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 */ 46struct 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 */ 64struct 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 77static inline struct msg_queue *msq_obtain_object(struct ipc_namespace *ns, int id) 78{ 79 struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&msg_ids(ns), id); 80 81 if (IS_ERR(ipcp)) 82 return ERR_CAST(ipcp); 83 84 return container_of(ipcp, struct msg_queue, q_perm); 85} 86 87static 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 98static inline void msg_rmid(struct ipc_namespace *ns, struct msg_queue *s) 99{ 100 ipc_rmid(&msg_ids(ns), &s->q_perm); 101} 102 103static 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 */ 119static 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 162static 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 169static inline void ss_del(struct msg_sender *mss) 170{ 171 if (mss->list.next != NULL) 172 list_del(&mss->list); 173} 174 175static 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 186static void expunge_all(struct msg_queue *msq, int res) 187{ 188 struct msg_receiver *msr, *t; 189 190 list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) { 191 msr->r_msg = NULL; /* initialize expunge ordering */ 192 wake_up_process(msr->r_tsk); 193 /* 194 * Ensure that the wakeup is visible before setting r_msg as 195 * the receiving end depends on it: either spinning on a nil, 196 * or dealing with -EAGAIN cases. See lockless receive part 1 197 * and 2 in do_msgrcv(). 198 */ 199 smp_wmb(); /* barrier (B) */ 200 msr->r_msg = ERR_PTR(res); 201 } 202} 203 204/* 205 * freeque() wakes up waiters on the sender and receiver waiting queue, 206 * removes the message queue from message queue ID IDR, and cleans up all the 207 * messages associated with this queue. 208 * 209 * msg_ids.rwsem (writer) and the spinlock for this message queue are held 210 * before freeque() is called. msg_ids.rwsem remains locked on exit. 211 */ 212static 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 */ 234static 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 241SYSCALL_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 258static inline unsigned long 259copy_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 303static inline unsigned long 304copy_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 */ 339static 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 403out_unlock0: 404 ipc_unlock_object(&msq->q_perm); 405out_unlock1: 406 rcu_read_unlock(); 407out_up: 408 up_write(&msg_ids(ns).rwsem); 409 return err; 410} 411 412static 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; 517out_unlock: 518 rcu_read_unlock(); 519 return err; 520} 521 522SYSCALL_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 547static 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 569static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg) 570{ 571 struct msg_receiver *msr, *t; 572 573 list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) { 574 if (testmsg(msg, msr->r_msgtype, msr->r_mode) && 575 !security_msg_queue_msgrcv(msq, msg, msr->r_tsk, 576 msr->r_msgtype, msr->r_mode)) { 577 578 list_del(&msr->r_list); 579 if (msr->r_maxsize < msg->m_ts) { 580 /* initialize pipelined send ordering */ 581 msr->r_msg = NULL; 582 wake_up_process(msr->r_tsk); 583 /* barrier (B) see barrier comment below */ 584 smp_wmb(); 585 msr->r_msg = ERR_PTR(-E2BIG); 586 } else { 587 msr->r_msg = NULL; 588 msq->q_lrpid = task_pid_vnr(msr->r_tsk); 589 msq->q_rtime = get_seconds(); 590 wake_up_process(msr->r_tsk); 591 /* 592 * Ensure that the wakeup is visible before 593 * setting r_msg, as the receiving can otherwise 594 * exit - once r_msg is set, the receiver can 595 * continue. See lockless receive part 1 and 2 596 * in do_msgrcv(). Barrier (B). 