Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/ipc/msg.c

  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         struct msg_msg          *r_msg;
 55 };
 56 
 57 /* one msg_sender for each sleeping sender */
 58 struct msg_sender {
 59         struct list_head        list;
 60         struct task_struct      *tsk;
 61         size_t                  msgsz;
 62 };
 63 
 64 #define SEARCH_ANY              1
 65 #define SEARCH_EQUAL            2
 66 #define SEARCH_NOTEQUAL         3
 67 #define SEARCH_LESSEQUAL        4
 68 #define SEARCH_NUMBER           5
 69 
 70 #define msg_ids(ns)     ((ns)->ids[IPC_MSG_IDS])
 71 
 72 static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
 73 {
 74         struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&msg_ids(ns), id);
 75 
 76         if (IS_ERR(ipcp))
 77                 return ERR_CAST(ipcp);
 78 
 79         return container_of(ipcp, struct msg_queue, q_perm);
 80 }
 81 
 82 static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns,
 83                                                         int id)
 84 {
 85         struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id);
 86 
 87         if (IS_ERR(ipcp))
 88                 return ERR_CAST(ipcp);
 89 
 90         return container_of(ipcp, struct msg_queue, q_perm);
 91 }
 92 
 93 static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
 94 {
 95         ipc_rmid(&msg_ids(ns), &s->q_perm);
 96 }
 97 
 98 static void msg_rcu_free(struct rcu_head *head)
 99 {
100         struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
101         struct msg_queue *msq = ipc_rcu_to_struct(p);
102 
103         security_msg_queue_free(msq);
104         ipc_rcu_free(head);
105 }
106 
107 /**
108  * newque - Create a new msg queue
109  * @ns: namespace
110  * @params: ptr to the structure that contains the key and msgflg
111  *
112  * Called with msg_ids.rwsem held (writer)
113  */
114 static int newque(struct ipc_namespace *ns, struct ipc_params *params)
115 {
116         struct msg_queue *msq;
117         int id, retval;
118         key_t key = params->key;
119         int msgflg = params->flg;
120 
121         msq = ipc_rcu_alloc(sizeof(*msq));
122         if (!msq)
123                 return -ENOMEM;
124 
125         msq->q_perm.mode = msgflg & S_IRWXUGO;
126         msq->q_perm.key = key;
127 
128         msq->q_perm.security = NULL;
129         retval = security_msg_queue_alloc(msq);
130         if (retval) {
131                 ipc_rcu_putref(msq, ipc_rcu_free);
132                 return retval;
133         }
134 
135         msq->q_stime = msq->q_rtime = 0;
136         msq->q_ctime = get_seconds();
137         msq->q_cbytes = msq->q_qnum = 0;
138         msq->q_qbytes = ns->msg_ctlmnb;
139         msq->q_lspid = msq->q_lrpid = 0;
140         INIT_LIST_HEAD(&msq->q_messages);
141         INIT_LIST_HEAD(&msq->q_receivers);
142         INIT_LIST_HEAD(&msq->q_senders);
143 
144         /* ipc_addid() locks msq upon success. */
145         id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
146         if (id < 0) {
147                 ipc_rcu_putref(msq, msg_rcu_free);
148                 return id;
149         }
150 
151         ipc_unlock_object(&msq->q_perm);
152         rcu_read_unlock();
153 
154         return msq->q_perm.id;
155 }
156 
157 static inline bool msg_fits_inqueue(struct msg_queue *msq, size_t msgsz)
158 {
159         return msgsz + msq->q_cbytes <= msq->q_qbytes &&
160                 1 + msq->q_qnum <= msq->q_qbytes;
161 }
162 
163 static inline void ss_add(struct msg_queue *msq,
164                           struct msg_sender *mss, size_t msgsz)
165 {
166         mss->tsk = current;
167         mss->msgsz = msgsz;
168         __set_current_state(TASK_INTERRUPTIBLE);
169         list_add_tail(&mss->list, &msq->q_senders);
170 }
171 
172 static inline void ss_del(struct msg_sender *mss)
173 {
174         if (mss->list.next)
175                 list_del(&mss->list);
176 }
177 
178 static void ss_wakeup(struct msg_queue *msq,
179                       struct wake_q_head *wake_q, bool kill)
180 {
181         struct msg_sender *mss, *t;
182         struct task_struct *stop_tsk = NULL;
183         struct list_head *h = &msq->q_senders;
184 
185         list_for_each_entry_safe(mss, t, h, list) {
186                 if (kill)
187                         mss->list.next = NULL;
188 
189                 /*
190                  * Stop at the first task we don't wakeup,
191                  * we've already iterated the original
192                  * sender queue.
