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 */
46 struct 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 */
64 struct 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
msq_obtain_object(struct ipc_namespace * ns,int id)77 static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
78 {
79 struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&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
msq_obtain_object_check(struct ipc_namespace * ns,int id)87 static 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
msg_rmid(struct ipc_namespace * ns,struct msg_queue * s)98 static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
99 {
100 ipc_rmid(&msg_ids(ns), &s->q_perm);
101 }
102
msg_rcu_free(struct rcu_head * head)103 static 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 */
newque(struct ipc_namespace * ns,struct ipc_params * params)119 static 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 msq->q_stime = msq->q_rtime = 0;
141 msq->q_ctime = get_seconds();
142 msq->q_cbytes = msq->q_qnum = 0;
143 msq->q_qbytes = ns->msg_ctlmnb;
144 msq->q_lspid = msq->q_lrpid = 0;
145 INIT_LIST_HEAD(&msq->q_messages);
146 INIT_LIST_HEAD(&msq->q_receivers);
147 INIT_LIST_HEAD(&msq->q_senders);
148
149 /* ipc_addid() locks msq upon success. */
150 id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
151 if (id < 0) {
152 ipc_rcu_putref(msq, msg_rcu_free);
153 return id;
154 }
155
156 ipc_unlock_object(&msq->q_perm);
157 rcu_read_unlock();
158
159 return msq->q_perm.id;
160 }
161
ss_add(struct msg_queue * msq,struct msg_sender * mss)162 static 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
ss_del(struct msg_sender * mss)169 static inline void ss_del(struct msg_sender *mss)
170 {
171 if (mss->list.next != NULL)
172 list_del(&mss->list);
173 }
174
ss_wakeup(struct list_head * h,int kill)175 static 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
expunge_all(struct msg_queue * msq,int res)186 static 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_wmb(); /* barrier (B) */
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 */
freeque(struct ipc_namespace * ns,struct kern_ipc_perm * ipcp)212 static 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 */
msg_security(struct kern_ipc_perm * ipcp,int msgflg)234 static 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
SYSCALL_DEFINE2(msgget,key_t,key,int,msgflg)241 SYSCALL_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
258 static inline unsigned long
copy_msqid_to_user(void __user * buf,struct msqid64_ds * in,int version)259 copy_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
303 static inline unsigned long
copy_msqid_from_user(struct msqid64_ds * out,void __user * buf,int version)304 copy_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 */
msgctl_down(struct ipc_namespace * ns,int msqid,int cmd,struct msqid_ds __user * buf,int version)339 static 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
403 out_unlock0:
404 ipc_unlock_object(&msq->q_perm);
405 out_unlock1:
406 rcu_read_unlock();
407 out_up:
408 up_write(&msg_ids(ns).rwsem);
409 return err;
410 }
411
msgctl_nolock(struct ipc_namespace * ns,int msqid,int cmd,int version,void __user * buf)412 static 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;
517 out_unlock:
518 rcu_read_unlock();
519 return err;
520 }
521
SYSCALL_DEFINE3(msgctl,int,msqid,int,cmd,struct msqid_ds __user *,buf)522 SYSCALL_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
testmsg(struct msg_msg * msg,long type,int mode)547 static 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
pipelined_send(struct msg_queue * msq,struct msg_msg * msg)569 static 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 /* barrier (B) see barrier comment below */
584 smp_wmb();
585 msr->r_msg = ERR_PTR(-E2BIG);
586 } else {
587 msr->r_msg = NULL;
588 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
589 msq->q_rtime = get_seconds();
590 wake_up_process(msr->r_tsk);
591 /*
592 * Ensure that the wakeup is visible before
593 * setting r_msg, as the receiving can otherwise
594 * exit - once r_msg is set, the receiver can
595 * continue. See lockless receive part 1 and 2
596 * in do_msgrcv(). Barrier (B).
