Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_shm.c
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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: releng/11.1/sys/kern/uipc_shm.c 320639 2017-07-04 05:37:58Z kib $"); 46 47 #include "opt_capsicum.h" 48 #include "opt_ktrace.h" 49 50 #include <sys/param.h> 51 #include <sys/capsicum.h> 52 #include <sys/conf.h> 53 #include <sys/fcntl.h> 54 #include <sys/file.h> 55 #include <sys/filedesc.h> 56 #include <sys/fnv_hash.h> 57 #include <sys/kernel.h> 58 #include <sys/uio.h> 59 #include <sys/signal.h> 60 #include <sys/jail.h> 61 #include <sys/ktrace.h> 62 #include <sys/lock.h> 63 #include <sys/malloc.h> 64 #include <sys/mman.h> 65 #include <sys/mutex.h> 66 #include <sys/priv.h> 67 #include <sys/proc.h> 68 #include <sys/refcount.h> 69 #include <sys/resourcevar.h> 70 #include <sys/rwlock.h> 71 #include <sys/stat.h> 72 #include <sys/syscallsubr.h> 73 #include <sys/sysctl.h> 74 #include <sys/sysproto.h> 75 #include <sys/systm.h> 76 #include <sys/sx.h> 77 #include <sys/time.h> 78 #include <sys/vnode.h> 79 #include <sys/unistd.h> 80 #include <sys/user.h> 81 82 #include <security/mac/mac_framework.h> 83 84 #include <vm/vm.h> 85 #include <vm/vm_param.h> 86 #include <vm/pmap.h> 87 #include <vm/vm_extern.h> 88 #include <vm/vm_map.h> 89 #include <vm/vm_kern.h> 90 #include <vm/vm_object.h> 91 #include <vm/vm_page.h> 92 #include <vm/vm_pageout.h> 93 #include <vm/vm_pager.h> 94 #include <vm/swap_pager.h> 95 96 struct shm_mapping { 97 char *sm_path; 98 Fnv32_t sm_fnv; 99 struct shmfd *sm_shmfd; 100 LIST_ENTRY(shm_mapping) sm_link; 101 }; 102 103 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 104 static LIST_HEAD(, shm_mapping) *shm_dictionary; 105 static struct sx shm_dict_lock; 106 static struct mtx shm_timestamp_lock; 107 static u_long shm_hash; 108 static struct unrhdr *shm_ino_unr; 109 static dev_t shm_dev_ino; 110 111 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 112 113 static void shm_init(void *arg); 114 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 115 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 116 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 117 118 static fo_rdwr_t shm_read; 119 static fo_rdwr_t shm_write; 120 static fo_truncate_t shm_truncate; 121 static fo_stat_t shm_stat; 122 static fo_close_t shm_close; 123 static fo_chmod_t shm_chmod; 124 static fo_chown_t shm_chown; 125 static fo_seek_t shm_seek; 126 static fo_fill_kinfo_t shm_fill_kinfo; 127 static fo_mmap_t shm_mmap; 128 129 /* File descriptor operations. */ 130 struct fileops shm_ops = { 131 .fo_read = shm_read, 132 .fo_write = shm_write, 133 .fo_truncate = shm_truncate, 134 .fo_ioctl = invfo_ioctl, 135 .fo_poll = invfo_poll, 136 .fo_kqfilter = invfo_kqfilter, 137 .fo_stat = shm_stat, 138 .fo_close = shm_close, 139 .fo_chmod = shm_chmod, 140 .fo_chown = shm_chown, 141 .fo_sendfile = vn_sendfile, 142 .fo_seek = shm_seek, 143 .fo_fill_kinfo = shm_fill_kinfo, 144 .fo_mmap = shm_mmap, 145 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE 146 }; 147 148 FEATURE(posix_shm, "POSIX shared memory"); 149 150 static int 151 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio) 152 { 153 vm_page_t m; 154 vm_pindex_t idx; 155 size_t tlen; 156 int error, offset, rv; 157 158 idx = OFF_TO_IDX(uio->uio_offset); 159 offset = uio->uio_offset & PAGE_MASK; 160 tlen = MIN(PAGE_SIZE - offset, len); 161 162 VM_OBJECT_WLOCK(obj); 163 164 /* 165 * Read I/O without either a corresponding resident page or swap 166 * page: use zero_region. This is intended to avoid instantiating 167 * pages on read from a sparse region. 