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TOMOYO Linux Cross Reference
Linux/ipc/msg.c

Version: ~ [ linux-6.0-rc6 ] ~ [ linux-5.19.10 ] ~ [ linux-5.18.19 ] ~ [ linux-5.17.15 ] ~ [ linux-5.16.20 ] ~ [ linux-5.15.69 ] ~ [ linux-5.14.21 ] ~ [ linux-5.13.19 ] ~ [ linux-5.12.19 ] ~ [ linux-5.11.22 ] ~ [ linux-5.10.144 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.214 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.259 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.294 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.329 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.302 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.9 ] ~ [ policy-sample ] ~
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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(&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_mb();
200                 msr->r_msg = ERR_PTR(res);
201         }
202 }
203 
204 /*
205  * freeque() wakes up waiters on the sender and receiver waiting queue,
206  * removes the message queue from message queue ID IDR, and cleans up all the
207  * messages associated with this queue.
208  *
209  * msg_ids.rwsem (writer) and the spinlock for this message queue are held
210  * before freeque() is called. msg_ids.rwsem remains locked on exit.
211  */
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                                 smp_mb(); /* see barrier comment below */
584                                 msr->r_msg = ERR_PTR(-E2BIG);
585                         } else {
586                                 msr->r_msg = NULL;
587                                 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
588                                 msq->q_rtime = get_seconds();
589                                 wake_up_process(msr->r_tsk);
590                                 /*
591                                  * Ensure that the wakeup is visible before
592                                  * setting r_msg, as the receiving end depends
593                                  * on it. See lockless receive part 1 and 2 in
594                                  * do_msgrcv().
595                                  */
596                                 smp_mb();
597                                 msr->r_msg = msg;
598 
599                                 return 1;
600                         }
601                 }
602         }
603 
604         return 0;
605 }
606 
607 long do_msgsnd(int msqid, long mtype, void __user *mtext,
608                 size_t msgsz, int msgflg)
609 {
610         struct msg_queue *msq;
611         struct msg_msg *msg;
612         int err;
613         struct ipc_namespace *ns;
614 
615         ns = current->nsproxy->ipc_ns;
616 
617         if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
618                 return -EINVAL;
619         if (mtype < 1)
620                 return -EINVAL;
621 
622         msg = load_msg(mtext, msgsz);
623         if (IS_ERR(msg))
624                 return PTR_ERR(msg);
625 
626         msg->m_type = mtype;
627         msg->m_ts = msgsz;
628 
629         rcu_read_lock();
630         msq = msq_obtain_object_check(ns, msqid);
631         if (IS_ERR(msq)) {
632                 err = PTR_ERR(msq);
633                 goto out_unlock1;
634         }
635 
636         ipc_lock_object(&msq->q_perm);
637 
638         for (;;) {
639                 struct msg_sender s;
640 
641                 err = -EACCES;
642                 if (ipcperms(ns, &msq->q_perm, S_IWUGO))
643                         goto out_unlock0;
644 
645                 /* raced with RMID? */
646                 if (!ipc_valid_object(&msq->q_perm)) {
647                         err = -EIDRM;
648                         goto out_unlock0;
649                 }
650 
651                 err = security_msg_queue_msgsnd(msq, msg, msgflg);
652                 if (err)
653                         goto out_unlock0;
654 
655                 if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
