57 #include <linux/rcupdate.h>
 58 #include <linux/workqueue.h>
 59 #include <linux/seq_file.h>
 60 #include <linux/proc_fs.h>
 61 #include <linux/audit.h>
 62 #include <linux/nsproxy.h>
 63 #include <linux/rwsem.h>
 64 #include <linux/memory.h>
 65 #include <linux/ipc_namespace.h>
 66 
 67 #include <asm/unistd.h>
 68 
 69 #include "util.h"
 70 
 71 struct ipc_proc_iface {
 72         const char *path;
 73         const char *header;
 74         int ids;
 75         int (*show)(struct seq_file *, void *);
 76 };
 77 
 78 /**
 79  * ipc_init - initialise ipc subsystem
 80  *
 81  * The various sysv ipc resources (semaphores, messages and shared
 82  * memory) are initialised.
 83  *
 84  * A callback routine is registered into the memory hotplug notifier
 85  * chain: since msgmni scales to lowmem this callback routine will be
 86  * called upon successful memory add / remove to recompute msmgni.
 87  */
 88 static int __init ipc_init(void)
 89 {
 90         int err_sem, err_msg;
 91 
 92         proc_mkdir("sysvipc", NULL);
 93         err_sem = sem_init();
 94         WARN(err_sem, "ipc: sysv sem_init failed: %d\n", err_sem);
 95         err_msg = msg_init();
 96         WARN(err_msg, "ipc: sysv msg_init failed: %d\n", err_msg);
 97         shm_init();
 98 
 99         return err_msg ? err_msg : err_sem;
100 }
101 device_initcall(ipc_init);
102 
103 static const struct rhashtable_params ipc_kht_params = {
104         .head_offset            = offsetof(struct kern_ipc_perm, khtnode),
105         .key_offset             = offsetof(struct kern_ipc_perm, key),
106         .key_len                = FIELD_SIZEOF(struct kern_ipc_perm, key),
107         .locks_mul              = 1,
108         .automatic_shrinking    = true,
109 };
110 
111 /**
112  * ipc_init_ids - initialise ipc identifiers
113  * @ids: ipc identifier set
114  *
115  * Set up the sequence range to use for the ipc identifier range (limited
116  * below IPCMNI) then initialise the keys hashtable and ids idr.
117  */
118 int ipc_init_ids(struct ipc_ids *ids)
119 {
120         int err;
121         ids->in_use = 0;
122         ids->seq = 0;
123         init_rwsem(&ids->rwsem);
124         err = rhashtable_init(&ids->key_ht, &ipc_kht_params);
125         if (err)
126                 return err;
127         idr_init(&ids->ipcs_idr);
128         ids->tables_initialized = true;
129         ids->max_id = -1;
130 #ifdef CONFIG_CHECKPOINT_RESTORE
131         ids->next_id = -1;
132 #endif
133         return 0;
134 }
135 
136 #ifdef CONFIG_PROC_FS
137 static 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  */
145 void __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 #endif
168 
169 /**
170  * ipc_findkey  - find a key in an ipc identifier set
171  * @ids: ipc identifier set
172  * @key: key to find
173  *
174  * Returns the locked pointer to the ipc structure if found or NULL
175  * otherwise. If key is found ipc points to the owning ipc structure
176  *
177  * Called with writer ipc_ids.rwsem held.
178  */
179 static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key)
180 {
181         struct kern_ipc_perm *ipcp = NULL;
182 
183         if (likely(ids->tables_initialized))
184                 ipcp = rhashtable_lookup_fast(&ids->key_ht, &key,
185                                               ipc_kht_params);
186 
187         if (ipcp) {
188                 rcu_read_lock();
189                 ipc_lock_object(ipcp);
190                 return ipcp;
191         }
192 
193         return NULL;
194 }
195 
196 #ifdef CONFIG_CHECKPOINT_RESTORE
197 /*
198  * Specify desired id for next allocated IPC object.