597 */
598 smp_wmb();
599 msr->r_msg = msg;
600
601 return 1;
602 }
603 }
604 }
605
606 return 0;
607 }
608
do_msgsnd(int msqid,long mtype,void __user * mtext,size_t msgsz,int msgflg)609 long do_msgsnd(int msqid, long mtype, void __user *mtext,
610 size_t msgsz, int msgflg)
611 {
612 struct msg_queue *msq;
613 struct msg_msg *msg;
614 int err;
615 struct ipc_namespace *ns;
616
617 ns = current->nsproxy->ipc_ns;
618
619 if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
620 return -EINVAL;
621 if (mtype < 1)
622 return -EINVAL;
623
624 msg = load_msg(mtext, msgsz);
625 if (IS_ERR(msg))
626 return PTR_ERR(msg);
627
628 msg->m_type = mtype;
629 msg->m_ts = msgsz;
630
631 rcu_read_lock();
632 msq = msq_obtain_object_check(ns, msqid);
633 if (IS_ERR(msq)) {
634 err = PTR_ERR(msq);
635 goto out_unlock1;
636 }
637
638 ipc_lock_object(&msq->q_perm);
639
640 for (;;) {
641 struct msg_sender s;
642
643 err = -EACCES;
644 if (ipcperms(ns, &msq->q_perm, S_IWUGO))
645 goto out_unlock0;
646
647 /* raced with RMID? */
648 if (!ipc_valid_object(&msq->q_perm)) {
649 err = -EIDRM;
650 goto out_unlock0;
651 }
652
653 err = security_msg_queue_msgsnd(msq, msg, msgflg);
654 if (err)
655 goto out_unlock0;
656
657 if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
658 1 + msq->q_qnum <= msq->q_qbytes) {
659 break;
660 }
661
662 /* queue full, wait: */
663 if (msgflg & IPC_NOWAIT) {
664 err = -EAGAIN;
665 goto out_unlock0;
666 }
667
668 /* enqueue the sender and prepare to block */
669 ss_add(msq, &s);
670
671 if (!ipc_rcu_getref(msq)) {
672 err = -EIDRM;
673 goto out_unlock0;
674 }
675
676 ipc_unlock_object(&msq->q_perm);
677 rcu_read_unlock();
678 schedule();
679
680 rcu_read_lock();
681 ipc_lock_object(&msq->q_perm);
682
683 ipc_rcu_putref(msq, msg_rcu_free);
684 /* raced with RMID? */
685 if (!ipc_valid_object(&msq->q_perm)) {
686 err = -EIDRM;
687 goto out_unlock0;
688 }
689
690 ss_del(&s);
691
692 if (signal_pending(current)) {
693 err = -ERESTARTNOHAND;
694 goto out_unlock0;
695 }
696
697 }
698 msq->q_lspid = task_tgid_vnr(current);
699 msq->q_stime = get_seconds();
700
701 if (!pipelined_send(msq, msg)) {
702 /* no one is waiting for this message, enqueue it */
703 list_add_tail(&msg->m_list, &msq->q_messages);
704 msq->q_cbytes += msgsz;
705 msq->q_qnum++;
706 atomic_add(msgsz, &ns->msg_bytes);
707 atomic_inc(&ns->msg_hdrs);
708 }
709
710 err = 0;
711 msg = NULL;
712
713 out_unlock0:
714 ipc_unlock_object(&msq->q_perm);
715 out_unlock1:
716 rcu_read_unlock();
717 if (msg != NULL)
718 free_msg(msg);
719 return err;
720 }
721
SYSCALL_DEFINE4(msgsnd,int,msqid,struct msgbuf __user *,msgp,size_t,msgsz,int,msgflg)722 SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
723 int, msgflg)
724 {
725 long mtype;
726
727 if (get_user(mtype, &msgp->mtype))
728 return -EFAULT;
729 return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
730 }
731
convert_mode(long * msgtyp,int msgflg)732 static inline int convert_mode(long *msgtyp, int msgflg)
733 {
734 if (msgflg & MSG_COPY)
735 return SEARCH_NUMBER;
736 /*
737 * find message of correct type.
