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 (vm_page_sleep_if_busy(m, "shmtrc")) 285 goto retry; 286 } else if (vm_pager_has_page(object, idx, NULL, NULL)) { 287 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL); 288 if (m == NULL) { 289 VM_OBJECT_WUNLOCK(object); 290 VM_WAIT; 291 VM_OBJECT_WLOCK(object); 292 goto retry; 293 } else if (m->valid != VM_PAGE_BITS_ALL) { 294 ma[0] = m; 295 rv = vm_pager_get_pages(object, ma, 1, 296 0); 297 m = vm_page_lookup(object, idx); 298 } else 299 /* A cached page was reactivated. */ 300 rv = VM_PAGER_OK; 301 vm_page_lock(m); 302 if (rv == VM_PAGER_OK) { 303 vm_page_deactivate(m); 304 vm_page_unlock(m); 305 vm_page_xunbusy(m); 306 } else { 307 vm_page_free(m); 308 vm_page_unlock(m); 309 VM_OBJECT_WUNLOCK(object); 310 return (EIO); 311 } 312 } 313 if (m != NULL) { 314 pmap_zero_page_area(m, base, PAGE_SIZE - base); 315 KASSERT(m->valid == VM_PAGE_BITS_ALL, 316 ("shm_dotruncate: page %p is invalid", m)); 317 vm_page_dirty(m); 318 vm_pager_page_unswapped(m); 319 } 320 } 321 delta = ptoa(object->size - nobjsize); 322 323 /* Toss in memory pages. */ 324 if (nobjsize < object->size) 325 vm_object_page_remove(object, nobjsize, object->size, 326 0); 327 328 /* Toss pages from swap. */ 329 if (object->type == OBJT_SWAP) 330 swap_pager_freespace(object, nobjsize, delta); 331 332 /* Free the swap accounted for shm */ 333 swap_release_by_cred(delta, object->cred); 334 object->charge -= delta; 335 } else { 336 /* Attempt to reserve the swap */ 337 delta = ptoa(nobjsize - object->size); 338 if (!swap_reserve_by_cred(delta, object->cred)) { 339 VM_OBJECT_WUNLOCK(object); 340 return (ENOMEM); 341 } 342 object->charge += delta; 343 } 344 shmfd->shm_size = length; 345 mtx_lock(&shm_timestamp_lock); 346 vfs_timestamp(&shmfd->shm_ctime); 347 shmfd->shm_mtime = shmfd->shm_ctime; 348 mtx_unlock(&shm_timestamp_lock); 349 object->size = nobjsize; 350 VM_OBJECT_WUNLOCK(object); 351 return (0); 352 } 353 354 /* 355 * shmfd object management including creation and reference counting 356 * routines. 357 */ 358 static struct shmfd * 359 shm_alloc(struct ucred *ucred, mode_t mode) 360 { 361 struct shmfd *shmfd; 362 363 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 364 shmfd->shm_size = 0; 365 shmfd->shm_uid = ucred->cr_uid; 366 shmfd->shm_gid = ucred->cr_gid; 367 shmfd->shm_mode = mode; 368 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 369 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 370 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 371 VM_OBJECT_WLOCK(shmfd->shm_object); 372 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 373 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT); 374 VM_OBJECT_WUNLOCK(shmfd->shm_object); 375 vfs_timestamp(&shmfd->shm_birthtime); 376 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 377 shmfd->shm_birthtime; 378 refcount_init(&shmfd->shm_refs, 1); 379 #ifdef MAC 380 mac_posixshm_init(shmfd); 381 mac_posixshm_create(ucred, shmfd); 382 #endif 383 384 return (shmfd); 385 } 386 387 static struct shmfd * 388 shm_hold(struct shmfd *shmfd) 389 { 390 391 refcount_acquire(&shmfd->shm_refs); 392 return (shmfd); 393 } 394 395 static void 396 shm_drop(struct shmfd *shmfd) 397 { 398 399 if (refcount_release(&shmfd->shm_refs)) { 400 #ifdef MAC 401 mac_posixshm_destroy(shmfd); 402 #endif 403 vm_object_deallocate(shmfd->shm_object); 404 free(shmfd, M_SHMFD); 405 } 406 } 407 408 /* 409 * Determine if the credentials have sufficient permissions for a 410 * specified combination of FREAD and FWRITE. 