656                                 1 + msq->q_qnum <= msq->q_qbytes) {
657                         break;
658                 }
659 
660                 /* queue full, wait: */
661                 if (msgflg & IPC_NOWAIT) {
662                         err = -EAGAIN;
663                         goto out_unlock0;
664                 }
665 
666                 /* enqueue the sender and prepare to block */
667                 ss_add(msq, &s);
668 
669                 if (!ipc_rcu_getref(msq)) {
670                         err = -EIDRM;
671                         goto out_unlock0;
672                 }
673 
674                 ipc_unlock_object(&msq->q_perm);
675                 rcu_read_unlock();
676                 schedule();
677 
678                 rcu_read_lock();
679                 ipc_lock_object(&msq->q_perm);
680 
681                 ipc_rcu_putref(msq, msg_rcu_free);
682                 /* raced with RMID? */
683                 if (!ipc_valid_object(&msq->q_perm)) {
684                         err = -EIDRM;
685                         goto out_unlock0;
686                 }
687 
688                 ss_del(&s);
689 
690                 if (signal_pending(current)) {
691                         err = -ERESTARTNOHAND;
692                         goto out_unlock0;
693                 }
694 
695         }
696         msq->q_lspid = task_tgid_vnr(current);
697         msq->q_stime = get_seconds();
698 
699         if (!pipelined_send(msq, msg)) {
700                 /* no one is waiting for this message, enqueue it */
701                 list_add_tail(&msg->m_list, &msq->q_messages);
702                 msq->q_cbytes += msgsz;
703                 msq->q_qnum++;
704                 atomic_add(msgsz, &ns->msg_bytes);
705                 atomic_inc(&ns->msg_hdrs);
706         }
707 
708         err = 0;
709         msg = NULL;
710 
711 out_unlock0:
712         ipc_unlock_object(&msq->q_perm);
713 out_unlock1:
714         rcu_read_unlock();
715         if (msg != NULL)
716                 free_msg(msg);
717         return err;
718 }
719 
720 SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
721                 int, msgflg)
722 {
723         long mtype;
724 
725         if (get_user(mtype, &msgp->mtype))
726                 return -EFAULT;
727         return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
728 }
729 
730 static inline int convert_mode(long *msgtyp, int msgflg)
731 {
732         if (msgflg & MSG_COPY)
733                 return SEARCH_NUMBER;
734         /*
735          *  find message of correct type.
736          *  msgtyp = 0 => get first.
737          *  msgtyp > 0 => get first message of matching type.
738          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
739          */
740         if (*msgtyp == 0)
741                 return SEARCH_ANY;
742         if (*msgtyp < 0) {
743                 if (*msgtyp == LONG_MIN) /* -LONG_MIN is undefined */
744                         *msgtyp = LONG_MAX;
745                 else
746                         *msgtyp = -*msgtyp;
747                 return SEARCH_LESSEQUAL;
748         }
749         if (msgflg & MSG_EXCEPT)
750                 return SEARCH_NOTEQUAL;
751         return SEARCH_EQUAL;
752 }
753 
754 static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
755 {
756         struct msgbuf __user *msgp = dest;
757         size_t msgsz;
758 
759         if (put_user(msg->m_type, &msgp->mtype))
760                 return -EFAULT;
761 
762         msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
763         if (store_msg(msgp->mtext, msg, msgsz))
764                 return -EFAULT;
765         return msgsz;
766 }
767 
768 #ifdef CONFIG_CHECKPOINT_RESTORE
769 /*
770  * This function creates new kernel message structure, large enough to store
771  * bufsz message bytes.
772  */
773 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
774 {
775         struct msg_msg *copy;
776 
777         /*
778          * Create dummy message to copy real message to.
