xref: /openbmc/linux/ipc/util.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
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 <manfreds@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  */
14 
15 #include <linux/config.h>
16 #include <linux/mm.h>
17 #include <linux/shm.h>
18 #include <linux/init.h>
19 #include <linux/msg.h>
20 #include <linux/smp_lock.h>
21 #include <linux/vmalloc.h>
22 #include <linux/slab.h>
23 #include <linux/highuid.h>
24 #include <linux/security.h>
25 #include <linux/rcupdate.h>
26 #include <linux/workqueue.h>
27 #include <linux/seq_file.h>
28 #include <linux/proc_fs.h>
29 
30 #include <asm/unistd.h>
31 
32 #include "util.h"
33 
34 struct ipc_proc_iface {
35 	const char *path;
36 	const char *header;
37 	struct ipc_ids *ids;
38 	int (*show)(struct seq_file *, void *);
39 };
40 
41 /**
42  *	ipc_init	-	initialise IPC subsystem
43  *
44  *	The various system5 IPC resources (semaphores, messages and shared
45  *	memory are initialised
46  */
47 
48 static int __init ipc_init(void)
49 {
50 	sem_init();
51 	msg_init();
52 	shm_init();
53 	return 0;
54 }
55 __initcall(ipc_init);
56 
57 /**
58  *	ipc_init_ids		-	initialise IPC identifiers
59  *	@ids: Identifier set
60  *	@size: Number of identifiers
61  *
62  *	Given a size for the ipc identifier range (limited below IPCMNI)
63  *	set up the sequence range to use then allocate and initialise the
64  *	array itself.
65  */
66 
67 void __init ipc_init_ids(struct ipc_ids* ids, int size)
68 {
69 	int i;
70 	sema_init(&ids->sem,1);
71 
72 	if(size > IPCMNI)
73 		size = IPCMNI;
74 	ids->in_use = 0;
75 	ids->max_id = -1;
76 	ids->seq = 0;
77 	{
78 		int seq_limit = INT_MAX/SEQ_MULTIPLIER;
79 		if(seq_limit > USHRT_MAX)
80 			ids->seq_max = USHRT_MAX;
81 		 else
82 		 	ids->seq_max = seq_limit;
83 	}
84 
85 	ids->entries = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*size +
86 				     sizeof(struct ipc_id_ary));
87 
88 	if(ids->entries == NULL) {
89 		printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
90 		size = 0;
91 		ids->entries = &ids->nullentry;
92 	}
93 	ids->entries->size = size;
94 	for(i=0;i<size;i++)
95 		ids->entries->p[i] = NULL;
96 }
97 
98 #ifdef CONFIG_PROC_FS
99 static struct file_operations sysvipc_proc_fops;
100 /**
101  *	ipc_init_proc_interface	-  Create a proc interface for sysipc types
102  *				   using a seq_file interface.
103  *	@path: Path in procfs
104  *	@header: Banner to be printed at the beginning of the file.
105  *	@ids: ipc id table to iterate.
106  *	@show: show routine.
107  */
108 void __init ipc_init_proc_interface(const char *path, const char *header,
109 				    struct ipc_ids *ids,
110 				    int (*show)(struct seq_file *, void *))
111 {
112 	struct proc_dir_entry *pde;
113 	struct ipc_proc_iface *iface;
114 
115 	iface = kmalloc(sizeof(*iface), GFP_KERNEL);
116 	if (!iface)
117 		return;
118 	iface->path	= path;
119 	iface->header	= header;
120 	iface->ids	= ids;
121 	iface->show	= show;
122 
123 	pde = create_proc_entry(path,
124 				S_IRUGO,        /* world readable */
125 				NULL            /* parent dir */);
126 	if (pde) {
127 		pde->data = iface;
128 		pde->proc_fops = &sysvipc_proc_fops;
129 	} else {
130 		kfree(iface);
131 	}
132 }
133 #endif
134 
135 /**
136  *	ipc_findkey	-	find a key in an ipc identifier set
137  *	@ids: Identifier set
138  *	@key: The key to find
139  *
140  *	Requires ipc_ids.sem locked.
