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