xref: /openbmc/linux/ipc/mqueue.c (revision 22246614)
1 /*
2  * POSIX message queues filesystem for Linux.
3  *
4  * Copyright (C) 2003,2004  Krzysztof Benedyczak    (golbi@mat.uni.torun.pl)
5  *                          Michal Wronski          (michal.wronski@gmail.com)
6  *
7  * Spinlocks:               Mohamed Abbas           (abbas.mohamed@intel.com)
8  * Lockless receive & send, fd based notify:
9  * 			    Manfred Spraul	    (manfred@colorfullife.com)
10  *
11  * Audit:                   George Wilson           (ltcgcw@us.ibm.com)
12  *
13  * This file is released under the GPL.
14  */
15 
16 #include <linux/capability.h>
17 #include <linux/init.h>
18 #include <linux/pagemap.h>
19 #include <linux/file.h>
20 #include <linux/mount.h>
21 #include <linux/namei.h>
22 #include <linux/sysctl.h>
23 #include <linux/poll.h>
24 #include <linux/mqueue.h>
25 #include <linux/msg.h>
26 #include <linux/skbuff.h>
27 #include <linux/netlink.h>
28 #include <linux/syscalls.h>
29 #include <linux/audit.h>
30 #include <linux/signal.h>
31 #include <linux/mutex.h>
32 #include <linux/nsproxy.h>
33 #include <linux/pid.h>
34 
35 #include <net/sock.h>
36 #include "util.h"
37 
38 #define MQUEUE_MAGIC	0x19800202
39 #define DIRENT_SIZE	20
40 #define FILENT_SIZE	80
41 
42 #define SEND		0
43 #define RECV		1
44 
45 #define STATE_NONE	0
46 #define STATE_PENDING	1
47 #define STATE_READY	2
48 
49 /* default values */
50 #define DFLT_QUEUESMAX	256	/* max number of message queues */
51 #define DFLT_MSGMAX 	10	/* max number of messages in each queue */
52 #define HARD_MSGMAX 	(131072/sizeof(void*))
53 #define DFLT_MSGSIZEMAX 8192	/* max message size */
54 
55 
56 struct ext_wait_queue {		/* queue of sleeping tasks */
57 	struct task_struct *task;
58 	struct list_head list;
59 	struct msg_msg *msg;	/* ptr of loaded message */
60 	int state;		/* one of STATE_* values */
61 };
62 
63 struct mqueue_inode_info {
64 	spinlock_t lock;
65 	struct inode vfs_inode;
66 	wait_queue_head_t wait_q;
67 
68 	struct msg_msg **messages;
69 	struct mq_attr attr;
70 
71 	struct sigevent notify;
72 	struct pid* notify_owner;
73 	struct user_struct *user;	/* user who created, for accounting */
74 	struct sock *notify_sock;
75 	struct sk_buff *notify_cookie;
76 
77 	/* for tasks waiting for free space and messages, respectively */
78 	struct ext_wait_queue e_wait_q[2];
79 
80 	unsigned long qsize; /* size of queue in memory (sum of all msgs) */
81 };
82 
83 static const struct inode_operations mqueue_dir_inode_operations;
84 static const struct file_operations mqueue_file_operations;
85 static struct super_operations mqueue_super_ops;
86 static void remove_notification(struct mqueue_inode_info *info);
87 
88 static spinlock_t mq_lock;
89 static struct kmem_cache *mqueue_inode_cachep;
90 static struct vfsmount *mqueue_mnt;
91 
92 static unsigned int queues_count;
93 static unsigned int queues_max 	= DFLT_QUEUESMAX;
94 static unsigned int msg_max 	= DFLT_MSGMAX;
95 static unsigned int msgsize_max = DFLT_MSGSIZEMAX;
96 
97 static struct ctl_table_header * mq_sysctl_table;
98 
99 static inline struct mqueue_inode_info *MQUEUE_I(struct inode *inode)
100 {
101 	return container_of(inode, struct mqueue_inode_info, vfs_inode);
102 }
103 
104 static struct inode *mqueue_get_inode(struct super_block *sb, int mode,
105 							struct mq_attr *attr)
106 {
107 	struct inode *inode;
108 
109 	inode = new_inode(sb);
110 	if (inode) {
111 		inode->i_mode = mode;
112 		inode->i_uid = current->fsuid;
113 		inode->i_gid = current->fsgid;
114 		inode->i_blocks = 0;
115 		inode->i_mtime = inode->i_ctime = inode->i_atime =
116 				CURRENT_TIME;
117 
118 		if (S_ISREG(mode)) {
119 			struct mqueue_inode_info *info;
120 			struct task_struct *p = current;
121 			struct user_struct *u = p->user;
122 			unsigned long mq_bytes, mq_msg_tblsz;
123 
124 			inode->i_fop = &mqueue_file_operations;
125 			inode->i_size = FILENT_SIZE;
126 			/* mqueue specific info */
127 			info = MQUEUE_I(inode);
128 			spin_lock_init(&info->lock);
129 			init_waitqueue_head(&info->wait_q);
130 			INIT_LIST_HEAD(&info->e_wait_q[0].list);
131 			INIT_LIST_HEAD(&info->e_wait_q[1].list);
132 			info->messages = NULL;
133 			info->notify_owner = NULL;
134 			info->qsize = 0;
135 			info->user = NULL;	/* set when all is ok */
136 			memset(&info->attr, 0, sizeof(info->attr));
137 			info->attr.mq_maxmsg = DFLT_MSGMAX;
138 			info->attr.mq_msgsize = DFLT_MSGSIZEMAX;
139 			if (attr) {
140 				info->attr.mq_maxmsg = attr->mq_maxmsg;