193                  */
194                 else if (stop_tsk == mss->tsk)
195                         break;
196                 /*
197                  * We are not in an EIDRM scenario here, therefore
198                  * verify that we really need to wakeup the task.
199                  * To maintain current semantics and wakeup order,
200                  * move the sender to the tail on behalf of the
201                  * blocked task.
202                  */
203                 else if (!msg_fits_inqueue(msq, mss->msgsz)) {
204                         if (!stop_tsk)
205                                 stop_tsk = mss->tsk;
206 
207                         list_move_tail(&mss->list, &msq->q_senders);
208                         continue;
209                 }
210 
211                 wake_q_add(wake_q, mss->tsk);
212         }
213 }
214 
215 static void expunge_all(struct msg_queue *msq, int res,
216                         struct wake_q_head *wake_q)
217 {
218         struct msg_receiver *msr, *t;
219 
220         list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
221                 wake_q_add(wake_q, msr->r_tsk);
222                 WRITE_ONCE(msr->r_msg, ERR_PTR(res));
223         }
224 }
225 
226 /*
227  * freeque() wakes up waiters on the sender and receiver waiting queue,
228  * removes the message queue from message queue ID IDR, and cleans up all the
229  * messages associated with this queue.
230  *
231  * msg_ids.rwsem (writer) and the spinlock for this message queue are held
232  * before freeque() is called. msg_ids.rwsem remains locked on exit.
233  */
234 static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
235 {
236         struct msg_msg *msg, *t;
237         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
238         DEFINE_WAKE_Q(wake_q);
239 
240         expunge_all(msq, -EIDRM, &wake_q);
241         ss_wakeup(msq, &wake_q, true);
242         msg_rmid(ns, msq);
243         ipc_unlock_object(&msq->q_perm);
244         wake_up_q(&wake_q);
245         rcu_read_unlock();
246 
247         list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
248                 atomic_dec(&ns->msg_hdrs);
249                 free_msg(msg);
250         }
251         atomic_sub(msq->q_cbytes, &ns->msg_bytes);
252         ipc_rcu_putref(msq, msg_rcu_free);
253 }
254 
255 /*
256  * Called with msg_ids.rwsem and ipcp locked.
257  */
258 static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
259 {
260         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
261 
262         return security_msg_queue_associate(msq, msgflg);
263 }
264 
265 SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
266 {
267         struct ipc_namespace *ns;
268         static const struct ipc_ops msg_ops = {
269                 .getnew = newque,
270                 .associate = msg_security,
271         };
272         struct ipc_params msg_params;
273 
274         ns = current->nsproxy->ipc_ns;
275 
276         msg_params.key = key;
277         msg_params.flg = msgflg;
278 
279         return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
280 }
281 
282 static inline unsigned long
283 copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
284 {
285         switch (version) {
286         case IPC_64:
287                 return copy_to_user(buf, in, sizeof(*in));
288         case IPC_OLD:
289         {
290                 struct msqid_ds out;
291 
292                 memset(&out, 0, sizeof(out));
293 
294                 ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
295 
296                 out.msg_stime           = in->msg_stime;
297                 out.msg_rtime           = in->msg_rtime;
298                 out.msg_ctime           = in->msg_ctime;
299 
300                 if (in->msg_cbytes > USHRT_MAX)
301                         out.msg_cbytes  = USHRT_MAX;
302                 else
303                         out.msg_cbytes  = in->msg_cbytes;
304                 out.msg_lcbytes         = in->msg_cbytes;
305 
306                 if (in->msg_qnum > USHRT_MAX)
307                         out.msg_qnum    = USHRT_MAX;