411 */ 412 static int 413 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 414 { 415 accmode_t accmode; 416 int error; 417 418 accmode = 0; 419 if (flags & FREAD) 420 accmode |= VREAD; 421 if (flags & FWRITE) 422 accmode |= VWRITE; 423 mtx_lock(&shm_timestamp_lock); 424 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 425 accmode, ucred, NULL); 426 mtx_unlock(&shm_timestamp_lock); 427 return (error); 428 } 429 430 /* 431 * Dictionary management. We maintain an in-kernel dictionary to map 432 * paths to shmfd objects. We use the FNV hash on the path to store 433 * the mappings in a hash table. 434 */ 435 static void 436 shm_dict_init(void *arg) 437 { 438 439 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 440 sx_init(&shm_dict_lock, "shm dictionary"); 441 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 442 } 443 SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL); 444 445 static struct shmfd * 446 shm_lookup(char *path, Fnv32_t fnv) 447 { 448 struct shm_mapping *map; 449 450 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 451 if (map->sm_fnv != fnv) 452 continue; 453 if (strcmp(map->sm_path, path) == 0) 454 return (map->sm_shmfd); 455 } 456 457 return (NULL); 458 } 459 460 static void 461 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 462 { 463 struct shm_mapping *map; 464 465 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 466 map->sm_path = path; 467 map->sm_fnv = fnv; 468 map->sm_shmfd = shm_hold(shmfd); 469 shmfd->shm_path = path; 470 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 471 } 472 473 static int 474 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 475 { 476 struct shm_mapping *map; 477 int error; 478 479 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 480 if (map->sm_fnv != fnv) 481 continue; 482 if (strcmp(map->sm_path, path) == 0) { 483 #ifdef MAC 484 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 485 if (error) 486 return (error); 487 #endif 488 error = shm_access(map->sm_shmfd, ucred, 489 FREAD | FWRITE); 490 if (error) 491 return (error); 492 map->sm_shmfd->shm_path = NULL; 493 LIST_REMOVE(map, sm_link); 494 shm_drop(map->sm_shmfd); 495 free(map->sm_path, M_SHMFD); 496 free(map, M_SHMFD); 497 return (0); 498 } 499 } 500 501 return (ENOENT); 502 } 503 504 /* System calls. */ 505 int 506 sys_shm_open(struct thread *td, struct shm_open_args *uap) 507 { 508 struct filedesc *fdp; 509 struct shmfd *shmfd; 510 struct file *fp; 511 char *path; 512 Fnv32_t fnv; 513 mode_t cmode; 514 int fd, error; 515 516 #ifdef CAPABILITY_MODE 517 /* 518 * shm_open(2) is only allowed for anonymous objects. 519 */ 520 if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON)) 521 return (ECAPMODE); 522 #endif 523 524 if ((uap->flags & O_ACCMODE) != O_RDONLY && 525 (uap->flags & O_ACCMODE) != O_RDWR) 526 return (EINVAL); 527 528 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0) 529 return (EINVAL); 530 531 fdp = td->td_proc->p_fd; 532 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS; 533 534 error = falloc(td, &fp, &fd, O_CLOEXEC); 535 if (error) 536 return (error); 537 538 /* A SHM_ANON path pointer creates an anonymous object. */ 539 if (uap->path == SHM_ANON) { 540 /* A read-only anonymous object is pointless. */ 541 if ((uap->flags & O_ACCMODE) == O_RDONLY) { 542 fdclose(fdp, fp, fd, td); 543 fdrop(fp, td); 544 return (EINVAL); 545 } 546 shmfd = shm_alloc(td->td_ucred, cmode); 547 } else { 548 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 549 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 550 551 /* Require paths to start with a '/' character. */ 552 if (error == 0 && path[0] != '/') 553 error = EINVAL; 554 if (error) { 555 fdclose(fdp, fp, fd, td); 556 fdrop(fp, td); 557 free(path, M_SHMFD); 558 return (error); 559 } 560 561 fnv = fnv_32_str(path, FNV1_32_INIT); 562 sx_xlock(&shm_dict_lock); 563 shmfd = shm_lookup(path, fnv); 564 if (shmfd == NULL) { 565 /* Object does not yet exist, create it if requested. */ 566 if (uap->flags & O_CREAT) { 567 #ifdef MAC 568 error = mac_posixshm_check_create(td->td_ucred, 569 path); 570 if (error == 0) { 571 #endif 572 shmfd = shm_alloc(td->td_ucred, cmode); 573 shm_insert(path, fnv, shmfd); 574 #ifdef MAC 575 } 576 #endif 577 } else { 578 free(path, M_SHMFD); 579 error = ENOENT; 580 } 581 } else { 582 /* 583 * Object already exists, obtain a new 584 * reference if requested and permitted. 