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TOMOYO Linux Cross Reference
Linux/ipc/msg.c

Version: ~ [ linux-5.5-rc1 ] ~ [ linux-5.4.2 ] ~ [ linux-5.3.15 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.88 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.158 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.206 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.206 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.78 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  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 <asm/uaccess.h>
 43 #include "util.h"
 44 
 45 /*
 46  * one msg_receiver structure for each sleeping receiver:
 47  */
 48 struct msg_receiver {
 49         struct list_head        r_list;
 50         struct task_struct      *r_tsk;
 51 
 52         int                     r_mode;
 53         long                    r_msgtype;
 54         long                    r_maxsize;
 55 
 56         struct msg_msg          *volatile r_msg;
 57 };
 58 
 59 /* one msg_sender for each sleeping sender */
 60 struct msg_sender {
 61         struct list_head        list;
 62         struct task_struct      *tsk;
 63 };
 64 
 65 #define SEARCH_ANY              1
 66 #define SEARCH_EQUAL            2
 67 #define SEARCH_NOTEQUAL         3
 68 #define SEARCH_LESSEQUAL        4
 69 #define SEARCH_NUMBER           5
 70 
 71 #define msg_ids(ns)     ((ns)->ids[IPC_MSG_IDS])
 72 
 73 static void freeque(struct ipc_namespace *, struct kern_ipc_perm *);
 74 static int newque(struct ipc_namespace *, struct ipc_params *);
 75 #ifdef CONFIG_PROC_FS
 76 static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
 77 #endif
 78 
 79 /*
 80  * Scale msgmni with the available lowmem size: the memory dedicated to msg
 81  * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
 82  * Also take into account the number of nsproxies created so far.
 83  * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
 84  */
 85 void recompute_msgmni(struct ipc_namespace *ns)
 86 {
 87         struct sysinfo i;
 88         unsigned long allowed;
 89         int nb_ns;
 90 
 91         si_meminfo(&i);
 92         allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
 93                 / MSGMNB;
 94         nb_ns = atomic_read(&nr_ipc_ns);
 95         allowed /= nb_ns;
 96 
 97         if (allowed < MSGMNI) {
 98                 ns->msg_ctlmni = MSGMNI;
 99                 return;
100         }
101 
102         if (allowed > IPCMNI / nb_ns) {
103                 ns->msg_ctlmni = IPCMNI / nb_ns;
104                 return;
105         }
106 
107         ns->msg_ctlmni = allowed;
108 }
109 
110 void msg_init_ns(struct ipc_namespace *ns)
111 {
112         ns->msg_ctlmax = MSGMAX;
113         ns->msg_ctlmnb = MSGMNB;
114 
115         recompute_msgmni(ns);
116 
117         atomic_set(&ns->msg_bytes, 0);
118         atomic_set(&ns->msg_hdrs, 0);
119         ipc_init_ids(&ns->ids[IPC_MSG_IDS]);
120 }
121 
122 #ifdef CONFIG_IPC_NS
123 void msg_exit_ns(struct ipc_namespace *ns)
124 {
125         free_ipcs(ns, &msg_ids(ns), freeque);
126         idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr);
127 }
128 #endif
129 
130 void __init msg_init(void)
131 {
132         msg_init_ns(&init_ipc_ns);
133 
134         printk(KERN_INFO "msgmni has been set to %d\n",
135                 init_ipc_ns.msg_ctlmni);
136 
137         ipc_init_proc_interface("sysvipc/msg",
138                                 "       key      msqid perms      cbytes       qnum lspid lrpid   uid   gid  cuid  cgid      stime      rtime      ctime\n",
139                                 IPC_MSG_IDS, sysvipc_msg_proc_show);
140 }
141 
142 static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id)
143 {
144         struct kern_ipc_perm *ipcp = ipc_obtain_object(&msg_ids(ns), id);
145 
146         if (IS_ERR(ipcp))
147                 return ERR_CAST(ipcp);
148 
149         return container_of(ipcp, struct msg_queue, q_perm);
150 }
151 
152 static inline struct msg_queue *msq_obtain_object_check(struct ipc_namespace *ns,
153                                                         int id)
154 {
155         struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&msg_ids(ns), id);
156 
157         if (IS_ERR(ipcp))
158                 return ERR_CAST(ipcp);
