1 /*- 2 * Copyright (c) 2006, 2011 Robert N. M. Watson 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 * SUCH DAMAGE. 25 */ 26 27 /* 28 * Support for shared swap-backed anonymous memory objects via 29 * shm_open(2) and shm_unlink(2). While most of the implementation is 30 * here, vm_mmap.c contains mapping logic changes. 31 * 32 * TODO: 33 * 34 * (1) Need to export data to a userland tool via a sysctl. Should ipcs(1) 35 * and ipcrm(1) be expanded or should new tools to manage both POSIX 36 * kernel semaphores and POSIX shared memory be written? 37 * 38 * (2) Add support for this file type to fstat(1). 39 * 40 * (3) Resource limits? Does this need its own resource limits or are the 41 * existing limits in mmap(2) sufficient? 42 */ 43 44 #include <sys/cdefs.h> 45 __FBSDID("$FreeBSD$"); 46 47 #include "opt_capsicum.h" 48 49 #include <sys/param.h> 50 #include <sys/capability.h> 51 #include <sys/fcntl.h> 52 #include <sys/file.h> 53 #include <sys/filedesc.h> 54 #include <sys/fnv_hash.h> 55 #include <sys/kernel.h> 56 #include <sys/lock.h> 57 #include <sys/malloc.h> 58 #include <sys/mman.h> 59 #include <sys/mutex.h> 60 #include <sys/priv.h> 61 #include <sys/proc.h> 62 #include <sys/refcount.h> 63 #include <sys/resourcevar.h> 64 #include <sys/rwlock.h> 65 #include <sys/stat.h> 66 #include <sys/sysctl.h> 67 #include <sys/sysproto.h> 68 #include <sys/systm.h> 69 #include <sys/sx.h> 70 #include <sys/time.h> 71 #include <sys/vnode.h> 72 73 #include <security/mac/mac_framework.h> 74 75 #include <vm/vm.h> 76 #include <vm/vm_param.h> 77 #include <vm/pmap.h> 78 #include <vm/vm_extern.h> 79 #include <vm/vm_map.h> 80 #include <vm/vm_kern.h> 81 #include <vm/vm_object.h> 82 #include <vm/vm_page.h> 83 #include <vm/vm_pageout.h> 84 #include <vm/vm_pager.h> 85 #include <vm/swap_pager.h> 86 87 struct shm_mapping { 88 char *sm_path; 89 Fnv32_t sm_fnv; 90 struct shmfd *sm_shmfd; 91 LIST_ENTRY(shm_mapping) sm_link; 92 }; 93 94 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 95 static LIST_HEAD(, shm_mapping) *shm_dictionary; 96 static struct sx shm_dict_lock; 97 static struct mtx shm_timestamp_lock; 98 static u_long shm_hash; 99 100 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 101 102 static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags); 103 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode); 104 static void shm_dict_init(void *arg); 105 static void shm_drop(struct shmfd *shmfd); 106 static struct shmfd *shm_hold(struct shmfd *shmfd); 107 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 108 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 109 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 110 static int shm_dotruncate(struct shmfd *shmfd, off_t length); 111 112 static fo_rdwr_t shm_read; 113 static fo_rdwr_t shm_write; 114 static fo_truncate_t shm_truncate; 115 static fo_ioctl_t shm_ioctl; 116 static fo_poll_t shm_poll; 117 static fo_kqfilter_t shm_kqfilter; 118 static fo_stat_t shm_stat; 119 static fo_close_t shm_close; 120 static fo_chmod_t shm_chmod; 121 static fo_chown_t shm_chown; 122 123 /* File descriptor operations. */ 124 static struct fileops shm_ops = { 125 .fo_read = shm_read, 126 .fo_write = shm_write, 127 .fo_truncate = shm_truncate, 128 .fo_ioctl = shm_ioctl, 129 .fo_poll = shm_poll, 130 .fo_kqfilter = shm_kqfilter, 131 .fo_stat = shm_stat, 132 .fo_close = shm_close, 133 .fo_chmod = shm_chmod, 134 .fo_chown = shm_chown, 135 .fo_flags = DFLAG_PASSABLE 136 }; 137 138 FEATURE(posix_shm, "POSIX shared memory"); 139 140 static int 141 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 