597 */ 598 smp_wmb(); 599 msr->r_msg = msg; 600 601 return 1; 602 } 603 } 604 } 605 606 return 0; 607} 608 609long do_msgsnd(int msqid, long mtype, void __user *mtext, 610 size_t msgsz, int msgflg) 611{ 612 struct msg_queue *msq; 613 struct msg_msg *msg; 614 int err; 615 struct ipc_namespace *ns; 616 617 ns = current->nsproxy->ipc_ns; 618 619 if (msgsz > ns->msg_ctlmax || (long) msgsz < 0 || msqid < 0) 620 return -EINVAL; 621 if (mtype < 1) 622 return -EINVAL; 623 624 msg = load_msg(mtext, msgsz); 625 if (IS_ERR(msg)) 626 return PTR_ERR(msg); 627 628 msg->m_type = mtype; 629 msg->m_ts = msgsz; 630 631 rcu_read_lock(); 632 msq = msq_obtain_object_check(ns, msqid); 633 if (IS_ERR(msq)) { 634 err = PTR_ERR(msq); 635 goto out_unlock1; 636 } 637 638 ipc_lock_object(&msq->q_perm); 639 640 for (;;) { 641 struct msg_sender s; 642 643 err = -EACCES; 644 if (ipcperms(ns, &msq->q_perm, S_IWUGO)) 645 goto out_unlock0; 646 647 /* raced with RMID? */ 648 if (!ipc_valid_object(&msq->q_perm)) { 649 err = -EIDRM; 650 goto out_unlock0; 651 } 652 653 err = security_msg_queue_msgsnd(msq, msg, msgflg); 654 if (err) 655 goto out_unlock0; 656 657 if (msgsz + msq->q_cbytes <= msq->q_qbytes && 658 1 + msq->q_qnum <= msq->q_qbytes) { 659 break; 660 } 661 662 /* queue full, wait: */ 663 if (msgflg & IPC_NOWAIT) { 664 err = -EAGAIN; 665 goto out_unlock0; 666 } 667 668 /* enqueue the sender and prepare to block */ 669 ss_add(msq, &s); 670 671 if (!ipc_rcu_getref(msq)) { 672 err = -EIDRM; 673 goto out_unlock0; 674 } 675 676 ipc_unlock_object(&msq->q_perm); 677 rcu_read_unlock(); 678 schedule(); 679 680 rcu_read_lock(); 681 ipc_lock_object(&msq->q_perm); 682 683 ipc_rcu_putref(msq, ipc_rcu_free); 684 /* raced with RMID? */ 685 if (!ipc_valid_object(&msq->q_perm)) { 686 err = -EIDRM; 687 goto out_unlock0; 688 } 689 690 ss_del(&s); 691 692 if (signal_pending(current)) { 693 err = -ERESTARTNOHAND; 694 goto out_unlock0; 695 } 696 697 } 698 msq->q_lspid = task_tgid_vnr(current); 699 msq->q_stime = get_seconds(); 700 701 if (!pipelined_send(msq, msg)) { 702 /* no one is waiting for this message, enqueue it */ 703 list_add_tail(&msg->m_list, &msq->q_messages); 704 msq->q_cbytes += msgsz; 705 msq->q_qnum++; 706 atomic_add(msgsz, &ns->msg_bytes); 707 atomic_inc(&ns->msg_hdrs); 708 } 709 710 err = 0; 711 msg = NULL; 712 713out_unlock0: 714 ipc_unlock_object(&msq->q_perm); 715out_unlock1: 716 rcu_read_unlock(); 717 if (msg != NULL) 718 free_msg(msg); 719 return err; 720} 721 722SYSCALL_DEFINE4(msgsnd, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, 723 int, msgflg) 724{ 725 long mtype; 726 727 if (get_user(mtype, &msgp->mtype)) 728 return -EFAULT; 729 return do_msgsnd(msqid, mtype, msgp->mtext, msgsz, msgflg); 730} 731 732static inline int convert_mode(long *msgtyp, int msgflg) 733{ 734 if (msgflg & MSG_COPY) 735 return SEARCH_NUMBER; 736 /* 737 * find message of correct type. 738 * msgtyp = 0 => get first. 739 * msgtyp > 0 => get first message of matching type. 740 * msgtyp < 0 => get message with least type must be < abs(msgtype). 741 */ 742 if (*msgtyp == 0) 743 return SEARCH_ANY; 744 if (*msgtyp < 0) { 745 *msgtyp = -*msgtyp; 746 return SEARCH_LESSEQUAL; 747 } 748 if (msgflg & MSG_EXCEPT) 749 return SEARCH_NOTEQUAL; 750 return SEARCH_EQUAL; 751} 752 753static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz) 754{ 755 struct msgbuf __user *msgp = dest; 756 size_t msgsz; 757 758 if (put_user(msg->m_type, &msgp->mtype)) 759 return -EFAULT; 760 761 msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz; 762 if (store_msg(msgp->mtext, msg, msgsz)) 763 return -EFAULT; 764 return msgsz; 765} 766 767#ifdef CONFIG_CHECKPOINT_RESTORE 768/* 769 * This function creates new kernel message structure, large enough to store 770 * bufsz message bytes. 