141  *	Returns the identifier if found or -1 if not.
142  */
143 
144 int ipc_findkey(struct ipc_ids* ids, key_t key)
145 {
146 	int id;
147 	struct kern_ipc_perm* p;
148 	int max_id = ids->max_id;
149 
150 	/*
151 	 * rcu_dereference() is not needed here
152 	 * since ipc_ids.sem is held
153 	 */
154 	for (id = 0; id <= max_id; id++) {
155 		p = ids->entries->p[id];
156 		if(p==NULL)
157 			continue;
158 		if (key == p->key)
159 			return id;
160 	}
161 	return -1;
162 }
163 
164 /*
165  * Requires ipc_ids.sem locked
166  */
167 static int grow_ary(struct ipc_ids* ids, int newsize)
168 {
169 	struct ipc_id_ary* new;
170 	struct ipc_id_ary* old;
171 	int i;
172 	int size = ids->entries->size;
173 
174 	if(newsize > IPCMNI)
175 		newsize = IPCMNI;
176 	if(newsize <= size)
177 		return newsize;
178 
179 	new = ipc_rcu_alloc(sizeof(struct kern_ipc_perm *)*newsize +
180 			    sizeof(struct ipc_id_ary));
181 	if(new == NULL)
182 		return size;
183 	new->size = newsize;
184 	memcpy(new->p, ids->entries->p, sizeof(struct kern_ipc_perm *)*size +
185 					sizeof(struct ipc_id_ary));
186 	for(i=size;i<newsize;i++) {
187 		new->p[i] = NULL;
188 	}
189 	old = ids->entries;
190 
191 	/*
192 	 * Use rcu_assign_pointer() to make sure the memcpyed contents
193 	 * of the new array are visible before the new array becomes visible.
194 	 */
195 	rcu_assign_pointer(ids->entries, new);
196 
197 	ipc_rcu_putref(old);
198 	return newsize;
199 }
200 
201 /**
202  *	ipc_addid 	-	add an IPC identifier
203  *	@ids: IPC identifier set
204  *	@new: new IPC permission set
205  *	@size: new size limit for the id array
206  *
207  *	Add an entry 'new' to the IPC arrays. The permissions object is
208  *	initialised and the first free entry is set up and the id assigned
209  *	is returned. The list is returned in a locked state on success.
210  *	On failure the list is not locked and -1 is returned.
211  *
212  *	Called with ipc_ids.sem held.
213  */
214 
215 int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
216 {
217 	int id;
218 
219 	size = grow_ary(ids,size);
220 
221 	/*
222 	 * rcu_dereference()() is not needed here since
223 	 * ipc_ids.sem is held
224 	 */
225 	for (id = 0; id < size; id++) {
226 		if(ids->entries->p[id] == NULL)
227 			goto found;
228 	}
229 	return -1;
230 found:
231 	ids->in_use++;
232 	if (id > ids->max_id)
233 		ids->max_id = id;
234 
235 	new->cuid = new->uid = current->euid;
236 	new->gid = new->cgid = current->egid;
237 
238 	new->seq = ids->seq++;
239 	if(ids->seq > ids->seq_max)
240 		ids->seq = 0;
241 
242 	spin_lock_init(&new->lock);
243 	new->deleted = 0;
244 	rcu_read_lock();
245 	spin_lock(&new->lock);
246 	ids->entries->p[id] = new;
247 	return id;
248 }
249 
250 /**
251  *	ipc_rmid	-	remove an IPC identifier
252  *	@ids: identifier set
253  *	@id: Identifier to remove
254  *
255  *	The identifier must be valid, and in use. The kernel will panic if
256  *	fed an invalid identifier. The entry is removed and internal
257  *	variables recomputed. The object associated with the identifier
258  *	is returned.
259  *	ipc_ids.sem and the spinlock for this ID is hold before this function
260  *	is called, and remain locked on the exit.