159 
160         return container_of(ipcp, struct msg_queue, q_perm);
161 }
162 
163 static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s)
164 {
165         ipc_rmid(&msg_ids(ns), &s->q_perm);
166 }
167 
168 static void msg_rcu_free(struct rcu_head *head)
169 {
170         struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
171         struct msg_queue *msq = ipc_rcu_to_struct(p);
172 
173         security_msg_queue_free(msq);
174         ipc_rcu_free(head);
175 }
176 
177 /**
178  * newque - Create a new msg queue
179  * @ns: namespace
180  * @params: ptr to the structure that contains the key and msgflg
181  *
182  * Called with msg_ids.rwsem held (writer)
183  */
184 static int newque(struct ipc_namespace *ns, struct ipc_params *params)
185 {
186         struct msg_queue *msq;
187         int id, retval;
188         key_t key = params->key;
189         int msgflg = params->flg;
190 
191         msq = ipc_rcu_alloc(sizeof(*msq));
192         if (!msq)
193                 return -ENOMEM;
194 
195         msq->q_perm.mode = msgflg & S_IRWXUGO;
196         msq->q_perm.key = key;
197 
198         msq->q_perm.security = NULL;
199         retval = security_msg_queue_alloc(msq);
200         if (retval) {
201                 ipc_rcu_putref(msq, ipc_rcu_free);
202                 return retval;
203         }
204 
205         /* ipc_addid() locks msq upon success. */
206         id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni);
207         if (id < 0) {
208                 ipc_rcu_putref(msq, msg_rcu_free);
209                 return id;
210         }
211 
212         msq->q_stime = msq->q_rtime = 0;
213         msq->q_ctime = get_seconds();
214         msq->q_cbytes = msq->q_qnum = 0;
215         msq->q_qbytes = ns->msg_ctlmnb;
216         msq->q_lspid = msq->q_lrpid = 0;
217         INIT_LIST_HEAD(&msq->q_messages);
218         INIT_LIST_HEAD(&msq->q_receivers);
219         INIT_LIST_HEAD(&msq->q_senders);
220 
221         ipc_unlock_object(&msq->q_perm);
222         rcu_read_unlock();
223 
224         return msq->q_perm.id;
225 }
226 
227 static inline void ss_add(struct msg_queue *msq, struct msg_sender *mss)
228 {
229         mss->tsk = current;
230         current->state = TASK_INTERRUPTIBLE;
231         list_add_tail(&mss->list, &msq->q_senders);
232 }
233 
234 static inline void ss_del(struct msg_sender *mss)
235 {
236         if (mss->list.next != NULL)
237                 list_del(&mss->list);
238 }
239 
240 static void ss_wakeup(struct list_head *h, int kill)
241 {
242         struct msg_sender *mss, *t;
243 
244         list_for_each_entry_safe(mss, t, h, list) {
245                 if (kill)
246                         mss->list.next = NULL;
247                 wake_up_process(mss->tsk);
248         }
249 }
250 
251 static void expunge_all(struct msg_queue *msq, int res)
252 {
253         struct msg_receiver *msr, *t;
254 
255         list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
256                 msr->r_msg = NULL;
257                 wake_up_process(msr->r_tsk);
258                 smp_mb();
259                 msr->r_msg = ERR_PTR(res);
260         }
261 }
262 
263 /*
264  * freeque() wakes up waiters on the sender and receiver waiting queue,
265  * removes the message queue from message queue ID IDR, and cleans up all the
266  * messages associated with this queue.
267  *
268  * msg_ids.rwsem (writer) and the spinlock for this message queue are held
269  * before freeque() is called. msg_ids.rwsem remains locked on exit.
270  */
271 static void freeque(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
272 {
273         struct msg_msg *msg, *t;
274         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
275 
276         expunge_all(msq, -EIDRM);
277         ss_wakeup(&msq->q_senders, 1);
278         msg_rmid(ns, msq);
279         ipc_unlock_object(&msq->q_perm);
280         rcu_read_unlock();
281 
282         list_for_each_entry_safe(msg, t, &msq->q_messages, m_list) {
283                 atomic_dec(&ns->msg_hdrs);
284                 free_msg(msg);
285         }
286         atomic_sub(msq->q_cbytes, &ns->msg_bytes);
287         ipc_rcu_putref(msq, msg_rcu_free);
288 }
289 
290 /*
291  * Called with msg_ids.rwsem and ipcp locked.
