msg.c revision 0050ee05
1/*
2 * linux/ipc/msg.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 *
5 * Removed all the remaining kerneld mess
6 * Catch the -EFAULT stuff properly
7 * Use GFP_KERNEL for messages as in 1.2
8 * Fixed up the unchecked user space derefs
9 * Copyright (C) 1998 Alan Cox & Andi Kleen
10 *
11 * /proc/sysvipc/msg support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
12 *
13 * mostly rewritten, threaded and wake-one semantics added
14 * MSGMAX limit removed, sysctl's added
15 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
16 *
17 * support for audit of ipc object properties and permission changes
18 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
19 *
20 * namespaces support
21 * OpenVZ, SWsoft Inc.
22 * Pavel Emelianov <xemul@openvz.org>
23 */
24
25#include <linux/capability.h>
26#include <linux/msg.h>
27#include <linux/spinlock.h>
28#include <linux/init.h>
29#include <linux/mm.h>
30#include <linux/proc_fs.h>
31#include <linux/list.h>
32#include <linux/security.h>
33#include <linux/sched.h>
34#include <linux/syscalls.h>
35#include <linux/audit.h>
36#include <linux/seq_file.h>
37#include <linux/rwsem.h>
38#include <linux/nsproxy.h>
39#include <linux/ipc_namespace.h>
40
41#include <asm/current.h>
42#include <linux/uaccess.h>
43#include "util.h"
44
45/* one msg_receiver structure for each sleeping receiver */
46struct msg_receiver {
47	struct list_head	r_list;
48	struct task_struct	*r_tsk;
49
50	int			r_mode;
51	long			r_msgtype;
52	long			r_maxsize;
53
54	/*
55	 * Mark r_msg volatile so that the compiler
56	 * does not try to get smart and optimize
57	 * it. We rely on this for the lockless
58	 * receive algorithm.
59	 */
60	struct msg_msg		*volatile r_msg;
61};
62
63/* one msg_sender for each sleeping sender */
64struct msg_sender {
65	struct list_head	list;
66	struct task_struct	*tsk;
67};
68
69#define SEARCH_ANY		1
70#define SEARCH_EQUAL		2
71#define SEARCH_NOTEQUAL		3
72#define SEARCH_LESSEQUAL	4
73#define SEARCH_NUMBER		5
74
75#define msg_ids(ns)	((ns)->ids[IPC_MSG_IDS])
76
77static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
78{
79	struct kern_ipc_perm *ipcp = ipc_obtain_object(&msg_ids(ns), id);
80
81	if (IS_ERR(ipcp))
82		return ERR_CAST(ipcp);
83
84	return container_of(ipcp, struct msg_queue, q_perm);
85}
86
87static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns,
88							int id)
89{
90	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id);
91
92	if (IS_ERR(ipcp))
93		return ERR_CAST(ipcp);
94
95	return container_of(ipcp, struct msg_queue, q_perm);
96}
97
98static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
99{
100	ipc_rmid(&msg_ids(ns), &s->q_perm);
101}
102
103static void msg_rcu_free(struct rcu_head *head)
104{
105	struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
106	struct msg_queue *msq = ipc_rcu_to_struct(p);
107
108	security_msg_queue_free(msq);
109	ipc_rcu_free(head);
110}
111
112/**
113 * newque - Create a new msg queue
114 * @ns: namespace
115 * @params: ptr to the structure that contains the key and msgflg
116 *
117 * Called with msg_ids.rwsem held (writer)
118 */