199  */
200 #define ipc_idr_alloc(ids, new)                                         \
201         idr_alloc(&(ids)->ipcs_idr, (new),                              \
202                   (ids)->next_id < 0 ? 0 : ipcid_to_idx((ids)->next_id),\
203                   0, GFP_NOWAIT)
204 
205 static inline int ipc_buildid(int id, struct ipc_ids *ids,
206                               struct kern_ipc_perm *new)
207 {
208         if (ids->next_id < 0) { /* default, behave as !CHECKPOINT_RESTORE */
209                 new->seq = ids->seq++;
210                 if (ids->seq > IPCID_SEQ_MAX)
211                         ids->seq = 0;
212         } else {
213                 new->seq = ipcid_to_seqx(ids->next_id);
214                 ids->next_id = -1;
215         }
216 
217         return SEQ_MULTIPLIER * new->seq + id;
218 }
219 
220 #else
221 #define ipc_idr_alloc(ids, new)                                 \
222         idr_alloc(&(ids)->ipcs_idr, (new), 0, 0, GFP_NOWAIT)
223 
224 static inline int ipc_buildid(int id, struct ipc_ids *ids,
225                               struct kern_ipc_perm *new)
226 {
227         new->seq = ids->seq++;
228         if (ids->seq > IPCID_SEQ_MAX)
229                 ids->seq = 0;
230 
231         return SEQ_MULTIPLIER * new->seq + id;
232 }
233 
234 #endif /* CONFIG_CHECKPOINT_RESTORE */
235 
236 /**
237  * ipc_addid - add an ipc identifier
238  * @ids: ipc identifier set
239  * @new: new ipc permission set
240  * @limit: 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 writer ipc_ids.rwsem held.
248  */
249 int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit)
250 {
251         kuid_t euid;
252         kgid_t egid;
253         int id, err;
254 
255         if (limit > IPCMNI)
256                 limit = IPCMNI;
257 
258         if (!ids->tables_initialized || ids->in_use >= limit)
259                 return -ENOSPC;
260 
261         idr_preload(GFP_KERNEL);
262 
263         refcount_set(&new->refcount, 1);
264         spin_lock_init(&new->lock);
265         new->deleted = false;
266         rcu_read_lock();
267         spin_lock(&new->lock);
268 
269         current_euid_egid(&euid, &egid);
270         new->cuid = new->uid = euid;
271         new->gid = new->cgid = egid;
272 
273         id = ipc_idr_alloc(ids, new);
274         idr_preload_end();
275 
276         if (id >= 0 && new->key != IPC_PRIVATE) {
277                 err = rhashtable_insert_fast(&ids->key_ht, &new->khtnode,
278                                              ipc_kht_params);
279                 if (err < 0) {
280                         idr_remove(&ids->ipcs_idr, id);
281                         id = err;
282                 }
283         }
284         if (id < 0) {
285                 spin_unlock(&new->lock);
286                 rcu_read_unlock();
287                 return id;
288         }
289 
290         ids->in_use++;
291         if (id > ids->max_id)
292                 ids->max_id = id;
293 
294         new->id = ipc_buildid(id, ids, new);
295 
296         return id;
297 }
298 
299 /**
300  * ipcget_new - create a new ipc object
301  * @ns: ipc namespace
302  * @ids: ipc identifier set
303  * @ops: the actual creation routine to call
304  * @params: its parameters
305  *
306  * This routine is called by sys_msgget, sys_semget() and sys_shmget()
307  * when the key is IPC_PRIVATE.
308  */
309 static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids,
310                 const struct ipc_ops *ops, struct ipc_params *params)
311 {
312         int err;
313 
314         down_write(&ids->rwsem);
315         err = ops->getnew(ns, params);
316         up_write(&ids->rwsem);
317         return err;
318 }
319 
320 /**
321  * ipc_check_perms - check security and permissions for an ipc object
322  * @ns: ipc namespace
323  * @ipcp: ipc permission set
324  * @ops: the actual security routine to call
325  * @params: its parameters
326  *
327  * This routine is called by sys_msgget(), sys_semget() and sys_shmget()
328  * when the key is not IPC_PRIVATE and that key already exists in the
329  * ds IDR.
330  *
331  * On success, the ipc id is returned.
332  *
333  * It is called with ipc_ids.rwsem and ipcp->lock held.
334  */
335 static int ipc_check_perms(struct ipc_namespace *ns,
336                            struct kern_ipc_perm *ipcp,
337                            const struct ipc_ops *ops,
338                            struct ipc_params *params)
339 {
340         int err;
341 
342         if (ipcperms(ns, ipcp, params->flg))
343                 err = -EACCES;
344         else {
345                 err = ops->associate(ipcp, params->flg);
346                 if (!err)
347                         err = ipcp->id;
348         }
349 
350         return err;
351 }
352 
353 /**
354  * ipcget_public - get an ipc object or create a new one
355  * @ns: ipc namespace
356  * @ids: ipc identifier set
357  * @ops: the actual creation routine to call
358  * @params: its parameters
359  *
360  * This routine is called by sys_msgget, sys_semget() and sys_shmget()
361  * when the key is not IPC_PRIVATE.