292  */
293 static inline int msg_security(struct kern_ipc_perm *ipcp, int msgflg)
294 {
295         struct msg_queue *msq = container_of(ipcp, struct msg_queue, q_perm);
296 
297         return security_msg_queue_associate(msq, msgflg);
298 }
299 
300 SYSCALL_DEFINE2(msgget, key_t, key, int, msgflg)
301 {
302         struct ipc_namespace *ns;
303         struct ipc_ops msg_ops;
304         struct ipc_params msg_params;
305 
306         ns = current->nsproxy->ipc_ns;
307 
308         msg_ops.getnew = newque;
309         msg_ops.associate = msg_security;
310         msg_ops.more_checks = NULL;
311 
312         msg_params.key = key;
313         msg_params.flg = msgflg;
314 
315         return ipcget(ns, &msg_ids(ns), &msg_ops, &msg_params);
316 }
317 
318 static inline unsigned long
319 copy_msqid_to_user(void __user *buf, struct msqid64_ds *in, int version)
320 {
321         switch(version) {
322         case IPC_64:
323                 return copy_to_user(buf, in, sizeof(*in));
324         case IPC_OLD:
325         {
326                 struct msqid_ds out;
327 
328                 memset(&out, 0, sizeof(out));
329 
330                 ipc64_perm_to_ipc_perm(&in->msg_perm, &out.msg_perm);
331 
332                 out.msg_stime           = in->msg_stime;
333                 out.msg_rtime           = in->msg_rtime;
334                 out.msg_ctime           = in->msg_ctime;
335 
336                 if (in->msg_cbytes > USHRT_MAX)
337                         out.msg_cbytes  = USHRT_MAX;
338                 else
339                         out.msg_cbytes  = in->msg_cbytes;
340                 out.msg_lcbytes         = in->msg_cbytes;
341 
342                 if (in->msg_qnum > USHRT_MAX)
343                         out.msg_qnum    = USHRT_MAX;
344                 else
345                         out.msg_qnum    = in->msg_qnum;
346 
347                 if (in->msg_qbytes > USHRT_MAX)
348                         out.msg_qbytes  = USHRT_MAX;
349                 else
350                         out.msg_qbytes  = in->msg_qbytes;
351                 out.msg_lqbytes         = in->msg_qbytes;
352 
353                 out.msg_lspid           = in->msg_lspid;
354                 out.msg_lrpid           = in->msg_lrpid;
355 
356                 return copy_to_user(buf, &out, sizeof(out));
357         }
358         default:
359                 return -EINVAL;
360         }
361 }
362 
363 static inline unsigned long
364 copy_msqid_from_user(struct msqid64_ds *out, void __user *buf, int version)
365 {
366         switch(version) {
367         case IPC_64:
368                 if (copy_from_user(out, buf, sizeof(*out)))
369                         return -EFAULT;
370                 return 0;
371         case IPC_OLD:
372         {
373                 struct msqid_ds tbuf_old;
374 
375                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
376                         return -EFAULT;
377 
378                 out->msg_perm.uid       = tbuf_old.msg_perm.uid;
379                 out->msg_perm.gid       = tbuf_old.msg_perm.gid;
380                 out->msg_perm.mode      = tbuf_old.msg_perm.mode;
381 
382                 if (tbuf_old.msg_qbytes == 0)
383                         out->msg_qbytes = tbuf_old.msg_lqbytes;
384                 else
385                         out->msg_qbytes = tbuf_old.msg_qbytes;
386 
387                 return 0;
388         }
389         default:
390                 return -EINVAL;
391         }
392 }
393 
394 /*
395  * This function handles some msgctl commands which require the rwsem
396  * to be held in write mode.
397  * NOTE: no locks must be held, the rwsem is taken inside this function.