141 				info->attr.mq_msgsize = attr->mq_msgsize;
142 			}
143 			mq_msg_tblsz = info->attr.mq_maxmsg * sizeof(struct msg_msg *);
144 			mq_bytes = (mq_msg_tblsz +
145 				(info->attr.mq_maxmsg * info->attr.mq_msgsize));
146 
147 			spin_lock(&mq_lock);
148 			if (u->mq_bytes + mq_bytes < u->mq_bytes ||
149 		 	    u->mq_bytes + mq_bytes >
150 			    p->signal->rlim[RLIMIT_MSGQUEUE].rlim_cur) {
151 				spin_unlock(&mq_lock);
152 				goto out_inode;
153 			}
154 			u->mq_bytes += mq_bytes;
155 			spin_unlock(&mq_lock);
156 
157 			info->messages = kmalloc(mq_msg_tblsz, GFP_KERNEL);
158 			if (!info->messages) {
159 				spin_lock(&mq_lock);
160 				u->mq_bytes -= mq_bytes;
161 				spin_unlock(&mq_lock);
162 				goto out_inode;
163 			}
164 			/* all is ok */
165 			info->user = get_uid(u);
166 		} else if (S_ISDIR(mode)) {
167 			inc_nlink(inode);
168 			/* Some things misbehave if size == 0 on a directory */
169 			inode->i_size = 2 * DIRENT_SIZE;
170 			inode->i_op = &mqueue_dir_inode_operations;
171 			inode->i_fop = &simple_dir_operations;
172 		}
173 	}
174 	return inode;
175 out_inode:
176 	make_bad_inode(inode);
177 	iput(inode);
178 	return NULL;
179 }
180 
181 static int mqueue_fill_super(struct super_block *sb, void *data, int silent)
182 {
183 	struct inode *inode;
184 
185 	sb->s_blocksize = PAGE_CACHE_SIZE;
186 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
187 	sb->s_magic = MQUEUE_MAGIC;
188 	sb->s_op = &mqueue_super_ops;
189 
190 	inode = mqueue_get_inode(sb, S_IFDIR | S_ISVTX | S_IRWXUGO, NULL);
191 	if (!inode)
192 		return -ENOMEM;
193 
194 	sb->s_root = d_alloc_root(inode);
195 	if (!sb->s_root) {
196 		iput(inode);
197 		return -ENOMEM;
198 	}
199 
200 	return 0;
201 }
202 
203 static int mqueue_get_sb(struct file_system_type *fs_type,
204 			 int flags, const char *dev_name,
205 			 void *data, struct vfsmount *mnt)
206 {
207 	return get_sb_single(fs_type, flags, data, mqueue_fill_super, mnt);
208 }
209 
210 static void init_once(struct kmem_cache *cachep, void *foo)
211 {
212 	struct mqueue_inode_info *p = (struct mqueue_inode_info *) foo;
213 
214 	inode_init_once(&p->vfs_inode);
215 }
216 
217 static struct inode *mqueue_alloc_inode(struct super_block *sb)
218 {
219 	struct mqueue_inode_info *ei;
220 
221 	ei = kmem_cache_alloc(mqueue_inode_cachep, GFP_KERNEL);
222 	if (!ei)
223 		return NULL;
224 	return &ei->vfs_inode;
225 }
226 
227 static void mqueue_destroy_inode(struct inode *inode)
228 {
229 	kmem_cache_free(mqueue_inode_cachep, MQUEUE_I(inode));
230 }
231 
232 static void mqueue_delete_inode(struct inode *inode)
233 {
234 	struct mqueue_inode_info *info;
235 	struct user_struct *user;
236 	unsigned long mq_bytes;
237 	int i;
238 
239 	if (S_ISDIR(inode->i_mode)) {
240 		clear_inode(inode);
241 		return;
242 	}
243 	info = MQUEUE_I(inode);
244 	spin_lock(&info->lock);
245 	for (i = 0; i < info->attr.mq_curmsgs; i++)
246 		free_msg(info->messages[i]);
247 	kfree(info->messages);
248 	spin_unlock(&info->lock);
249 
250 	clear_inode(inode);
251 
252 	mq_bytes = (info->attr.mq_maxmsg * sizeof(struct msg_msg *) +
253 		   (info->attr.mq_maxmsg * info->attr.mq_msgsize));
254 	user = info->user;
255 	if (user) {
256 		spin_lock(&mq_lock);
257 		user->mq_bytes -= mq_bytes;
258 		queues_count--;
259 		spin_unlock(&mq_lock);
260 		free_uid(user);
261 	}
262 }
263 
264 static int mqueue_create(struct inode *dir, struct dentry *dentry,
265 				int mode, struct nameidata *nd)
266 {
267 	struct inode *inode;
268 	struct mq_attr *attr = dentry->d_fsdata;
269 	int error;
270 
271 	spin_lock(&mq_lock);
272 	if (queues_count >= queues_max && !capable(CAP_SYS_RESOURCE)) {
273 		error = -ENOSPC;
274 		goto out_lock;
275 	}
276 	queues_count++;
277 	spin_unlock(&mq_lock);
278 
279 	inode = mqueue_get_inode(dir->i_sb, mode, attr);
280 	if (!inode) {
281 		error = -ENOMEM;
282 		spin_lock(&mq_lock);
283 		queues_count--;
284 		goto out_lock;
285 	}
286 
287 	dir->i_size += DIRENT_SIZE;
288 	dir->i_ctime = dir->i_mtime = dir->i_atime = CURRENT_TIME;
289 
290 	d_instantiate(dentry, inode);
291 	dget(dentry);
292 	return 0;
293 out_lock:
294 	spin_unlock(&mq_lock);
295 	return error;
296 }
297 
298 static int mqueue_unlink(struct inode *dir, struct dentry *dentry)
299 {
300   	struct inode *inode = dentry->d_inode;
301 
302 	dir->i_ctime = dir->i_mtime = dir->i_atime = CURRENT_TIME;
303 	dir->i_size -= DIRENT_SIZE;
304   	drop_nlink(inode);
305   	dput(dentry);
306   	return 0;
307 }
308 
309 /*
310 *	This is routine for system read from queue file.