771 */ 772static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz) 773{ 774 struct msg_msg *copy; 775 776 /* 777 * Create dummy message to copy real message to. 778 */ 779 copy = load_msg(buf, bufsz); 780 if (!IS_ERR(copy)) 781 copy->m_ts = bufsz; 782 return copy; 783} 784 785static inline void free_copy(struct msg_msg *copy) 786{ 787 if (copy) 788 free_msg(copy); 789} 790#else 791static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz) 792{ 793 return ERR_PTR(-ENOSYS); 794} 795 796static inline void free_copy(struct msg_msg *copy) 797{ 798} 799#endif 800 801static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode) 802{ 803 struct msg_msg *msg, *found = NULL; 804 long count = 0; 805 806 list_for_each_entry(msg, &msq->q_messages, m_list) { 807 if (testmsg(msg, *msgtyp, mode) && 808 !security_msg_queue_msgrcv(msq, msg, current, 809 *msgtyp, mode)) { 810 if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) { 811 *msgtyp = msg->m_type - 1; 812 found = msg; 813 } else if (mode == SEARCH_NUMBER) { 814 if (*msgtyp == count) 815 return msg; 816 } else 817 return msg; 818 count++; 819 } 820 } 821 822 return found ?: ERR_PTR(-EAGAIN); 823} 824 825long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg, 826 long (*msg_handler)(void __user *, struct msg_msg *, size_t)) 827{ 828 int mode; 829 struct msg_queue *msq; 830 struct ipc_namespace *ns; 831 struct msg_msg *msg, *copy = NULL; 832 833 ns = current->nsproxy->ipc_ns; 834 835 if (msqid < 0 || (long) bufsz < 0) 836 return -EINVAL; 837 838 if (msgflg & MSG_COPY) { 839 if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT)) 840 return -EINVAL; 841 copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax)); 842 if (IS_ERR(copy)) 843 return PTR_ERR(copy); 844 } 845 mode = convert_mode(&msgtyp, msgflg); 846 847 rcu_read_lock(); 848 msq = msq_obtain_object_check(ns, msqid); 849 if (IS_ERR(msq)) { 850 rcu_read_unlock(); 851 free_copy(copy); 852 return PTR_ERR(msq); 853 } 854 855 for (;;) { 856 struct msg_receiver msr_d; 857 858 msg = ERR_PTR(-EACCES); 859 if (ipcperms(ns, &msq->q_perm, S_IRUGO)) 860 goto out_unlock1; 861 862 ipc_lock_object(&msq->q_perm); 863 864 /* raced with RMID? */ 865 if (!ipc_valid_object(&msq->q_perm)) { 866 msg = ERR_PTR(-EIDRM); 867 goto out_unlock0; 868 } 869 870 msg = find_msg(msq, &msgtyp, mode); 871 if (!IS_ERR(msg)) { 872 /* 873 * Found a suitable message. 874 * Unlink it from the queue. 875 */ 876 if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) { 877 msg = ERR_PTR(-E2BIG); 878 goto out_unlock0; 879 } 880 /* 881 * If we are copying, then do not unlink message and do 882 * not update queue parameters. 883 */ 884 if (msgflg & MSG_COPY) { 885 msg = copy_msg(msg, copy); 886 goto out_unlock0; 887 } 888 889 list_del(&msg->m_list); 890 msq->q_qnum--; 891 msq->q_rtime = get_seconds(); 892 msq->q_lrpid = task_tgid_vnr(current); 893 msq->q_cbytes -= msg->m_ts; 894 atomic_sub(msg->m_ts, &ns->msg_bytes); 895 atomic_dec(&ns->msg_hdrs); 896 ss_wakeup(&msq->q_senders, 0); 897 898 goto out_unlock0; 899 } 900 901 /* No message waiting. Wait for a message */ 902 if (msgflg & IPC_NOWAIT) { 903 msg = ERR_PTR(-ENOMSG); 904 goto out_unlock0; 905 } 906 907 list_add_tail(&msr_d.r_list, &msq->q_receivers); 908 msr_d.r_tsk = current; 909 msr_d.r_msgtype = msgtyp; 910 msr_d.r_mode = mode; 911 if (msgflg & MSG_NOERROR) 912 msr_d.r_maxsize = INT_MAX; 913 else 914 msr_d.r_maxsize = bufsz; 915 msr_d.r_msg = ERR_PTR(-EAGAIN); 916 __set_current_state(TASK_INTERRUPTIBLE); 917 918 ipc_unlock_object(&msq->q_perm); 919 rcu_read_unlock(); 920 schedule(); 921 922 /* Lockless receive, part 1: 923 * Disable preemption. We don't hold a reference to the queue 924 * and getting a reference would defeat the idea of a lockless 925 * operation, thus the code relies on rcu to guarantee the 926 * existence of msq: 927 * Prior to destruction, expunge_all(-EIRDM) changes r_msg. 928 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed. 929 * rcu_read_lock() prevents preemption between reading r_msg 930 * and acquiring the q_perm.lock in ipc_lock_object(). 