308                 else
309                         out.msg_qnum    = in->msg_qnum;
310 
311                 if (in->msg_qbytes > USHRT_MAX)
312                         out.msg_qbytes  = USHRT_MAX;
313                 else
314                         out.msg_qbytes  = in->msg_qbytes;
315                 out.msg_lqbytes         = in->msg_qbytes;
316 
317                 out.msg_lspid           = in->msg_lspid;
318                 out.msg_lrpid           = in->msg_lrpid;
319 
320                 return copy_to_user(buf, &out, sizeof(out));
321         }
322         default:
323                 return -EINVAL;
324         }
325 }
326 
327 static inline unsigned long
328 copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
329 {
330         switch (version) {
331         case IPC_64:
332                 if (copy_from_user(out, buf, sizeof(*out)))
333                         return -EFAULT;
334                 return 0;
335         case IPC_OLD:
336         {
337                 struct msqid_ds tbuf_old;
338 
339                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
340                         return -EFAULT;
341 
342                 out->msg_perm.uid       = tbuf_old.msg_perm.uid;
343                 out->msg_perm.gid       = tbuf_old.msg_perm.gid;
344                 out->msg_perm.mode      = tbuf_old.msg_perm.mode;
345 
346                 if (tbuf_old.msg_qbytes == 0)
347                         out->msg_qbytes = tbuf_old.msg_lqbytes;
348                 else
349                         out->msg_qbytes = tbuf_old.msg_qbytes;
350 
351                 return 0;
352         }
353         default:
354                 return -EINVAL;
355         }
356 }
357 
358 /*
359  * This function handles some msgctl commands which require the rwsem
360  * to be held in write mode.
361  * NOTE: no locks must be held, the rwsem is taken inside this function.
362  */
363 static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
364                        struct msqid_ds __user *buf, int version)
365 {
366         struct kern_ipc_perm *ipcp;
367         struct msqid64_ds uninitialized_var(msqid64);
368         struct msg_queue *msq;
369         int err;
370 
371         if (cmd == IPC_SET) {
372                 if (copy_msqid_from_user(&msqid64, buf, version))
373                         return -EFAULT;
374         }
375 
376         down_write(&msg_ids(ns).rwsem);
377         rcu_read_lock();
378 
379         ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
380                                       &msqid64.msg_perm, msqid64.msg_qbytes);
381         if (IS_ERR(ipcp)) {
382                 err = PTR_ERR(ipcp);
383                 goto out_unlock1;
384         }
385 
386         msq = container_of(ipcp, struct msg_queue, q_perm);
387 
388         err = security_msg_queue_msgctl(msq, cmd);
389         if (err)
390                 goto out_unlock1;
391 
392         switch (cmd) {
393         case IPC_RMID:
394                 ipc_lock_object(&msq->q_perm);
395                 /* freeque unlocks the ipc object and rcu */
396                 freeque(ns, ipcp);
397                 goto out_up;
398         case IPC_SET:
399         {
400                 DEFINE_WAKE_Q(wake_q);
401 
402                 if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
403                     !capable(CAP_SYS_RESOURCE)) {
404                         err = -EPERM;
405                         goto out_unlock1;
406                 }
407 
408                 ipc_lock_object(&msq->q_perm);
409                 err = ipc_update_perm(&msqid64.msg_perm, ipcp);
410                 if (err)
411                         goto out_unlock0;
412 
413                 msq->q_qbytes = msqid64.msg_qbytes;
414 
415                 msq->q_ctime = get_seconds();
416                 /*
417                  * Sleeping receivers might be excluded by
418                  * stricter permissions.
419                  */
420                 expunge_all(msq, -EAGAIN, &wake_q);
421                 /*
422                  * Sleeping senders might be able to send
423                  * due to a larger queue size.
