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 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2006, 2011, 2016-2017 Robert N. M. Watson 5 * All rights reserved. 6 * 7 * Portions of this software were developed by BAE Systems, the University of 8 * Cambridge Computer Laboratory, and Memorial University under DARPA/AFRL 9 * contract FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent 10 * Computing (TC) research program. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Support for shared swap-backed anonymous memory objects via 36 * shm_open(2) and shm_unlink(2). While most of the implementation is 37 * here, vm_mmap.c contains mapping logic changes. 38 * 39 * TODO: 40 * 41 * (1) Need to export data to a userland tool via a sysctl. Should ipcs(1) 42 * and ipcrm(1) be expanded or should new tools to manage both POSIX 43 * kernel semaphores and POSIX shared memory be written? 44 * 45 * (2) Add support for this file type to fstat(1). 46 * 47 * (3) Resource limits? Does this need its own resource limits or are the 48 * existing limits in mmap(2) sufficient? 49 */ 50 51 #include <sys/cdefs.h> 52 __FBSDID("$FreeBSD: releng/12.0/sys/kern/uipc_shm.c 326271 2017-11-27 15:20:12Z pfg $"); 53 54 #include "opt_capsicum.h" 55 #include "opt_ktrace.h" 56 57 #include <sys/param.h> 58 #include <sys/capsicum.h> 59 #include <sys/conf.h> 60 #include <sys/fcntl.h> 61 #include <sys/file.h> 62 #include <sys/filedesc.h> 63 #include <sys/fnv_hash.h> 64 #include <sys/kernel.h> 65 #include <sys/uio.h> 66 #include <sys/signal.h> 67 #include <sys/jail.h> 68 #include <sys/ktrace.h> 69 #include <sys/lock.h> 70 #include <sys/malloc.h> 71 #include <sys/mman.h> 72 #include <sys/mutex.h> 73 #include <sys/priv.h> 74 #include <sys/proc.h> 75 #include <sys/refcount.h> 76 #include <sys/resourcevar.h> 77 #include <sys/rwlock.h> 78 #include <sys/stat.h> 79 #include <sys/syscallsubr.h> 80 #include <sys/sysctl.h> 81 #include <sys/sysproto.h> 82 #include <sys/systm.h> 83 #include <sys/sx.h> 84 #include <sys/time.h> 85 #include <sys/vnode.h> 86 #include <sys/unistd.h> 87 #include <sys/user.h> 88 89 #include <security/audit/audit.h> 90 #include <security/mac/mac_framework.h> 91 92 #include <vm/vm.h> 93 #include <vm/vm_param.h> 94 #include <vm/pmap.h> 95 #include <vm/vm_extern.h> 96 #include <vm/vm_map.h> 97 #include <vm/vm_kern.h> 98 #include <vm/vm_object.h> 99 #include <vm/vm_page.h> 100 #include <vm/vm_pageout.h> 101 #include <vm/vm_pager.h> 102 #include <vm/swap_pager.h> 103 104 struct shm_mapping { 105 char *sm_path; 106 Fnv32_t sm_fnv; 107 struct shmfd *sm_shmfd; 108 LIST_ENTRY(shm_mapping) sm_link; 109 }; 110 111 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 112 static LIST_HEAD(, shm_mapping) *shm_dictionary; 113 static struct sx shm_dict_lock; 114 static struct mtx shm_timestamp_lock; 115 static u_long shm_hash; 116 static struct unrhdr *shm_ino_unr; 117 static dev_t shm_dev_ino; 118 119 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 120 121 static void shm_init(void *arg); 122 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 123 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 124 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 125 126 static fo_rdwr_t shm_read; 127 static fo_rdwr_t shm_write; 128 static fo_truncate_t shm_truncate; 129 static fo_stat_t shm_stat; 130 static fo_close_t shm_close; 131 static fo_chmod_t shm_chmod; 132 static fo_chown_t shm_chown; 133 static fo_seek_t shm_seek; 134 static fo_fill_kinfo_t shm_fill_kinfo; 135 static fo_mmap_t shm_mmap; 136 137 /* File descriptor operations. */ 138 struct fileops shm_ops = { 139 .fo_read = shm_read, 140 .fo_write = shm_write, 141 .fo_truncate = shm_truncate, 