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 /* ipc_addid() locks msq upon success. */ 141 id = ipc_addid(&msg_ids(ns), &msq->q_perm, ns->msg_ctlmni); 142 if (id < 0) { 143 ipc_rcu_putref(msq, msg_rcu_free); 144 return id; 145 } 146 147 msq->q_stime = msq->q_rtime = 0; 148 msq->q_ctime = get_seconds(); 149 msq->q_cbytes = msq->q_qnum = 0; 150 msq->q_qbytes = ns->msg_ctlmnb; 151 msq->q_lspid = msq->q_lrpid = 0; 152 INIT_LIST_HEAD(&msq->q_messages); 153 INIT_LIST_HEAD(&msq->q_receivers); 154 INIT_LIST_HEAD(&msq->q_senders); 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, ipc_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 *msgtyp = -*msgtyp; 744 return SEARCH_LESSEQUAL; 745 } 746 if (msgflg & MSG_EXCEPT) 747 return SEARCH_NOTEQUAL; 748 return SEARCH_EQUAL; 749 } 750 751 static long do_msg_fill(void __user *dest, struct msg_msg *msg, size_t bufsz) 752 { 753 struct msgbuf __user *msgp = dest; 754 size_t msgsz; 755 756 if (put_user(msg->m_type, &msgp->mtype)) 757 return -EFAULT; 758 759 msgsz = (bufsz > msg->m_ts) ? msg->m_ts : bufsz; 760 if (store_msg(msgp->mtext, msg, msgsz)) 761 return -EFAULT; 762 return msgsz; 763 } 764 765 #ifdef CONFIG_CHECKPOINT_RESTORE 766 /* 767 * This function creates new kernel message structure, large enough to store 768 * bufsz message bytes. 769 */ 770 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz) 771 { 772 struct msg_msg *copy; 773 774 /* 775 * Create dummy message to copy real message to. 776 */ 777 copy = load_msg(buf, bufsz); 778 if (!IS_ERR(copy)) 779 copy->m_ts = bufsz; 780 return copy; 781 } 782 783 static inline void free_copy(struct msg_msg *copy) 784 { 785 if (copy) 786 free_msg(copy); 787 } 788 #else 789 static inline struct msg_msg *prepare_copy(void __user *buf, size_t bufsz) 790 { 791 return ERR_PTR(-ENOSYS); 792 } 793 794 static inline void free_copy(struct msg_msg *copy) 795 { 796 } 797 #endif 798 799 static struct msg_msg *find_msg(struct msg_queue *msq, long *msgtyp, int mode) 800 { 801 struct msg_msg *msg, *found = NULL; 802 long count = 0; 803 804 list_for_each_entry(msg, &msq->q_messages, m_list) { 805 if (testmsg(msg, *msgtyp, mode) && 806 !security_msg_queue_msgrcv(msq, msg, current, 807 *msgtyp, mode)) { 808 if (mode == SEARCH_LESSEQUAL && msg->m_type != 1) { 809 *msgtyp = msg->m_type - 1; 810 found = msg; 811 } else if (mode == SEARCH_NUMBER) { 812 if (*msgtyp == count) 813 return msg; 814 } else 815 return msg; 816 count++; 817 } 818 } 819 820 return found ?: ERR_PTR(-EAGAIN); 821 } 822 823 long do_msgrcv(int msqid, void __user *buf, size_t bufsz, long msgtyp, int msgflg, 824 long (*msg_handler)(void __user *, struct msg_msg *, size_t)) 825 { 826 int mode; 827 struct msg_queue *msq; 828 struct ipc_namespace *ns; 829 struct msg_msg *msg, *copy = NULL; 830 831 ns = current->nsproxy->ipc_ns; 832 833 if (msqid < 0 || (long) bufsz < 0) 834 return -EINVAL; 835 836 if (msgflg & MSG_COPY) { 837 if ((msgflg & MSG_EXCEPT) || !