119static int newque(struct ipc_namespace *ns, struct ipc_params *params)
120{
121	struct msg_queue *msq;
122	int id, retval;
123	key_t key = params->key;
124	int msgflg = params->flg;
125
126	msq = ipc_rcu_alloc(sizeof(*msq));
127	if (!msq)
128		return -ENOMEM;
129
130	msq->q_perm.mode = msgflg & S_IRWXUGO;
131	msq->q_perm.key = key;
132
133	msq->q_perm.security = NULL;
134	retval = security_msg_queue_alloc(msq);
135	if (retval) {
136		ipc_rcu_putref(msq, ipc_rcu_free);
137		return retval;
138	}
139
140	/* ipc_addid() locks msq upon success. */
141	id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
142	if (id < 0) {
143		ipc_rcu_putref(msq, msg_rcu_free);
144		return id;
145	}
146
147	msq->q_stime = msq->q_rtime = 0;
148	msq->q_ctime = get_seconds();
149	msq->q_cbytes = msq->q_qnum = 0;
150	msq->q_qbytes = ns->msg_ctlmnb;
151	msq->q_lspid = msq->q_lrpid = 0;
152	INIT_LIST_HEAD(&msq->q_messages);
153	INIT_LIST_HEAD(&msq->q_receivers);
154	INIT_LIST_HEAD(&msq->q_senders);
155
156	ipc_unlock_object(&msq->q_perm);
157	rcu_read_unlock();
158
159	return msq->q_perm.id;
160}
161
162static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
163{
164	mss->tsk = current;
165	__set_current_state(TASK_INTERRUPTIBLE);
166	list_add_tail(&mss->list, &msq->q_senders);
167}
168
169static inline void ss_del(struct msg_sender *mss)
170{
171	if (mss->list.next != NULL)
172		list_del(&mss->list);
173}
174
175static void ss_wakeup(struct list_head *h, int kill)
176{
177	struct msg_sender *mss, *t;
178
179	list_for_each_entry_safe(mss, t, h, list) {
180		if (kill)
181			mss->list.next = NULL;
182		wake_up_process(mss->tsk);
183	}
184}
185
186static void expunge_all(struct msg_queue *msq, int res)
187{
188	struct msg_receiver *msr, *t;
189
190	list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
191		msr->r_msg = NULL; /* initialize expunge ordering */
192		wake_up_process(msr->r_tsk);
193		/*
194		 * Ensure that the wakeup is visible before setting r_msg as
195		 * the receiving end depends on it: either spinning on a nil,
196		 * or dealing with -EAGAIN cases. See lockless receive part 1
197		 * and 2 in do_msgrcv().
198		 */
199		smp_mb();
200		msr->r_msg = ERR_PTR(res);
201	}
202}
203
204/*
205 * freeque() wakes up waiters on the sender and receiver waiting queue,
206 * removes the message queue from message queue ID IDR, and cleans up all the
207 * messages associated with this queue.
208 *
209 * msg_ids.rwsem (writer) and the spinlock for this message queue are held
210 * before freeque() is called. msg_ids.rwsem remains locked on exit.
211 */
212static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
213{
214	struct msg_msg *msg, *t;
215	struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
216
217	expunge_all(msq, -EIDRM);
218	ss_wakeup(&msq->q_senders, 1);
219	msg_rmid(ns, msq);
220	ipc_unlock_object(&msq->q_perm);
221	rcu_read_unlock();
222
223	list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
224		atomic_dec(&ns->msg_hdrs);
225		free_msg(msg);
226	}
227	atomic_sub(msq->q_cbytes, &ns->msg_bytes);
228	ipc_rcu_putref(msq, msg_rcu_free);
229}
230
231/*
232 * Called with msg_ids.rwsem and ipcp locked.