142 int flags, struct thread *td) 143 { 144 145 return (EOPNOTSUPP); 146 } 147 148 static int 149 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 150 int flags, struct thread *td) 151 { 152 153 return (EOPNOTSUPP); 154 } 155 156 static int 157 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 158 struct thread *td) 159 { 160 struct shmfd *shmfd; 161 #ifdef MAC 162 int error; 163 #endif 164 165 shmfd = fp->f_data; 166 #ifdef MAC 167 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 168 if (error) 169 return (error); 170 #endif 171 return (shm_dotruncate(shmfd, length)); 172 } 173 174 static int 175 shm_ioctl(struct file *fp, u_long com, void *data, 176 struct ucred *active_cred, struct thread *td) 177 { 178 179 return (EOPNOTSUPP); 180 } 181 182 static int 183 shm_poll(struct file *fp, int events, struct ucred *active_cred, 184 struct thread *td) 185 { 186 187 return (EOPNOTSUPP); 188 } 189 190 static int 191 shm_kqfilter(struct file *fp, struct knote *kn) 192 { 193 194 return (EOPNOTSUPP); 195 } 196 197 static int 198 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 199 struct thread *td) 200 { 201 struct shmfd *shmfd; 202 #ifdef MAC 203 int error; 204 #endif 205 206 shmfd = fp->f_data; 207 208 #ifdef MAC 209 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 210 if (error) 211 return (error); 212 #endif 213 214 /* 215 * Attempt to return sanish values for fstat() on a memory file 216 * descriptor. 217 */ 218 bzero(sb, sizeof(*sb)); 219 sb->st_blksize = PAGE_SIZE; 220 sb->st_size = shmfd->shm_size; 221 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize; 222 mtx_lock(&shm_timestamp_lock); 223 sb->st_atim = shmfd->shm_atime; 224 sb->st_ctim = shmfd->shm_ctime; 225 sb->st_mtim = shmfd->shm_mtime; 226 sb->st_birthtim = shmfd->shm_birthtime; 227 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 228 sb->st_uid = shmfd->shm_uid; 229 sb->st_gid = shmfd->shm_gid; 230 mtx_unlock(&shm_timestamp_lock); 231 232 return (0); 233 } 234 235 static int 236 shm_close(struct file *fp, struct thread *td) 237 { 238 struct shmfd *shmfd; 239 240 shmfd = fp->f_data; 241 fp->f_data = NULL; 242 shm_drop(shmfd); 243 244 return (0); 245 } 246 247 static int 248 shm_dotruncate(struct shmfd *shmfd, off_t length) 249 { 250 vm_object_t object; 251 vm_page_t m, ma[1]; 252 vm_pindex_t idx, nobjsize; 253 vm_ooffset_t delta; 254 int base, rv; 255 256 object = shmfd->shm_object; 257 VM_OBJECT_WLOCK(object); 258 if (length == shmfd->shm_size) { 259 VM_OBJECT_WUNLOCK(object); 260 return (0); 261 } 262 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 263 264 /* Are we shrinking? If so, trim the end. */ 265 if (length < shmfd->shm_size) { 266 /* 267 * Disallow any requests to shrink the size if this 268 * object is mapped into the kernel. 269 */ 270 if (shmfd->shm_kmappings > 0) { 271 VM_OBJECT_WUNLOCK(object); 272 return (EBUSY); 273 } 274 275 /* 276 * Zero the truncated part of the last page. 277 */ 278 base = length & PAGE_MASK; 279 if (base != 0) { 280 idx = OFF_TO_IDX(length); 281 retry: 282 m = vm_page_lookup(object, idx); 283 if (m != NULL) { 284 if ((m->oflags & VPO_BUSY) != 0 || 285 m->busy != 0) { 286 vm_page_sleep(m, "shmtrc"); 287 goto retry; 288 } 289 } else if (vm_pager_has_page(object, idx, NULL, NULL)) { 290 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL); 291 if (m == NULL) { 292 VM_OBJECT_WUNLOCK(object); 293 VM_WAIT; 294 VM_OBJECT_WLOCK(object); 295 goto retry; 296 } else if (m->valid != VM_PAGE_BITS_ALL) { 297 ma[0] = m; 298 rv = vm_pager_get_pages(object, ma, 1, 299 0); 300 m = vm_page_lookup(object, idx); 