168 */ 169 if (uio->uio_rw == UIO_READ && vm_page_lookup(obj, idx) == NULL && 170 !vm_pager_has_page(obj, idx, NULL, NULL)) { 171 VM_OBJECT_WUNLOCK(obj); 172 return (uiomove(__DECONST(void *, zero_region), tlen, uio)); 173 } 174 175 /* 176 * Parallel reads of the page content from disk are prevented 177 * by exclusive busy. 178 * 179 * Although the tmpfs vnode lock is held here, it is 180 * nonetheless safe to sleep waiting for a free page. The 181 * pageout daemon does not need to acquire the tmpfs vnode 182 * lock to page out tobj's pages because tobj is a OBJT_SWAP 183 * type object. 184 */ 185 m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY); 186 if (m->valid != VM_PAGE_BITS_ALL) { 187 vm_page_xbusy(m); 188 if (vm_pager_has_page(obj, idx, NULL, NULL)) { 189 rv = vm_pager_get_pages(obj, &m, 1, NULL, NULL); 190 if (rv != VM_PAGER_OK) { 191 printf( 192 "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n", 193 obj, idx, m->valid, rv); 194 vm_page_lock(m); 195 vm_page_free(m); 196 vm_page_unlock(m); 197 VM_OBJECT_WUNLOCK(obj); 198 return (EIO); 199 } 200 } else 201 vm_page_zero_invalid(m, TRUE); 202 vm_page_xunbusy(m); 203 } 204 vm_page_lock(m); 205 vm_page_hold(m); 206 if (m->queue == PQ_NONE) { 207 vm_page_deactivate(m); 208 } else { 209 /* Requeue to maintain LRU ordering. */ 210 vm_page_requeue(m); 211 } 212 vm_page_unlock(m); 213 VM_OBJECT_WUNLOCK(obj); 214 error = uiomove_fromphys(&m, offset, tlen, uio); 215 if (uio->uio_rw == UIO_WRITE && error == 0) { 216 VM_OBJECT_WLOCK(obj); 217 vm_page_dirty(m); 218 vm_pager_page_unswapped(m); 219 VM_OBJECT_WUNLOCK(obj); 220 } 221 vm_page_lock(m); 222 vm_page_unhold(m); 223 vm_page_unlock(m); 224 225 return (error); 226 } 227 228 int 229 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio) 230 { 231 ssize_t resid; 232 size_t len; 233 int error; 234 235 error = 0; 236 while ((resid = uio->uio_resid) > 0) { 237 if (obj_size <= uio->uio_offset) 238 break; 239 len = MIN(obj_size - uio->uio_offset, resid); 240 if (len == 0) 241 break; 242 error = uiomove_object_page(obj, len, uio); 243 if (error != 0 || resid == uio->uio_resid) 244 break; 245 } 246 return (error); 247 } 248 249 static int 250 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td) 251 { 252 struct shmfd *shmfd; 253 off_t foffset; 254 int error; 255 256 shmfd = fp->f_data; 257 foffset = foffset_lock(fp, 0); 258 error = 0; 259 switch (whence) { 260 case L_INCR: 261 if (foffset < 0 || 262 (offset > 0 && foffset > OFF_MAX - offset)) { 263 error = EOVERFLOW; 264 break; 265 } 266 offset += foffset; 267 break; 268 case L_XTND: 269 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) { 270 error = EOVERFLOW; 271 break; 272 } 273 offset += shmfd->shm_size; 274 break; 275 case L_SET: 276 break; 277 default: 278 error = EINVAL; 279 } 280 if (error == 0) { 281 if (offset < 0 || offset > shmfd->shm_size) 282 error = EINVAL; 283 else 284 td->td_uretoff.tdu_off = offset; 285 } 286 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0); 287 return (error); 288 } 289 290 static int 291 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 292 int flags, struct thread *td) 293 { 294 struct shmfd *shmfd; 295 void *rl_cookie; 296 int error; 297 298 shmfd = fp->f_data; 299 #ifdef MAC 300 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd); 301 if (error) 302 return (error); 303 #endif 304 foffset_lock_uio(fp, uio, flags); 305 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset, 306 