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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 | ||
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 | ||
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 | ||
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 | ||
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 | */ | |
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 | ||
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 | ||
169 | static inline void ss_del(struct msg_sender *mss) | |
170 | { | |
171 | if (mss->list.next != NULL) | |
172 | list_del(&mss->list); | |
173 | } | |
174 | ||
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 | ||
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 | */ | |
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 | */ | |
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 | ||
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 | |
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 | |
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 | */ | |
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 | ||
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 | ||
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 | ||
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 | ||
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 | ||
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, ipc_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 | ||
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 | ||
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 | *msgtyp = -*msgtyp; | |
746 | return SEARCH_LESSEQUAL; | |
747 | } | |
748 | if (msgflg & MSG_EXCEPT) | |
749 | return SEARCH_NOTEQUAL; | |
750 | return SEARCH_EQUAL; | |
751 | } | |
752 | ||
753 | static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz) | |
754 | { | |
755 | struct msgbuf __user *msgp = dest; | |
756 | size_t msgsz; | |
757 | ||
758 | if (put_user(msg->m_type, &msgp->mtype)) | |
759 | return -EFAULT; | |
760 | ||
761 | msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz; | |
762 | if (store_msg(msgp->mtext, msg, msgsz)) | |
763 | return -EFAULT; | |
764 | return msgsz; | |
765 | } | |
766 | ||
767 | #ifdef CONFIG_CHECKPOINT_RESTORE | |
768 | /* | |
769 | * This function creates new kernel message structure, large enough to store | |
770 | * bufsz message bytes. | |
771 | */ | |
772 | static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz) | |
773 | { | |
774 | struct msg_msg *copy; | |
775 | ||
776 | /* | |
777 | * Create dummy message to copy real message to. | |
778 | */ | |
779 | copy = load_msg(buf, bufsz); | |
780 | if (!IS_ERR(copy)) | |
781 | copy->m_ts = bufsz; | |
782 | return copy; | |
783 | } | |
784 | ||
785 | static inline void free_copy(struct msg_msg *copy) | |
786 | { | |
787 | if (copy) | |
788 | free_msg(copy); | |
789 | } | |
790 | #else | |
791 | static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz) | |
792 | { | |
793 | return ERR_PTR(-ENOSYS); | |
794 | } | |
795 | ||
796 | static inline void free_copy(struct msg_msg *copy) | |
797 | { | |
798 | } | |
799 | #endif | |
800 | ||
801 | static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode) | |
802 | { | |
803 | struct msg_msg *msg, *found = NULL; | |
804 | long count = 0; | |
805 | ||
806 | list_for_each_entry(msg, &msq->q_messages, m_list) { | |
807 | if (testmsg(msg, *msgtyp, mode) && | |
808 | !security_msg_queue_msgrcv(msq, msg, current, | |
809 | *msgtyp, mode)) { | |
810 | if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) { | |
811 | *msgtyp = msg->m_type - 1; | |
812 | found = msg; | |
813 | } else if (mode == SEARCH_NUMBER) { | |
814 | if (*msgtyp == count) | |
815 | return msg; | |
816 | } else | |
817 | return msg; | |
818 | count++; | |
819 | } | |
820 | } | |
821 | ||
822 | return found ?: ERR_PTR(-EAGAIN); | |
823 | } | |
824 | ||
825 | long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg, | |