362  * It adds a new entry if the key is not found and does some permission
363  * / security checkings if the key is found.
364  *
365  * On success, the ipc id is returned.
366  */
367 static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids,
368                 const struct ipc_ops *ops, struct ipc_params *params)
369 {
370         struct kern_ipc_perm *ipcp;
371         int flg = params->flg;
372         int err;
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->rwsem);
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
385                         err = ops->getnew(ns, params);
386         } else {
387                 /* ipc object has been locked by ipc_findkey() */
388 
389                 if (flg & IPC_CREAT && flg & IPC_EXCL)
390                         err = -EEXIST;
391                 else {
392                         err = 0;
393                         if (ops->more_checks)
394                                 err = ops->more_checks(ipcp, params);
395                         if (!err)
396                                 /*
397                                  * ipc_check_perms returns the IPC id on
398                                  * success
399                                  */
400                                 err = ipc_check_perms(ns, ipcp, ops, params);
401                 }
402                 ipc_unlock(ipcp);
403         }
404         up_write(&ids->rwsem);
405 
406         return err;
407 }
408 
409 /**
410  * ipc_kht_remove - remove an ipc from the key hashtable
411  * @ids: ipc identifier set
412  * @ipcp: ipc perm structure containing the key to remove
413  *
414  * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
415  * before this function is called, and remain locked on the exit.
416  */
417 static void ipc_kht_remove(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
418 {
419         if (ipcp->key != IPC_PRIVATE)
420                 rhashtable_remove_fast(&ids->key_ht, &ipcp->khtnode,
421                                        ipc_kht_params);
422 }
423 
424 /**
425  * ipc_rmid - remove an ipc identifier
426  * @ids: ipc identifier set
427  * @ipcp: ipc perm structure containing the identifier to remove
428  *
429  * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
430  * before this function is called, and remain locked on the exit.
431  */
432 void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
433 {
434         int lid = ipcid_to_idx(ipcp->id);
435 
436         idr_remove(&ids->ipcs_idr, lid);
437         ipc_kht_remove(ids, ipcp);
438         ids->in_use--;
439         ipcp->deleted = true;
440 
441         if (unlikely(lid == ids->max_id)) {
442                 do {
443                         lid--;
444                         if (lid == -1)
445                                 break;
446                 } while (!idr_find(&ids->ipcs_idr, lid));
447                 ids->max_id = lid;
448         }
449 }
450 
451 /**
452  * ipc_set_key_private - switch the key of an existing ipc to IPC_PRIVATE
453  * @ids: ipc identifier set
454  * @ipcp: ipc perm structure containing the key to modify
455  *
456  * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held
457  * before this function is called, and remain locked on the exit.
458  */
459 void ipc_set_key_private(struct ipc_ids *ids, struct kern_ipc_perm *ipcp)
460 {
461         ipc_kht_remove(ids, ipcp);
462         ipcp->key = IPC_PRIVATE;
463 }
464 
465 int ipc_rcu_getref(struct kern_ipc_perm *ptr)
466 {
467         return refcount_inc_not_zero(&ptr->refcount);
468 }
469 
470 void ipc_rcu_putref(struct kern_ipc_perm *ptr,
471                         void (*func)(struct rcu_head *head))
472 {
473         if (!refcount_dec_and_test(&ptr->refcount))
474                 return;
475 
476         call_rcu(&ptr->rcu, func);
477 }
478 
479 /**
480  * ipcperms - check ipc permissions
481  * @ns: ipc namespace
482  * @ipcp: ipc permission set
483  * @flag: desired permission set
484  *
485  * Check user, group, other permissions for access
486  * to ipc resources. return 0 if allowed
487  *
488  * @flag will most probably be 0 or ``S_...UGO`` from <linux/stat.h>
489  */
490 int ipcperms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, short flag)
491 {
492         kuid_t euid = current_euid();
493         int requested_mode, granted_mode;
494 
495         audit_ipc_obj(ipcp);
496         requested_mode = (flag >> 6) | (flag >> 3) | flag;
497         granted_mode = ipcp->mode;
498         if (uid_eq(euid, ipcp->cuid) ||
499             uid_eq(euid, ipcp->uid))
500                 granted_mode >>= 6;
501         else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
502                 granted_mode >>= 3;
503         /* is there some bit set in requested_mode but not in granted_mode? */
504         if ((requested_mode & ~granted_mode & 0007) &&
505             !ns_capable(ns->user_ns, CAP_IPC_OWNER))
506                 return -1;
507 
508         return security_ipc_permission(ipcp, flag);
509 }
510 
511 /*
512  * Functions to convert between the kern_ipc_perm structure and the
513  * old/new ipc_perm structures
514  */
515 
516 /**
517  * kernel_to_ipc64_perm - convert kernel ipc permissions to user
518  * @in: kernel permissions
519  * @out: new style ipc permissions
520  *
521  * Turn the kernel object @in into a set of permissions descriptions
522  * for returning to userspace (@out).