311 *	To avoid mess with doing here some sort of mq_receive we allow
312 *	to read only queue size & notification info (the only values
313 *	that are interesting from user point of view and aren't accessible
314 *	through std routines)
315 */
316 static ssize_t mqueue_read_file(struct file *filp, char __user *u_data,
317 				size_t count, loff_t * off)
318 {
319 	struct mqueue_inode_info *info = MQUEUE_I(filp->f_path.dentry->d_inode);
320 	char buffer[FILENT_SIZE];
321 	size_t slen;
322 	loff_t o;
323 
324 	if (!count)
325 		return 0;
326 
327 	spin_lock(&info->lock);
328 	snprintf(buffer, sizeof(buffer),
329 			"QSIZE:%-10lu NOTIFY:%-5d SIGNO:%-5d NOTIFY_PID:%-6d\n",
330 			info->qsize,
331 			info->notify_owner ? info->notify.sigev_notify : 0,
332 			(info->notify_owner &&
333 			 info->notify.sigev_notify == SIGEV_SIGNAL) ?
334 				info->notify.sigev_signo : 0,
335 			pid_vnr(info->notify_owner));
336 	spin_unlock(&info->lock);
337 	buffer[sizeof(buffer)-1] = '\0';
338 	slen = strlen(buffer)+1;
339 
340 	o = *off;
341 	if (o > slen)
342 		return 0;
343 
344 	if (o + count > slen)
345 		count = slen - o;
346 
347 	if (copy_to_user(u_data, buffer + o, count))
348 		return -EFAULT;
349 
350 	*off = o + count;
351 	filp->f_path.dentry->d_inode->i_atime = filp->f_path.dentry->d_inode->i_ctime = CURRENT_TIME;
352 	return count;
353 }
354 
355 static int mqueue_flush_file(struct file *filp, fl_owner_t id)
356 {
357 	struct mqueue_inode_info *info = MQUEUE_I(filp->f_path.dentry->d_inode);
358 
359 	spin_lock(&info->lock);
360 	if (task_tgid(current) == info->notify_owner)
361 		remove_notification(info);
362 
363 	spin_unlock(&info->lock);
364 	return 0;
365 }
366 
367 static unsigned int mqueue_poll_file(struct file *filp, struct poll_table_struct *poll_tab)
368 {
369 	struct mqueue_inode_info *info = MQUEUE_I(filp->f_path.dentry->d_inode);
370 	int retval = 0;
371 
372 	poll_wait(filp, &info->wait_q, poll_tab);
373 
374 	spin_lock(&info->lock);
375 	if (info->attr.mq_curmsgs)
376 		retval = POLLIN | POLLRDNORM;
377 
378 	if (info->attr.mq_curmsgs < info->attr.mq_maxmsg)
379 		retval |= POLLOUT | POLLWRNORM;
380 	spin_unlock(&info->lock);
381 
382 	return retval;
383 }
384 
385 /* Adds current to info->e_wait_q[sr] before element with smaller prio */
386 static void wq_add(struct mqueue_inode_info *info, int sr,
387 			struct ext_wait_queue *ewp)
388 {
389 	struct ext_wait_queue *walk;
390 
391 	ewp->task = current;
392 
393 	list_for_each_entry(walk, &info->e_wait_q[sr].list, list) {
394 		if (walk->task->static_prio <= current->static_prio) {
395 			list_add_tail(&ewp->list, &walk->list);
396 			return;
397 		}
398 	}
399 	list_add_tail(&ewp->list, &info->e_wait_q[sr].list);
400 }
401 
402 /*
403  * Puts current task to sleep. Caller must hold queue lock. After return
404  * lock isn't held.
405  * sr: SEND or RECV
406  */
407 static int wq_sleep(struct mqueue_inode_info *info, int sr,
408 			long timeout, struct ext_wait_queue *ewp)
409 {
410 	int retval;
411 	signed long time;
412 
413 	wq_add(info, sr, ewp);
414 
415 	for (;;) {
416 		set_current_state(TASK_INTERRUPTIBLE);
417 
418 		spin_unlock(&info->lock);
419 		time = schedule_timeout(timeout);
420 
421 		while (ewp->state == STATE_PENDING)
422 			cpu_relax();
423 
424 		if (ewp->state == STATE_READY) {
425 			retval = 0;
426 			goto out;
427 		}
428 		spin_lock(&info->lock);
429 		if (ewp->state == STATE_READY) {
430 			retval = 0;
431 			goto out_unlock;
432 		}
433 		if (signal_pending(current)) {
434 			retval = -ERESTARTSYS;
435 			break;
436 		}
437 		if (time == 0) {
438 			retval = -ETIMEDOUT;
439 			break;
440 		}
441 	}
442 	list_del(&ewp->list);
443 out_unlock:
444 	spin_unlock(&info->lock);
445 out:
446 	return retval;
447 }
448 
449 /*
450  * Returns waiting task that should be serviced first or NULL if none exists
451  */
452 static struct ext_wait_queue *wq_get_first_waiter(
453 		struct mqueue_inode_info *info, int sr)
454 {
455 	struct list_head *ptr;
456 
457 	ptr = info->e_wait_q[sr].list.prev;
458 	if (ptr == &info->e_wait_q[sr].list)
459 		return NULL;
460 	return list_entry(ptr, struct ext_wait_queue, list);
461 }
462 
463 /* Auxiliary functions to manipulate messages' list */
464 static void msg_insert(struct msg_msg *ptr, struct mqueue_inode_info *info)
465 {
466 	int k;
467 
468 	k = info->attr.mq_curmsgs - 1;
469 	while (k >= 0 && info->messages[k]->m_type >= ptr->m_type) {
470 		info->messages[k + 1] = info->messages[k];
471 		k--;
472 	}
473 	info->attr.mq_curmsgs++;