424                  */
425                 ss_wakeup(msq, &wake_q, false);
426                 ipc_unlock_object(&msq->q_perm);
427                 wake_up_q(&wake_q);
428 
429                 goto out_unlock1;
430         }
431         default:
432                 err = -EINVAL;
433                 goto out_unlock1;
434         }
435 
436 out_unlock0:
437         ipc_unlock_object(&msq->q_perm);
438 out_unlock1:
439         rcu_read_unlock();
440 out_up:
441         up_write(&msg_ids(ns).rwsem);
442         return err;
443 }
444 
445 static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
446                          int cmd, int version, void __user *buf)
447 {
448         int err;
449         struct msg_queue *msq;
450 
451         switch (cmd) {
452         case IPC_INFO:
453         case MSG_INFO:
454         {
455                 struct msginfo msginfo;
456                 int max_id;
457 
458                 if (!buf)
459                         return -EFAULT;
460 
461                 /*
462                  * We must not return kernel stack data.
463                  * due to padding, it's not enough
464                  * to set all member fields.
465                  */
466                 err = security_msg_queue_msgctl(NULL, cmd);
467                 if (err)
468                         return err;
469 
470                 memset(&msginfo, 0, sizeof(msginfo));
471                 msginfo.msgmni = ns->msg_ctlmni;
472                 msginfo.msgmax = ns->msg_ctlmax;
473                 msginfo.msgmnb = ns->msg_ctlmnb;
474                 msginfo.msgssz = MSGSSZ;
475                 msginfo.msgseg = MSGSEG;
476                 down_read(&msg_ids(ns).rwsem);
477                 if (cmd == MSG_INFO) {
478                         msginfo.msgpool = msg_ids(ns).in_use;
479                         msginfo.msgmap = atomic_read(&ns->msg_hdrs);
480                         msginfo.msgtql = atomic_read(&ns->msg_bytes);
481                 } else {
482                         msginfo.msgmap = MSGMAP;
483                         msginfo.msgpool = MSGPOOL;
484                         msginfo.msgtql = MSGTQL;
485                 }
486                 max_id = ipc_get_maxid(&msg_ids(ns));
487                 up_read(&msg_ids(ns).rwsem);
488                 if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
489                         return -EFAULT;
490                 return (max_id < 0) ? 0 : max_id;
491         }
492 
493         case MSG_STAT:
494         case IPC_STAT:
495         {
496                 struct msqid64_ds tbuf;
497                 int success_return;
498 
499                 if (!buf)
500                         return -EFAULT;
501 
502                 memset(&tbuf, 0, sizeof(tbuf));
503 
504                 rcu_read_lock();
505                 if (cmd == MSG_STAT) {
506                         msq = msq_obtain_object(ns, msqid);
507                         if (IS_ERR(msq)) {
508                                 err = PTR_ERR(msq);
509                                 goto out_unlock;
510                         }
511                         success_return = msq->q_perm.id;
512                 } else {
513                         msq = msq_obtain_object_check(ns, msqid);
514                         if (IS_ERR(msq)) {
515                                 err = PTR_ERR(msq);
516                                 goto out_unlock;
517                         }
518                         success_return = 0;
519                 }
520 
521                 err = -EACCES;
522                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
523                         goto out_unlock;
524 
525                 err = security_msg_queue_msgctl(msq, cmd);
526                 if (err)
527                         goto out_unlock;
528 
529                 kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
530                 tbuf.msg_stime  = msq->q_stime;
531                 tbuf.msg_rtime  = msq->q_rtime;
532                 tbuf.msg_ctime  = msq->q_ctime;
533                 tbuf.msg_cbytes = msq->q_cbytes;
534                 tbuf.msg_qnum   = msq->q_qnum;
535                 tbuf.msg_qbytes = msq->q_qbytes;
536                 tbuf.msg_lspid  = msq->q_lspid;
537                 tbuf.msg_lrpid  = msq->q_lrpid;