398  */
399 static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
400                        struct msqid_ds __user *buf, int version)
401 {
402         struct kern_ipc_perm *ipcp;
403         struct msqid64_ds uninitialized_var(msqid64);
404         struct msg_queue *msq;
405         int err;
406 
407         if (cmd == IPC_SET) {
408                 if (copy_msqid_from_user(&msqid64, buf, version))
409                         return -EFAULT;
410         }
411 
412         down_write(&msg_ids(ns).rwsem);
413         rcu_read_lock();
414 
415         ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,
416                                       &msqid64.msg_perm, msqid64.msg_qbytes);
417         if (IS_ERR(ipcp)) {
418                 err = PTR_ERR(ipcp);
419                 goto out_unlock1;
420         }
421 
422         msq = container_of(ipcp, struct msg_queue, q_perm);
423 
424         err = security_msg_queue_msgctl(msq, cmd);
425         if (err)
426                 goto out_unlock1;
427 
428         switch (cmd) {
429         case IPC_RMID:
430                 ipc_lock_object(&msq->q_perm);
431                 /* freeque unlocks the ipc object and rcu */
432                 freeque(ns, ipcp);
433                 goto out_up;
434         case IPC_SET:
435                 if (msqid64.msg_qbytes > ns->msg_ctlmnb &&
436                     !capable(CAP_SYS_RESOURCE)) {
437                         err = -EPERM;
438                         goto out_unlock1;
439                 }
440 
441                 ipc_lock_object(&msq->q_perm);
442                 err = ipc_update_perm(&msqid64.msg_perm, ipcp);
443                 if (err)
444                         goto out_unlock0;
445 
446                 msq->q_qbytes = msqid64.msg_qbytes;
447 
448                 msq->q_ctime = get_seconds();
449                 /* sleeping receivers might be excluded by
450                  * stricter permissions.
451                  */
452                 expunge_all(msq, -EAGAIN);
453                 /* sleeping senders might be able to send
454                  * due to a larger queue size.
455                  */
456                 ss_wakeup(&msq->q_senders, 0);
457                 break;
458         default:
459                 err = -EINVAL;
460                 goto out_unlock1;
461         }
462 
463 out_unlock0:
464         ipc_unlock_object(&msq->q_perm);
465 out_unlock1:
466         rcu_read_unlock();
467 out_up:
468         up_write(&msg_ids(ns).rwsem);
469         return err;
470 }
471 
472 static int msgctl_nolock(struct ipc_namespace *ns, int msqid,
473                          int cmd, int version, void __user *buf)
474 {
475         int err;
476         struct msg_queue *msq;
477 
478         switch (cmd) {
479         case IPC_INFO:
480         case MSG_INFO:
481         {
482                 struct msginfo msginfo;
483                 int max_id;
484 
485                 if (!buf)
486                         return -EFAULT;
487 
488                 /*
489                  * We must not return kernel stack data.
490                  * due to padding, it's not enough
491                  * to set all member fields.
492                  */
493                 err = security_msg_queue_msgctl(NULL, cmd);
494                 if (err)
495                         return err;
496 
497                 memset(&msginfo, 0, sizeof(msginfo));
498                 msginfo.msgmni = ns->msg_ctlmni;
499                 msginfo.msgmax = ns->msg_ctlmax;
500                 msginfo.msgmnb = ns->msg_ctlmnb;
501                 msginfo.msgssz = MSGSSZ;
502                 msginfo.msgseg = MSGSEG;
503                 down_read(&msg_ids(ns).rwsem);
504                 if (cmd == MSG_INFO) {
505                         msginfo.msgpool = msg_ids(ns).in_use;
506                         msginfo.msgmap = atomic_read(&ns->msg_hdrs);
507                         msginfo.msgtql = atomic_read(&ns->msg_bytes);
508                 } else {
509                         msginfo.msgmap = MSGMAP;
510                         msginfo.msgpool = MSGPOOL;
511                         msginfo.msgtql = MSGTQL;
512                 }
513                 max_id = ipc_get_maxid(&msg_ids(ns));
514                 up_read(&msg_ids(ns).rwsem);
515                 if (copy_to_user(buf, &msginfo, sizeof(struct msginfo)))
516                         return -EFAULT;
517                 return (max_id < 0) ? 0 : max_id;
518         }
519 
520         case MSG_STAT:
521         case IPC_STAT:
522         {
523                 struct msqid64_ds tbuf;
524                 int success_return;
525 
526                 if (!buf)
527                         return -EFAULT;
528 
529                 memset(&tbuf, 0, sizeof(tbuf));
530 
531                 rcu_read_lock();
532                 if (cmd == MSG_STAT) {
533                         msq = msq_obtain_object(ns, msqid);