738 * msgtyp = 0 => get first.
739 * msgtyp > 0 => get first message of matching type.
740 * msgtyp < 0 => get message with least type must be < abs(msgtype).
741 */
742 if (*msgtyp == 0)
743 return SEARCH_ANY;
744 if (*msgtyp < 0) {
745 if (*msgtyp == LONG_MIN) /* -LONG_MIN is undefined */
746 *msgtyp = LONG_MAX;
747 else
748 *msgtyp = -*msgtyp;
749 return SEARCH_LESSEQUAL;
750 }
751 if (msgflg & MSG_EXCEPT)
752 return SEARCH_NOTEQUAL;
753 return SEARCH_EQUAL;
754 }
755
do_msg_fill(void __user * dest,struct msg_msg * msg,size_t bufsz)756 static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
757 {
758 struct msgbuf __user *msgp = dest;
759 size_t msgsz;
760
761 if (put_user(msg->m_type, &msgp->mtype))
762 return -EFAULT;
763
764 msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
765 if (store_msg(msgp->mtext, msg, msgsz))
766 return -EFAULT;
767 return msgsz;
768 }
769
770 #ifdef CONFIG_CHECKPOINT_RESTORE
771 /*
772 * This function creates new kernel message structure, large enough to store
773 * bufsz message bytes.
774 */
prepare_copy(void __user * buf,size_t bufsz)775 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
776 {
777 struct msg_msg *copy;
778
779 /*
780 * Create dummy message to copy real message to.
781 */
782 copy = load_msg(buf, bufsz);
783 if (!IS_ERR(copy))
784 copy->m_ts = bufsz;
785 return copy;
786 }
787
free_copy(struct msg_msg * copy)788 static inline void free_copy(struct msg_msg *copy)
789 {
790 if (copy)
791 free_msg(copy);
792 }
793 #else
prepare_copy(void __user * buf,size_t bufsz)794 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
795 {
796 return ERR_PTR(-ENOSYS);
797 }
798
free_copy(struct msg_msg * copy)799 static inline void free_copy(struct msg_msg *copy)
800 {
801 }
802 #endif
803
find_msg(struct msg_queue * msq,long * msgtyp,int mode)804 static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
805 {
806 struct msg_msg *msg, *found = NULL;
807 long count = 0;
808
809 list_for_each_entry(msg, &msq->q_messages, m_list) {
810 if (testmsg(msg, *msgtyp, mode) &&
811 !security_msg_queue_msgrcv(msq, msg, current,
812 *msgtyp, mode)) {
813 if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
814 *msgtyp = msg->m_type - 1;
815 found = msg;
816 } else if (mode == SEARCH_NUMBER) {
817 if (*msgtyp == count)
818 return msg;
819 } else
820 return msg;
821 count++;
822 }
823 }
824
825 return found ?: ERR_PTR(-EAGAIN);
826 }
827
do_msgrcv(int msqid,void __user * buf,size_t bufsz,long msgtyp,int msgflg,long (* msg_handler)(void __user *,struct msg_msg *,size_t))828 long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
829 long (*msg_handler)(void __user *, struct msg_msg *, size_t))
830 {
831 int mode;
832 struct msg_queue *msq;
833 struct ipc_namespace *ns;
834 struct msg_msg *msg, *copy = NULL;
835
836 ns = current->nsproxy->ipc_ns;
837
838 if (msqid < 0 || (long) bufsz < 0)
839 return -EINVAL;
840
841 if (msgflg & MSG_COPY) {
842 if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
843 return -EINVAL;
844 copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
845 if (IS_ERR(copy))
846 return PTR_ERR(copy);
847 }
848 mode = convert_mode(&msgtyp, msgflg);
849
850 rcu_read_lock();
851 msq = msq_obtain_object_check(ns, msqid);
852 if (IS_ERR(msq)) {
853 rcu_read_unlock();
854 free_copy(copy);
855 return PTR_ERR(msq);
856 }
857
858 for (;;) {
859 struct msg_receiver msr_d;
860
861 msg = ERR_PTR(-EACCES);
862 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
863 goto out_unlock1;
864
865 ipc_lock_object(&msq->q_perm);
866
867 /* raced with RMID? */
868 if (!ipc_valid_object(&msq->q_perm)) {
869 msg = ERR_PTR(-EIDRM);
870 goto out_unlock0;
871 }
872
873 msg = find_msg(msq, &msgtyp, mode);
874 if (!IS_ERR(msg)) {
875 /*
876 * Found a suitable message.