261  */
262 
263 struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id)
264 {
265 	struct kern_ipc_perm* p;
266 	int lid = id % SEQ_MULTIPLIER;
267 	if(lid >= ids->entries->size)
268 		BUG();
269 
270 	/*
271 	 * do not need a rcu_dereference()() here to force ordering
272 	 * on Alpha, since the ipc_ids.sem is held.
273 	 */
274 	p = ids->entries->p[lid];
275 	ids->entries->p[lid] = NULL;
276 	if(p==NULL)
277 		BUG();
278 	ids->in_use--;
279 
280 	if (lid == ids->max_id) {
281 		do {
282 			lid--;
283 			if(lid == -1)
284 				break;
285 		} while (ids->entries->p[lid] == NULL);
286 		ids->max_id = lid;
287 	}
288 	p->deleted = 1;
289 	return p;
290 }
291 
292 /**
293  *	ipc_alloc	-	allocate ipc space
294  *	@size: size desired
295  *
296  *	Allocate memory from the appropriate pools and return a pointer to it.
297  *	NULL is returned if the allocation fails
298  */
299 
300 void* ipc_alloc(int size)
301 {
302 	void* out;
303 	if(size > PAGE_SIZE)
304 		out = vmalloc(size);
305 	else
306 		out = kmalloc(size, GFP_KERNEL);
307 	return out;
308 }
309 
310 /**
311  *	ipc_free        -       free ipc space
312  *	@ptr: pointer returned by ipc_alloc
313  *	@size: size of block
314  *
315  *	Free a block created with ipc_alloc. The caller must know the size
316  *	used in the allocation call.
317  */
318 
319 void ipc_free(void* ptr, int size)
320 {
321 	if(size > PAGE_SIZE)
322 		vfree(ptr);
323 	else
324 		kfree(ptr);
325 }
326 
327 /*
328  * rcu allocations:
329  * There are three headers that are prepended to the actual allocation:
330  * - during use: ipc_rcu_hdr.
331  * - during the rcu grace period: ipc_rcu_grace.
332  * - [only if vmalloc]: ipc_rcu_sched.
333  * Their lifetime doesn't overlap, thus the headers share the same memory.
334  * Unlike a normal union, they are right-aligned, thus some container_of
335  * forward/backward casting is necessary:
336  */
337 struct ipc_rcu_hdr
338 {
339 	int refcount;
340 	int is_vmalloc;
341 	void *data[0];
342 };
343 
344 
345 struct ipc_rcu_grace
346 {
347 	struct rcu_head rcu;
348 	/* "void *" makes sure alignment of following data is sane. */
349 	void *data[0];
350 };
351 
352 struct ipc_rcu_sched
353 {
354 	struct work_struct work;
355 	/* "void *" makes sure alignment of following data is sane. */
356 	void *data[0];
357 };
358 
359 #define HDRLEN_KMALLOC		(sizeof(struct ipc_rcu_grace) > sizeof(struct ipc_rcu_hdr) ? \
360 					sizeof(struct ipc_rcu_grace) : sizeof(struct ipc_rcu_hdr))
361 #define HDRLEN_VMALLOC		(sizeof(struct ipc_rcu_sched) > HDRLEN_KMALLOC ? \
362 					sizeof(struct ipc_rcu_sched) : HDRLEN_KMALLOC)
363 
364 static inline int rcu_use_vmalloc(int size)
365 {
366 	/* Too big for a single page? */
367 	if (HDRLEN_KMALLOC + size > PAGE_SIZE)
368 		return 1;
369 	return 0;
370 }
371 
372 /**
373  *	ipc_rcu_alloc	-	allocate ipc and rcu space
374  *	@size: size desired
375  *
376  *	Allocate memory for the rcu header structure +  the object.
377  *	Returns the pointer to the object.
378  *	NULL is returned if the allocation fails.
379  */
380 
381 void* ipc_rcu_alloc(int size)
382 {
383 	void* out;
384 	/*
385 	 * We prepend the allocation with the rcu struct, and
386 	 * workqueue if necessary (for vmalloc).