523  */
524 void kernel_to_ipc64_perm(struct kern_ipc_perm *in, struct ipc64_perm *out)
525 {
526         out->key        = in->key;
527         out->uid        = from_kuid_munged(current_user_ns(), in->uid);
528         out->gid        = from_kgid_munged(current_user_ns(), in->gid);
529         out->cuid       = from_kuid_munged(current_user_ns(), in->cuid);
530         out->cgid       = from_kgid_munged(current_user_ns(), in->cgid);
531         out->mode       = in->mode;
532         out->seq        = in->seq;
533 }
534 
535 /**
536  * ipc64_perm_to_ipc_perm - convert new ipc permissions to old
537  * @in: new style ipc permissions
538  * @out: old style ipc permissions
539  *
540  * Turn the new style permissions object @in into a compatibility
541  * object and store it into the @out pointer.
542  */
543 void ipc64_perm_to_ipc_perm(struct ipc64_perm *in, struct ipc_perm *out)
544 {
545         out->key        = in->key;
546         SET_UID(out->uid, in->uid);
547         SET_GID(out->gid, in->gid);
548         SET_UID(out->cuid, in->cuid);
549         SET_GID(out->cgid, in->cgid);
550         out->mode       = in->mode;
551         out->seq        = in->seq;
552 }
553 
554 /**
555  * ipc_obtain_object_idr
556  * @ids: ipc identifier set
557  * @id: ipc id to look for
558  *
559  * Look for an id in the ipc ids idr and return associated ipc object.
560  *
561  * Call inside the RCU critical section.
562  * The ipc object is *not* locked on exit.
563  */
564 struct kern_ipc_perm *ipc_obtain_object_idr(struct ipc_ids *ids, int id)
565 {
566         struct kern_ipc_perm *out;
567         int lid = ipcid_to_idx(id);
568 
569         if (unlikely(!ids->tables_initialized))
570                 return ERR_PTR(-EINVAL);
571 
572         out = idr_find(&ids->ipcs_idr, lid);
573         if (!out)
574                 return ERR_PTR(-EINVAL);
575 
576         return out;
577 }
578 
579 /**
580  * ipc_lock - lock an ipc structure without rwsem held
581  * @ids: ipc identifier set
582  * @id: ipc id to look for
583  *
584  * Look for an id in the ipc ids idr and lock the associated ipc object.
585  *
586  * The ipc object is locked on successful exit.
587  */
588 struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id)
589 {
590         struct kern_ipc_perm *out;
591 
592         rcu_read_lock();
593         out = ipc_obtain_object_idr(ids, id);
594         if (IS_ERR(out))
595                 goto err;
596 
597         spin_lock(&out->lock);
598 
599         /*
600          * ipc_rmid() may have already freed the ID while ipc_lock()
601          * was spinning: here verify that the structure is still valid.
602          * Upon races with RMID, return -EIDRM, thus indicating that
603          * the ID points to a removed identifier.
604          */
605         if (ipc_valid_object(out))
606                 return out;
607 
608         spin_unlock(&out->lock);
609         out = ERR_PTR(-EIDRM);
610 err:
611         rcu_read_unlock();
612         return out;
613 }
614 
615 /**
616  * ipc_obtain_object_check
617  * @ids: ipc identifier set
618  * @id: ipc id to look for
619  *
620  * Similar to ipc_obtain_object_idr() but also checks
621  * the ipc object reference counter.
622  *
623  * Call inside the RCU critical section.
624  * The ipc object is *not* locked on exit.
625  */
626 struct kern_ipc_perm *ipc_obtain_object_check(struct ipc_ids *ids, int id)
627 {
628         struct kern_ipc_perm *out = ipc_obtain_object_idr(ids, id);
629 
630         if (IS_ERR(out))
631                 goto out;
632 
633         if (ipc_checkid(out, id))
634                 return ERR_PTR(-EINVAL);
635 out:
636         return out;
637 }
638 
639 /**
640  * ipcget - Common sys_*get() code
641  * @ns: namespace
642  * @ids: ipc identifier set
643  * @ops: operations to be called on ipc object creation, permission checks
644  *       and further checks
645  * @params: the parameters needed by the previous operations.