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 307 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 308 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 309 foffset_unlock_uio(fp, uio, flags); 310 return (error); 311 } 312 313 static int 314 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 315 int flags, struct thread *td) 316 { 317 struct shmfd *shmfd; 318 void *rl_cookie; 319 int error; 320 321 shmfd = fp->f_data; 322 #ifdef MAC 323 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd); 324 if (error) 325 return (error); 326 #endif 327 foffset_lock_uio(fp, uio, flags); 328 if ((flags & FOF_OFFSET) == 0) { 329 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX, 330 &shmfd->shm_mtx); 331 } else { 332 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset, 333 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 334 } 335 336 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 337 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 338 foffset_unlock_uio(fp, uio, flags); 339 return (error); 340 } 341 342 static int 343 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 344 struct thread *td) 345 { 346 struct shmfd *shmfd; 347 #ifdef MAC 348 int error; 349 #endif 350 351 shmfd = fp->f_data; 352 #ifdef MAC 353 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 354 if (error) 355 return (error); 356 #endif 357 return (shm_dotruncate(shmfd, length)); 358 } 359 360 static int 361 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 362 struct thread *td) 363 { 364 struct shmfd *shmfd; 365 #ifdef MAC 366 int error; 367 #endif 368 369 shmfd = fp->f_data; 370 371 #ifdef MAC 372 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 373 if (error) 374 return (error); 375 #endif 376 377 /* 378 * Attempt to return sanish values for fstat() on a memory file 379 * descriptor. 380 */ 381 bzero(sb, sizeof(*sb)); 382 sb->st_blksize = PAGE_SIZE; 383 sb->st_size = shmfd->shm_size; 384 sb->st_blocks = howmany(sb->st_size, sb->st_blksize); 385 mtx_lock(&shm_timestamp_lock); 386 sb->st_atim = shmfd->shm_atime; 387 sb->st_ctim = shmfd->shm_ctime; 388 sb->st_mtim = shmfd->shm_mtime; 389 sb->st_birthtim = shmfd->shm_birthtime; 390 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 391 sb->st_uid = shmfd->shm_uid; 392 sb->st_gid = shmfd->shm_gid; 393 mtx_unlock(&shm_timestamp_lock); 394 sb->st_dev = shm_dev_ino; 395 sb->st_ino = shmfd->shm_ino; 396 397 return (0); 398 } 399 400 static int 401 shm_close(struct file *fp, struct thread *td) 402 { 403 struct shmfd *shmfd; 404 405 shmfd = fp->f_data; 406 fp->f_data = NULL; 407 shm_drop(shmfd); 408 409 return (0); 410 } 411 412 int 413 shm_dotruncate(struct shmfd *shmfd, off_t length) 414 { 415 vm_object_t object; 416 vm_page_t m; 417 vm_pindex_t idx, nobjsize; 418 vm_ooffset_t delta; 419 int base, rv; 420 421 object = shmfd->shm_object; 422 VM_OBJECT_WLOCK(object); 423 if (length == shmfd->shm_size) { 424 VM_OBJECT_WUNLOCK(object); 425 return (0); 426 } 427 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 428 429 /* Are we shrinking? If so, trim the end. */ 430 if (length < shmfd->shm_size) { 431 /* 432 * Disallow any requests to shrink the size if this 433 * object is mapped into the kernel. 