474 	info->qsize += ptr->m_ts;
475 	info->messages[k + 1] = ptr;
476 }
477 
478 static inline struct msg_msg *msg_get(struct mqueue_inode_info *info)
479 {
480 	info->qsize -= info->messages[--info->attr.mq_curmsgs]->m_ts;
481 	return info->messages[info->attr.mq_curmsgs];
482 }
483 
484 static inline void set_cookie(struct sk_buff *skb, char code)
485 {
486 	((char*)skb->data)[NOTIFY_COOKIE_LEN-1] = code;
487 }
488 
489 /*
490  * The next function is only to split too long sys_mq_timedsend
491  */
492 static void __do_notify(struct mqueue_inode_info *info)
493 {
494 	/* notification
495 	 * invoked when there is registered process and there isn't process
496 	 * waiting synchronously for message AND state of queue changed from
497 	 * empty to not empty. Here we are sure that no one is waiting
498 	 * synchronously. */
499 	if (info->notify_owner &&
500 	    info->attr.mq_curmsgs == 1) {
501 		struct siginfo sig_i;
502 		switch (info->notify.sigev_notify) {
503 		case SIGEV_NONE:
504 			break;
505 		case SIGEV_SIGNAL:
506 			/* sends signal */
507 
508 			sig_i.si_signo = info->notify.sigev_signo;
509 			sig_i.si_errno = 0;
510 			sig_i.si_code = SI_MESGQ;
511 			sig_i.si_value = info->notify.sigev_value;
512 			sig_i.si_pid = task_tgid_vnr(current);
513 			sig_i.si_uid = current->uid;
514 
515 			kill_pid_info(info->notify.sigev_signo,
516 				      &sig_i, info->notify_owner);
517 			break;
518 		case SIGEV_THREAD:
519 			set_cookie(info->notify_cookie, NOTIFY_WOKENUP);
520 			netlink_sendskb(info->notify_sock, info->notify_cookie);
521 			break;
522 		}
523 		/* after notification unregisters process */
524 		put_pid(info->notify_owner);
525 		info->notify_owner = NULL;
526 	}
527 	wake_up(&info->wait_q);
528 }
529 
530 static long prepare_timeout(const struct timespec __user *u_arg)
531 {
532 	struct timespec ts, nowts;
533 	long timeout;
534 
535 	if (u_arg) {
536 		if (unlikely(copy_from_user(&ts, u_arg,
537 					sizeof(struct timespec))))
538 			return -EFAULT;
539 
540 		if (unlikely(ts.tv_nsec < 0 || ts.tv_sec < 0
541 			|| ts.tv_nsec >= NSEC_PER_SEC))
542 			return -EINVAL;
543 		nowts = CURRENT_TIME;
544 		/* first subtract as jiffies can't be too big */
545 		ts.tv_sec -= nowts.tv_sec;
546 		if (ts.tv_nsec < nowts.tv_nsec) {
547 			ts.tv_nsec += NSEC_PER_SEC;
548 			ts.tv_sec--;
549 		}
550 		ts.tv_nsec -= nowts.tv_nsec;
551 		if (ts.tv_sec < 0)
552 			return 0;
553 
554 		timeout = timespec_to_jiffies(&ts) + 1;
555 	} else
556 		return MAX_SCHEDULE_TIMEOUT;
557 
558 	return timeout;
559 }
560 
561 static void remove_notification(struct mqueue_inode_info *info)
562 {
563 	if (info->notify_owner != NULL &&
564 	    info->notify.sigev_notify == SIGEV_THREAD) {
565 		set_cookie(info->notify_cookie, NOTIFY_REMOVED);
566 		netlink_sendskb(info->notify_sock, info->notify_cookie);
567 	}
568 	put_pid(info->notify_owner);
569 	info->notify_owner = NULL;
570 }
571 
572 static int mq_attr_ok(struct mq_attr *attr)
573 {
574 	if (attr->mq_maxmsg <= 0 || attr->mq_msgsize <= 0)
575 		return 0;
576 	if (capable(CAP_SYS_RESOURCE)) {
577 		if (attr->mq_maxmsg > HARD_MSGMAX)
578 			return 0;
579 	} else {
580 		if (attr->mq_maxmsg > msg_max ||
581 				attr->mq_msgsize > msgsize_max)
582 			return 0;
583 	}
584 	/* check for overflow */
585 	if (attr->mq_msgsize > ULONG_MAX/attr->mq_maxmsg)
586 		return 0;
587 	if ((unsigned long)(attr->mq_maxmsg * attr->mq_msgsize) +
588 	    (attr->mq_maxmsg * sizeof (struct msg_msg *)) <
589 	    (unsigned long)(attr->mq_maxmsg * attr->mq_msgsize))
590 		return 0;
591 	return 1;
592 }
593 
594 /*
595  * Invoked when creating a new queue via sys_mq_open
596  */
597 static struct file *do_create(struct dentry *dir, struct dentry *dentry,
598 			int oflag, mode_t mode, struct mq_attr __user *u_attr)
599 {
600 	struct mq_attr attr;
601 	struct file *result;
602 	int ret;
603 
604 	if (u_attr) {
605 		ret = -EFAULT;
606 		if (copy_from_user(&attr, u_attr, sizeof(attr)))
607 			goto out;
608 		ret = -EINVAL;
609 		if (!mq_attr_ok(&attr))
610 			goto out;
611 		/* store for use during create */
612 		dentry->d_fsdata = &attr;
613 	}
614 
615 	mode &= ~current->fs->umask;
616 	ret = mnt_want_write(mqueue_mnt);
617 	if (ret)
618 		goto out;
619 	ret = vfs_create(dir->d_inode, dentry, mode, NULL);
620 	dentry->d_fsdata = NULL;
621 	if (ret)
622 		goto out_drop_write;
623 
624 	result = dentry_open(dentry, mqueue_mnt, oflag);
625 	/*
626 	 * dentry_open() took a persistent mnt_want_write(),
627 	 * so we can now drop this one.