301 } else 302 /* A cached page was reactivated. */ 303 rv = VM_PAGER_OK; 304 vm_page_lock(m); 305 if (rv == VM_PAGER_OK) { 306 vm_page_deactivate(m); 307 vm_page_unlock(m); 308 vm_page_wakeup(m); 309 } else { 310 vm_page_free(m); 311 vm_page_unlock(m); 312 VM_OBJECT_WUNLOCK(object); 313 return (EIO); 314 } 315 } 316 if (m != NULL) { 317 pmap_zero_page_area(m, base, PAGE_SIZE - base); 318 KASSERT(m->valid == VM_PAGE_BITS_ALL, 319 ("shm_dotruncate: page %p is invalid", m)); 320 vm_page_dirty(m); 321 vm_pager_page_unswapped(m); 322 } 323 } 324 delta = ptoa(object->size - nobjsize); 325 326 /* Toss in memory pages. */ 327 if (nobjsize < object->size) 328 vm_object_page_remove(object, nobjsize, object->size, 329 0); 330 331 /* Toss pages from swap. */ 332 if (object->type == OBJT_SWAP) 333 swap_pager_freespace(object, nobjsize, delta); 334 335 /* Free the swap accounted for shm */ 336 swap_release_by_cred(delta, object->cred); 337 object->charge -= delta; 338 } else { 339 /* Attempt to reserve the swap */ 340 delta = ptoa(nobjsize - object->size); 341 if (!swap_reserve_by_cred(delta, object->cred)) { 342 VM_OBJECT_WUNLOCK(object); 343 return (ENOMEM); 344 } 345 object->charge += delta; 346 } 347 shmfd->shm_size = length; 348 mtx_lock(&shm_timestamp_lock); 349 vfs_timestamp(&shmfd->shm_ctime); 350 shmfd->shm_mtime = shmfd->shm_ctime; 351 mtx_unlock(&shm_timestamp_lock); 352 object->size = nobjsize; 353 VM_OBJECT_WUNLOCK(object); 354 return (0); 355 } 356 357 /* 358 * shmfd object management including creation and reference counting 359 * routines. 360 */ 361 static struct shmfd * 362 shm_alloc(struct ucred *ucred, mode_t mode) 363 { 364 struct shmfd *shmfd; 365 366 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 367 shmfd->shm_size = 0; 368 shmfd->shm_uid = ucred->cr_uid; 369 shmfd->shm_gid = ucred->cr_gid; 370 shmfd->shm_mode = mode; 371 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 372 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 373 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 374 VM_OBJECT_WLOCK(shmfd->shm_object); 375 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 376 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT); 377 VM_OBJECT_WUNLOCK(shmfd->shm_object); 378 vfs_timestamp(&shmfd->shm_birthtime); 379 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 380 shmfd->shm_birthtime; 381 refcount_init(&shmfd->shm_refs, 1); 382 #ifdef MAC 383 mac_posixshm_init(shmfd); 384 mac_posixshm_create(ucred, shmfd); 385 #endif 386 387 return (shmfd); 388 } 389 390 static struct shmfd * 391 shm_hold(struct shmfd *shmfd) 392 { 393 394 refcount_acquire(&shmfd->shm_refs); 395 return (shmfd); 396 } 397 398 static void 399 shm_drop(struct shmfd *shmfd) 400 { 401 402 if (refcount_release(&shmfd->shm_refs)) { 403 #ifdef MAC 404 mac_posixshm_destroy(shmfd); 405 #endif 406 vm_object_deallocate(shmfd->shm_object); 407 free(shmfd, M_SHMFD); 408 } 409 } 410 411 /* 412 * Determine if the credentials have sufficient permissions for a 413 * specified combination of FREAD and FWRITE. 414 */ 415 static int 416 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 417 { 418 accmode_t accmode; 419 int error; 420 421 accmode = 0; 422 if (flags & FREAD) 423 accmode |= VREAD; 424 if (flags & FWRITE) 425 accmode |= VWRITE; 426 mtx_lock(&shm_timestamp_lock); 427 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 428 accmode, ucred, NULL); 429 mtx_unlock(&shm_timestamp_lock); 430 return (error); 431 } 432 433 /* 434 * Dictionary management. We maintain an in-kernel dictionary to map 435 * paths to shmfd objects. We use the FNV hash on the path to store 436 * the mappings in a hash table. 