434 */ 435 if (shmfd->shm_kmappings > 0) { 436 VM_OBJECT_WUNLOCK(object); 437 return (EBUSY); 438 } 439 440 /* 441 * Zero the truncated part of the last page. 442 */ 443 base = length & PAGE_MASK; 444 if (base != 0) { 445 idx = OFF_TO_IDX(length); 446 retry: 447 m = vm_page_lookup(object, idx); 448 if (m != NULL) { 449 if (vm_page_sleep_if_busy(m, "shmtrc")) 450 goto retry; 451 } else if (vm_pager_has_page(object, idx, NULL, NULL)) { 452 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL); 453 if (m == NULL) { 454 VM_OBJECT_WUNLOCK(object); 455 VM_WAIT; 456 VM_OBJECT_WLOCK(object); 457 goto retry; 458 } 459 rv = vm_pager_get_pages(object, &m, 1, NULL, 460 NULL); 461 vm_page_lock(m); 462 if (rv == VM_PAGER_OK) { 463 vm_page_deactivate(m); 464 vm_page_unlock(m); 465 vm_page_xunbusy(m); 466 } else { 467 vm_page_free(m); 468 vm_page_unlock(m); 469 VM_OBJECT_WUNLOCK(object); 470 return (EIO); 471 } 472 } 473 if (m != NULL) { 474 pmap_zero_page_area(m, base, PAGE_SIZE - base); 475 KASSERT(m->valid == VM_PAGE_BITS_ALL, 476 ("shm_dotruncate: page %p is invalid", m)); 477 vm_page_dirty(m); 478 vm_pager_page_unswapped(m); 479 } 480 } 481 delta = ptoa(object->size - nobjsize); 482 483 /* Toss in memory pages. */ 484 if (nobjsize < object->size) 485 vm_object_page_remove(object, nobjsize, object->size, 486 0); 487 488 /* Toss pages from swap. */ 489 if (object->type == OBJT_SWAP) 490 swap_pager_freespace(object, nobjsize, delta); 491 492 /* Free the swap accounted for shm */ 493 swap_release_by_cred(delta, object->cred); 494 object->charge -= delta; 495 } else { 496 /* Attempt to reserve the swap */ 497 delta = ptoa(nobjsize - object->size); 498 if (!swap_reserve_by_cred(delta, object->cred)) { 499 VM_OBJECT_WUNLOCK(object); 500 return (ENOMEM); 501 } 502 object->charge += delta; 503 } 504 shmfd->shm_size = length; 505 mtx_lock(&shm_timestamp_lock); 506 vfs_timestamp(&shmfd->shm_ctime); 507 shmfd->shm_mtime = shmfd->shm_ctime; 508 mtx_unlock(&shm_timestamp_lock); 509 object->size = nobjsize; 510 VM_OBJECT_WUNLOCK(object); 511 return (0); 512 } 513 514 /* 515 * shmfd object management including creation and reference counting 516 * routines. 517 */ 518 struct shmfd * 519 shm_alloc(struct ucred *ucred, mode_t mode) 520 { 521 struct shmfd *shmfd; 522 int ino; 523 524 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 525 shmfd->shm_size = 0; 526 shmfd->shm_uid = ucred->cr_uid; 527 shmfd->shm_gid = ucred->cr_gid; 528 shmfd->shm_mode = mode; 529 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 530 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 531 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 532 shmfd->shm_object->pg_color = 0; 533 VM_OBJECT_WLOCK(shmfd->shm_object); 534 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 535 vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT); 536 VM_OBJECT_WUNLOCK(shmfd->shm_object); 537 vfs_timestamp(&shmfd->shm_birthtime); 538 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 539 shmfd->shm_birthtime; 540 ino = alloc_unr(shm_ino_unr); 541 if (ino == -1) 542 shmfd->shm_ino = 0; 543 else 544 shmfd->shm_ino = ino; 545 refcount_init(&shmfd->shm_refs, 1); 546 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF); 547 rangelock_init(&shmfd->shm_rl); 548 #ifdef MAC 549 mac_posixshm_init(shmfd); 550 mac_posixshm_create(ucred, shmfd); 551 #endif 552 553 return (shmfd); 554 } 555 556 struct shmfd * 557 shm_hold(struct shmfd *shmfd) 558 { 559 560 refcount_acquire(&shmfd->shm_refs); 561 return (shmfd); 562 } 563 564 void 565 shm_drop(struct shmfd *shmfd) 566 { 567 568 if (refcount_release(&shmfd->shm_refs)) { 569 #ifdef MAC 570 mac_posixshm_destroy(shmfd); 571 #endif 572 rangelock_destroy(&shmfd->shm_rl); 573 mtx_destroy(&shmfd->shm_mtx); 574 vm_object_deallocate(shmfd->shm_object); 575 if (shmfd->shm_ino != 0) 576 free_unr(shm_ino_unr, shmfd->shm_ino); 577 free(shmfd, M_SHMFD); 578 } 579 } 580 581 /* 582 * Determine if the credentials have sufficient permissions for a 583 * specified combination of FREAD and FWRITE. 