628 	 */
629 	mnt_drop_write(mqueue_mnt);
630 	return result;
631 
632 out_drop_write:
633 	mnt_drop_write(mqueue_mnt);
634 out:
635 	dput(dentry);
636 	mntput(mqueue_mnt);
637 	return ERR_PTR(ret);
638 }
639 
640 /* Opens existing queue */
641 static struct file *do_open(struct dentry *dentry, int oflag)
642 {
643 static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
644 					MAY_READ | MAY_WRITE };
645 
646 	if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY)) {
647 		dput(dentry);
648 		mntput(mqueue_mnt);
649 		return ERR_PTR(-EINVAL);
650 	}
651 
652 	if (permission(dentry->d_inode, oflag2acc[oflag & O_ACCMODE], NULL)) {
653 		dput(dentry);
654 		mntput(mqueue_mnt);
655 		return ERR_PTR(-EACCES);
656 	}
657 
658 	return dentry_open(dentry, mqueue_mnt, oflag);
659 }
660 
661 asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode,
662 				struct mq_attr __user *u_attr)
663 {
664 	struct dentry *dentry;
665 	struct file *filp;
666 	char *name;
667 	int fd, error;
668 
669 	error = audit_mq_open(oflag, mode, u_attr);
670 	if (error != 0)
671 		return error;
672 
673 	if (IS_ERR(name = getname(u_name)))
674 		return PTR_ERR(name);
675 
676 	fd = get_unused_fd_flags(O_CLOEXEC);
677 	if (fd < 0)
678 		goto out_putname;
679 
680 	mutex_lock(&mqueue_mnt->mnt_root->d_inode->i_mutex);
681 	dentry = lookup_one_len(name, mqueue_mnt->mnt_root, strlen(name));
682 	if (IS_ERR(dentry)) {
683 		error = PTR_ERR(dentry);
684 		goto out_err;
685 	}
686 	mntget(mqueue_mnt);
687 
688 	if (oflag & O_CREAT) {
689 		if (dentry->d_inode) {	/* entry already exists */
690 			audit_inode(name, dentry);
691 			error = -EEXIST;
692 			if (oflag & O_EXCL)
693 				goto out;
694 			filp = do_open(dentry, oflag);
695 		} else {
696 			filp = do_create(mqueue_mnt->mnt_root, dentry,
697 						oflag, mode, u_attr);
698 		}
699 	} else {
700 		error = -ENOENT;
701 		if (!dentry->d_inode)
702 			goto out;
703 		audit_inode(name, dentry);
704 		filp = do_open(dentry, oflag);
705 	}
706 
707 	if (IS_ERR(filp)) {
708 		error = PTR_ERR(filp);
709 		goto out_putfd;
710 	}
711 
712 	fd_install(fd, filp);
713 	goto out_upsem;
714 
715 out:
716 	dput(dentry);
717 	mntput(mqueue_mnt);
718 out_putfd:
719 	put_unused_fd(fd);
720 out_err:
721 	fd = error;
722 out_upsem:
723 	mutex_unlock(&mqueue_mnt->mnt_root->d_inode->i_mutex);
724 out_putname:
725 	putname(name);
726 	return fd;
727 }
728 
729 asmlinkage long sys_mq_unlink(const char __user *u_name)
730 {
731 	int err;
732 	char *name;
733 	struct dentry *dentry;
734 	struct inode *inode = NULL;
735 
736 	name = getname(u_name);
737 	if (IS_ERR(name))
738 		return PTR_ERR(name);
739 
740 	mutex_lock_nested(&mqueue_mnt->mnt_root->d_inode->i_mutex,
741 			I_MUTEX_PARENT);
742 	dentry = lookup_one_len(name, mqueue_mnt->mnt_root, strlen(name));
743 	if (IS_ERR(dentry)) {
744 		err = PTR_ERR(dentry);
745 		goto out_unlock;
746 	}
747 
748 	if (!dentry->d_inode) {
749 		err = -ENOENT;
750 		goto out_err;
751 	}
752 
753 	inode = dentry->d_inode;
754 	if (inode)
755 		atomic_inc(&inode->i_count);
756 	err = mnt_want_write(mqueue_mnt);
757 	if (err)
758 		goto out_err;
759 	err = vfs_unlink(dentry->d_parent->d_inode, dentry);
760 	mnt_drop_write(mqueue_mnt);
761 out_err:
762 	dput(dentry);
763 
764 out_unlock:
765 	mutex_unlock(&mqueue_mnt->mnt_root->d_inode->i_mutex);
766 	putname(name);
767 	if (inode)
768 		iput(inode);
769 
770 	return err;
771 }
772 
773 /* Pipelined send and receive functions.
774  *
775  * If a receiver finds no waiting message, then it registers itself in the
776  * list of waiting receivers. A sender checks that list before adding the new
777  * message into the message array. If there is a waiting receiver, then it
778  * bypasses the message array and directly hands the message over to the
779  * receiver.
780  * The receiver accepts the message and returns without grabbing the queue
781  * spinlock. Therefore an intermediate STATE_PENDING state and memory barriers
782  * are necessary. The same algorithm is used for sysv semaphores, see
783  * ipc/sem.c for more details.
784  *
785  * The same algorithm is used for senders.
786  */
787 
788 /* pipelined_send() - send a message directly to the task waiting in
789  * sys_mq_timedreceive() (without inserting message into a queue).