387 	 */
388 	if (rcu_use_vmalloc(size)) {
389 		out = vmalloc(HDRLEN_VMALLOC + size);
390 		if (out) {
391 			out += HDRLEN_VMALLOC;
392 			container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 1;
393 			container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
394 		}
395 	} else {
396 		out = kmalloc(HDRLEN_KMALLOC + size, GFP_KERNEL);
397 		if (out) {
398 			out += HDRLEN_KMALLOC;
399 			container_of(out, struct ipc_rcu_hdr, data)->is_vmalloc = 0;
400 			container_of(out, struct ipc_rcu_hdr, data)->refcount = 1;
401 		}
402 	}
403 
404 	return out;
405 }
406 
407 void ipc_rcu_getref(void *ptr)
408 {
409 	container_of(ptr, struct ipc_rcu_hdr, data)->refcount++;
410 }
411 
412 /**
413  *	ipc_schedule_free	- free ipc + rcu space
414  *
415  * Since RCU callback function is called in bh,
416  * we need to defer the vfree to schedule_work
417  */
418 static void ipc_schedule_free(struct rcu_head *head)
419 {
420 	struct ipc_rcu_grace *grace =
421 		container_of(head, struct ipc_rcu_grace, rcu);
422 	struct ipc_rcu_sched *sched =
423 			container_of(&(grace->data[0]), struct ipc_rcu_sched, data[0]);
424 
425 	INIT_WORK(&sched->work, vfree, sched);
426 	schedule_work(&sched->work);
427 }
428 
429 /**
430  *	ipc_immediate_free	- free ipc + rcu space
431  *
432  *	Free from the RCU callback context
433  *
434  */
435 static void ipc_immediate_free(struct rcu_head *head)
436 {
437 	struct ipc_rcu_grace *free =
438 		container_of(head, struct ipc_rcu_grace, rcu);
439 	kfree(free);
440 }
441 
442 void ipc_rcu_putref(void *ptr)
443 {
444 	if (--container_of(ptr, struct ipc_rcu_hdr, data)->refcount > 0)
445 		return;
446 
447 	if (container_of(ptr, struct ipc_rcu_hdr, data)->is_vmalloc) {
448 		call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
449 				ipc_schedule_free);
450 	} else {
451 		call_rcu(&container_of(ptr, struct ipc_rcu_grace, data)->rcu,
452 				ipc_immediate_free);
453 	}
454 }
455 
456 /**
457  *	ipcperms	-	check IPC permissions
458  *	@ipcp: IPC permission set
459  *	@flag: desired permission set.
460  *
461  *	Check user, group, other permissions for access
462  *	to ipc resources. return 0 if allowed
463  */
464 
465 int ipcperms (struct kern_ipc_perm *ipcp, short flag)
466 {	/* flag will most probably be 0 or S_...UGO from <linux/stat.h> */
467 	int requested_mode, granted_mode;
468 
469 	requested_mode = (flag >> 6) | (flag >> 3) | flag;
470 	granted_mode = ipcp->mode;
471 	if (current->euid == ipcp->cuid || current->euid == ipcp->uid)
472 		granted_mode >>= 6;
473 	else if (in_group_p(ipcp->cgid) || in_group_p(ipcp->gid))
474 		granted_mode >>= 3;
475 	/* is there some bit set in requested_mode but not in granted_mode? */
476 	if ((requested_mode & ~granted_mode & 0007) &&
477 	    !capable(CAP_IPC_OWNER))
478 		return -1;
479 
480 	return security_ipc_permission(ipcp, flag);
481 }
482 
483 /*
484  * Functions to convert between the kern_ipc_perm structure and the
485  * old/new ipc_perm structures
486  */
487 
488 /**
489  *	kernel_to_ipc64_perm	-	convert kernel ipc permissions to user
490  *	@in: kernel permissions
491  *	@out: new style IPC permissions
492  *
493  *	Turn the kernel object 'in' into a set of permissions descriptions
494  *	for returning to userspace (out).