826 | long (*msg_handler)(void __user *, struct msg_msg *, size_t)) | |
827 | { | |
828 | int mode; | |
829 | struct msg_queue *msq; | |
830 | struct ipc_namespace *ns; | |
831 | struct msg_msg *msg, *copy = NULL; | |
832 | ||
833 | ns = current->nsproxy->ipc_ns; | |
834 | ||
835 | if (msqid < 0 || (long) bufsz < 0) | |
836 | return -EINVAL; | |
837 | ||
838 | if (msgflg & MSG_COPY) { | |
839 | if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT)) | |
840 | return -EINVAL; | |
841 | copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax)); | |
842 | if (IS_ERR(copy)) | |
843 | return PTR_ERR(copy); | |
844 | } | |
845 | mode = convert_mode(&msgtyp, msgflg); | |
846 | ||
847 | rcu_read_lock(); | |
848 | msq = msq_obtain_object_check(ns, msqid); | |
849 | if (IS_ERR(msq)) { | |
850 | rcu_read_unlock(); | |
851 | free_copy(copy); | |
852 | return PTR_ERR(msq); | |
853 | } | |
854 | ||
855 | for (;;) { | |
856 | struct msg_receiver msr_d; | |
857 | ||
858 | msg = ERR_PTR(-EACCES); | |
859 | if (ipcperms(ns, &msq->q_perm, S_IRUGO)) | |
860 | goto out_unlock1; | |
861 | ||
862 | ipc_lock_object(&msq->q_perm); | |
863 | ||
864 | /* raced with RMID? */ | |
865 | if (!ipc_valid_object(&msq->q_perm)) { | |
866 | msg = ERR_PTR(-EIDRM); | |
867 | goto out_unlock0; | |
868 | } | |
869 | ||
870 | msg = find_msg(msq, &msgtyp, mode); | |
871 | if (!IS_ERR(msg)) { | |
872 | /* | |
873 | * Found a suitable message. | |
874 | * Unlink it from the queue. | |
875 | */ | |
876 | if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) { | |
877 | msg = ERR_PTR(-E2BIG); | |
878 | goto out_unlock0; | |
879 | } | |
880 | /* | |
881 | * If we are copying, then do not unlink message and do | |
882 | * not update queue parameters. | |
883 | */ | |
884 | if (msgflg & MSG_COPY) { | |
885 | msg = copy_msg(msg, copy); | |
886 | goto out_unlock0; | |
887 | } | |
888 | ||
889 | list_del(&msg->m_list); | |
890 | msq->q_qnum--; | |
891 | msq->q_rtime = get_seconds(); | |
892 | msq->q_lrpid = task_tgid_vnr(current); | |
893 | msq->q_cbytes -= msg->m_ts; | |
894 | atomic_sub(msg->m_ts, &ns->msg_bytes); | |
895 | atomic_dec(&ns->msg_hdrs); | |
896 | ss_wakeup(&msq->q_senders, 0); | |
897 | ||
898 | goto out_unlock0; | |
899 | } | |
900 | ||
901 | /* No message waiting. Wait for a message */ | |
902 | if (msgflg & IPC_NOWAIT) { | |
903 | msg = ERR_PTR(-ENOMSG); | |
904 | goto out_unlock0; | |
905 | } | |
906 | ||
907 | list_add_tail(&msr_d.r_list, &msq->q_receivers); | |
908 | msr_d.r_tsk = current; | |
909 | msr_d.r_msgtype = msgtyp; | |
910 | msr_d.r_mode = mode; | |
911 | if (msgflg & MSG_NOERROR) | |
912 | msr_d.r_maxsize = INT_MAX; | |
913 | else | |
914 | msr_d.r_maxsize = bufsz; | |
915 | msr_d.r_msg = ERR_PTR(-EAGAIN); | |
916 | __set_current_state(TASK_INTERRUPTIBLE); | |
917 | ||
918 | ipc_unlock_object(&msq->q_perm); | |
919 | rcu_read_unlock(); | |
920 | schedule(); | |
921 | ||
922 | /* Lockless receive, part 1: | |
923 | * Disable preemption. We don't hold a reference to the queue | |
924 | * and getting a reference would defeat the idea of a lockless | |
925 | * operation, thus the code relies on rcu to guarantee the | |
926 | * existence of msq: | |
927 | * Prior to destruction, expunge_all(-EIRDM) changes r_msg. | |
928 | * Thus if r_msg is -EAGAIN, then the queue not yet destroyed. | |
929 | * rcu_read_lock() prevents preemption between reading r_msg | |
930 | * and acquiring the q_perm.lock in ipc_lock_object(). | |
931 | */ | |
932 | rcu_read_lock(); | |
933 | ||
934 | /* Lockless receive, part 2: | |
935 | * Wait until pipelined_send or expunge_all are outside of | |
936 | * wake_up_process(). There is a race with exit(), see | |
937 | * ipc/mqueue.c for the details. The correct serialization | |
938 | * ensures that a receiver cannot continue without the wakeup | |
939 | * being visibible _before_ setting r_msg: | |
940 | * | |
941 | * CPU 0 CPU 1 | |
942 | * <loop receiver> | |
943 | * smp_rmb(); (A) <-- pair -. <waker thread> | |