233 */
234static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
235{
236	struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
237
238	return security_msg_queue_associate(msq, msgflg);
239}
240
241SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
242{
243	struct ipc_namespace *ns;
244	static const struct ipc_ops msg_ops = {
245		.getnew = newque,
246		.associate = msg_security,
247	};
248	struct ipc_params msg_params;
249
250	ns = current->nsproxy->ipc_ns;
251
252	msg_params.key = key;
253	msg_params.flg = msgflg;
254
255	return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
256}
257
258static inline unsigned long
259copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
260{
261	switch (version) {
262	case IPC_64:
263		return copy_to_user(buf, in, sizeof(*in));
264	case IPC_OLD:
265	{
266		struct msqid_ds out;
267
268		memset(&out, 0, sizeof(out));
269
270		ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
271
272		out.msg_stime		= in->msg_stime;
273		out.msg_rtime		= in->msg_rtime;
274		out.msg_ctime		= in->msg_ctime;
275
276		if (in->msg_cbytes > USHRT_MAX)
277			out.msg_cbytes	= USHRT_MAX;
278		else
279			out.msg_cbytes	= in->msg_cbytes;
280		out.msg_lcbytes		= in->msg_cbytes;
281
282		if (in->msg_qnum > USHRT_MAX)
283			out.msg_qnum	= USHRT_MAX;
284		else
285			out.msg_qnum	= in->msg_qnum;
286
287		if (in->msg_qbytes > USHRT_MAX)
288			out.msg_qbytes	= USHRT_MAX;
289		else
290			out.msg_qbytes	= in->msg_qbytes;
291		out.msg_lqbytes		= in->msg_qbytes;
292
293		out.msg_lspid		= in->msg_lspid;
294		out.msg_lrpid		= in->msg_lrpid;
295
296		return copy_to_user(buf, &out, sizeof(out));
297	}
298	default:
299		return -EINVAL;
300	}
301}
302
303static inline unsigned long
304copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
305{
306	switch (version) {
307	case IPC_64:
308		if (copy_from_user(out, buf, sizeof(*out)))
309			return -EFAULT;
310		return 0;
311	case IPC_OLD:
312	{
313		struct msqid_ds tbuf_old;
314
315		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
316			return -EFAULT;
317
318		out->msg_perm.uid	= tbuf_old.msg_perm.uid;
319		out->msg_perm.gid	= tbuf_old.msg_perm.gid;
320		out->msg_perm.mode	= tbuf_old.msg_perm.mode;
321
322		if (tbuf_old.msg_qbytes == 0)
323			out->msg_qbytes	= tbuf_old.msg_lqbytes;
324		else
325			out->msg_qbytes	= tbuf_old.msg_qbytes;
326
327		return 0;
328	}
329	default:
330		return -EINVAL;
331	}
332}
333
334/*
335 * This function handles some msgctl commands which require the rwsem
336 * to be held in write mode.
337 * NOTE: no locks must be held, the rwsem is taken inside this function.
338 */
339static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
340		       struct msqid_ds __user *buf, int version)
341{
342	struct kern_ipc_perm *ipcp;
343	struct msqid64_ds uninitialized_var(msqid64);
344	struct msg_queue *msq;
345	int err;
346
347	if (cmd == IPC_SET) {
348		if (copy_msqid_from_user(&msqid64, buf, version))
349			return -EFAULT;
350	}
351
352	down_write(&msg_ids(ns).rwsem);
353	rcu_read_lock();
354
355	ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
356				      &msqid64.msg_perm, msqid64.msg_qbytes);
357	if (IS_ERR(ipcp)) {
358		err = PTR_ERR(ipcp);
359		goto out_unlock1;
360	}
361
362	msq = container_of(ipcp, struct msg_queue, q_perm);
363
364	err = security_msg_queue_msgctl(msq, cmd);
365	if (err)
366		goto out_unlock1;
367
368	switch (cmd) {
369	case IPC_RMID:
370		ipc_lock_object(&msq->q_perm);
371		/* freeque unlocks the ipc object and rcu */
372		freeque(ns, ipcp);
373		goto out_up;
374	case IPC_SET:
375		if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
376		    !capable(CAP_SYS_RESOURCE)) {
377			err = -EPERM;
378			goto out_unlock1;
379		}
380
381		ipc_lock_object(&msq->q_perm);
382		err = ipc_update_perm(&msqid64.msg_perm, ipcp);
383		if (err)
384			goto out_unlock0;
385
386		msq->q_qbytes = msqid64.msg_qbytes;
387
388		msq->q_ctime = get_seconds();
389		/* sleeping receivers might be excluded by
390		 * stricter permissions.