437 */ 438 static void 439 shm_dict_init(void *arg) 440 { 441 442 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 443 sx_init(&shm_dict_lock, "shm dictionary"); 444 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 445 } 446 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL); 447 448 static struct shmfd * 449 shm_lookup(char *path, Fnv32_t fnv) 450 { 451 struct shm_mapping *map; 452 453 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 454 if (map->sm_fnv != fnv) 455 continue; 456 if (strcmp(map->sm_path, path) == 0) 457 return (map->sm_shmfd); 458 } 459 460 return (NULL); 461 } 462 463 static void 464 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 465 { 466 struct shm_mapping *map; 467 468 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 469 map->sm_path = path; 470 map->sm_fnv = fnv; 471 map->sm_shmfd = shm_hold(shmfd); 472 shmfd->shm_path = path; 473 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 474 } 475 476 static int 477 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 478 { 479 struct shm_mapping *map; 480 int error; 481 482 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 483 if (map->sm_fnv != fnv) 484 continue; 485 if (strcmp(map->sm_path, path) == 0) { 486 #ifdef MAC 487 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 488 if (error) 489 return (error); 490 #endif 491 error = shm_access(map->sm_shmfd, ucred, 492 FREAD | FWRITE); 493 if (error) 494 return (error); 495 map->sm_shmfd->shm_path = NULL; 496 LIST_REMOVE(map, sm_link); 497 shm_drop(map->sm_shmfd); 498 free(map->sm_path, M_SHMFD); 499 free(map, M_SHMFD); 500 return (0); 501 } 502 } 503 504 return (ENOENT); 505 } 506 507 /* System calls. */ 508 int 509 sys_shm_open(struct thread *td, struct shm_open_args *uap) 510 { 511 struct filedesc *fdp; 512 struct shmfd *shmfd; 513 struct file *fp; 514 char *path; 515 Fnv32_t fnv; 516 mode_t cmode; 517 int fd, error; 518 519 #ifdef CAPABILITY_MODE 520 /* 521 * shm_open(2) is only allowed for anonymous objects. 522 */ 523 if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON)) 524 return (ECAPMODE); 525 #endif 526 527 if ((uap->flags & O_ACCMODE) != O_RDONLY && 528 (uap->flags & O_ACCMODE) != O_RDWR) 529 return (EINVAL); 530 531 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) 532 return (EINVAL); 533 534 fdp = td->td_proc->p_fd; 535 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 536 537 error = falloc(td, &fp, &fd, O_CLOEXEC); 538 if (error) 539 return (error); 540 541 /* A SHM_ANON path pointer creates an anonymous object. */ 542 if (uap->path == SHM_ANON) { 543 /* A read-only anonymous object is pointless. */ 544 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 545 fdclose(fdp, fp, fd, td); 546 fdrop(fp, td); 547 return (EINVAL); 548 } 549 shmfd = shm_alloc(td->td_ucred, cmode); 550 } else { 551 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 552 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 553 554 /* Require paths to start with a '/' character. */ 555 if (error == 0 && path[0] != '/') 556 error = EINVAL; 557 if (error) { 558 fdclose(fdp, fp, fd, td); 559 fdrop(fp, td); 560 free(path, M_SHMFD); 561 return (error); 562 } 563 564 fnv = fnv_32_str(path, FNV1_32_INIT); 565 sx_xlock(&shm_dict_lock); 566 shmfd = shm_lookup(path, fnv); 567 if (shmfd == NULL) { 568 /* Object does not yet exist, create it if requested. */ 569 if (uap->flags & O_CREAT) { 570 #ifdef MAC 571 error = mac_posixshm_check_create(td->td_ucred, 572 path); 573 if (error == 0) { 574 #endif 575 shmfd = shm_alloc(td->td_ucred, cmode); 576 shm_insert(path, fnv, shmfd); 577 #ifdef MAC 578 } 579 #endif 580 } else { 581 free(path, M_SHMFD); 582 error = ENOENT; 583 } 584 } else { 585 /* 586 * Object already exists, obtain a new 587 * reference if requested and permitted. 