790  */
791 static inline void pipelined_send(struct mqueue_inode_info *info,
792 				  struct msg_msg *message,
793 				  struct ext_wait_queue *receiver)
794 {
795 	receiver->msg = message;
796 	list_del(&receiver->list);
797 	receiver->state = STATE_PENDING;
798 	wake_up_process(receiver->task);
799 	smp_wmb();
800 	receiver->state = STATE_READY;
801 }
802 
803 /* pipelined_receive() - if there is task waiting in sys_mq_timedsend()
804  * gets its message and put to the queue (we have one free place for sure). */
805 static inline void pipelined_receive(struct mqueue_inode_info *info)
806 {
807 	struct ext_wait_queue *sender = wq_get_first_waiter(info, SEND);
808 
809 	if (!sender) {
810 		/* for poll */
811 		wake_up_interruptible(&info->wait_q);
812 		return;
813 	}
814 	msg_insert(sender->msg, info);
815 	list_del(&sender->list);
816 	sender->state = STATE_PENDING;
817 	wake_up_process(sender->task);
818 	smp_wmb();
819 	sender->state = STATE_READY;
820 }
821 
822 asmlinkage long sys_mq_timedsend(mqd_t mqdes, const char __user *u_msg_ptr,
823 	size_t msg_len, unsigned int msg_prio,
824 	const struct timespec __user *u_abs_timeout)
825 {
826 	struct file *filp;
827 	struct inode *inode;
828 	struct ext_wait_queue wait;
829 	struct ext_wait_queue *receiver;
830 	struct msg_msg *msg_ptr;
831 	struct mqueue_inode_info *info;
832 	long timeout;
833 	int ret;
834 
835 	ret = audit_mq_timedsend(mqdes, msg_len, msg_prio, u_abs_timeout);
836 	if (ret != 0)
837 		return ret;
838 
839 	if (unlikely(msg_prio >= (unsigned long) MQ_PRIO_MAX))
840 		return -EINVAL;
841 
842 	timeout = prepare_timeout(u_abs_timeout);
843 
844 	ret = -EBADF;
845 	filp = fget(mqdes);
846 	if (unlikely(!filp))
847 		goto out;
848 
849 	inode = filp->f_path.dentry->d_inode;
850 	if (unlikely(filp->f_op != &mqueue_file_operations))
851 		goto out_fput;
852 	info = MQUEUE_I(inode);
853 	audit_inode(NULL, filp->f_path.dentry);
854 
855 	if (unlikely(!(filp->f_mode & FMODE_WRITE)))
856 		goto out_fput;
857 
858 	if (unlikely(msg_len > info->attr.mq_msgsize)) {
859 		ret = -EMSGSIZE;
860 		goto out_fput;
861 	}
862 
863 	/* First try to allocate memory, before doing anything with
864 	 * existing queues. */
865 	msg_ptr = load_msg(u_msg_ptr, msg_len);
866 	if (IS_ERR(msg_ptr)) {
867 		ret = PTR_ERR(msg_ptr);
868 		goto out_fput;
869 	}
870 	msg_ptr->m_ts = msg_len;
871 	msg_ptr->m_type = msg_prio;
872 
873 	spin_lock(&info->lock);
874 
875 	if (info->attr.mq_curmsgs == info->attr.mq_maxmsg) {
876 		if (filp->f_flags & O_NONBLOCK) {
877 			spin_unlock(&info->lock);
878 			ret = -EAGAIN;
879 		} else if (unlikely(timeout < 0)) {
880 			spin_unlock(&info->lock);
881 			ret = timeout;
882 		} else {
883 			wait.task = current;
884 			wait.msg = (void *) msg_ptr;
885 			wait.state = STATE_NONE;
886 			ret = wq_sleep(info, SEND, timeout, &wait);
887 		}
888 		if (ret < 0)
889 			free_msg(msg_ptr);
890 	} else {
891 		receiver = wq_get_first_waiter(info, RECV);
892 		if (receiver) {
893 			pipelined_send(info, msg_ptr, receiver);
894 		} else {
895 			/* adds message to the queue */
896 			msg_insert(msg_ptr, info);
897 			__do_notify(info);
898 		}
899 		inode->i_atime = inode->i_mtime = inode->i_ctime =
900 				CURRENT_TIME;
901 		spin_unlock(&info->lock);
902 		ret = 0;
903 	}
904 out_fput:
905 	fput(filp);
906 out:
907 	return ret;
908 }
909 
910 asmlinkage ssize_t sys_mq_timedreceive(mqd_t mqdes, char __user *u_msg_ptr,
911 	size_t msg_len, unsigned int __user *u_msg_prio,
912 	const struct timespec __user *u_abs_timeout)
913 {
914 	long timeout;
915 	ssize_t ret;
916 	struct msg_msg *msg_ptr;
917 	struct file *filp;
918 	struct inode *inode;
919 	struct mqueue_inode_info *info;
920 	struct ext_wait_queue wait;
921 
922 	ret = audit_mq_timedreceive(mqdes, msg_len, u_msg_prio, u_abs_timeout);
923 	if (ret != 0)
924 		return ret;
925 
926 	timeout = prepare_timeout(u_abs_timeout);
927 
928 	ret = -EBADF;
929 	filp = fget(mqdes);
930 	if (unlikely(!filp))
931 		goto out;
932 
933 	inode = filp->f_path.dentry->d_inode;
934 	if (unlikely(filp->f_op != &mqueue_file_operations))
935 		goto out_fput;
936 	info = MQUEUE_I(inode);
937 	audit_inode(NULL, filp->f_path.dentry);
938 
939 	if (unlikely(!(filp->f_mode & FMODE_READ)))
940 		goto out_fput;
941 
942 	/* checks if buffer is big enough */
943 	if (unlikely(msg_len < info->attr.mq_msgsize)) {
944 		ret = -EMSGSIZE;
945 		goto out_fput;
946 	}
947 
948 	spin_lock(&info->lock);
949 	if (info->attr.mq_curmsgs == 0) {
950 		if (filp->f_flags & O_NONBLOCK) {
951 			spin_unlock(&info->lock);
952 			ret = -EAGAIN;
953 			msg_ptr = NULL;
954 		} else if (unlikely(timeout < 0)) {
955 			spin_unlock(&info->lock);
956 			ret = timeout;
957 			msg_ptr = NULL;
958 		} else {
959 			wait.task = current;
960 			wait.state = STATE_NONE;
961 			ret = wq_sleep(info, RECV, timeout, &wait);
962 			msg_ptr = wait.msg;
963 		}
964 	} else {
965 		msg_ptr = msg_get(info);
966 
967 		inode->i_atime = inode->i_mtime = inode->i_ctime =
968 				CURRENT_TIME;
969 
970 		/* There is now free space in queue. */
971 		pipelined_receive(info);
972 		spin_unlock(&info->lock);
973 		ret = 0;
974 	}
975 	if (ret == 0) {
976 		ret = msg_ptr->m_ts;
977 
978 		if ((u_msg_prio && put_user(msg_ptr->m_type, u_msg_prio)) ||
979 			store_msg(u_msg_ptr, msg_ptr, msg_ptr->m_ts)) {
980 			ret = -EFAULT;
981 		}
982 		free_msg(msg_ptr);
983 	}
984 out_fput:
985 	fput(filp);
986 out:
987 	return ret;
988 }
989 
990 /*
991  * Notes: the case when user wants us to deregister (with NULL as pointer)
992  * and he isn't currently owner of notification, will be silently discarded.