538                 rcu_read_unlock();
539 
540                 if (copy_msqid_to_user(buf, &tbuf, version))
541                         return -EFAULT;
542                 return success_return;
543         }
544 
545         default:
546                 return -EINVAL;
547         }
548 
549         return err;
550 out_unlock:
551         rcu_read_unlock();
552         return err;
553 }
554 
555 SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
556 {
557         int version;
558         struct ipc_namespace *ns;
559 
560         if (msqid < 0 || cmd < 0)
561                 return -EINVAL;
562 
563         version = ipc_parse_version(&cmd);
564         ns = current->nsproxy->ipc_ns;
565 
566         switch (cmd) {
567         case IPC_INFO:
568         case MSG_INFO:
569         case MSG_STAT:  /* msqid is an index rather than a msg queue id */
570         case IPC_STAT:
571                 return msgctl_nolock(ns, msqid, cmd, version, buf);
572         case IPC_SET:
573         case IPC_RMID:
574                 return msgctl_down(ns, msqid, cmd, buf, version);
575         default:
576                 return  -EINVAL;
577         }
578 }
579 
580 static int testmsg(struct msg_msg *msg, long type, int mode)
581 {
582         switch (mode) {
583         case SEARCH_ANY:
584         case SEARCH_NUMBER:
585                 return 1;
586         case SEARCH_LESSEQUAL:
587                 if (msg->m_type <= type)
588                         return 1;
589                 break;
590         case SEARCH_EQUAL:
591                 if (msg->m_type == type)
592                         return 1;
593                 break;
594         case SEARCH_NOTEQUAL:
595                 if (msg->m_type != type)
596                         return 1;
597                 break;
598         }
599         return 0;
600 }
601 
602 static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg,
603                                  struct wake_q_head *wake_q)
604 {
605         struct msg_receiver *msr, *t;
606 
607         list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
608                 if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
609                     !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
610                                                msr->r_msgtype, msr->r_mode)) {
611 
612                         list_del(&msr->r_list);
613                         if (msr->r_maxsize < msg->m_ts) {
614                                 wake_q_add(wake_q, msr->r_tsk);
615                                 WRITE_ONCE(msr->r_msg, ERR_PTR(-E2BIG));
616                         } else {
617                                 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
618                                 msq->q_rtime = get_seconds();
619 
620                                 wake_q_add(wake_q, msr->r_tsk);
621                                 WRITE_ONCE(msr->r_msg, msg);
622                                 return 1;
623                         }
624                 }
625         }
626 
627         return 0;
628 }
629 
630 long do_msgsnd(int msqid, long mtype, void __user *mtext,
631                 size_t msgsz, int msgflg)
632 {
633         struct msg_queue *msq;
634         struct msg_msg *msg;
635         int err;
636         struct ipc_namespace *ns;
637         DEFINE_WAKE_Q(wake_q);
638 
639         ns = current->nsproxy->ipc_ns;
640 
641         if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
642                 return -EINVAL;
643         if (mtype < 1)
644                 return -EINVAL;
645 
646         msg = load_msg(mtext, msgsz);
647         if (IS_ERR(msg))
648                 return PTR_ERR(msg);
649 
650         msg->m_type = mtype;
651         msg->m_ts = msgsz;
652 
653         rcu_read_lock();
654         msq = msq_obtain_object_check(ns, msqid);
655         if (IS_ERR(msq)) {
656                 err = PTR_ERR(msq);
657                 goto out_unlock1;
658         }
659 
660         ipc_lock_object(&msq->q_perm);
661 
662         for (;;) {
663                 struct msg_sender s;
664 
665                 err = -EACCES;
666                 if (ipcperms(ns, &msq->q_perm, S_IWUGO))
667                         goto out_unlock0;
668 
669                 /* raced with RMID? */
670                 if (!ipc_valid_object(&msq->q_perm)) {