877 * Unlink it from the queue.
878 */
879 if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
880 msg = ERR_PTR(-E2BIG);
881 goto out_unlock0;
882 }
883 /*
884 * If we are copying, then do not unlink message and do
885 * not update queue parameters.
886 */
887 if (msgflg & MSG_COPY) {
888 msg = copy_msg(msg, copy);
889 goto out_unlock0;
890 }
891
892 list_del(&msg->m_list);
893 msq->q_qnum--;
894 msq->q_rtime = get_seconds();
895 msq->q_lrpid = task_tgid_vnr(current);
896 msq->q_cbytes -= msg->m_ts;
897 atomic_sub(msg->m_ts, &ns->msg_bytes);
898 atomic_dec(&ns->msg_hdrs);
899 ss_wakeup(&msq->q_senders, 0);
900
901 goto out_unlock0;
902 }
903
904 /* No message waiting. Wait for a message */
905 if (msgflg & IPC_NOWAIT) {
906 msg = ERR_PTR(-ENOMSG);
907 goto out_unlock0;
908 }
909
910 list_add_tail(&msr_d.r_list, &msq->q_receivers);
911 msr_d.r_tsk = current;
912 msr_d.r_msgtype = msgtyp;
913 msr_d.r_mode = mode;
914 if (msgflg & MSG_NOERROR)
915 msr_d.r_maxsize = INT_MAX;
916 else
917 msr_d.r_maxsize = bufsz;
918 msr_d.r_msg = ERR_PTR(-EAGAIN);
919 __set_current_state(TASK_INTERRUPTIBLE);
920
921 ipc_unlock_object(&msq->q_perm);
922 rcu_read_unlock();
923 schedule();
924
925 /* Lockless receive, part 1:
926 * Disable preemption. We don't hold a reference to the queue
927 * and getting a reference would defeat the idea of a lockless
928 * operation, thus the code relies on rcu to guarantee the
929 * existence of msq:
930 * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
931 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
932 * rcu_read_lock() prevents preemption between reading r_msg
933 * and acquiring the q_perm.lock in ipc_lock_object().
934 */
935 rcu_read_lock();
936
937 /* Lockless receive, part 2:
938 * Wait until pipelined_send or expunge_all are outside of
939 * wake_up_process(). There is a race with exit(), see
940 * ipc/mqueue.c for the details. The correct serialization
941 * ensures that a receiver cannot continue without the wakeup
942 * being visibible _before_ setting r_msg:
943 *
944 * CPU 0 CPU 1
945 * <loop receiver>
946 * smp_rmb(); (A) <-- pair -. <waker thread>
947 * <load ->r_msg> | msr->r_msg = NULL;
948 * | wake_up_process();
949 * <continue> `------> smp_wmb(); (B)
950 * msr->r_msg = msg;
951 *
952 * Where (A) orders the message value read and where (B) orders
953 * the write to the r_msg -- done in both pipelined_send and
954 * expunge_all.
955 */
956 for (;;) {
957 /*
958 * Pairs with writer barrier in pipelined_send
959 * or expunge_all.