534                         if (IS_ERR(msq)) {
535                                 err = PTR_ERR(msq);
536                                 goto out_unlock;
537                         }
538                         success_return = msq->q_perm.id;
539                 } else {
540                         msq = msq_obtain_object_check(ns, msqid);
541                         if (IS_ERR(msq)) {
542                                 err = PTR_ERR(msq);
543                                 goto out_unlock;
544                         }
545                         success_return = 0;
546                 }
547 
548                 err = -EACCES;
549                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
550                         goto out_unlock;
551 
552                 err = security_msg_queue_msgctl(msq, cmd);
553                 if (err)
554                         goto out_unlock;
555 
556                 kernel_to_ipc64_perm(&msq->q_perm, &tbuf.msg_perm);
557                 tbuf.msg_stime  = msq->q_stime;
558                 tbuf.msg_rtime  = msq->q_rtime;
559                 tbuf.msg_ctime  = msq->q_ctime;
560                 tbuf.msg_cbytes = msq->q_cbytes;
561                 tbuf.msg_qnum   = msq->q_qnum;
562                 tbuf.msg_qbytes = msq->q_qbytes;
563                 tbuf.msg_lspid  = msq->q_lspid;
564                 tbuf.msg_lrpid  = msq->q_lrpid;
565                 rcu_read_unlock();
566 
567                 if (copy_msqid_to_user(buf, &tbuf, version))
568                         return -EFAULT;
569                 return success_return;
570         }
571 
572         default:
573                 return -EINVAL;
574         }
575 
576         return err;
577 out_unlock:
578         rcu_read_unlock();
579         return err;
580 }
581 
582 SYSCALL_DEFINE3(msgctl, int, msqid, int, cmd, struct msqid_ds __user *, buf)
583 {
584         int version;
585         struct ipc_namespace *ns;
586 
587         if (msqid < 0 || cmd < 0)
588                 return -EINVAL;
589 
590         version = ipc_parse_version(&cmd);
591         ns = current->nsproxy->ipc_ns;
592 
593         switch (cmd) {
594         case IPC_INFO:
595         case MSG_INFO:
596         case MSG_STAT:  /* msqid is an index rather than a msg queue id */
597         case IPC_STAT:
598                 return msgctl_nolock(ns, msqid, cmd, version, buf);
599         case IPC_SET:
600         case IPC_RMID:
601                 return msgctl_down(ns, msqid, cmd, buf, version);
602         default:
603                 return  -EINVAL;
604         }
605 }
606 
607 static int testmsg(struct msg_msg *msg, long type, int mode)
608 {
609         switch(mode)
610         {
611                 case SEARCH_ANY:
612                 case SEARCH_NUMBER:
613                         return 1;
614                 case SEARCH_LESSEQUAL:
615                         if (msg->m_type <=type)
616                                 return 1;
617                         break;
618                 case SEARCH_EQUAL:
619                         if (msg->m_type == type)
620                                 return 1;
621                         break;
622                 case SEARCH_NOTEQUAL:
623                         if (msg->m_type != type)
624                                 return 1;
625                         break;
626         }
627         return 0;
628 }
629 
630 static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg)
631 {
632         struct msg_receiver *msr, *t;
633 
634         list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) {
635                 if (testmsg(msg, msr->r_msgtype, msr->r_mode) &&
636                     !security_msg_queue_msgrcv(msq, msg, msr->r_tsk,
637                                                msr->r_msgtype, msr->r_mode)) {
638 
639                         list_del(&msr->r_list);
640                         if (msr->r_maxsize < msg->m_ts) {
641                                 msr->r_msg = NULL;
642                                 wake_up_process(msr->r_tsk);
643                                 smp_mb();
644                                 msr->r_msg = ERR_PTR(-E2BIG);
645                         } else {
646                                 msr->r_msg = NULL;
647                                 msq->q_lrpid = task_pid_vnr(msr->r_tsk);
648                                 msq->q_rtime = get_seconds();
649                                 wake_up_process(msr->r_tsk);
650                                 smp_mb();
651                                 msr->r_msg = msg;
652 
653                                 return 1;
654                         }
655                 }
656         }
657         return 0;
658 }
659 
660 long do_msgsnd(int msqid, long mtype, void __user *mtext,
661                 size_t msgsz, int msgflg)
662 {
663         struct msg_queue *msq;
664         struct msg_msg *msg;
665         int err;