495  */
496 
497 
498 void kernel_to_ipc64_perm (struct kern_ipc_perm *in, struct ipc64_perm *out)
499 {
500 	out->key	= in->key;
501 	out->uid	= in->uid;
502 	out->gid	= in->gid;
503 	out->cuid	= in->cuid;
504 	out->cgid	= in->cgid;
505 	out->mode	= in->mode;
506 	out->seq	= in->seq;
507 }
508 
509 /**
510  *	ipc64_perm_to_ipc_perm	-	convert old ipc permissions to new
511  *	@in: new style IPC permissions
512  *	@out: old style IPC permissions
513  *
514  *	Turn the new style permissions object in into a compatibility
515  *	object and store it into the 'out' pointer.
516  */
517 
518 void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out)
519 {
520 	out->key	= in->key;
521 	SET_UID(out->uid, in->uid);
522 	SET_GID(out->gid, in->gid);
523 	SET_UID(out->cuid, in->cuid);
524 	SET_GID(out->cgid, in->cgid);
525 	out->mode	= in->mode;
526 	out->seq	= in->seq;
527 }
528 
529 /*
530  * So far only shm_get_stat() calls ipc_get() via shm_get(), so ipc_get()
531  * is called with shm_ids.sem locked.  Since grow_ary() is also called with
532  * shm_ids.sem down(for Shared Memory), there is no need to add read
533  * barriers here to gurantee the writes in grow_ary() are seen in order
534  * here (for Alpha).
535  *
536  * However ipc_get() itself does not necessary require ipc_ids.sem down. So
537  * if in the future ipc_get() is used by other places without ipc_ids.sem
538  * down, then ipc_get() needs read memery barriers as ipc_lock() does.
539  */
540 struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
541 {
542 	struct kern_ipc_perm* out;
543 	int lid = id % SEQ_MULTIPLIER;
544 	if(lid >= ids->entries->size)
545 		return NULL;
546 	out = ids->entries->p[lid];
547 	return out;
548 }
549 
550 struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
551 {
552 	struct kern_ipc_perm* out;
553 	int lid = id % SEQ_MULTIPLIER;
554 	struct ipc_id_ary* entries;
555 
556 	rcu_read_lock();
557 	entries = rcu_dereference(ids->entries);
558 	if(lid >= entries->size) {
559 		rcu_read_unlock();
560 		return NULL;
561 	}
562 	out = entries->p[lid];
563 	if(out == NULL) {
564 		rcu_read_unlock();
565 		return NULL;
566 	}
567 	spin_lock(&out->lock);
568 
569 	/* ipc_rmid() may have already freed the ID while ipc_lock
570 	 * was spinning: here verify that the structure is still valid
571 	 */
572 	if (out->deleted) {
573 		spin_unlock(&out->lock);
574 		rcu_read_unlock();
575 		return NULL;
576 	}
577 	return out;
578 }
579 
580 void ipc_lock_by_ptr(struct kern_ipc_perm *perm)
581 {
582 	rcu_read_lock();
583 	spin_lock(&perm->lock);
584 }
585 
586 void ipc_unlock(struct kern_ipc_perm* perm)
587 {
588 	spin_unlock(&perm->lock);
589 	rcu_read_unlock();
590 }
591 
592 int ipc_buildid(struct ipc_ids* ids, int id, int seq)
593 {
594 	return SEQ_MULTIPLIER*seq + id;
595 }
596 
597 int ipc_checkid(struct ipc_ids* ids, struct kern_ipc_perm* ipcp, int uid)
598 {
599 	if(uid/SEQ_MULTIPLIER != ipcp->seq)
600 		return 1;
601 	return 0;
602 }
603 
604 #ifdef __ARCH_WANT_IPC_PARSE_VERSION
605 
606 
607 /**
608  *	ipc_parse_version	-	IPC call version
609  *	@cmd: pointer to command
610  *
611  *	Return IPC_64 for new style IPC and IPC_OLD for old style IPC.
612  *	The cmd value is turned from an encoding command and version into
613  *	just the command code.