993  * It isn't explicitly defined in the POSIX.
994  */
995 asmlinkage long sys_mq_notify(mqd_t mqdes,
996 				const struct sigevent __user *u_notification)
997 {
998 	int ret;
999 	struct file *filp;
1000 	struct sock *sock;
1001 	struct inode *inode;
1002 	struct sigevent notification;
1003 	struct mqueue_inode_info *info;
1004 	struct sk_buff *nc;
1005 
1006 	ret = audit_mq_notify(mqdes, u_notification);
1007 	if (ret != 0)
1008 		return ret;
1009 
1010 	nc = NULL;
1011 	sock = NULL;
1012 	if (u_notification != NULL) {
1013 		if (copy_from_user(&notification, u_notification,
1014 					sizeof(struct sigevent)))
1015 			return -EFAULT;
1016 
1017 		if (unlikely(notification.sigev_notify != SIGEV_NONE &&
1018 			     notification.sigev_notify != SIGEV_SIGNAL &&
1019 			     notification.sigev_notify != SIGEV_THREAD))
1020 			return -EINVAL;
1021 		if (notification.sigev_notify == SIGEV_SIGNAL &&
1022 			!valid_signal(notification.sigev_signo)) {
1023 			return -EINVAL;
1024 		}
1025 		if (notification.sigev_notify == SIGEV_THREAD) {
1026 			long timeo;
1027 
1028 			/* create the notify skb */
1029 			nc = alloc_skb(NOTIFY_COOKIE_LEN, GFP_KERNEL);
1030 			ret = -ENOMEM;
1031 			if (!nc)
1032 				goto out;
1033 			ret = -EFAULT;
1034 			if (copy_from_user(nc->data,
1035 					notification.sigev_value.sival_ptr,
1036 					NOTIFY_COOKIE_LEN)) {
1037 				goto out;
1038 			}
1039 
1040 			/* TODO: add a header? */
1041 			skb_put(nc, NOTIFY_COOKIE_LEN);
1042 			/* and attach it to the socket */
1043 retry:
1044 			filp = fget(notification.sigev_signo);
1045 			ret = -EBADF;
1046 			if (!filp)
1047 				goto out;
1048 			sock = netlink_getsockbyfilp(filp);
1049 			fput(filp);
1050 			if (IS_ERR(sock)) {
1051 				ret = PTR_ERR(sock);
1052 				sock = NULL;
1053 				goto out;
1054 			}
1055 
1056 			timeo = MAX_SCHEDULE_TIMEOUT;
1057 			ret = netlink_attachskb(sock, nc, 0, &timeo, NULL);
1058 			if (ret == 1)
1059 		       		goto retry;
1060 			if (ret) {
1061 				sock = NULL;
1062 				nc = NULL;
1063 				goto out;
1064 			}
1065 		}
1066 	}
1067 
1068 	ret = -EBADF;
1069 	filp = fget(mqdes);
1070 	if (!filp)
1071 		goto out;
1072 
1073 	inode = filp->f_path.dentry->d_inode;
1074 	if (unlikely(filp->f_op != &mqueue_file_operations))
1075 		goto out_fput;
1076 	info = MQUEUE_I(inode);
1077 
1078 	ret = 0;
1079 	spin_lock(&info->lock);
1080 	if (u_notification == NULL) {
1081 		if (info->notify_owner == task_tgid(current)) {
1082 			remove_notification(info);
1083 			inode->i_atime = inode->i_ctime = CURRENT_TIME;
1084 		}
1085 	} else if (info->notify_owner != NULL) {
1086 		ret = -EBUSY;
1087 	} else {
1088 		switch (notification.sigev_notify) {
1089 		case SIGEV_NONE:
1090 			info->notify.sigev_notify = SIGEV_NONE;
1091 			break;
1092 		case SIGEV_THREAD:
1093 			info->notify_sock = sock;
1094 			info->notify_cookie = nc;
1095 			sock = NULL;
1096 			nc = NULL;
1097 			info->notify.sigev_notify = SIGEV_THREAD;
1098 			break;
1099 		case SIGEV_SIGNAL:
1100 			info->notify.sigev_signo = notification.sigev_signo;
1101 			info->notify.sigev_value = notification.sigev_value;
1102 			info->notify.sigev_notify = SIGEV_SIGNAL;
1103 			break;
1104 		}
1105 
1106 		info->notify_owner = get_pid(task_tgid(current));
1107 		inode->i_atime = inode->i_ctime = CURRENT_TIME;
1108 	}
1109 	spin_unlock(&info->lock);
1110 out_fput:
1111 	fput(filp);
1112 out:
1113 	if (sock) {
1114 		netlink_detachskb(sock, nc);
1115 	} else if (nc) {
1116 		dev_kfree_skb(nc);
1117 	}
1118 	return ret;
1119 }
1120 
1121 asmlinkage long sys_mq_getsetattr(mqd_t mqdes,
1122 			const struct mq_attr __user *u_mqstat,
1123 			struct mq_attr __user *u_omqstat)
1124 {
1125 	int ret;
1126 	struct mq_attr mqstat, omqstat;
1127 	struct file *filp;
1128 	struct inode *inode;
1129 	struct mqueue_inode_info *info;
1130 
1131 	if (u_mqstat != NULL) {
1132 		if (copy_from_user(&mqstat, u_mqstat, sizeof(struct mq_attr)))
1133 			return -EFAULT;
1134 		if (mqstat.mq_flags & (~O_NONBLOCK))
1135 			return -EINVAL;
1136 	}
1137 
1138 	ret = -EBADF;
1139 	filp = fget(mqdes);
1140 	if (!filp)
1141 		goto out;
1142 