960 */
961 smp_rmb(); /* barrier (A) */
962 msg = (struct msg_msg *)msr_d.r_msg;
963 if (msg)
964 break;
965
966 /*
967 * The cpu_relax() call is a compiler barrier
968 * which forces everything in this loop to be
969 * re-loaded.
970 */
971 cpu_relax();
972 }
973
974 /* Lockless receive, part 3:
975 * If there is a message or an error then accept it without
976 * locking.
977 */
978 if (msg != ERR_PTR(-EAGAIN))
979 goto out_unlock1;
980
981 /* Lockless receive, part 3:
982 * Acquire the queue spinlock.
983 */
984 ipc_lock_object(&msq->q_perm);
985
986 /* Lockless receive, part 4:
987 * Repeat test after acquiring the spinlock.
988 */
989 msg = (struct msg_msg *)msr_d.r_msg;
990 if (msg != ERR_PTR(-EAGAIN))
991 goto out_unlock0;
992
993 list_del(&msr_d.r_list);
994 if (signal_pending(current)) {
995 msg = ERR_PTR(-ERESTARTNOHAND);
996 goto out_unlock0;
997 }
998
999 ipc_unlock_object(&msq->q_perm);
1000 }
1001
1002 out_unlock0:
1003 ipc_unlock_object(&msq->q_perm);
1004 out_unlock1:
1005 rcu_read_unlock();
1006 if (IS_ERR(msg)) {
1007 free_copy(copy);
1008 return PTR_ERR(msg);
1009 }
1010
1011 bufsz = msg_handler(buf, msg, bufsz);
1012 free_msg(msg);
1013
1014 return bufsz;
1015 }
1016
SYSCALL_DEFINE5(msgrcv,int,msqid,struct msgbuf __user *,msgp,size_t,msgsz,long,msgtyp,int,msgflg)1017 SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
1018 long, msgtyp, int, msgflg)
1019 {
1020 return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
1021 }
1022
1023
msg_init_ns(struct ipc_namespace * ns)1024 void msg_init_ns(struct ipc_namespace *ns)
1025 {
1026 ns->msg_ctlmax = MSGMAX;
1027 ns->msg_ctlmnb = MSGMNB;
1028 ns->msg_ctlmni = MSGMNI;
1029
1030 atomic_set(&ns->msg_bytes, 0);
1031 atomic_set(&ns->msg_hdrs, 0);
1032 ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
1033 }
1034
1035 #ifdef CONFIG_IPC_NS
msg_exit_ns(struct ipc_namespace * ns)1036 void msg_exit_ns(struct ipc_namespace *ns)
1037 {
1038 free_ipcs(ns, &msg_ids(ns), freeque);
1039 idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
1040 }
1041 #endif
1042
1043 #ifdef CONFIG_PROC_FS
sysvipc_msg_proc_show(struct seq_file * s,void * it)1044 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
1045 {
1046 struct user_namespace *user_ns = seq_user_ns(s);
1047 struct msg_queue *msq = it;
1048
1049 seq_printf(s,
1050 "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1051 msq->q_perm.key,
1052 msq->q_perm.id,
1053 msq->q_perm.mode,
1054 msq->q_cbytes,
1055 msq->q_qnum,
1056 msq->q_lspid,
1057 msq->q_lrpid,
1058 from_kuid_munged(user_ns, msq->q_perm.uid),
1059 from_kgid_munged(user_ns, msq->q_perm.gid),
1060 from_kuid_munged(user_ns, msq->q_perm.cuid),
1061 from_kgid_munged(user_ns, msq->q_perm.cgid),
1062 msq->q_stime,
1063 msq->q_rtime,
1064 msq->q_ctime);
1065
1066 return 0;
1067 }
1068 #endif
1069
msg_init(void)1070 void __init msg_init(void)
1071 {
1072 msg_init_ns(&init_ipc_ns);
1073
1074 ipc_init_proc_interface("sysvipc/msg",
1075 " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n",
1076 IPC_MSG_IDS, sysvipc_msg_proc_show);
1077 }
1078