779          */
780         copy = load_msg(buf, bufsz);
781         if (!IS_ERR(copy))
782                 copy->m_ts = bufsz;
783         return copy;
784 }
785 
786 static inline void free_copy(struct msg_msg *copy)
787 {
788         if (copy)
789                 free_msg(copy);
790 }
791 #else
792 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
793 {
794         return ERR_PTR(-ENOSYS);
795 }
796 
797 static inline void free_copy(struct msg_msg *copy)
798 {
799 }
800 #endif
801 
802 static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
803 {
804         struct msg_msg *msg, *found = NULL;
805         long count = 0;
806 
807         list_for_each_entry(msg, &msq->q_messages, m_list) {
808                 if (testmsg(msg, *msgtyp, mode) &&
809                     !security_msg_queue_msgrcv(msq, msg, current,
810                                                *msgtyp, mode)) {
811                         if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
812                                 *msgtyp = msg->m_type - 1;
813                                 found = msg;
814                         } else if (mode == SEARCH_NUMBER) {
815                                 if (*msgtyp == count)
816                                         return msg;
817                         } else
818                                 return msg;
819                         count++;
820                 }
821         }
822 
823         return found ?: ERR_PTR(-EAGAIN);
824 }
825 
826 long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
827                long (*msg_handler)(void __user *, struct msg_msg *, size_t))
828 {
829         int mode;
830         struct msg_queue *msq;
831         struct ipc_namespace *ns;
832         struct msg_msg *msg, *copy = NULL;
833 
834         ns = current->nsproxy->ipc_ns;
835 
836         if (msqid < 0 || (long) bufsz < 0)
837                 return -EINVAL;
838 
839         if (msgflg & MSG_COPY) {
840                 if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT))
841                         return -EINVAL;
842                 copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
843                 if (IS_ERR(copy))
844                         return PTR_ERR(copy);
845         }
846         mode = convert_mode(&msgtyp, msgflg);
847 
848         rcu_read_lock();
849         msq = msq_obtain_object_check(ns, msqid);
850         if (IS_ERR(msq)) {
851                 rcu_read_unlock();
852                 free_copy(copy);
853                 return PTR_ERR(msq);
854         }
855 
856         for (;;) {
857                 struct msg_receiver msr_d;
858 
859                 msg = ERR_PTR(-EACCES);
860                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
861                         goto out_unlock1;
862 
863                 ipc_lock_object(&msq->q_perm);
864 
865                 /* raced with RMID? */
866                 if (!ipc_valid_object(&msq->q_perm)) {
867                         msg = ERR_PTR(-EIDRM);
868                         goto out_unlock0;
869                 }
870 
871                 msg = find_msg(msq, &msgtyp, mode);
872                 if (!IS_ERR(msg)) {
873                         /*
874                          * Found a suitable message.
875                          * Unlink it from the queue.
876                          */
877                         if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
878                                 msg = ERR_PTR(-E2BIG);
879                                 goto out_unlock0;
880                         }
881                         /*
882                          * If we are copying, then do not unlink message and do
883                          * not update queue parameters.
884                          */
885                         if (msgflg & MSG_COPY) {
886                                 msg = copy_msg(msg, copy);
887                                 goto out_unlock0;
888                         }
889 
890                         list_del(&msg->m_list);
891                         msq->q_qnum--;
892                         msq->q_rtime = get_seconds();
893                         msq->q_lrpid = task_tgid_vnr(current);
894                         msq->q_cbytes -= msg->m_ts;
895                         atomic_sub(msg->m_ts, &ns->msg_bytes);
896                         atomic_dec(&ns->msg_hdrs);
897                         ss_wakeup(&msq->q_senders, 0);
898 
899                         goto out_unlock0;
900                 }
901 
902                 /* No message waiting. Wait for a message */
903                 if (msgflg & IPC_NOWAIT) {
904                         msg = ERR_PTR(-ENOMSG);
905                         goto out_unlock0;
906                 }
907 
908                 list_add_tail(&msr_d.r_list, &msq->q_receivers);
909                 msr_d.r_tsk = current;
910                 msr_d.r_msgtype = msgtyp;
911                 msr_d.r_mode = mode;
912                 if (msgflg & MSG_NOERROR)
913                         msr_d.r_maxsize = INT_MAX;
914                 else
915                         msr_d.r_maxsize = bufsz;
916                 msr_d.r_msg = ERR_PTR(-EAGAIN);
917                 __set_current_state(TASK_INTERRUPTIBLE);
918 
919                 ipc_unlock_object(&msq->q_perm);
920                 rcu_read_unlock();
921                 schedule();
922 
923                 /* Lockless receive, part 1:
924                  * Disable preemption.  We don't hold a reference to the queue
925                  * and getting a reference would defeat the idea of a lockless
926                  * operation, thus the code relies on rcu to guarantee the
927                  * existence of msq:
928                  * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
929                  * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
930                  * rcu_read_lock() prevents preemption between reading r_msg
931                  * and acquiring the q_perm.lock in ipc_lock_object().