584 */ 585 int 586 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 587 { 588 accmode_t accmode; 589 int error; 590 591 accmode = 0; 592 if (flags & FREAD) 593 accmode |= VREAD; 594 if (flags & FWRITE) 595 accmode |= VWRITE; 596 mtx_lock(&shm_timestamp_lock); 597 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 598 accmode, ucred, NULL); 599 mtx_unlock(&shm_timestamp_lock); 600 return (error); 601 } 602 603 /* 604 * Dictionary management. We maintain an in-kernel dictionary to map 605 * paths to shmfd objects. We use the FNV hash on the path to store 606 * the mappings in a hash table. 607 */ 608 static void 609 shm_init(void *arg) 610 { 611 612 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 613 sx_init(&shm_dict_lock, "shm dictionary"); 614 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 615 shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL); 616 KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized")); 617 shm_dev_ino = devfs_alloc_cdp_inode(); 618 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized")); 619 } 620 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL); 621 622 static struct shmfd * 623 shm_lookup(char *path, Fnv32_t fnv) 624 { 625 struct shm_mapping *map; 626 627 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 628 if (map->sm_fnv != fnv) 629 continue; 630 if (strcmp(map->sm_path, path) == 0) 631 return (map->sm_shmfd); 632 } 633 634 return (NULL); 635 } 636 637 static void 638 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 639 { 640 struct shm_mapping *map; 641 642 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 643 map->sm_path = path; 644 map->sm_fnv = fnv; 645 map->sm_shmfd = shm_hold(shmfd); 646 shmfd->shm_path = path; 647 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 648 } 649 650 static int 651 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 652 { 653 struct shm_mapping *map; 654 int error; 655 656 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 657 if (map->sm_fnv != fnv) 658 continue; 659 if (strcmp(map->sm_path, path) == 0) { 660 #ifdef MAC 661 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 662 if (error) 663 return (error); 664 #endif 665 error = shm_access(map->sm_shmfd, ucred, 666 FREAD | FWRITE); 667 if (error) 668 return (error); 669 map->sm_shmfd->shm_path = NULL; 670 LIST_REMOVE(map, sm_link); 671 shm_drop(map->sm_shmfd); 672 free(map->sm_path, M_SHMFD); 673 free(map, M_SHMFD); 674 return (0); 675 } 676 } 677 678 return (ENOENT); 679 } 680 681 int 682 kern_shm_open(struct thread *td, const char *userpath, int flags, mode_t mode, 683 struct filecaps *fcaps) 684 { 685 struct filedesc *fdp; 686 struct shmfd *shmfd; 687 struct file *fp; 688 char *path; 689 const char *pr_path; 690 size_t pr_pathlen; 691 Fnv32_t fnv; 692 mode_t cmode; 693 int fd, error; 694 695 #ifdef CAPABILITY_MODE 696 /* 697 * shm_open(2) is only allowed for anonymous objects. 