391		 */
392		expunge_all(msq, -EAGAIN);
393		/* sleeping senders might be able to send
394		 * due to a larger queue size.
395		 */
396		ss_wakeup(&msq->q_senders, 0);
397		break;
398	default:
399		err = -EINVAL;
400		goto out_unlock1;
401	}
402
403out_unlock0:
404	ipc_unlock_object(&msq->q_perm);
405out_unlock1:
406	rcu_read_unlock();
407out_up:
408	up_write(&msg_ids(ns).rwsem);
409	return err;
410}
411
412static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
413			 int cmd, int version, void __user *buf)
414{
415	int err;
416	struct msg_queue *msq;
417
418	switch (cmd) {
419	case IPC_INFO:
420	case MSG_INFO:
421	{
422		struct msginfo msginfo;
423		int max_id;
424
425		if (!buf)
426			return -EFAULT;
427
428		/*
429		 * We must not return kernel stack data.
430		 * due to padding, it's not enough
431		 * to set all member fields.
432		 */
433		err = security_msg_queue_msgctl(NULL, cmd);
434		if (err)
435			return err;
436
437		memset(&msginfo, 0, sizeof(msginfo));
438		msginfo.msgmni = ns->msg_ctlmni;
439		msginfo.msgmax = ns->msg_ctlmax;
440		msginfo.msgmnb = ns->msg_ctlmnb;
441		msginfo.msgssz = MSGSSZ;
442		msginfo.msgseg = MSGSEG;
443		down_read(&msg_ids(ns).rwsem);
444		if (cmd == MSG_INFO) {
445			msginfo.msgpool = msg_ids(ns).in_use;
446			msginfo.msgmap = atomic_read(&ns->msg_hdrs);
447			msginfo.msgtql = atomic_read(&ns->msg_bytes);
448		} else {
449			msginfo.msgmap = MSGMAP;
450			msginfo.msgpool = MSGPOOL;
451			msginfo.msgtql = MSGTQL;
452		}
453		max_id = ipc_get_maxid(&msg_ids(ns));
454		up_read(&msg_ids(ns).rwsem);
455		if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
456			return -EFAULT;
457		return (max_id < 0) ? 0 : max_id;
458	}
459
460	case MSG_STAT:
461	case IPC_STAT:
462	{
463		struct msqid64_ds tbuf;
464		int success_return;
465
466		if (!buf)
467			return -EFAULT;
468
469		memset(&tbuf, 0, sizeof(tbuf));
470
471		rcu_read_lock();
472		if (cmd == MSG_STAT) {
473			msq = msq_obtain_object(ns, msqid);
474			if (IS_ERR(msq)) {
475				err = PTR_ERR(msq);
476				goto out_unlock;
477			}
478			success_return = msq->q_perm.id;
479		} else {
480			msq = msq_obtain_object_check(ns, msqid);
481			if (IS_ERR(msq)) {
482				err = PTR_ERR(msq);
483				goto out_unlock;
484			}
485			success_return = 0;
486		}
487
488		err = -EACCES;
489		if (ipcperms(ns, &msq->q_perm, S_IRUGO))
490			goto out_unlock;
491
492		err = security_msg_queue_msgctl(msq, cmd);
493		if (err)
494			goto out_unlock;
495
496		kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
497		tbuf.msg_stime  = msq->q_stime;
498		tbuf.msg_rtime  = msq->q_rtime;
499		tbuf.msg_ctime  = msq->q_ctime;
500		tbuf.msg_cbytes = msq->q_cbytes;
501		tbuf.msg_qnum   = msq->q_qnum;
502		tbuf.msg_qbytes = msq->q_qbytes;
503		tbuf.msg_lspid  = msq->q_lspid;
504		tbuf.msg_lrpid  = msq->q_lrpid;
505		rcu_read_unlock();
506
507		if (copy_msqid_to_user(buf, &tbuf, version))
508			return -EFAULT;
509		return success_return;
510	}
511
512	default:
513		return -EINVAL;
514	}
515
516	return err;
517out_unlock:
518	rcu_read_unlock();
519	return err;
520}
521
522SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
523{
524	int version;
525	struct ipc_namespace *ns;
526
527	if (msqid < 0 || cmd < 0)
528		return -EINVAL;
529
530	version = ipc_parse_version(&cmd);
531	ns = current->nsproxy->ipc_ns;
532
533	switch (cmd) {
534	case IPC_INFO:
535	case MSG_INFO:
536	case MSG_STAT:	/* msqid is an index rather than a msg queue id */
537	case IPC_STAT:
538		return msgctl_nolock(ns, msqid, cmd, version, buf);
539	case IPC_SET:
540	case IPC_RMID:
541		return msgctl_down(ns, msqid, cmd, buf, version);
542	default:
543		return  -EINVAL;
544	}
545}
546
547static int testmsg(struct msg_msg *msg, long type, int mode)
548{
549	switch (mode) {
550	case SEARCH_ANY:
551	case SEARCH_NUMBER:
552		return 1;
553	case SEARCH_LESSEQUAL:
554		if (msg->m_type <= type)
555			return 1;
556		break;
557	case SEARCH_EQUAL:
558		if (msg->m_type == type)
559			return 1;
560		break;
561	case SEARCH_NOTEQUAL:
562		if (msg->m_type != type)
563			return 1;
564		break;
565	}
566	return 0;
567}
568
569static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
570{
571	struct msg_receiver *msr, *t;
572
573	list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
574		if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
575		    !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
576					       msr->r_msgtype, msr->r_mode)) {
577
578			list_del(&msr->r_list);
579			if (msr->r_maxsize < msg->m_ts) {
580				/* initialize pipelined send ordering */
581				msr->r_msg = NULL;
582				wake_up_process(msr->r_tsk);
583				smp_mb(); /* see barrier comment below */
584				msr->r_msg = ERR_PTR(-E2BIG);
585			} else {
586				msr->r_msg = NULL;
587				msq->q_lrpid = task_pid_vnr(msr->r_tsk);
588				msq->q_rtime = get_seconds();
589				wake_up_process(msr->r_tsk);
590				/*
591				 * Ensure that the wakeup is visible before
592				 * setting r_msg, as the receiving end depends
593				 * on it. See lockless receive part 1 and 2 in
594				 * do_msgrcv().
595				 */
596				smp_mb();
597				msr->r_msg = msg;
598
599				return 1;
600			}
601		}
602	}
603
604	return 0;
605}
606
607long do_msgsnd(int msqid, long mtype, void __user *mtext,
608		size_t msgsz, int msgflg)
609{
610	struct msg_queue *msq;
611	struct msg_msg *msg;
612	int err;
613	struct ipc_namespace *ns;
614
615	ns = current->nsproxy->ipc_ns;
616
617	if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
618		return -EINVAL;
619	if (mtype < 1)
620		return -EINVAL;
621
622	msg = load_msg(mtext, msgsz);
623	if (IS_ERR(msg))
624		return PTR_ERR(msg);
625
626	msg->m_type = mtype;
627	msg->m_ts = msgsz;
628
629	rcu_read_lock();
630	msq = msq_obtain_object_check(ns, msqid);
631	if (IS_ERR(msq)) {
632		err = PTR_ERR(msq);
633		goto out_unlock1;
634	}
635
636	ipc_lock_object(&msq->q_perm);
637
638	for (;;) {
639		struct msg_sender s;
640
641		err = -EACCES;
642		if (ipcperms(ns, &msq->q_perm, S_IWUGO))
643			goto out_unlock0;
644
645		/* raced with RMID? */
646		if (!ipc_valid_object(&msq->q_perm)) {