646  *
647  * Common routine called by sys_msgget(), sys_semget() and sys_shmget().
648  */
649 int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
650                         const struct ipc_ops *ops, struct ipc_params *params)
651 {
652         if (params->key == IPC_PRIVATE)
653                 return ipcget_new(ns, ids, ops, params);
654         else
655                 return ipcget_public(ns, ids, ops, params);
656 }
657 
658 /**
659  * ipc_update_perm - update the permissions of an ipc object
660  * @in:  the permission given as input.
661  * @out: the permission of the ipc to set.
662  */
663 int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out)
664 {
665         kuid_t uid = make_kuid(current_user_ns(), in->uid);
666         kgid_t gid = make_kgid(current_user_ns(), in->gid);
667         if (!uid_valid(uid) || !gid_valid(gid))
668                 return -EINVAL;
669 
670         out->uid = uid;
671         out->gid = gid;
672         out->mode = (out->mode & ~S_IRWXUGO)
673                 | (in->mode & S_IRWXUGO);
674 
675         return 0;
676 }
677 
678 /**
679  * ipcctl_pre_down_nolock - retrieve an ipc and check permissions for some IPC_XXX cmd
680  * @ns:  ipc namespace
681  * @ids:  the table of ids where to look for the ipc
682  * @id:   the id of the ipc to retrieve
683  * @cmd:  the cmd to check
684  * @perm: the permission to set
685  * @extra_perm: one extra permission parameter used by msq
686  *
687  * This function does some common audit and permissions check for some IPC_XXX
688  * cmd and is called from semctl_down, shmctl_down and msgctl_down.
689  * It must be called without any lock held and:
690  *
691  *   - retrieves the ipc with the given id in the given table.
692  *   - performs some audit and permission check, depending on the given cmd
693  *   - returns a pointer to the ipc object or otherwise, the corresponding
694  *     error.
695  *
696  * Call holding the both the rwsem and the rcu read lock.
697  */
698 struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns,
699                                         struct ipc_ids *ids, int id, int cmd,
700                                         struct ipc64_perm *perm, int extra_perm)
701 {
702         kuid_t euid;
703         int err = -EPERM;
704         struct kern_ipc_perm *ipcp;
705 
706         ipcp = ipc_obtain_object_check(ids, id);
707         if (IS_ERR(ipcp)) {
708                 err = PTR_ERR(ipcp);
709                 goto err;
710         }
711 
712         audit_ipc_obj(ipcp);
713         if (cmd == IPC_SET)
714                 audit_ipc_set_perm(extra_perm, perm->uid,
715                                    perm->gid, perm->mode);
716 
717         euid = current_euid();
718         if (uid_eq(euid, ipcp->cuid) || uid_eq(euid, ipcp->uid)  ||
719             ns_capable(ns->user_ns, CAP_SYS_ADMIN))
720                 return ipcp; /* successful lookup */
721 err:
722         return ERR_PTR(err);
723 }
724 
725 #ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
726 
727 
728 /**
729  * ipc_parse_version - ipc call version
730  * @cmd: pointer to command
731  *
732  * Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
733  * The @cmd value is turned from an encoding command and version into
734  * just the command code.
735  */
736 int ipc_parse_version(int *cmd)
737 {
738         if (*cmd & IPC_64) {
739                 *cmd ^= IPC_64;
740                 return IPC_64;
741         } else {
742                 return IPC_OLD;
743         }
744 }
745 
746 #endif /* CONFIG_ARCH_WANT_IPC_PARSE_VERSION */
747 
748 #ifdef CONFIG_PROC_FS
749 struct ipc_proc_iter {
750         struct ipc_namespace *ns;
751         struct pid_namespace *pid_ns;
752         struct ipc_proc_iface *iface;
753 };
754 
755 struct pid_namespace *ipc_seq_pid_ns(struct seq_file *s)
756 {
757         struct ipc_proc_iter *iter = s->private;
758         return iter->pid_ns;
759 }
760 
761 /*
762  * This routine locks the ipc structure found at least at position pos.