931 */ 932 rcu_read_lock(); 933 934 /* Lockless receive, part 2: 935 * Wait until pipelined_send or expunge_all are outside of 936 * wake_up_process(). There is a race with exit(), see 937 * ipc/mqueue.c for the details. The correct serialization 938 * ensures that a receiver cannot continue without the wakeup 939 * being visibible _before_ setting r_msg: 940 * 941 * CPU 0 CPU 1 942 * <loop receiver> 943 * smp_rmb(); (A) <-- pair -. <waker thread> 944 * <load ->r_msg> | msr->r_msg = NULL; 945 * | wake_up_process(); 946 * <continue> `------> smp_wmb(); (B) 947 * msr->r_msg = msg; 948 * 949 * Where (A) orders the message value read and where (B) orders 950 * the write to the r_msg -- done in both pipelined_send and 951 * expunge_all. 952 */ 953 for (;;) { 954 /* 955 * Pairs with writer barrier in pipelined_send 956 * or expunge_all. 957 */ 958 smp_rmb(); /* barrier (A) */ 959 msg = (struct msg_msg *)msr_d.r_msg; 960 if (msg) 961 break; 962 963 /* 964 * The cpu_relax() call is a compiler barrier 965 * which forces everything in this loop to be 966 * re-loaded. 967 */ 968 cpu_relax(); 969 } 970 971 /* Lockless receive, part 3: 972 * If there is a message or an error then accept it without 973 * locking. 974 */ 975 if (msg != ERR_PTR(-EAGAIN)) 976 goto out_unlock1; 977 978 /* Lockless receive, part 3: 979 * Acquire the queue spinlock. 980 */ 981 ipc_lock_object(&msq->q_perm); 982 983 /* Lockless receive, part 4: 984 * Repeat test after acquiring the spinlock. 985 */ 986 msg = (struct msg_msg *)msr_d.r_msg; 987 if (msg != ERR_PTR(-EAGAIN)) 988 goto out_unlock0; 989 990 list_del(&msr_d.r_list); 991 if (signal_pending(current)) { 992 msg = ERR_PTR(-ERESTARTNOHAND); 993 goto out_unlock0; 994 } 995 996 ipc_unlock_object(&msq->q_perm); 997 } 998 999out_unlock0: 1000 ipc_unlock_object(&msq->q_perm); 1001out_unlock1: 1002 rcu_read_unlock(); 1003 if (IS_ERR(msg)) { 1004 free_copy(copy); 1005 return PTR_ERR(msg); 1006 } 1007 1008 bufsz = msg_handler(buf, msg, bufsz); 1009 free_msg(msg); 1010 1011 return bufsz; 1012} 1013 1014SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, 1015 long, msgtyp, int, msgflg) 1016{ 1017 return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill); 1018} 1019 1020 1021void msg_init_ns(struct ipc_namespace *ns) 1022{ 1023 ns->msg_ctlmax = MSGMAX; 1024 ns->msg_ctlmnb = MSGMNB; 1025 ns->msg_ctlmni = MSGMNI; 1026 1027 atomic_set(&ns->msg_bytes, 0); 1028 atomic_set(&ns->msg_hdrs, 0); 1029 ipc_init_ids(&ns->ids[IPC_MSG_IDS]); 1030} 1031 1032#ifdef CONFIG_IPC_NS 1033void msg_exit_ns(struct ipc_namespace *ns) 1034{ 1035 free_ipcs(ns, &msg_ids(ns), freeque); 1036 idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr); 1037} 1038#endif 1039 1040#ifdef CONFIG_PROC_FS 1041static int sysvipc_msg_proc_show(struct seq_file *s, void *it) 1042{ 1043 struct user_namespace *user_ns = seq_user_ns(s); 1044 struct msg_queue *msq = it; 1045 1046 seq_printf(s, 1047 "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n", 1048 msq->q_perm.key, 1049 msq->q_perm.id, 1050 msq->q_perm.mode, 1051 msq->q_cbytes, 1052 msq->q_qnum, 1053 msq->q_lspid, 1054 msq->q_lrpid, 1055 from_kuid_munged(user_ns, msq->q_perm.uid), 1056 from_kgid_munged(user_ns, msq->q_perm.gid), 1057 from_kuid_munged(user_ns, msq->q_perm.cuid), 1058 from_kgid_munged(user_ns, msq->q_perm.cgid), 1059 msq->q_stime, 1060 msq->q_rtime, 1061 msq->q_ctime); 1062 1063 return 0; 1064} 1065#endif 1066 1067void __init msg_init(void) 1068{ 1069 msg_init_ns(&init_ipc_ns); 1070 1071 ipc_init_proc_interface("sysvipc/msg", 1072 " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n", 1073 IPC_MSG_IDS, sysvipc_msg_proc_show); 1074} 1075