666         struct ipc_namespace *ns;
667 
668         ns = current->nsproxy->ipc_ns;
669 
670         if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0)
671                 return -EINVAL;
672         if (mtype < 1)
673                 return -EINVAL;
674 
675         msg = load_msg(mtext, msgsz);
676         if (IS_ERR(msg))
677                 return PTR_ERR(msg);
678 
679         msg->m_type = mtype;
680         msg->m_ts = msgsz;
681 
682         rcu_read_lock();
683         msq = msq_obtain_object_check(ns, msqid);
684         if (IS_ERR(msq)) {
685                 err = PTR_ERR(msq);
686                 goto out_unlock1;
687         }
688 
689         ipc_lock_object(&msq->q_perm);
690 
691         for (;;) {
692                 struct msg_sender s;
693 
694                 err = -EACCES;
695                 if (ipcperms(ns, &msq->q_perm, S_IWUGO))
696                         goto out_unlock0;
697 
698                 /* raced with RMID? */
699                 if (msq->q_perm.deleted) {
700                         err = -EIDRM;
701                         goto out_unlock0;
702                 }
703 
704                 err = security_msg_queue_msgsnd(msq, msg, msgflg);
705                 if (err)
706                         goto out_unlock0;
707 
708                 if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
709                                 1 + msq->q_qnum <= msq->q_qbytes) {
710                         break;
711                 }
712 
713                 /* queue full, wait: */
714                 if (msgflg & IPC_NOWAIT) {
715                         err = -EAGAIN;
716                         goto out_unlock0;
717                 }
718 
719                 ss_add(msq, &s);
720 
721                 if (!ipc_rcu_getref(msq)) {
722                         err = -EIDRM;
723                         goto out_unlock0;
724                 }
725 
726                 ipc_unlock_object(&msq->q_perm);
727                 rcu_read_unlock();
728                 schedule();
729 
730                 rcu_read_lock();
731                 ipc_lock_object(&msq->q_perm);
732 
733                 ipc_rcu_putref(msq, ipc_rcu_free);
734                 if (msq->q_perm.deleted) {
735                         err = -EIDRM;
736                         goto out_unlock0;
737                 }
738 
739                 ss_del(&s);
740 
741                 if (signal_pending(current)) {
742                         err = -ERESTARTNOHAND;
743                         goto out_unlock0;
744                 }
745 
746         }
747         msq->q_lspid = task_tgid_vnr(current);
748         msq->q_stime = get_seconds();
749 
750         if (!pipelined_send(msq, msg)) {
751                 /* no one is waiting for this message, enqueue it */
752                 list_add_tail(&msg->m_list, &msq->q_messages);
753                 msq->q_cbytes += msgsz;
754                 msq->q_qnum++;
755                 atomic_add(msgsz, &ns->msg_bytes);
756                 atomic_inc(&ns->msg_hdrs);
757         }
758 
759         err = 0;
760         msg = NULL;
761 
762 out_unlock0:
763         ipc_unlock_object(&msq->q_perm);
764 out_unlock1:
765         rcu_read_unlock();
766         if (msg != NULL)
767                 free_msg(msg);
768         return err;
769 }
770 
771 SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
772                 int, msgflg)
773 {
774         long mtype;
775 
776         if (get_user(mtype, &msgp->mtype))
777                 return -EFAULT;
778         return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg);
779 }
780 
781 static inline int convert_mode(long *msgtyp, int msgflg)
782 {
783         if (msgflg & MSG_COPY)
784                 return SEARCH_NUMBER;
785         /*
786          *  find message of correct type.
787          *  msgtyp = 0 => get first.
788          *  msgtyp > 0 => get first message of matching type.
789          *  msgtyp < 0 => get message with least type must be < abs(msgtype).
790          */
791         if (*msgtyp == 0)
792                 return SEARCH_ANY;
793         if (*msgtyp < 0) {
794                 *msgtyp = -*msgtyp;
795                 return SEARCH_LESSEQUAL;
796         }
797         if (msgflg & MSG_EXCEPT)
798                 return SEARCH_NOTEQUAL;
799         return SEARCH_EQUAL;
800 }
801 
802 static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz)
803 {
804         struct msgbuf __user *msgp = dest;
805         size_t msgsz;
806 
807         if (put_user(msg->m_type, &msgp->mtype))
808                 return -EFAULT;
809 
810         msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz;
811         if (store_msg(msgp->mtext, msg, msgsz))
812                 return -EFAULT;
813         return msgsz;
814 }
815 
816 #ifdef CONFIG_CHECKPOINT_RESTORE
817 /*
818  * This function creates new kernel message structure, large enough to store
819  * bufsz message bytes.