142 .fo_ioctl = invfo_ioctl, 143 .fo_poll = invfo_poll, 144 .fo_kqfilter = invfo_kqfilter, 145 .fo_stat = shm_stat, 146 .fo_close = shm_close, 147 .fo_chmod = shm_chmod, 148 .fo_chown = shm_chown, 149 .fo_sendfile = vn_sendfile, 150 .fo_seek = shm_seek, 151 .fo_fill_kinfo = shm_fill_kinfo, 152 .fo_mmap = shm_mmap, 153 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE 154 }; 155 156 FEATURE(posix_shm, "POSIX shared memory"); 157 158 static int 159 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio) 160 { 161 vm_page_t m; 162 vm_pindex_t idx; 163 size_t tlen; 164 int error, offset, rv; 165 166 idx = OFF_TO_IDX(uio->uio_offset); 167 offset = uio->uio_offset & PAGE_MASK; 168 tlen = MIN(PAGE_SIZE - offset, len); 169 170 VM_OBJECT_WLOCK(obj); 171 172 /* 173 * Read I/O without either a corresponding resident page or swap 174 * page: use zero_region. This is intended to avoid instantiating 175 * pages on read from a sparse region. 176 */ 177 if (uio->uio_rw == UIO_READ && vm_page_lookup(obj, idx) == NULL && 178 !vm_pager_has_page(obj, idx, NULL, NULL)) { 179 VM_OBJECT_WUNLOCK(obj); 180 return (uiomove(__DECONST(void *, zero_region), tlen, uio)); 181 } 182 183 /* 184 * Parallel reads of the page content from disk are prevented 185 * by exclusive busy. 186 * 187 * Although the tmpfs vnode lock is held here, it is 188 * nonetheless safe to sleep waiting for a free page. The 189 * pageout daemon does not need to acquire the tmpfs vnode 190 * lock to page out tobj's pages because tobj is a OBJT_SWAP 191 * type object. 192 */ 193 m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY); 194 if (m->valid != VM_PAGE_BITS_ALL) { 195 vm_page_xbusy(m); 196 if (vm_pager_has_page(obj, idx, NULL, NULL)) { 197 rv = vm_pager_get_pages(obj, &m, 1, NULL, NULL); 198 if (rv != VM_PAGER_OK) { 199 printf( 200 "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n", 201 obj, idx, m->valid, rv); 202 vm_page_lock(m); 203 vm_page_free(m); 204 vm_page_unlock(m); 205 VM_OBJECT_WUNLOCK(obj); 206 return (EIO); 207 } 208 } else 209 vm_page_zero_invalid(m, TRUE); 210 vm_page_xunbusy(m); 211 } 212 vm_page_lock(m); 213 vm_page_hold(m); 214 if (vm_page_active(m)) 215 vm_page_reference(m); 216 else 217 vm_page_activate(m); 218 vm_page_unlock(m); 219 VM_OBJECT_WUNLOCK(obj); 220 error = uiomove_fromphys(&m, offset, tlen, uio); 221 if (uio->uio_rw == UIO_WRITE && error == 0) { 222 VM_OBJECT_WLOCK(obj); 223 vm_page_dirty(m); 224 vm_pager_page_unswapped(m); 225 VM_OBJECT_WUNLOCK(obj); 226 } 227 vm_page_lock(m); 228 vm_page_unhold(m); 229 vm_page_unlock(m); 230 231 return (error); 232 } 233 234 int 235 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio) 236 { 237 ssize_t resid; 238 size_t len; 239 int error; 240 241 error = 0; 242 while ((resid = uio->uio_resid) > 0) { 243 if (obj_size <= uio->uio_offset) 244 break; 245 len = MIN(obj_size - uio->uio_offset, resid); 246 if (len == 0) 247 break; 248 error = uiomove_object_page(obj, len, uio); 249 if (error != 0 || resid == uio->uio_resid) 250 break; 251 } 252 return (error); 253 } 254 255 static int 256 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td) 257 { 258 struct shmfd *shmfd; 259 off_t foffset; 260 int error; 261 262 shmfd = fp->f_data; 263 foffset = foffset_lock(fp, 0); 264 error = 0; 265 switch (whence) { 266 case L_INCR: 267 if (foffset < 0 || 268 (offset > 0 && foffset > OFF_MAX - offset)) { 269 error = EOVERFLOW; 270 break; 271 } 272 offset += foffset; 273 break; 274 case L_XTND: 275 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) { 276 error = EOVERFLOW; 277 break; 278 } 279 offset += shmfd->shm_size; 280 break; 281 case L_SET: 282 break; 283 default: 284 error = EINVAL; 285 } 286 