647			err = -EIDRM;
648			goto out_unlock0;
649		}
650
651		err = security_msg_queue_msgsnd(msq, msg, msgflg);
652		if (err)
653			goto out_unlock0;
654
655		if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
656				1 + msq->q_qnum <= msq->q_qbytes) {
657			break;
658		}
659
660		/* queue full, wait: */
661		if (msgflg & IPC_NOWAIT) {
662			err = -EAGAIN;
663			goto out_unlock0;
664		}
665
666		/* enqueue the sender and prepare to block */
667		ss_add(msq, &s);
668
669		if (!ipc_rcu_getref(msq)) {
670			err = -EIDRM;
671			goto out_unlock0;
672		}
673
674		ipc_unlock_object(&msq->q_perm);
675		rcu_read_unlock();
676		schedule();
677
678		rcu_read_lock();
679		ipc_lock_object(&msq->q_perm);
680
681		ipc_rcu_putref(msq, ipc_rcu_free);
682		/* raced with RMID? */
683		if (!ipc_valid_object(&msq->q_perm)) {
684			err = -EIDRM;
685			goto out_unlock0;
686		}
687
688		ss_del(&s);
689
690		if (signal_pending(current)) {
691			err = -ERESTARTNOHAND;
692			goto out_unlock0;
693		}
694
695	}
696	msq->q_lspid = task_tgid_vnr(current);
697	msq->q_stime = get_seconds();
698
699	if (!pipelined_send(msq, msg)) {
700		/* no one is waiting for this message, enqueue it */
701		list_add_tail(&msg->m_list, &msq->q_messages);
702		msq->q_cbytes += msgsz;
703		msq->q_qnum++;
704		atomic_add(msgsz, &ns->msg_bytes);
705		atomic_inc(&ns->msg_hdrs);
706	}
707
708	err = 0;
709	msg = NULL;
710
711out_unlock0:
712	ipc_unlock_object(&msq->q_perm);
713out_unlock1:
714	rcu_read_unlock();
715	if (msg != NULL)
716		free_msg(msg);
717	return err;
718}
719
720SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
721		int, msgflg)
722{
723	long mtype;
724
725	if (get_user(mtype, &msgp->mtype))
726		return -EFAULT;
727	return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
728}
729
730static inline int convert_mode(long *msgtyp, int msgflg)
731{
732	if (msgflg & MSG_COPY)
733		return SEARCH_NUMBER;
734	/*
735	 *  find message of correct type.
736	 *  msgtyp = 0 => get first.
737	 *  msgtyp > 0 => get first message of matching type.
738	 *  msgtyp < 0 => get message with least type must be < abs(msgtype).
739	 */
740	if (*msgtyp == 0)
741		return SEARCH_ANY;
742	if (*msgtyp < 0) {
743		*msgtyp = -*msgtyp;
744		return SEARCH_LESSEQUAL;
745	}
746	if (msgflg & MSG_EXCEPT)
747		return SEARCH_NOTEQUAL;
748	return SEARCH_EQUAL;
749}
750
751static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
752{
753	struct msgbuf __user *msgp = dest;
754	size_t msgsz;
755
756	if (put_user(msg->m_type, &msgp->mtype))
757		return -EFAULT;
758
759	msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
760	if (store_msg(msgp->mtext, msg, msgsz))
761		return -EFAULT;
762	return msgsz;
763}
764
765#ifdef CONFIG_CHECKPOINT_RESTORE
766/*
767 * This function creates new kernel message structure, large enough to store
768 * bufsz message bytes.
769 */
770static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
771{
772	struct msg_msg *copy;
773
774	/*
775	 * Create dummy message to copy real message to.