671                         err = -EIDRM;
672                         goto out_unlock0;
673                 }
674 
675                 err = security_msg_queue_msgsnd(msq, msg, msgflg);
676                 if (err)
677                         goto out_unlock0;
678 
679                 if (msg_fits_inqueue(msq, msgsz))
680                         break;
681 
682                 /* queue full, wait: */
683                 if (msgflg & IPC_NOWAIT) {
684                         err = -EAGAIN;
685                         goto out_unlock0;
686                 }
687 
688                 /* enqueue the sender and prepare to block */
689                 ss_add(msq, &s, msgsz);
690 
691                 if (!ipc_rcu_getref(msq)) {
692                         err = -EIDRM;
693                         goto out_unlock0;
694                 }
695 
696                 ipc_unlock_object(&msq->q_perm);
697                 rcu_read_unlock();
698                 schedule();
699 
700                 rcu_read_lock();
701                 ipc_lock_object(&msq->q_perm);
702 
703                 ipc_rcu_putref(msq, msg_rcu_free);
704                 /* raced with RMID? */
705                 if (!ipc_valid_object(&msq->q_perm)) {
706                         err = -EIDRM;
707                         goto out_unlock0;
708                 }
709                 ss_del(&s);
710 
711                 if (signal_pending(current)) {
712                         err = -ERESTARTNOHAND;
713                         goto out_unlock0;
714                 }
715 
716         }
717 
718         msq->q_lspid = task_tgid_vnr(current);
719         msq->q_stime = get_seconds();
720 
721         if (!pipelined_send(msq, msg, &wake_q)) {
722                 /* no one is waiting for this message, enqueue it */
723                 list_add_tail(&msg->m_list, &msq->q_messages);
724                 msq->q_cbytes += msgsz;
725                 msq->q_qnum++;
726                 atomic_add(msgsz, &ns->msg_bytes);
727                 atomic_inc(&ns->msg_hdrs);
728         }
729 
730         err = 0;
731         msg = NULL;
732 
733 out_unlock0:
734         ipc_unlock_object(&msq->q_perm);
735         wake_up_q(&wake_q);
736 out_unlock1:
737         rcu_read_unlock();
738         if (msg != NULL)
739                 free_msg(msg);
740         return err;
741 }
742 
743 SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
744                 int, msgflg)
745 {
746         long mtype;
747 
748         if (get_user(mtype, &msgp->mtype))
749                 return -EFAULT;
750         return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
751 }
752 
753 static inline int convert_mode(long *msgtyp, int msgflg)
754 {
755         if (msgflg & MSG_COPY)
756                 return SEARCH_NUMBER;
757         /*
758          *  find message of correct type.
759          *  msgtyp = 0 => get first.
760          *  msgtyp > 0 => get first message of matching type.
761          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
762          */
763         if (*msgtyp == 0)
764                 return SEARCH_ANY;
765         if (*msgtyp < 0) {
766                 if (*msgtyp == LONG_MIN) /* -LONG_MIN is undefined */
767                         *msgtyp = LONG_MAX;
768                 else
769                         *msgtyp = -*msgtyp;
770                 return SEARCH_LESSEQUAL;
771         }
772         if (msgflg & MSG_EXCEPT)
773                 return SEARCH_NOTEQUAL;
774         return SEARCH_EQUAL;
775 }
776 
777 static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
778 {
779         struct msgbuf __user *msgp = dest;
780         size_t msgsz;
781 
782         if (put_user(msg->m_type, &msgp->mtype))
783                 return -EFAULT;
784 
785         msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
786         if (store_msg(msgp->mtext, msg, msgsz))
787                 return -EFAULT;
788         return msgsz;
789 }
790 
791 #ifdef CONFIG_CHECKPOINT_RESTORE
792 /*
793  * This function creates new kernel message structure, large enough to store
794  * bufsz message bytes.
795  */
796 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
797 {
798         struct msg_msg *copy;
799 
800         /*
801          * Create dummy message to copy real message to.