763  */
764 static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos,
765                                               loff_t *new_pos)
766 {
767         struct kern_ipc_perm *ipc;
768         int total, id;
769 
770         total = 0;
771         for (id = 0; id < pos && total < ids->in_use; id++) {
772                 ipc = idr_find(&ids->ipcs_idr, id);
773                 if (ipc != NULL)
774                         total++;
775         }
776 
777         if (total >= ids->in_use)
778                 return NULL;
779 
780         for (; pos < IPCMNI; pos++) {
781                 ipc = idr_find(&ids->ipcs_idr, pos);
782                 if (ipc != NULL) {
783                         *new_pos = pos + 1;
784                         rcu_read_lock();
785                         ipc_lock_object(ipc);
786                         return ipc;
787                 }
788         }
789 
790         /* Out of range - return NULL to terminate iteration */
791         return NULL;
792 }
793 
794 static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
795 {
796         struct ipc_proc_iter *iter = s->private;
797         struct ipc_proc_iface *iface = iter->iface;
798         struct kern_ipc_perm *ipc = it;
799 
800         /* If we had an ipc id locked before, unlock it */
801         if (ipc && ipc != SEQ_START_TOKEN)
802                 ipc_unlock(ipc);
803 
804         return sysvipc_find_ipc(&iter->ns->ids[iface->ids], *pos, pos);
805 }
806 
807 /*
808  * File positions: pos 0 -> header, pos n -> ipc id = n - 1.
809  * SeqFile iterator: iterator value locked ipc pointer or SEQ_TOKEN_START.
810  */
811 static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
812 {
813         struct ipc_proc_iter *iter = s->private;
814         struct ipc_proc_iface *iface = iter->iface;
815         struct ipc_ids *ids;
816 
817         ids = &iter->ns->ids[iface->ids];
818 
819         /*
820          * Take the lock - this will be released by the corresponding
821          * call to stop().
822          */
823         down_read(&ids->rwsem);
824 
825         /* pos < 0 is invalid */
826         if (*pos < 0)
827                 return NULL;
828 
829         /* pos == 0 means header */
830         if (*pos == 0)
831                 return SEQ_START_TOKEN;
832 
833         /* Find the (pos-1)th ipc */
834         return sysvipc_find_ipc(ids, *pos - 1, pos);
835 }
836 
837 static void sysvipc_proc_stop(struct seq_file *s, void *it)
838 {
839         struct kern_ipc_perm *ipc = it;
840         struct ipc_proc_iter *iter = s->private;
841         struct ipc_proc_iface *iface = iter->iface;
842         struct ipc_ids *ids;
843 
844         /* If we had a locked structure, release it */
845         if (ipc && ipc != SEQ_START_TOKEN)
846                 ipc_unlock(ipc);
847 
848         ids = &iter->ns->ids[iface->ids];
849         /* Release the lock we took in start() */
850         up_read(&ids->rwsem);
851 }
852 
853 static int sysvipc_proc_show(struct seq_file *s, void *it)
854 {
855         struct ipc_proc_iter *iter = s->private;
856         struct ipc_proc_iface *iface = iter->iface;
857 
858         if (it == SEQ_START_TOKEN) {
859                 seq_puts(s, iface->header);
860                 return 0;
861         }
862 
863         return iface->show(s, it);
864 }
865 
866 static const struct seq_operations sysvipc_proc_seqops = {
867         .start = sysvipc_proc_start,
868         .stop  = sysvipc_proc_stop,
869         .next  = sysvipc_proc_next,
870         .show  = sysvipc_proc_show,
871 };
872 
873 static int sysvipc_proc_open(struct inode *inode, struct file *file)
874 {
875         struct ipc_proc_iter *iter;
876 
877         iter = __seq_open_private(file, &sysvipc_proc_seqops, sizeof(*iter));
878         if (!iter)
879                 return -ENOMEM;
880 
881         iter->iface = PDE_DATA(inode);
882         iter->ns    = get_ipc_ns(current->nsproxy->ipc_ns);
883         iter->pid_ns = get_pid_ns(task_active_pid_ns(current));
884 
885         return 0;
886 }
887 
888 static int sysvipc_proc_release(struct inode *inode, struct file *file)
889 {
890         struct seq_file *seq = file->private_data;
891         struct ipc_proc_iter *iter = seq->private;
892         put_ipc_ns(iter->ns);
893         put_pid_ns(iter->pid_ns);
894         return seq_release_private(inode, file);
895 }
896 
897 static const struct file_operations sysvipc_proc_fops = {
898         .open    = sysvipc_proc_open,
899         .read    = seq_read,
900         .llseek  = seq_lseek,
901         .release = sysvipc_proc_release,
902 };
903 #endif /* CONFIG_PROC_FS */
904 

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