(msgflg & IPC_NOWAIT)) 838 return -EINVAL; 839 copy = prepare_copy(buf, min_t(size_t, bufsz, ns->msg_ctlmax)); 840 if (IS_ERR(copy)) 841 return PTR_ERR(copy); 842 } 843 mode = convert_mode(&msgtyp, msgflg); 844 845 rcu_read_lock(); 846 msq = msq_obtain_object_check(ns, msqid); 847 if (IS_ERR(msq)) { 848 rcu_read_unlock(); 849 free_copy(copy); 850 return PTR_ERR(msq); 851 } 852 853 for (;;) { 854 struct msg_receiver msr_d; 855 856 msg = ERR_PTR(-EACCES); 857 if (ipcperms(ns, &msq->q_perm, S_IRUGO)) 858 goto out_unlock1; 859 860 ipc_lock_object(&msq->q_perm); 861 862 /* raced with RMID? */ 863 if (!ipc_valid_object(&msq->q_perm)) { 864 msg = ERR_PTR(-EIDRM); 865 goto out_unlock0; 866 } 867 868 msg = find_msg(msq, &msgtyp, mode); 869 if (!IS_ERR(msg)) { 870 /* 871 * Found a suitable message. 872 * Unlink it from the queue. 873 */ 874 if ((bufsz < msg->m_ts) && !(msgflg & MSG_NOERROR)) { 875 msg = ERR_PTR(-E2BIG); 876 goto out_unlock0; 877 } 878 /* 879 * If we are copying, then do not unlink message and do 880 * not update queue parameters. 881 */ 882 if (msgflg & MSG_COPY) { 883 msg = copy_msg(msg, copy); 884 goto out_unlock0; 885 } 886 887 list_del(&msg->m_list); 888 msq->q_qnum--; 889 msq->q_rtime = get_seconds(); 890 msq->q_lrpid = task_tgid_vnr(current); 891 msq->q_cbytes -= msg->m_ts; 892 atomic_sub(msg->m_ts, &ns->msg_bytes); 893 atomic_dec(&ns->msg_hdrs); 894 ss_wakeup(&msq->q_senders, 0); 895 896 goto out_unlock0; 897 } 898 899 /* No message waiting. Wait for a message */ 900 if (msgflg & IPC_NOWAIT) { 901 msg = ERR_PTR(-ENOMSG); 902 goto out_unlock0; 903 } 904 905 list_add_tail(&msr_d.r_list, &msq->q_receivers); 906 msr_d.r_tsk = current; 907 msr_d.r_msgtype = msgtyp; 908 msr_d.r_mode = mode; 909 if (msgflg & MSG_NOERROR) 910 msr_d.r_maxsize = INT_MAX; 911 else 912 msr_d.r_maxsize = bufsz; 913 msr_d.r_msg = ERR_PTR(-EAGAIN); 914 __set_current_state(TASK_INTERRUPTIBLE); 915 916 ipc_unlock_object(&msq->q_perm); 917 rcu_read_unlock(); 918 schedule(); 919 920 /* Lockless receive, part 1: 921 * Disable preemption. We don't hold a reference to the queue 922 * and getting a reference would defeat the idea of a lockless 923 * operation, thus the code relies on rcu to guarantee the 924 * existence of msq: 925 * Prior to destruction, expunge_all(-EIRDM) changes r_msg. 926 * Thus if r_msg is -EAGAIN, then the queue not yet destroyed. 927 * rcu_read_lock() prevents preemption between reading r_msg 928 * and acquiring the q_perm.lock in ipc_lock_object(). 929 */ 930 rcu_read_lock(); 931 932 /* Lockless receive, part 2: 933 * Wait until pipelined_send or expunge_all are outside of 934 * wake_up_process(). There is a race with exit(), see 935 * ipc/mqueue.c for the details. 