585 */ 586 free(path, M_SHMFD); 587 if ((uap->flags & (O_CREAT | O_EXCL)) == 588 (O_CREAT | O_EXCL)) 589 error = EEXIST; 590 else { 591 #ifdef MAC 592 error = mac_posixshm_check_open(td->td_ucred, 593 shmfd, FFLAGS(uap->flags & O_ACCMODE)); 594 if (error == 0) 595 #endif 596 error = shm_access(shmfd, td->td_ucred, 597 FFLAGS(uap->flags & O_ACCMODE)); 598 } 599 600 /* 601 * Truncate the file back to zero length if 602 * O_TRUNC was specified and the object was 603 * opened with read/write. 604 */ 605 if (error == 0 && 606 (uap->flags & (O_ACCMODE | O_TRUNC)) == 607 (O_RDWR | O_TRUNC)) { 608 #ifdef MAC 609 error = mac_posixshm_check_truncate( 610 td->td_ucred, fp->f_cred, shmfd); 611 if (error == 0) 612 #endif 613 shm_dotruncate(shmfd, 0); 614 } 615 if (error == 0) 616 shm_hold(shmfd); 617 } 618 sx_xunlock(&shm_dict_lock); 619 620 if (error) { 621 fdclose(fdp, fp, fd, td); 622 fdrop(fp, td); 623 return (error); 624 } 625 } 626 627 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 628 629 td->td_retval[0] = fd; 630 fdrop(fp, td); 631 632 return (0); 633 } 634 635 int 636 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap) 637 { 638 char *path; 639 Fnv32_t fnv; 640 int error; 641 642 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 643 error = copyinstr(uap->path, path, MAXPATHLEN, NULL); 644 if (error) { 645 free(path, M_TEMP); 646 return (error); 647 } 648 649 fnv = fnv_32_str(path, FNV1_32_INIT); 650 sx_xlock(&shm_dict_lock); 651 error = shm_remove(path, fnv, td->td_ucred); 652 sx_xunlock(&shm_dict_lock); 653 free(path, M_TEMP); 654 655 return (error); 656 } 657 658 /* 659 * mmap() helper to validate mmap() requests against shm object state 660 * and give mmap() the vm_object to use for the mapping. 661 */ 662 int 663 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff, 664 vm_object_t *obj) 665 { 666 667 /* 668 * XXXRW: This validation is probably insufficient, and subject to 669 * sign errors. It should be fixed. 670 */ 671 if (foff >= shmfd->shm_size || 672 foff + objsize > round_page(shmfd->shm_size)) 673 return (EINVAL); 674 675 mtx_lock(&shm_timestamp_lock); 676 vfs_timestamp(&shmfd->shm_atime); 677 mtx_unlock(&shm_timestamp_lock); 678 vm_object_reference(shmfd->shm_object); 679 *obj = shmfd->shm_object; 680 return (0); 681 } 682 683 static int 684 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 685 struct thread *td) 686 { 687 struct shmfd *shmfd; 688 int error; 689 690 error = 0; 691 shmfd = fp->f_data; 692 mtx_lock(&shm_timestamp_lock); 693 /* 694 * SUSv4 says that x bits of permission need not be affected. 695 * Be consistent with our shm_open there. 696 */ 697 #ifdef MAC 698 error = mac_posixshm_check_setmode(active_cred, shmfd, mode); 699 if (error != 0) 700 goto out; 701 #endif 702 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, 703 shmfd->shm_gid, VADMIN, active_cred, NULL); 704 if (error != 0) 705 goto out; 706 shmfd->shm_mode = mode & ACCESSPERMS; 707 out: 708 mtx_unlock(&shm_timestamp_lock); 709 return (error); 710 } 711 712 static int 713 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 714 struct thread *td) 715 { 716 struct shmfd *shmfd; 717 int error; 718 719 error = 0; 720 shmfd = fp->f_data; 721 mtx_lock(&shm_timestamp_lock); 722 #ifdef MAC 723 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid); 724 if (error != 0) 725 goto out; 726 #endif 727 if (uid == (uid_t)-1) 728 uid = shmfd->shm_uid; 729 if (gid == (gid_t)-1) 730 gid = shmfd->shm_gid; 731 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) || 732 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) && 733 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0))) 734 goto out; 735 shmfd->shm_uid = uid; 736 shmfd->shm_gid = gid; 737 out: 738 mtx_unlock(&shm_timestamp_lock); 739 return (error); 740 } 741 742 /* 743 * Helper routines to allow the backing object of a shared memory file 744 * descriptor to be mapped in the kernel. 745 */ 746 int 747 shm_map(struct file *fp, size_t size, off_t offset, void **memp) 748 { 749 struct shmfd *shmfd; 750 vm_offset_t kva, ofs; 751 vm_object_t obj; 752 int rv; 753 754 if (fp->f_type != DTYPE_SHM) 755 return (EINVAL); 756 shmfd = fp->f_data; 757 obj = shmfd->shm_object; 758 VM_OBJECT_WLOCK(obj); 759 /* 760 * XXXRW: This validation is probably insufficient, and subject to 761 * sign errors. It should be fixed. 762 */ 763 if (offset >= shmfd->shm_size || 764 offset + size > round_page(shmfd->shm_size)) { 765 VM_OBJECT_WUNLOCK(obj); 766 return (EINVAL); 767 } 768 769 shmfd->shm_kmappings++; 770 vm_object_reference_locked(obj); 771 VM_OBJECT_WUNLOCK(obj); 772 773 /* Map the object into the kernel_map and wire it. */ 774 kva = vm_map_min(kernel_map); 775 ofs = offset & PAGE_MASK; 776 offset = trunc_page(offset); 777 size = round_page(size + ofs); 778 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 779 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE, 780 VM_PROT_READ | VM_PROT_WRITE, 0); 781 if (rv == KERN_SUCCESS) { 782 rv = vm_map_wire(kernel_map, kva, kva + size, 783 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 784 if (rv == KERN_SUCCESS) { 785 *memp = (void *)(kva + ofs); 786 return (0); 787 } 788 vm_map_remove(kernel_map, kva, kva + size); 789 } else 790 vm_object_deallocate(obj); 791 792 /* On failure, drop our mapping reference. */ 793 VM_OBJECT_WLOCK(obj); 794 shmfd->shm_kmappings--; 795 VM_OBJECT_WUNLOCK(obj); 796 797 return (vm_mmap_to_errno(rv)); 798 } 799 800 /* 801 * We require the caller to unmap the entire entry. This allows us to 802 * safely decrement shm_kmappings when a mapping is removed. 803 */ 804 int 805 shm_unmap(struct file *fp, void *mem, size_t size) 806 { 807 struct shmfd *shmfd; 808 vm_map_entry_t entry; 809 vm_offset_t kva, ofs; 810 vm_object_t obj; 811 vm_pindex_t pindex; 812 vm_prot_t prot; 813 boolean_t wired; 814 vm_map_t map; 815 int rv; 816 817 if (fp->f_type != DTYPE_SHM) 818 return (EINVAL); 819 shmfd = fp->f_data; 820 kva = (vm_offset_t)mem; 821 ofs = kva & PAGE_MASK; 822 kva = trunc_page(kva); 823 size = round_page(size + ofs); 824 map = kernel_map; 825 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 826 &obj, &pindex, &prot, &wired); 827 if (rv != KERN_SUCCESS) 828 return (EINVAL); 829 if (entry->start != kva || entry->end != kva + size) { 830 vm_map_lookup_done(map, entry); 831 return (EINVAL); 832 } 833 vm_map_lookup_done(map, entry); 834 if (obj != shmfd->shm_object) 835 return (EINVAL); 836 vm_map_remove(map, kva, kva + size); 837 VM_OBJECT_WLOCK(obj); 838 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 839 shmfd->shm_kmappings--; 840 VM_OBJECT_WUNLOCK(obj); 841 return (0); 842 } 843 844 void 845 shm_path(struct shmfd *shmfd, char *path, size_t size) 846 { 847 848 if (shmfd->shm_path == NULL) 849 return; 850 sx_slock(&shm_dict_lock); 851 if (shmfd->shm_path != NULL) 852 strlcpy(path, shmfd->shm_path, size); 853 sx_sunlock(&shm_dict_lock); 854 } 855