944 | * <load ->r_msg> | msr->r_msg = NULL; | |
945 | * | wake_up_process(); | |
946 | * <continue> `------> smp_wmb(); (B) | |
947 | * msr->r_msg = msg; | |
948 | * | |
949 | * Where (A) orders the message value read and where (B) orders | |
950 | * the write to the r_msg -- done in both pipelined_send and | |
951 | * expunge_all. | |
952 | */ | |
953 | for (;;) { | |
954 | /* | |
955 | * Pairs with writer barrier in pipelined_send | |
956 | * or expunge_all. | |
957 | */ | |
958 | smp_rmb(); /* barrier (A) */ | |
959 | msg = (struct msg_msg *)msr_d.r_msg; | |
960 | if (msg) | |
961 | break; | |
962 | ||
963 | /* | |
964 | * The cpu_relax() call is a compiler barrier | |
965 | * which forces everything in this loop to be | |
966 | * re-loaded. | |
967 | */ | |
968 | cpu_relax(); | |
969 | } | |
970 | ||
971 | /* Lockless receive, part 3: | |
972 | * If there is a message or an error then accept it without | |
973 | * locking. | |
974 | */ | |
975 | if (msg != ERR_PTR(-EAGAIN)) | |
976 | goto out_unlock1; | |
977 | ||
978 | /* Lockless receive, part 3: | |
979 | * Acquire the queue spinlock. | |
980 | */ | |
981 | ipc_lock_object(&msq->q_perm); | |
982 | ||
983 | /* Lockless receive, part 4: | |
984 | * Repeat test after acquiring the spinlock. | |
985 | */ | |
986 | msg = (struct msg_msg *)msr_d.r_msg; | |
987 | if (msg != ERR_PTR(-EAGAIN)) | |
988 | goto out_unlock0; | |
989 | ||
990 | list_del(&msr_d.r_list); | |
991 | if (signal_pending(current)) { | |
992 | msg = ERR_PTR(-ERESTARTNOHAND); | |
993 | goto out_unlock0; | |
994 | } | |
995 | ||
996 | ipc_unlock_object(&msq->q_perm); | |
997 | } | |
998 | ||
999 | out_unlock0: | |
1000 | ipc_unlock_object(&msq->q_perm); | |
1001 | out_unlock1: | |
1002 | rcu_read_unlock(); | |
1003 | if (IS_ERR(msg)) { | |
1004 | free_copy(copy); | |
1005 | return PTR_ERR(msg); | |
1006 | } | |
1007 | ||
1008 | bufsz = msg_handler(buf, msg, bufsz); | |
1009 | free_msg(msg); | |
1010 | ||
1011 | return bufsz; | |
1012 | } | |
1013 | ||
1014 | SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, | |
1015 | long, msgtyp, int, msgflg) | |
1016 | { | |
1017 | return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill); | |
1018 | } | |
1019 | ||
1020 | ||
1021 | void msg_init_ns(struct ipc_namespace *ns) | |
1022 | { | |
1023 | ns->msg_ctlmax = MSGMAX; | |
1024 | ns->msg_ctlmnb = MSGMNB; | |
1025 | ns->msg_ctlmni = MSGMNI; | |
1026 | ||
1027 | atomic_set(&ns->msg_bytes, 0); | |
1028 | atomic_set(&ns->msg_hdrs, 0); | |
1029 | ipc_init_ids(&ns->ids[IPC_MSG_IDS]); | |
1030 | } | |
1031 | ||
1032 | #ifdef CONFIG_IPC_NS | |
1033 | void msg_exit_ns(struct ipc_namespace *ns) | |
1034 | { | |
1035 | free_ipcs(ns, &msg_ids(ns), freeque); | |
1036 | idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr); | |
1037 | } | |
1038 | #endif | |
1039 | ||
1040 | #ifdef CONFIG_PROC_FS | |
1041 | static int sysvipc_msg_proc_show(struct seq_file *s, void *it) | |
1042 | { | |
1043 | struct user_namespace *user_ns = seq_user_ns(s); | |
1044 | struct msg_queue *msq = it; | |
1045 | ||
1046 | seq_printf(s, | |
1047 | "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n", | |
1048 | msq->q_perm.key, | |
1049 | msq->q_perm.id, | |
1050 | msq->q_perm.mode, | |
1051 | msq->q_cbytes, | |
1052 | msq->q_qnum, | |
1053 | msq->q_lspid, | |
1054 | msq->q_lrpid, | |
1055 | from_kuid_munged(user_ns, msq->q_perm.uid), | |
1056 | from_kgid_munged(user_ns, msq->q_perm.gid), | |
1057 | from_kuid_munged(user_ns, msq->q_perm.cuid), | |
1058 | from_kgid_munged(user_ns, msq->q_perm.cgid), | |
1059 | msq->q_stime, | |
1060 | msq->q_rtime, | |
1061 | msq->q_ctime); | |
1062 | ||
1063 | return 0; | |
1064 | } | |
1065 | #endif | |
1066 | ||
1067 | void __init msg_init(void) | |
1068 | { | |
1069 | msg_init_ns(&init_ipc_ns); | |
1070 | ||
1071 | ipc_init_proc_interface("sysvipc/msg", | |
1072 | " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n", | |
1073 | IPC_MSG_IDS, sysvipc_msg_proc_show); | |
1074 | } |