if (error == 0) { 287 if (offset < 0 || offset > shmfd->shm_size) 288 error = EINVAL; 289 else 290 td->td_uretoff.tdu_off = offset; 291 } 292 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0); 293 return (error); 294 } 295 296 static int 297 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 298 int flags, struct thread *td) 299 { 300 struct shmfd *shmfd; 301 void *rl_cookie; 302 int error; 303 304 shmfd = fp->f_data; 305 #ifdef MAC 306 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd); 307 if (error) 308 return (error); 309 #endif 310 foffset_lock_uio(fp, uio, flags); 311 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset, 312 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 313 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 314 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 315 foffset_unlock_uio(fp, uio, flags); 316 return (error); 317 } 318 319 static int 320 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 321 int flags, struct thread *td) 322 { 323 struct shmfd *shmfd; 324 void *rl_cookie; 325 int error; 326 327 shmfd = fp->f_data; 328 #ifdef MAC 329 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd); 330 if (error) 331 return (error); 332 #endif 333 foffset_lock_uio(fp, uio, flags); 334 if ((flags & FOF_OFFSET) == 0) { 335 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX, 336 &shmfd->shm_mtx); 337 } else { 338 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset, 339 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 340 } 341 342 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 343 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 344 foffset_unlock_uio(fp, uio, flags); 345 return (error); 346 } 347 348 static int 349 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 350 struct thread *td) 351 { 352 struct shmfd *shmfd; 353 #ifdef MAC 354 int error; 355 #endif 356 357 shmfd = fp->f_data; 358 #ifdef MAC 359 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 360 if (error) 361 return (error); 362 #endif 363 return (shm_dotruncate(shmfd, length)); 364 } 365 366 static int 367 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 368 struct thread *td) 369 { 370 struct shmfd *shmfd; 371 #ifdef MAC 372 int error; 373 #endif 374 375 shmfd = fp->f_data; 376 377 #ifdef MAC 378 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 379 if (error) 380 return (error); 381 #endif 382 383 /* 384 * Attempt to return sanish values for fstat() on a memory file 385 * descriptor. 386 */ 387 bzero(sb, sizeof(*sb)); 388 sb->st_blksize = PAGE_SIZE; 389 sb->st_size = shmfd->shm_size; 390 sb->st_blocks = howmany(sb->st_size, sb->st_blksize); 391 mtx_lock(&shm_timestamp_lock); 392 sb->st_atim = shmfd->shm_atime; 393 sb->st_ctim = shmfd->shm_ctime; 394 sb->st_mtim = shmfd->shm_mtime; 395 sb->st_birthtim = shmfd->shm_birthtime; 396 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 397 sb->st_uid = shmfd->shm_uid; 398 sb->st_gid = shmfd->shm_gid; 399 mtx_unlock(&shm_timestamp_lock); 400 sb->st_dev = shm_dev_ino; 401 sb->st_ino = shmfd->shm_ino; 402 403 return (0); 404 } 405 406 static int 407 shm_close(struct file *fp, struct thread *td) 408 { 409 struct shmfd *shmfd; 410 411 shmfd = fp->f_data; 412 fp->f_data = NULL; 413 shm_drop(shmfd); 414 415 return (0); 416 } 417 418 int 419 shm_dotruncate(struct shmfd *shmfd, off_t length) 420 { 421 vm_object_t object; 422 vm_page_t m; 423 vm_pindex_t idx, nobjsize; 424 vm_ooffset_t delta; 425 int base, rv; 426 427 KASSERT(length >= 0, ("shm_dotruncate: length < 0")); 428 object = shmfd->shm_object; 429 VM_OBJECT_WLOCK(object); 430 if (length == shmfd->shm_size) { 431 VM_OBJECT_WUNLOCK(object); 432 return (0); 433 } 434 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 435 436 /* Are we shrinking? If so, trim the end. */ 437 if (length < shmfd->shm_size) { 438 /* 439 * Disallow any requests to shrink the size if this 440 * object is mapped into the kernel. 