698 */ 699 if (IN_CAPABILITY_MODE(td) && (userpath != SHM_ANON)) 700 return (ECAPMODE); 701 #endif 702 703 if ((flags & O_ACCMODE) != O_RDONLY && (flags & O_ACCMODE) != O_RDWR) 704 return (EINVAL); 705 706 if ((flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0) 707 return (EINVAL); 708 709 fdp = td->td_proc->p_fd; 710 cmode = (mode & ~fdp->fd_cmask) & ACCESSPERMS; 711 712 error = falloc_caps(td, &fp, &fd, O_CLOEXEC, fcaps); 713 if (error) 714 return (error); 715 716 /* A SHM_ANON path pointer creates an anonymous object. */ 717 if (userpath == SHM_ANON) { 718 /* A read-only anonymous object is pointless. */ 719 if ((flags & O_ACCMODE) == O_RDONLY) { 720 fdclose(td, fp, fd); 721 fdrop(fp, td); 722 return (EINVAL); 723 } 724 shmfd = shm_alloc(td->td_ucred, cmode); 725 } else { 726 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 727 pr_path = td->td_ucred->cr_prison->pr_path; 728 729 /* Construct a full pathname for jailed callers. */ 730 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0 731 : strlcpy(path, pr_path, MAXPATHLEN); 732 error = copyinstr(userpath, path + pr_pathlen, 733 MAXPATHLEN - pr_pathlen, NULL); 734 #ifdef KTRACE 735 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI)) 736 ktrnamei(path); 737 #endif 738 /* Require paths to start with a '/' character. */ 739 if (error == 0 && path[pr_pathlen] != '/') 740 error = EINVAL; 741 if (error) { 742 fdclose(td, fp, fd); 743 fdrop(fp, td); 744 free(path, M_SHMFD); 745 return (error); 746 } 747 748 fnv = fnv_32_str(path, FNV1_32_INIT); 749 sx_xlock(&shm_dict_lock); 750 shmfd = shm_lookup(path, fnv); 751 if (shmfd == NULL) { 752 /* Object does not yet exist, create it if requested. */ 753 if (flags & O_CREAT) { 754 #ifdef MAC 755 error = mac_posixshm_check_create(td->td_ucred, 756 path); 757 if (error == 0) { 758 #endif 759 shmfd = shm_alloc(td->td_ucred, cmode); 760 shm_insert(path, fnv, shmfd); 761 #ifdef MAC 762 } 763 #endif 764 } else { 765 free(path, M_SHMFD); 766 error = ENOENT; 767 } 768 } else { 769 /* 770 * Object already exists, obtain a new 771 * reference if requested and permitted. 772 */ 773 free(path, M_SHMFD); 774 if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL)) 775 error = EEXIST; 776 else { 777 #ifdef MAC 778 error = mac_posixshm_check_open(td->td_ucred, 779 shmfd, FFLAGS(flags & O_ACCMODE)); 780 if (error == 0) 781 #endif 782 error = shm_access(shmfd, td->td_ucred, 783 FFLAGS(flags & O_ACCMODE)); 784 } 785 786 /* 787 * Truncate the file back to zero length if 788 * O_TRUNC was specified and the object was 789 * opened with read/write. 790 */ 791 if (error == 0 && 792 (flags & (O_ACCMODE | O_TRUNC)) == 793 (O_RDWR | O_TRUNC)) { 794 #ifdef MAC 795 error = mac_posixshm_check_truncate( 796 td->td_ucred, fp->f_cred, shmfd); 797 if (error == 0) 798 #endif 799 shm_dotruncate(shmfd, 0); 800 } 801 if (error == 0) 802 shm_hold(shmfd); 803 } 804 sx_xunlock(&shm_dict_lock); 805 806 if (error) { 807 fdclose(td, fp, fd); 808 fdrop(fp, td); 809 return (error); 810 } 811 } 812 813 finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 814 815 td->td_retval[0] = fd; 816 fdrop(fp, td); 817 818 return (0); 819 } 820 821 /* System calls. */ 822 int 823 sys_shm_open(struct thread *td, struct shm_open_args *uap) 824 { 825 826 return (kern_shm_open(td, uap->path, uap->flags, uap->mode, NULL)); 827 } 828 829 int 830 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap) 831 { 832 char *path; 833 const char *pr_path; 834 size_t pr_pathlen; 835 Fnv32_t fnv; 836 int error; 837 838 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 839 pr_path = td->td_ucred->cr_prison->pr_path; 840 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0 841 : strlcpy(path, pr_path, MAXPATHLEN); 842 error = copyinstr(uap->path, path + pr_pathlen, MAXPATHLEN - pr_pathlen, 843 NULL); 844 if (error) { 845 free(path, M_TEMP); 846 return (error); 847 } 848 #ifdef KTRACE 849 if (KTRPOINT(curthread, KTR_NAMEI)) 850 ktrnamei(path); 851 #endif 852 fnv = fnv_32_str(path, FNV1_32_INIT); 853 sx_xlock(&shm_dict_lock); 854 error = shm_remove(path, fnv, td->td_ucred); 855 sx_xunlock(&shm_dict_lock); 856 free(path, M_TEMP); 857 858 return (error); 859 } 860 861 int 862 shm_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t objsize, 863 vm_prot_t prot, vm_prot_t cap_maxprot, int flags, 864 vm_ooffset_t foff, struct thread *td) 865 { 866 struct shmfd *shmfd; 867 vm_prot_t maxprot; 868 int error; 869 870 shmfd = fp->f_data; 871 maxprot = VM_PROT_NONE; 872 873 /* FREAD should always be set. */ 874 if ((fp->f_flag & FREAD) != 0) 875 maxprot |= VM_PROT_EXECUTE | VM_PROT_READ; 876 if ((fp->f_flag & FWRITE) != 0) 877 maxprot |= VM_PROT_WRITE; 878 879 /* Don't permit shared writable mappings on read-only descriptors. */ 880 if ((flags & MAP_SHARED) != 0 && 881 (maxprot & VM_PROT_WRITE) == 0 && 882 (prot & VM_PROT_WRITE) != 0) 883 return (EACCES); 884 maxprot &= cap_maxprot; 885 886 /* See comment in vn_mmap(). */ 887 if ( 888 #ifdef _LP64 889 objsize > OFF_MAX || 890 #endif 891 foff < 0 || foff > OFF_MAX - objsize) 892 return (EINVAL); 893 894 #ifdef MAC 895 error = mac_posixshm_check_mmap(td->td_ucred, shmfd, prot, flags); 896 if (error != 0) 897 return (error); 898 #endif 899 900 mtx_lock(&shm_timestamp_lock); 901 vfs_timestamp(&shmfd->shm_atime); 902 mtx_unlock(&shm_timestamp_lock); 903 vm_object_reference(shmfd->shm_object); 904 905 error = vm_mmap_object(map, addr, objsize, prot, maxprot, flags, 906 shmfd->shm_object, foff, FALSE, td); 907 if (error != 0) 908 vm_object_deallocate(shmfd->shm_object); 909 return (error); 910 } 911 912 static int 913 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 914 struct thread *td) 915 { 916 struct shmfd *shmfd; 917 int error; 918 919 error = 0; 920 shmfd = fp->f_data; 921 mtx_lock(&shm_timestamp_lock); 922 /* 923 * SUSv4 says that x bits of permission need not be affected. 924 * Be consistent with our shm_open there. 925 */ 926 #ifdef MAC 927 error = mac_posixshm_check_setmode(active_cred, shmfd, mode); 928 if (error != 0) 929 goto out; 930 #endif 931 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, 932 shmfd->shm_gid, VADMIN, active_cred, NULL); 933 if (error != 0) 934 goto out; 935 shmfd->shm_mode = mode & ACCESSPERMS; 936 out: 937 mtx_unlock(&shm_timestamp_lock); 938 return (error); 939 } 940 941 static int 942 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 943 struct thread *td) 944 { 945 struct shmfd *shmfd; 946 int error; 947 948 error = 0; 949 shmfd = fp->f_data; 950 mtx_lock(&shm_timestamp_lock); 951 #ifdef MAC 952 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid); 953 if (error != 0) 954 goto out; 955 #endif 956 if (uid == (uid_t)-1) 957 uid = shmfd->shm_uid; 958 if (gid == (gid_t)-1) 959 gid = shmfd->shm_gid; 960 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) || 961 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) && 962 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0))) 963 goto out; 964 shmfd->shm_uid = uid; 965 shmfd->shm_gid = gid; 966 out: 967 mtx_unlock(&shm_timestamp_lock); 968 return (error); 969 } 970 971 /* 972 * Helper routines to allow the backing object of a shared memory file 973 * descriptor to be mapped in the kernel. 974 */ 975 int 976 shm_map(struct file *fp, size_t size, off_t offset, void **memp) 977 { 978 struct shmfd *shmfd; 979 vm_offset_t kva, ofs; 980 vm_object_t obj; 981 int rv; 982 983 if (fp->f_type != DTYPE_SHM) 984 return (EINVAL); 985 shmfd = fp->f_data; 986 obj = shmfd->shm_object; 987 VM_OBJECT_WLOCK(obj); 988 /* 989 * XXXRW: This validation is probably insufficient, and subject to 990 * sign errors. It should be fixed. 