802          */
803         copy = load_msg(buf, bufsz);
804         if (!IS_ERR(copy))
805                 copy->m_ts = bufsz;
806         return copy;
807 }
808 
809 static inline void free_copy(struct msg_msg *copy)
810 {
811         if (copy)
812                 free_msg(copy);
813 }
814 #else
815 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
816 {
817         return ERR_PTR(-ENOSYS);
818 }
819 
820 static inline void free_copy(struct msg_msg *copy)
821 {
822 }
823 #endif
824 
825 static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
826 {
827         struct msg_msg *msg, *found = NULL;
828         long count = 0;
829 
830         list_for_each_entry(msg, &msq->q_messages, m_list) {
831                 if (testmsg(msg, *msgtyp, mode) &&
832                     !security_msg_queue_msgrcv(msq, msg, current,
833                                                *msgtyp, mode)) {
834                         if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
835                                 *msgtyp = msg->m_type - 1;
836                                 found = msg;
837                         } else if (mode == SEARCH_NUMBER) {
838                                 if (*msgtyp == count)
839                                         return msg;
840                         } else
841                                 return msg;
842                         count++;
843                 }
844         }
845 
846         return found ?: ERR_PTR(-EAGAIN);
847 }
848 
849 long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
850                long (*msg_handler)(void __user *, struct msg_msg *, size_t))
851 {
852         int mode;
853         struct msg_queue *msq;
854         struct ipc_namespace *ns;
855         struct msg_msg *msg, *copy = NULL;
856         DEFINE_WAKE_Q(wake_q);
857 
858         ns = current->nsproxy->ipc_ns;
859 
860         if (msqid < 0 || (long) bufsz < 0)
861                 return -EINVAL;
862 
863         if (msgflg & MSG_COPY) {
864                 if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
865                         return -EINVAL;
866                 copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
867                 if (IS_ERR(copy))
868                         return PTR_ERR(copy);
869         }
870         mode = convert_mode(&msgtyp, msgflg);
871 
872         rcu_read_lock();
873         msq = msq_obtain_object_check(ns, msqid);
874         if (IS_ERR(msq)) {
875                 rcu_read_unlock();
876                 free_copy(copy);
877                 return PTR_ERR(msq);
878         }
879 
880         for (;;) {
881                 struct msg_receiver msr_d;
882 
883                 msg = ERR_PTR(-EACCES);
884                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
885                         goto out_unlock1;
886 
887                 ipc_lock_object(&msq->q_perm);
888 
889                 /* raced with RMID? */
890                 if (!ipc_valid_object(&msq->q_perm)) {
891                         msg = ERR_PTR(-EIDRM);
892                         goto out_unlock0;
893                 }
894 
895                 msg = find_msg(msq, &msgtyp, mode);
896                 if (!IS_ERR(msg)) {
897                         /*
898                          * Found a suitable message.
899                          * Unlink it from the queue.
900                          */
901                         if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
902                                 msg = ERR_PTR(-E2BIG);
903                                 goto out_unlock0;
904                         }
905                         /*
906                          * If we are copying, then do not unlink message and do
907                          * not update queue parameters.
908                          */
909                         if (msgflg & MSG_COPY) {
910                                 msg = copy_msg(msg, copy);
911                                 goto out_unlock0;
912                         }
913 
914                         list_del(&msg->m_list);
915                         msq->q_qnum--;
916                         msq->q_rtime = get_seconds();
917                         msq->q_lrpid = task_tgid_vnr(current);
918                         msq->q_cbytes -= msg->m_ts;
919                         atomic_sub(msg->m_ts, &ns->msg_bytes);
920                         atomic_dec(&ns->msg_hdrs);
921                         ss_wakeup(msq, &wake_q, false);
922 
923                         goto out_unlock0;
924                 }
925 
926                 /* No message waiting. Wait for a message */
927                 if (msgflg & IPC_NOWAIT) {
928                         msg = ERR_PTR(-ENOMSG);
929                         goto out_unlock0;
930                 }
931 
932                 list_add_tail(&msr_d.r_list, &msq->q_receivers);
933                 msr_d.r_tsk = current;
934                 msr_d.r_msgtype = msgtyp;
935                 msr_d.r_mode = mode;
936                 if (msgflg & MSG_NOERROR)
937                         msr_d.r_maxsize = INT_MAX;
938                 else
939                         msr_d.r_maxsize = bufsz;
940                 msr_d.r_msg = ERR_PTR(-EAGAIN);
941                 __set_current_state(TASK_INTERRUPTIBLE);
942 
943                 ipc_unlock_object(&msq->q_perm);
944                 rcu_read_unlock();
945                 schedule();
946 
947                 /*
948                  * Lockless receive, part 1:
949                  * We don't hold a reference to the queue and getting a
950                  * reference would defeat the idea of a lockless operation,
951                  * thus the code relies on rcu to guarantee the existence of
952                  * msq:
953                  * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
954                  * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
955                  */
956                 rcu_read_lock();
957 
958                 /*
959                  * Lockless receive, part 2:
960                  * The work in pipelined_send() and expunge_all():
961                  * - Set pointer to message
962                  * - Queue the receiver task for later wakeup
963                  * - Wake up the process after the lock is dropped.