441 */ 442 if (shmfd->shm_kmappings > 0) { 443 VM_OBJECT_WUNLOCK(object); 444 return (EBUSY); 445 } 446 447 /* 448 * Zero the truncated part of the last page. 449 */ 450 base = length & PAGE_MASK; 451 if (base != 0) { 452 idx = OFF_TO_IDX(length); 453 retry: 454 m = vm_page_lookup(object, idx); 455 if (m != NULL) { 456 if (vm_page_sleep_if_busy(m, "shmtrc")) 457 goto retry; 458 } else if (vm_pager_has_page(object, idx, NULL, NULL)) { 459 m = vm_page_alloc(object, idx, 460 VM_ALLOC_NORMAL | VM_ALLOC_WAITFAIL); 461 if (m == NULL) 462 goto retry; 463 rv = vm_pager_get_pages(object, &m, 1, NULL, 464 NULL); 465 vm_page_lock(m); 466 if (rv == VM_PAGER_OK) { 467 /* 468 * Since the page was not resident, 469 * and therefore not recently 470 * accessed, immediately enqueue it 471 * for asynchronous laundering. The 472 * current operation is not regarded 473 * as an access. 474 */ 475 vm_page_launder(m); 476 vm_page_unlock(m); 477 vm_page_xunbusy(m); 478 } else { 479 vm_page_free(m); 480 vm_page_unlock(m); 481 VM_OBJECT_WUNLOCK(object); 482 return (EIO); 483 } 484 } 485 if (m != NULL) { 486 pmap_zero_page_area(m, base, PAGE_SIZE - base); 487 KASSERT(m->valid == VM_PAGE_BITS_ALL, 488 ("shm_dotruncate: page %p is invalid", m)); 489 vm_page_dirty(m); 490 vm_pager_page_unswapped(m); 491 } 492 } 493 delta = IDX_TO_OFF(object->size - nobjsize); 494 495 /* Toss in memory pages. */ 496 if (nobjsize < object->size) 497 vm_object_page_remove(object, nobjsize, object->size, 498 0); 499 500 /* Toss pages from swap. */ 501 if (object->type == OBJT_SWAP) 502 swap_pager_freespace(object, nobjsize, delta); 503 504 /* Free the swap accounted for shm */ 505 swap_release_by_cred(delta, object->cred); 506 object->charge -= delta; 507 } else { 508 /* Try to reserve additional swap space. */ 509 delta = IDX_TO_OFF(nobjsize - object->size); 510 if (!swap_reserve_by_cred(delta, object->cred)) { 511 VM_OBJECT_WUNLOCK(object); 512 return (ENOMEM); 513 } 514 object->charge += delta; 515 } 516 shmfd->shm_size = length; 517 mtx_lock(&shm_timestamp_lock); 518 vfs_timestamp(&shmfd->shm_ctime); 519 shmfd->shm_mtime = shmfd->shm_ctime; 520 mtx_unlock(&shm_timestamp_lock); 521 object->size = nobjsize; 522 VM_OBJECT_WUNLOCK(object); 523 return (0); 524 } 525 526 /* 527 * shmfd object management including creation and reference counting 528 * routines. 529 */ 530 struct shmfd * 531 shm_alloc(struct ucred *ucred, mode_t mode) 532 { 533 struct shmfd *shmfd; 534 int ino; 535 536 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 537 shmfd->shm_size = 0; 538 shmfd->shm_uid = ucred->cr_uid; 539 shmfd->shm_gid = ucred->cr_gid; 540 shmfd->shm_mode = mode; 541 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL, 542 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 543 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 544 shmfd->shm_object->pg_color = 0; 545 VM_OBJECT_WLOCK(shmfd->shm_object); 546 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 547 vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT); 548 VM_OBJECT_WUNLOCK(shmfd->shm_object); 549 vfs_timestamp(&shmfd->shm_birthtime); 550 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 551 shmfd->shm_birthtime; 552 ino = alloc_unr(shm_ino_unr); 553 if (ino == -1) 554 shmfd->shm_ino = 0; 555 else 556 shmfd->shm_ino = ino; 557 refcount_init(&shmfd->shm_refs, 1); 558 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF); 559 rangelock_init(&shmfd->shm_rl); 560 #ifdef