588 */ 589 free(path, M_SHMFD); 590 if ((uap->flags & (O_CREAT | O_EXCL)) == 591 (O_CREAT | O_EXCL)) 592 error = EEXIST; 593 else { 594 #ifdef MAC 595 error = mac_posixshm_check_open(td->td_ucred, 596 shmfd, FFLAGS(uap->flags & O_ACCMODE)); 597 if (error == 0) 598 #endif 599 error = shm_access(shmfd, td->td_ucred, 600 FFLAGS(uap->flags & O_ACCMODE)); 601 } 602 603 /* 604 * Truncate the file back to zero length if 605 * O_TRUNC was specified and the object was 606 * opened with read/write. 607 */ 608 if (error == 0 && 609 (uap->flags & (O_ACCMODE | O_TRUNC)) == 610 (O_RDWR | O_TRUNC)) { 611 #ifdef MAC 612 error = mac_posixshm_check_truncate( 613 td->td_ucred, fp->f_cred, shmfd); 614 if (error == 0) 615 #endif 616 shm_dotruncate(shmfd, 0); 617 } 618 if (error == 0) 619 shm_hold(shmfd); 620 } 621 sx_xunlock(&shm_dict_lock); 622 623 if (error) { 624 fdclose(fdp, fp, fd, td); 625 fdrop(fp, td); 626 return (error); 627 } 628 } 629 630 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 631 632 td->td_retval[0] = fd; 633 fdrop(fp, td); 634 635 return (0); 636 } 637 638 int 639 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap) 640 { 641 char *path; 642 Fnv32_t fnv; 643 int error; 644 645 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 646 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 647 if (error) { 648 free(path, M_TEMP); 649 return (error); 650 } 651 652 fnv = fnv_32_str(path, FNV1_32_INIT); 653 sx_xlock(&shm_dict_lock); 654 error = shm_remove(path, fnv, td->td_ucred); 655 sx_xunlock(&shm_dict_lock); 656 free(path, M_TEMP); 657 658 return (error); 659 } 660 661 /* 662 * mmap() helper to validate mmap() requests against shm object state 663 * and give mmap() the vm_object to use for the mapping. 664 */ 665 int 666 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 667 vm_object_t *obj) 668 { 669 670 /* 671 * XXXRW: This validation is probably insufficient, and subject to 672 * sign errors. It should be fixed. 673 */ 674 if (foff >= shmfd->shm_size || 675 foff + objsize > round_page(shmfd->shm_size)) 676 return (EINVAL); 677 678 mtx_lock(&shm_timestamp_lock); 679 vfs_timestamp(&shmfd->shm_atime); 680 mtx_unlock(&shm_timestamp_lock); 681 vm_object_reference(shmfd->shm_object); 682 *obj = shmfd->shm_object; 683 return (0); 684 } 685 686 static int 687 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 688 struct thread *td) 689 { 690 struct shmfd *shmfd; 691 int error; 692 693 error = 0; 694 shmfd = fp->f_data; 695 mtx_lock(&shm_timestamp_lock); 696 /* 697 * SUSv4 says that x bits of permission need not be affected. 698 * Be consistent with our shm_open there. 699 */ 700 #ifdef MAC 701 error = mac_posixshm_check_setmode(active_cred, shmfd, mode); 702 if (error != 0) 703 goto out; 704 #endif 705 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, 706 shmfd->shm_gid, VADMIN, active_cred, NULL); 707 if (error != 0) 708 goto out; 709 shmfd->shm_mode = mode & ACCESSPERMS; 710 out: 711 mtx_unlock(&shm_timestamp_lock); 712 return (error); 713 } 714 715 static int 716 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 717 struct thread *td) 718 { 719 struct shmfd *shmfd; 720 int error; 721 722 error = 0; 723 shmfd = fp->f_data; 724 mtx_lock(&shm_timestamp_lock); 725 #ifdef MAC 726 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid); 