614  */
615 
616 int ipc_parse_version (int *cmd)
617 {
618 	if (*cmd & IPC_64) {
619 		*cmd ^= IPC_64;
620 		return IPC_64;
621 	} else {
622 		return IPC_OLD;
623 	}
624 }
625 
626 #endif /* __ARCH_WANT_IPC_PARSE_VERSION */
627 
628 #ifdef CONFIG_PROC_FS
629 static void *sysvipc_proc_next(struct seq_file *s, void *it, loff_t *pos)
630 {
631 	struct ipc_proc_iface *iface = s->private;
632 	struct kern_ipc_perm *ipc = it;
633 	loff_t p;
634 
635 	/* If we had an ipc id locked before, unlock it */
636 	if (ipc && ipc != SEQ_START_TOKEN)
637 		ipc_unlock(ipc);
638 
639 	/*
640 	 * p = *pos - 1 (because id 0 starts at position 1)
641 	 *          + 1 (because we increment the position by one)
642 	 */
643 	for (p = *pos; p <= iface->ids->max_id; p++) {
644 		if ((ipc = ipc_lock(iface->ids, p)) != NULL) {
645 			*pos = p + 1;
646 			return ipc;
647 		}
648 	}
649 
650 	/* Out of range - return NULL to terminate iteration */
651 	return NULL;
652 }
653 
654 /*
655  * File positions: pos 0 -> header, pos n -> ipc id + 1.
656  * SeqFile iterator: iterator value locked shp or SEQ_TOKEN_START.
657  */
658 static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos)
659 {
660 	struct ipc_proc_iface *iface = s->private;
661 	struct kern_ipc_perm *ipc;
662 	loff_t p;
663 
664 	/*
665 	 * Take the lock - this will be released by the corresponding
666 	 * call to stop().
667 	 */
668 	down(&iface->ids->sem);
669 
670 	/* pos < 0 is invalid */
671 	if (*pos < 0)
672 		return NULL;
673 
674 	/* pos == 0 means header */
675 	if (*pos == 0)
676 		return SEQ_START_TOKEN;
677 
678 	/* Find the (pos-1)th ipc */
679 	for (p = *pos - 1; p <= iface->ids->max_id; p++) {
680 		if ((ipc = ipc_lock(iface->ids, p)) != NULL) {
681 			*pos = p + 1;
682 			return ipc;
683 		}
684 	}
685 	return NULL;
686 }
687 
688 static void sysvipc_proc_stop(struct seq_file *s, void *it)
689 {
690 	struct kern_ipc_perm *ipc = it;
691 	struct ipc_proc_iface *iface = s->private;
692 
693 	/* If we had a locked segment, release it */
694 	if (ipc && ipc != SEQ_START_TOKEN)
695 		ipc_unlock(ipc);
696 
697 	/* Release the lock we took in start() */
698 	up(&iface->ids->sem);
699 }
700 
701 static int sysvipc_proc_show(struct seq_file *s, void *it)
702 {
703 	struct ipc_proc_iface *iface = s->private;
704 
705 	if (it == SEQ_START_TOKEN)
706 		return seq_puts(s, iface->header);
707 
708 	return iface->show(s, it);
709 }
710 
711 static struct seq_operations sysvipc_proc_seqops = {
712 	.start = sysvipc_proc_start,
713 	.stop  = sysvipc_proc_stop,
714 	.next  = sysvipc_proc_next,
715 	.show  = sysvipc_proc_show,
716 };
717 
718 static int sysvipc_proc_open(struct inode *inode, struct file *file) {
719 	int ret;
720 	struct seq_file *seq;
721 
722 	ret = seq_open(file, &sysvipc_proc_seqops);
723 	if (!ret) {
724 		seq = file->private_data;
725 		seq->private = PDE(inode)->data;
726 	}
727 	return ret;
728 }
729 
730 static struct file_operations sysvipc_proc_fops = {
731 	.open    = sysvipc_proc_open,
732 	.read    = seq_read,
733 	.llseek  = seq_lseek,
734 	.release = seq_release,
735 };
736 #endif /* CONFIG_PROC_FS */
737