936 */ 937 msg = (struct msg_msg *)msr_d.r_msg; 938 while (msg == NULL) { 939 cpu_relax(); 940 msg = (struct msg_msg *)msr_d.r_msg; 941 } 942 943 /* Lockless receive, part 3: 944 * If there is a message or an error then accept it without 945 * locking. 946 */ 947 if (msg != ERR_PTR(-EAGAIN)) 948 goto out_unlock1; 949 950 /* Lockless receive, part 3: 951 * Acquire the queue spinlock. 952 */ 953 ipc_lock_object(&msq->q_perm); 954 955 /* Lockless receive, part 4: 956 * Repeat test after acquiring the spinlock. 957 */ 958 msg = (struct msg_msg *)msr_d.r_msg; 959 if (msg != ERR_PTR(-EAGAIN)) 960 goto out_unlock0; 961 962 list_del(&msr_d.r_list); 963 if (signal_pending(current)) { 964 msg = ERR_PTR(-ERESTARTNOHAND); 965 goto out_unlock0; 966 } 967 968 ipc_unlock_object(&msq->q_perm); 969 } 970 971 out_unlock0: 972 ipc_unlock_object(&msq->q_perm); 973 out_unlock1: 974 rcu_read_unlock(); 975 if (IS_ERR(msg)) { 976 free_copy(copy); 977 return PTR_ERR(msg); 978 } 979 980 bufsz = msg_handler(buf, msg, bufsz); 981 free_msg(msg); 982 983 return bufsz; 984 } 985 986 SYSCALL_DEFINE5(msgrcv, int, msqid, struct msgbuf __user *, msgp, size_t, msgsz, 987 long, msgtyp, int, msgflg) 988 { 989 return do_msgrcv(msqid, msgp, msgsz, msgtyp, msgflg, do_msg_fill); 990 } 991 992 993 void msg_init_ns(struct ipc_namespace *ns) 994 { 995 ns->msg_ctlmax = MSGMAX; 996 ns->msg_ctlmnb = MSGMNB; 997 ns->msg_ctlmni = MSGMNI; 998 999 atomic_set(&ns->msg_bytes, 0); 1000 atomic_set(&ns->msg_hdrs, 0); 1001 ipc_init_ids(&ns->ids[IPC_MSG_IDS]); 1002 } 1003 1004 #ifdef CONFIG_IPC_NS 1005 void msg_exit_ns(struct ipc_namespace *ns) 1006 { 1007 free_ipcs(ns, &msg_ids(ns), freeque); 1008 idr_destroy(&ns->ids[IPC_MSG_IDS].ipcs_idr); 1009 } 1010 #endif 1011 1012 #ifdef CONFIG_PROC_FS 1013 static int sysvipc_msg_proc_show(struct seq_file *s, void *it) 1014 { 1015 struct user_namespace *user_ns = seq_user_ns(s); 1016 struct msg_queue *msq = it; 1017 1018 return seq_printf(s, 1019 "%10d %10d %4o %10lu %10lu %5u %5u %5u %5u %5u %5u %10lu %10lu %10lu\n", 1020 msq->q_perm.key, 1021 msq->q_perm.id, 1022 msq->q_perm.mode, 1023 msq->q_cbytes, 1024 msq->q_qnum, 1025 msq->q_lspid, 1026 msq->q_lrpid, 1027 from_kuid_munged(user_ns, msq->q_perm.uid), 1028 from_kgid_munged(user_ns, msq->q_perm.gid), 1029 from_kuid_munged(user_ns, msq->q_perm.cuid), 1030 from_kgid_munged(user_ns, msq->q_perm.cgid), 1031 msq->q_stime, 1032 msq->q_rtime, 1033 msq->q_ctime); 1034 } 1035 #endif 1036 1037 void __init msg_init(void) 1038 { 1039 msg_init_ns(&init_ipc_ns); 1040 1041 ipc_init_proc_interface("sysvipc/msg", 1042 " key msqid perms cbytes qnum lspid lrpid uid gid cuid cgid stime rtime ctime\n", 1043 IPC_MSG_IDS, sysvipc_msg_proc_show); 1044 } 1045