727 if (error != 0) 728 goto out; 729 #endif 730 if (uid == (uid_t)-1) 731 uid = shmfd->shm_uid; 732 if (gid == (gid_t)-1) 733 gid = shmfd->shm_gid; 734 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) || 735 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) && 736 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0))) 737 goto out; 738 shmfd->shm_uid = uid; 739 shmfd->shm_gid = gid; 740 out: 741 mtx_unlock(&shm_timestamp_lock); 742 return (error); 743 } 744 745 /* 746 * Helper routines to allow the backing object of a shared memory file 747 * descriptor to be mapped in the kernel. 748 */ 749 int 750 shm_map(struct file *fp, size_t size, off_t offset, void **memp) 751 { 752 struct shmfd *shmfd; 753 vm_offset_t kva, ofs; 754 vm_object_t obj; 755 int rv; 756 757 if (fp->f_type != DTYPE_SHM) 758 return (EINVAL); 759 shmfd = fp->f_data; 760 obj = shmfd->shm_object; 761 VM_OBJECT_WLOCK(obj); 762 /* 763 * XXXRW: This validation is probably insufficient, and subject to 764 * sign errors. It should be fixed. 765 */ 766 if (offset >= shmfd->shm_size || 767 offset + size > round_page(shmfd->shm_size)) { 768 VM_OBJECT_WUNLOCK(obj); 769 return (EINVAL); 770 } 771 772 shmfd->shm_kmappings++; 773 vm_object_reference_locked(obj); 774 VM_OBJECT_WUNLOCK(obj); 775 776 /* Map the object into the kernel_map and wire it. */ 777 kva = vm_map_min(kernel_map); 778 ofs = offset & PAGE_MASK; 779 offset = trunc_page(offset); 780 size = round_page(size + ofs); 781 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 782 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE, 783 VM_PROT_READ | VM_PROT_WRITE, 0); 784 if (rv == KERN_SUCCESS) { 785 rv = vm_map_wire(kernel_map, kva, kva + size, 786 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 787 if (rv == KERN_SUCCESS) { 788 *memp = (void *)(kva + ofs); 789 return (0); 790 } 791 vm_map_remove(kernel_map, kva, kva + size); 792 } else 793 vm_object_deallocate(obj); 794 795 /* On failure, drop our mapping reference. */ 796 VM_OBJECT_WLOCK(obj); 797 shmfd->shm_kmappings--; 798 VM_OBJECT_WUNLOCK(obj); 799 800 return (vm_mmap_to_errno(rv)); 801 } 802 803 /* 804 * We require the caller to unmap the entire entry. This allows us to 805 * safely decrement shm_kmappings when a mapping is removed. 806 */ 807 int 808 shm_unmap(struct file *fp, void *mem, size_t size) 809 { 810 struct shmfd *shmfd; 811 vm_map_entry_t entry; 812 vm_offset_t kva, ofs; 813 vm_object_t obj; 814 vm_pindex_t pindex; 815 vm_prot_t prot; 816 boolean_t wired; 817 vm_map_t map; 818 int rv; 819 820 if (fp->f_type != DTYPE_SHM) 821 return (EINVAL); 822 shmfd = fp->f_data; 823 kva = (vm_offset_t)mem; 824 ofs = kva & PAGE_MASK; 825 kva = trunc_page(kva); 826 size = round_page(size + ofs); 827 map = kernel_map; 828 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 829 &obj, &pindex, &prot, &wired); 830 if (rv != KERN_SUCCESS) 831 return (EINVAL); 832 if (entry->start != kva || entry->end != kva + size) { 833 vm_map_lookup_done(map, entry); 834 return (EINVAL); 835 } 836 vm_map_lookup_done(map, entry); 837 if (obj != shmfd->shm_object) 838 return (EINVAL); 839 vm_map_remove(map, kva, kva + size); 840 VM_OBJECT_WLOCK(obj); 841 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 842 shmfd->shm_kmappings--; 843 VM_OBJECT_WUNLOCK(obj); 844 return (0); 845 } 846 847 void 848 shm_path(struct shmfd *shmfd, char *path, size_t size) 849 { 850 851 if (shmfd->shm_path == NULL) 852 return; 853 sx_slock(&shm_dict_lock); 854 if (shmfd->shm_path != NULL) 855 strlcpy(path, shmfd->shm_path, size); 856 sx_sunlock(&shm_dict_lock); 857 } 858