932                  */
933                 rcu_read_lock();
934 
935                 /* Lockless receive, part 2:
936                  * Wait until pipelined_send or expunge_all are outside of
937                  * wake_up_process(). There is a race with exit(), see
938                  * ipc/mqueue.c for the details.
939                  */
940                 msg = (struct msg_msg *)msr_d.r_msg;
941                 while (msg == NULL) {
942                         cpu_relax();
943                         msg = (struct msg_msg *)msr_d.r_msg;
944                 }
945 
946                 /* Lockless receive, part 3:
947                  * If there is a message or an error then accept it without
948                  * locking.
949                  */
950                 if (msg != ERR_PTR(-EAGAIN))
951                         goto out_unlock1;
952 
953                 /* Lockless receive, part 3:
954                  * Acquire the queue spinlock.
955                  */
956                 ipc_lock_object(&msq->q_perm);
957 
958                 /* Lockless receive, part 4:
959                  * Repeat test after acquiring the spinlock.
960                  */
961                 msg = (struct msg_msg *)msr_d.r_msg;
962                 if (msg != ERR_PTR(-EAGAIN))
963                         goto out_unlock0;
964 
965                 list_del(&msr_d.r_list);
966                 if (signal_pending(current)) {
967                         msg = ERR_PTR(-ERESTARTNOHAND);
968                         goto out_unlock0;
969                 }
970 
971                 ipc_unlock_object(&msq->q_perm);
972         }
973 
974 out_unlock0:
975         ipc_unlock_object(&msq->q_perm);
976 out_unlock1:
977         rcu_read_unlock();
978         if (IS_ERR(msg)) {
979                 free_copy(copy);
980                 return PTR_ERR(msg);
981         }
982 
983         bufsz = msg_handler(buf, msg, bufsz);
984         free_msg(msg);
985 
986         return bufsz;
987 }
988 
989 SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
990                 long, msgtyp, int, msgflg)
991 {
992         return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
993 }
994 
995 
996 void msg_init_ns(struct ipc_namespace *ns)
997 {
998         ns->msg_ctlmax = MSGMAX;
999         ns->msg_ctlmnb = MSGMNB;
1000         ns->msg_ctlmni = MSGMNI;
1001 
1002         atomic_set(&ns->msg_bytes, 0);
1003         atomic_set(&ns->msg_hdrs, 0);
1004         ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
1005 }
1006 
1007 #ifdef CONFIG_IPC_NS
1008 void msg_exit_ns(struct ipc_namespace *ns)
1009 {
1010         free_ipcs(ns, &msg_ids(ns), freeque);
1011         idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
1012 }
1013 #endif
1014 
1015 #ifdef CONFIG_PROC_FS
1016 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
1017 {
1018         struct user_namespace *user_ns = seq_user_ns(s);
1019         struct msg_queue *msq = it;
1020 
1021         seq_printf(s,
1022                    "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1023                    msq->q_perm.key,
1024                    msq->q_perm.id,
1025                    msq->q_perm.mode,
1026                    msq->q_cbytes,
1027                    msq->q_qnum,
1028                    msq->q_lspid,
1029                    msq->q_lrpid,
1030                    from_kuid_munged(user_ns, msq->q_perm.uid),
1031                    from_kgid_munged(user_ns, msq->q_perm.gid),
1032                    from_kuid_munged(user_ns, msq->q_perm.cuid),
1033                    from_kgid_munged(user_ns, msq->q_perm.cgid),
1034                    msq->q_stime,
1035                    msq->q_rtime,
1036                    msq->q_ctime);
1037 
1038         return 0;
1039 }
1040 #endif
1041 
1042 void __init msg_init(void)
1043 {
1044         msg_init_ns(&init_ipc_ns);
1045 
1046         ipc_init_proc_interface("sysvipc/msg",
1047                                 "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
1048                                 IPC_MSG_IDS, sysvipc_msg_proc_show);
1049 }
1050 

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