964                  *
965                  * Should the process wake up before this wakeup (due to a
966                  * signal) it will either see the message and continue ...
967                  */
968                 msg = READ_ONCE(msr_d.r_msg);
969                 if (msg != ERR_PTR(-EAGAIN))
970                         goto out_unlock1;
971 
972                  /*
973                   * ... or see -EAGAIN, acquire the lock to check the message
974                   * again.
975                   */
976                 ipc_lock_object(&msq->q_perm);
977 
978                 msg = msr_d.r_msg;
979                 if (msg != ERR_PTR(-EAGAIN))
980                         goto out_unlock0;
981 
982                 list_del(&msr_d.r_list);
983                 if (signal_pending(current)) {
984                         msg = ERR_PTR(-ERESTARTNOHAND);
985                         goto out_unlock0;
986                 }
987 
988                 ipc_unlock_object(&msq->q_perm);
989         }
990 
991 out_unlock0:
992         ipc_unlock_object(&msq->q_perm);
993         wake_up_q(&wake_q);
994 out_unlock1:
995         rcu_read_unlock();
996         if (IS_ERR(msg)) {
997                 free_copy(copy);
998                 return PTR_ERR(msg);
999         }
1000 
1001         bufsz = msg_handler(buf, msg, bufsz);
1002         free_msg(msg);
1003 
1004         return bufsz;
1005 }
1006 
1007 SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
1008                 long, msgtyp, int, msgflg)
1009 {
1010         return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
1011 }
1012 
1013 
1014 void msg_init_ns(struct ipc_namespace *ns)
1015 {
1016         ns->msg_ctlmax = MSGMAX;
1017         ns->msg_ctlmnb = MSGMNB;
1018         ns->msg_ctlmni = MSGMNI;
1019 
1020         atomic_set(&ns->msg_bytes, 0);
1021         atomic_set(&ns->msg_hdrs, 0);
1022         ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
1023 }
1024 
1025 #ifdef CONFIG_IPC_NS
1026 void msg_exit_ns(struct ipc_namespace *ns)
1027 {
1028         free_ipcs(ns, &msg_ids(ns), freeque);
1029         idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
1030 }
1031 #endif
1032 
1033 #ifdef CONFIG_PROC_FS
1034 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
1035 {
1036         struct user_namespace *user_ns = seq_user_ns(s);
1037         struct msg_queue *msq = it;
1038 
1039         seq_printf(s,
1040                    "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1041                    msq->q_perm.key,
1042                    msq->q_perm.id,
1043                    msq->q_perm.mode,
1044                    msq->q_cbytes,
1045                    msq->q_qnum,
1046                    msq->q_lspid,
1047                    msq->q_lrpid,
1048                    from_kuid_munged(user_ns, msq->q_perm.uid),
1049                    from_kgid_munged(user_ns, msq->q_perm.gid),
1050                    from_kuid_munged(user_ns, msq->q_perm.cuid),
1051                    from_kgid_munged(user_ns, msq->q_perm.cgid),
1052                    msq->q_stime,
1053                    msq->q_rtime,
1054                    msq->q_ctime);
1055 
1056         return 0;
1057 }
1058 #endif
1059 
1060 void __init msg_init(void)
1061 {
1062         msg_init_ns(&init_ipc_ns);
1063 
1064         ipc_init_proc_interface("sysvipc/msg",
1065                                 "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
1066                                 IPC_MSG_IDS, sysvipc_msg_proc_show);
1067 }
1068 

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