820  */
821 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
822 {
823         struct msg_msg *copy;
824 
825         /*
826          * Create dummy message to copy real message to.
827          */
828         copy = load_msg(buf, bufsz);
829         if (!IS_ERR(copy))
830                 copy->m_ts = bufsz;
831         return copy;
832 }
833 
834 static inline void free_copy(struct msg_msg *copy)
835 {
836         if (copy)
837                 free_msg(copy);
838 }
839 #else
840 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz)
841 {
842         return ERR_PTR(-ENOSYS);
843 }
844 
845 static inline void free_copy(struct msg_msg *copy)
846 {
847 }
848 #endif
849 
850 static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode)
851 {
852         struct msg_msg *msg, *found = NULL;
853         long count = 0;
854 
855         list_for_each_entry(msg, &msq->q_messages, m_list) {
856                 if (testmsg(msg, *msgtyp, mode) &&
857                     !security_msg_queue_msgrcv(msq, msg, current,
858                                                *msgtyp, mode)) {
859                         if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) {
860                                 *msgtyp = msg->m_type - 1;
861                                 found = msg;
862                         } else if (mode == SEARCH_NUMBER) {
863                                 if (*msgtyp == count)
864                                         return msg;
865                         } else
866                                 return msg;
867                         count++;
868                 }
869         }
870 
871         return found ?: ERR_PTR(-EAGAIN);
872 }
873 
874 long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg,
875                long (*msg_handler)(void __user *, struct msg_msg *, size_t))
876 {
877         int mode;
878         struct msg_queue *msq;
879         struct ipc_namespace *ns;
880         struct msg_msg *msg, *copy = NULL;
881 
882         ns = current->nsproxy->ipc_ns;
883 
884         if (msqid < 0 || (long) bufsz < 0)
885                 return -EINVAL;
886 
887         if (msgflg & MSG_COPY) {
888                 copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax));
889                 if (IS_ERR(copy))
890                         return PTR_ERR(copy);
891         }
892         mode = convert_mode(&msgtyp, msgflg);
893 
894         rcu_read_lock();
895         msq = msq_obtain_object_check(ns, msqid);
896         if (IS_ERR(msq)) {
897                 rcu_read_unlock();
898                 free_copy(copy);
899                 return PTR_ERR(msq);
900         }
901 
902         for (;;) {
903                 struct msg_receiver msr_d;
904 
905                 msg = ERR_PTR(-EACCES);
906                 if (ipcperms(ns, &msq->q_perm, S_IRUGO))
907                         goto out_unlock1;
908 
909                 ipc_lock_object(&msq->q_perm);
910 
911                 /* raced with RMID? */
912                 if (msq->q_perm.deleted) {
913                         msg = ERR_PTR(-EIDRM);
914                         goto out_unlock0;
915                 }
916 
917                 msg = find_msg(msq, &msgtyp, mode);
918                 if (!IS_ERR(msg)) {
919                         /*
920                          * Found a suitable message.
921                          * Unlink it from the queue.
922                          */
923                         if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) {
924                                 msg = ERR_PTR(-E2BIG);
925                                 goto out_unlock0;
926                         }
927                         /*
928                          * If we are copying, then do not unlink message and do
929                          * not update queue parameters.