1143 	inode = filp->f_path.dentry->d_inode;
1144 	if (unlikely(filp->f_op != &mqueue_file_operations))
1145 		goto out_fput;
1146 	info = MQUEUE_I(inode);
1147 
1148 	spin_lock(&info->lock);
1149 
1150 	omqstat = info->attr;
1151 	omqstat.mq_flags = filp->f_flags & O_NONBLOCK;
1152 	if (u_mqstat) {
1153 		ret = audit_mq_getsetattr(mqdes, &mqstat);
1154 		if (ret != 0) {
1155 			spin_unlock(&info->lock);
1156 			goto out_fput;
1157 		}
1158 		if (mqstat.mq_flags & O_NONBLOCK)
1159 			filp->f_flags |= O_NONBLOCK;
1160 		else
1161 			filp->f_flags &= ~O_NONBLOCK;
1162 
1163 		inode->i_atime = inode->i_ctime = CURRENT_TIME;
1164 	}
1165 
1166 	spin_unlock(&info->lock);
1167 
1168 	ret = 0;
1169 	if (u_omqstat != NULL && copy_to_user(u_omqstat, &omqstat,
1170 						sizeof(struct mq_attr)))
1171 		ret = -EFAULT;
1172 
1173 out_fput:
1174 	fput(filp);
1175 out:
1176 	return ret;
1177 }
1178 
1179 static const struct inode_operations mqueue_dir_inode_operations = {
1180 	.lookup = simple_lookup,
1181 	.create = mqueue_create,
1182 	.unlink = mqueue_unlink,
1183 };
1184 
1185 static const struct file_operations mqueue_file_operations = {
1186 	.flush = mqueue_flush_file,
1187 	.poll = mqueue_poll_file,
1188 	.read = mqueue_read_file,
1189 };
1190 
1191 static struct super_operations mqueue_super_ops = {
1192 	.alloc_inode = mqueue_alloc_inode,
1193 	.destroy_inode = mqueue_destroy_inode,
1194 	.statfs = simple_statfs,
1195 	.delete_inode = mqueue_delete_inode,
1196 	.drop_inode = generic_delete_inode,
1197 };
1198 
1199 static struct file_system_type mqueue_fs_type = {
1200 	.name = "mqueue",
1201 	.get_sb = mqueue_get_sb,
1202 	.kill_sb = kill_litter_super,
1203 };
1204 
1205 static int msg_max_limit_min = DFLT_MSGMAX;
1206 static int msg_max_limit_max = HARD_MSGMAX;
1207 
1208 static int msg_maxsize_limit_min = DFLT_MSGSIZEMAX;
1209 static int msg_maxsize_limit_max = INT_MAX;
1210 
1211 static ctl_table mq_sysctls[] = {
1212 	{
1213 		.procname	= "queues_max",
1214 		.data		= &queues_max,
1215 		.maxlen		= sizeof(int),
1216 		.mode		= 0644,
1217 		.proc_handler	= &proc_dointvec,
1218 	},
1219 	{
1220 		.procname	= "msg_max",
1221 		.data		= &msg_max,
1222 		.maxlen		= sizeof(int),
1223 		.mode		= 0644,
1224 		.proc_handler	= &proc_dointvec_minmax,
1225 		.extra1		= &msg_max_limit_min,
1226 		.extra2		= &msg_max_limit_max,
1227 	},
1228 	{
1229 		.procname	= "msgsize_max",
1230 		.data		= &msgsize_max,
1231 		.maxlen		= sizeof(int),
1232 		.mode		= 0644,
1233 		.proc_handler	= &proc_dointvec_minmax,
1234 		.extra1		= &msg_maxsize_limit_min,
1235 		.extra2		= &msg_maxsize_limit_max,
1236 	},
1237 	{ .ctl_name = 0 }
1238 };
1239 
1240 static ctl_table mq_sysctl_dir[] = {
1241 	{
1242 		.procname	= "mqueue",
1243 		.mode		= 0555,
1244 		.child		= mq_sysctls,
1245 	},
1246 	{ .ctl_name = 0 }
1247 };
1248 
1249 static ctl_table mq_sysctl_root[] = {
1250 	{
1251 		.ctl_name	= CTL_FS,
1252 		.procname	= "fs",
1253 		.mode		= 0555,
1254 		.child		= mq_sysctl_dir,
1255 	},
1256 	{ .ctl_name = 0 }
1257 };
1258 
1259 static int __init init_mqueue_fs(void)
1260 {
1261 	int error;
1262 
1263 	mqueue_inode_cachep = kmem_cache_create("mqueue_inode_cache",
1264 				sizeof(struct mqueue_inode_info), 0,
1265 				SLAB_HWCACHE_ALIGN, init_once);
1266 	if (mqueue_inode_cachep == NULL)
1267 		return -ENOMEM;
1268 
1269 	/* ignore failues - they are not fatal */
1270 	mq_sysctl_table = register_sysctl_table(mq_sysctl_root);
1271 
1272 	error = register_filesystem(&mqueue_fs_type);
1273 	if (error)
1274 		goto out_sysctl;
1275 
1276 	if (IS_ERR(mqueue_mnt = kern_mount(&mqueue_fs_type))) {
1277 		error = PTR_ERR(mqueue_mnt);
1278 		goto out_filesystem;
1279 	}
1280 
1281 	/* internal initialization - not common for vfs */
1282 	queues_count = 0;
1283 	spin_lock_init(&mq_lock);
1284 
1285 	return 0;
1286 
1287 out_filesystem:
1288 	unregister_filesystem(&mqueue_fs_type);
1289 out_sysctl:
1290 	if (mq_sysctl_table)
1291 		unregister_sysctl_table(mq_sysctl_table);
1292 	kmem_cache_destroy(mqueue_inode_cachep);
1293 	return error;
1294 }
1295 
1296 __initcall(init_mqueue_fs);
1297