991 */ 992 if (offset >= shmfd->shm_size || 993 offset + size > round_page(shmfd->shm_size)) { 994 VM_OBJECT_WUNLOCK(obj); 995 return (EINVAL); 996 } 997 998 shmfd->shm_kmappings++; 999 vm_object_reference_locked(obj); 1000 VM_OBJECT_WUNLOCK(obj); 1001 1002 /* Map the object into the kernel_map and wire it. */ 1003 kva = vm_map_min(kernel_map); 1004 ofs = offset & PAGE_MASK; 1005 offset = trunc_page(offset); 1006 size = round_page(size + ofs); 1007 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0, 1008 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE, 1009 VM_PROT_READ | VM_PROT_WRITE, 0); 1010 if (rv == KERN_SUCCESS) { 1011 rv = vm_map_wire(kernel_map, kva, kva + size, 1012 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 1013 if (rv == KERN_SUCCESS) { 1014 *memp = (void *)(kva + ofs); 1015 return (0); 1016 } 1017 vm_map_remove(kernel_map, kva, kva + size); 1018 } else 1019 vm_object_deallocate(obj); 1020 1021 /* On failure, drop our mapping reference. */ 1022 VM_OBJECT_WLOCK(obj); 1023 shmfd->shm_kmappings--; 1024 VM_OBJECT_WUNLOCK(obj); 1025 1026 return (vm_mmap_to_errno(rv)); 1027 } 1028 1029 /* 1030 * We require the caller to unmap the entire entry. This allows us to 1031 * safely decrement shm_kmappings when a mapping is removed. 1032 */ 1033 int 1034 shm_unmap(struct file *fp, void *mem, size_t size) 1035 { 1036 struct shmfd *shmfd; 1037 vm_map_entry_t entry; 1038 vm_offset_t kva, ofs; 1039 vm_object_t obj; 1040 vm_pindex_t pindex; 1041 vm_prot_t prot; 1042 boolean_t wired; 1043 vm_map_t map; 1044 int rv; 1045 1046 if (fp->f_type != DTYPE_SHM) 1047 return (EINVAL); 1048 shmfd = fp->f_data; 1049 kva = (vm_offset_t)mem; 1050 ofs = kva & PAGE_MASK; 1051 kva = trunc_page(kva); 1052 size = round_page(size + ofs); 1053 map = kernel_map; 1054 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 1055 &obj, &pindex, &prot, &wired); 1056 if (rv != KERN_SUCCESS) 1057 return (EINVAL); 1058 if (entry->start != kva || entry->end != kva + size) { 1059 vm_map_lookup_done(map, entry); 1060 return (EINVAL); 1061 } 1062 vm_map_lookup_done(map, entry); 1063 if (obj != shmfd->shm_object) 1064 return (EINVAL); 1065 vm_map_remove(map, kva, kva + size); 1066 VM_OBJECT_WLOCK(obj); 1067 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 1068 shmfd->shm_kmappings--; 1069 VM_OBJECT_WUNLOCK(obj); 1070 return (0); 1071 } 1072 1073 static int 1074 shm_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp) 1075 { 1076 const char *path, *pr_path; 1077 struct shmfd *shmfd; 1078 size_t pr_pathlen; 1079 1080 kif->kf_type = KF_TYPE_SHM; 1081 shmfd = fp->f_data; 1082 1083 mtx_lock(&shm_timestamp_lock); 1084 kif->kf_un.kf_file.kf_file_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 1085 mtx_unlock(&shm_timestamp_lock); 1086 kif->kf_un.kf_file.kf_file_size = shmfd->shm_size; 1087 if (shmfd->shm_path != NULL) { 1088 sx_slock(&shm_dict_lock); 1089 if (shmfd->shm_path != NULL) { 1090 path = shmfd->shm_path; 1091 pr_path = curthread->td_ucred->cr_prison->pr_path; 1092 if (strcmp(pr_path, "/") != 0) { 1093 /* Return the jail-rooted pathname. */ 1094 pr_pathlen = strlen(pr_path); 1095 if (strncmp(path, pr_path, pr_pathlen) == 0 && 1096 path[pr_pathlen] == '/') 1097 path += pr_pathlen; 1098 } 1099 strlcpy(kif->kf_path, path, sizeof(kif->kf_path)); 1100 } 1101 sx_sunlock(&shm_dict_lock); 1102 } 1103 return (0); 1104 }
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