930                          */
931                         if (msgflg & MSG_COPY) {
932                                 msg = copy_msg(msg, copy);
933                                 goto out_unlock0;
934                         }
935 
936                         list_del(&msg->m_list);
937                         msq->q_qnum--;
938                         msq->q_rtime = get_seconds();
939                         msq->q_lrpid = task_tgid_vnr(current);
940                         msq->q_cbytes -= msg->m_ts;
941                         atomic_sub(msg->m_ts, &ns->msg_bytes);
942                         atomic_dec(&ns->msg_hdrs);
943                         ss_wakeup(&msq->q_senders, 0);
944 
945                         goto out_unlock0;
946                 }
947 
948                 /* No message waiting. Wait for a message */
949                 if (msgflg & IPC_NOWAIT) {
950                         msg = ERR_PTR(-ENOMSG);
951                         goto out_unlock0;
952                 }
953 
954                 list_add_tail(&msr_d.r_list, &msq->q_receivers);
955                 msr_d.r_tsk = current;
956                 msr_d.r_msgtype = msgtyp;
957                 msr_d.r_mode = mode;
958                 if (msgflg & MSG_NOERROR)
959                         msr_d.r_maxsize = INT_MAX;
960                 else
961                         msr_d.r_maxsize = bufsz;
962                 msr_d.r_msg = ERR_PTR(-EAGAIN);
963                 current->state = TASK_INTERRUPTIBLE;
964 
965                 ipc_unlock_object(&msq->q_perm);
966                 rcu_read_unlock();
967                 schedule();
968 
969                 /* Lockless receive, part 1:
970                  * Disable preemption.  We don't hold a reference to the queue
971                  * and getting a reference would defeat the idea of a lockless
972                  * operation, thus the code relies on rcu to guarantee the
973                  * existence of msq:
974                  * Prior to destruction, expunge_all(-EIRDM) changes r_msg.
975                  * Thus if r_msg is -EAGAIN, then the queue not yet destroyed.
976                  * rcu_read_lock() prevents preemption between reading r_msg
977                  * and acquiring the q_perm.lock in ipc_lock_object().
978                  */
979                 rcu_read_lock();
980 
981                 /* Lockless receive, part 2:
982                  * Wait until pipelined_send or expunge_all are outside of
983                  * wake_up_process(). There is a race with exit(), see
984                  * ipc/mqueue.c for the details.
985                  */
986                 msg = (struct msg_msg*)msr_d.r_msg;
987                 while (msg == NULL) {
988                         cpu_relax();
989                         msg = (struct msg_msg *)msr_d.r_msg;
990                 }
991 
992                 /* Lockless receive, part 3:
993                  * If there is a message or an error then accept it without
994                  * locking.
995                  */
996                 if (msg != ERR_PTR(-EAGAIN))
997                         goto out_unlock1;
998 
999                 /* Lockless receive, part 3:
1000                  * Acquire the queue spinlock.
1001                  */
1002                 ipc_lock_object(&msq->q_perm);
1003 
1004                 /* Lockless receive, part 4:
1005                  * Repeat test after acquiring the spinlock.
1006                  */
1007                 msg = (struct msg_msg*)msr_d.r_msg;
1008                 if (msg != ERR_PTR(-EAGAIN))
1009                         goto out_unlock0;
1010 
1011                 list_del(&msr_d.r_list);
1012                 if (signal_pending(current)) {
1013                         msg = ERR_PTR(-ERESTARTNOHAND);
1014                         goto out_unlock0;
1015                 }
1016 
1017                 ipc_unlock_object(&msq->q_perm);
1018         }
1019 
1020 out_unlock0:
1021         ipc_unlock_object(&msq->q_perm);
1022 out_unlock1:
1023         rcu_read_unlock();
1024         if (IS_ERR(msg)) {
1025                 free_copy(copy);
1026                 return PTR_ERR(msg);
1027         }
1028 
1029         bufsz = msg_handler(buf, msg, bufsz);
1030         free_msg(msg);
1031 
1032         return bufsz;
1033 }
1034 
1035 SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz,
1036                 long, msgtyp, int, msgflg)
1037 {
1038         return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill);
1039 }
1040 
1041 #ifdef CONFIG_PROC_FS
1042 static int sysvipc_msg_proc_show(struct seq_file *s, void *it)
1043 {
1044         struct user_namespace *user_ns = seq_user_ns(s);
1045         struct msg_queue *msq = it;
1046 
1047         return seq_printf(s,
1048                         "%10d %10d  %4o  %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n",
1049                         msq->q_perm.key,
1050                         msq->q_perm.id,
1051                         msq->q_perm.mode,
1052                         msq->q_cbytes,
1053                         msq->q_qnum,
1054                         msq->q_lspid,
1055                         msq->q_lrpid,
1056                         from_kuid_munged(user_ns, msq->q_perm.uid),
1057                         from_kgid_munged(user_ns, msq->q_perm.gid),
1058                         from_kuid_munged(user_ns, msq->q_perm.cuid),
1059                         from_kgid_munged(user_ns, msq->q_perm.cgid),
1060                         msq->q_stime,
1061                         msq->q_rtime,
1062                         msq->q_ctime);
1063 }
1064 #endif
1065 

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