776	 */
777	copy = load_msg(buf, bufsz);
778	if (!IS_ERR(copy))
779		copy->m_ts = bufsz;
780	return copy;
781}
782
783static inline void free_copy(struct msg_msg *copy)
784{
785	if (copy)
786		free_msg(copy);
787}
788#else
789static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
790{
791	return ERR_PTR(-ENOSYS);
792}
793
794static inline void free_copy(struct msg_msg *copy)
795{
796}
797#endif
798
799static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
800{
801	struct msg_msg *msg, *found = NULL;
802	long count = 0;
803
804	list_for_each_entry(msg, &msq->q_messages, m_list) {
805		if (testmsg(msg, *msgtyp, mode) &&
806		    !security_msg_queue_msgrcv(msq, msg, current,
807					       *msgtyp, mode)) {
808			if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
809				*msgtyp = msg->m_type - 1;
810				found = msg;
811			} else if (mode == SEARCH_NUMBER) {
812				if (*msgtyp == count)
813					return msg;
814			} else
815				return msg;
816			count++;
817		}
818	}
819
820	return found ?: ERR_PTR(-EAGAIN);
821}
822
823long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
824	       long (*msg_handler)(void __user *, struct msg_msg *, size_t))
825{
826	int mode;
827	struct msg_queue *msq;
828	struct ipc_namespace *ns;
829	struct msg_msg *msg, *copy = NULL;
830
831	ns = current->nsproxy->ipc_ns;
832
833	if (msqid < 0 || (long) bufsz < 0)
834		return -EINVAL;
835
836	if (msgflg & MSG_COPY) {
837		if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
838			return -EINVAL;
839		copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
840		if (IS_ERR(copy))
841			return PTR_ERR(copy);
842	}
843	mode = convert_mode(&msgtyp, msgflg);
844
845	rcu_read_lock();
846	msq = msq_obtain_object_check(ns, msqid);
847	if (IS_ERR(msq)) {
848		rcu_read_unlock();
849		free_copy(copy);
850		return PTR_ERR(msq);
851	}
852
853	for (;;) {
854		struct msg_receiver msr_d;
855
856		msg = ERR_PTR(-EACCES);
857		if (ipcperms(ns, &msq->q_perm, S_IRUGO))
858			goto out_unlock1;
859
860		ipc_lock_object(&msq->q_perm);
861
862		/* raced with RMID? */
863		if (!ipc_valid_object(&msq->q_perm)) {
864			msg = ERR_PTR(-EIDRM);
865			goto out_unlock0;
866		}
867
868		msg = find_msg(msq, &msgtyp, mode);
869		if (!IS_ERR(msg)) {
870			/*
871			 * Found a suitable message.
872			 * Unlink it from the queue.
873			 */
874			if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
875				msg = ERR_PTR(-E2BIG);
876				goto out_unlock0;
877			}
878			/*
879			 * If we are copying, then do not unlink message and do
880			 * not update queue parameters.
881			 */
882			if (msgflg & MSG_COPY) {
883				msg = copy_msg(msg, copy);
884				goto out_unlock0;
885			}
886
887			list_del(&msg->m_list);
888			msq->q_qnum--;
889			msq->q_rtime = get_seconds();
890			msq->q_lrpid = task_tgid_vnr(current);
891			msq->q_cbytes -= msg->m_ts;
892			atomic_sub(msg->m_ts, &ns->msg_bytes);
893			atomic_dec(&ns->msg_hdrs);
894			ss_wakeup(&msq->q_senders, 0);
895
896			goto out_unlock0;
897		}
898
899		/* No message waiting. Wait for a message */
900		if (msgflg & IPC_NOWAIT) {
901			msg = ERR_PTR(-ENOMSG);
902			goto out_unlock0;
903		}
904
905		list_add_tail(&msr_d.r_list, &msq->q_receivers);
906		msr_d.r_tsk = current;
907		msr_d.r_msgtype = msgtyp;
908		msr_d.r_mode = mode;
909		if (msgflg & MSG_NOERROR)
910			msr_d.r_maxsize = INT_MAX;
911		else
912			msr_d.r_maxsize = bufsz;
913		msr_d.r_msg = ERR_PTR(-EAGAIN);
914		__set_current_state(TASK_INTERRUPTIBLE);
915
916		ipc_unlock_object(&msq->q_perm);
917		rcu_read_unlock();
918		schedule();
919
920		/* Lockless receive, part 1:
921		 * Disable preemption.  We don't hold a reference to the queue
922		 * and getting a reference would defeat the idea of a lockless
923		 * operation, thus the code relies on rcu to guarantee the
924		 * existence of msq:
925		 * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
926		 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
927		 * rcu_read_lock() prevents preemption between reading r_msg
928		 * and acquiring the q_perm.lock in ipc_lock_object().
