projects/linux·blob v2.6.32-rc3 · refs

944 lines · 20.8 KiB

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