929		 */
930		rcu_read_lock();
931
932		/* Lockless receive, part 2:
933		 * Wait until pipelined_send or expunge_all are outside of
934		 * wake_up_process(). There is a race with exit(), see
935		 * ipc/mqueue.c for the details.
936		 */
937		msg = (struct msg_msg *)msr_d.r_msg;
938		while (msg == NULL) {
939			cpu_relax();
940			msg = (struct msg_msg *)msr_d.r_msg;
941		}
942
943		/* Lockless receive, part 3:
944		 * If there is a message or an error then accept it without
945		 * locking.
946		 */
947		if (msg != ERR_PTR(-EAGAIN))
948			goto out_unlock1;
949
950		/* Lockless receive, part 3:
951		 * Acquire the queue spinlock.
952		 */
953		ipc_lock_object(&msq->q_perm);
954
955		/* Lockless receive, part 4:
956		 * Repeat test after acquiring the spinlock.
957		 */
958		msg = (struct msg_msg *)msr_d.r_msg;
959		if (msg != ERR_PTR(-EAGAIN))
960			goto out_unlock0;
961
962		list_del(&msr_d.r_list);
963		if (signal_pending(current)) {
964			msg = ERR_PTR(-ERESTARTNOHAND);
965			goto out_unlock0;
966		}
967
968		ipc_unlock_object(&msq->q_perm);
969	}
970
971out_unlock0:
972	ipc_unlock_object(&msq->q_perm);
973out_unlock1:
974	rcu_read_unlock();
975	if (IS_ERR(msg)) {
976		free_copy(copy);
977		return PTR_ERR(msg);
978	}
979
980	bufsz = msg_handler(buf, msg, bufsz);
981	free_msg(msg);
982
983	return bufsz;
984}
985
986SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
987		long, msgtyp, int, msgflg)
988{
989	return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
990}
991
992
993void msg_init_ns(struct ipc_namespace *ns)
994{
995	ns->msg_ctlmax = MSGMAX;
996	ns->msg_ctlmnb = MSGMNB;
997	ns->msg_ctlmni = MSGMNI;
998
999	atomic_set(&ns->msg_bytes, 0);
1000	atomic_set(&ns->msg_hdrs, 0);
1001	ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
1002}
1003
1004#ifdef CONFIG_IPC_NS
1005void msg_exit_ns(struct ipc_namespace *ns)
1006{
1007	free_ipcs(ns, &msg_ids(ns), freeque);
1008	idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
1009}
1010#endif
1011
1012#ifdef CONFIG_PROC_FS
1013static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
1014{
1015	struct user_namespace *user_ns = seq_user_ns(s);
1016	struct msg_queue *msq = it;
1017
1018	return seq_printf(s,
1019			"%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1020			msq->q_perm.key,
1021			msq->q_perm.id,
1022			msq->q_perm.mode,
1023			msq->q_cbytes,
1024			msq->q_qnum,
1025			msq->q_lspid,
1026			msq->q_lrpid,
1027			from_kuid_munged(user_ns, msq->q_perm.uid),
1028			from_kgid_munged(user_ns, msq->q_perm.gid),
1029			from_kuid_munged(user_ns, msq->q_perm.cuid),
1030			from_kgid_munged(user_ns, msq->q_perm.cgid),
1031			msq->q_stime,
1032			msq->q_rtime,
1033			msq->q_ctime);
1034}
1035#endif
1036
1037void __init msg_init(void)
1038{
1039	msg_init_ns(&init_ipc_ns);
1040
1041	ipc_init_proc_interface("sysvipc/msg",
1042				"       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
1043				IPC_MSG_IDS, sysvipc_msg_proc_show);
1044}
1045