MAC 561 mac_posixshm_init(shmfd); 562 mac_posixshm_create(ucred, shmfd); 563 #endif 564 565 return (shmfd); 566 } 567 568 struct shmfd * 569 shm_hold(struct shmfd *shmfd) 570 { 571 572 refcount_acquire(&shmfd->shm_refs); 573 return (shmfd); 574 } 575 576 void 577 shm_drop(struct shmfd *shmfd) 578 { 579 580 if (refcount_release(&shmfd->shm_refs)) { 581 #ifdef MAC 582 mac_posixshm_destroy(shmfd); 583 #endif 584 rangelock_destroy(&shmfd->shm_rl); 585 mtx_destroy(&shmfd->shm_mtx); 586 vm_object_deallocate(shmfd->shm_object); 587 if (shmfd->shm_ino != 0) 588 free_unr(shm_ino_unr, shmfd->shm_ino); 589 free(shmfd, M_SHMFD); 590 } 591 } 592 593 /* 594 * Determine if the credentials have sufficient permissions for a 595 * specified combination of FREAD and FWRITE. 596 */ 597 int 598 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 599 { 600 accmode_t accmode; 601 int error; 602 603 accmode = 0; 604 if (flags & FREAD) 605 accmode |= VREAD; 606 if (flags & FWRITE) 607 accmode |= VWRITE; 608 mtx_lock(&shm_timestamp_lock); 609 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 610 accmode, ucred, NULL); 611 mtx_unlock(&shm_timestamp_lock); 612 return (error); 613 } 614 615 /* 616 * Dictionary management. We maintain an in-kernel dictionary to map 617 * paths to shmfd objects. We use the FNV hash on the path to store 618 * the mappings in a hash table. 619 */ 620 static void 621 shm_init(void *arg) 622 { 623 624 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 625 sx_init(&shm_dict_lock, "shm dictionary"); 626 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 627 shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL); 628 KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized")); 629 shm_dev_ino = devfs_alloc_cdp_inode(); 630 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized")); 631 } 632 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL); 633 634 static struct shmfd * 635 shm_lookup(char *path, Fnv32_t fnv) 636 { 637 struct shm_mapping *map; 638 639 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 640 if (map->sm_fnv != fnv) 641 continue; 642 if (strcmp(map->sm_path, path) == 0) 643 return (map->sm_shmfd); 644 } 645 646 return (NULL); 647 } 648 649 static void 650 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 651 { 652 struct shm_mapping *map; 653 654 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 655 map->sm_path = path; 656 map->sm_fnv = fnv; 657 map->sm_shmfd = shm_hold(shmfd); 658 shmfd->shm_path = path; 659 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 660 } 661 662 static int 663 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 664 { 665 struct shm_mapping *map; 666 int error; 667 668 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 669 if (map->sm_fnv != fnv) 670 continue; 671 if (strcmp(map->sm_path, path) == 0) { 672 #ifdef MAC 673 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 674 if (error) 675 return (error); 676 #endif 677 error = shm_access(map->sm_shmfd, ucred, 678 FREAD | FWRITE); 679 if (error) 680 return (error); 681 map->sm_shmfd->shm_path = NULL; 682 LIST_REMOVE(map, sm_link); 683 shm_drop(map->sm_shmfd); 684 free(map->sm_path, M_SHMFD); 685 free(map, M_SHMFD); 686 return (0); 687 } 688 } 689 690 return (ENOENT); 691 } 692 693 int 694 kern_shm_open(struct thread *td, const char *userpath, int flags, mode_t mode, 695 struct filecaps *fcaps) 696 { 697 struct filedesc *fdp; 698 struct shmfd *shmfd; 699 struct file *fp; 700 char *path; 701 const char *pr_path; 702 size_t pr_pathlen; 703 Fnv32_t fnv; 704 mode_t cmode; 705 int fd, error; 706 707 #ifdef CAPABILITY_MODE 708 /* 709 * shm_open(2) is only allowed for anonymous objects. 710 */ 711 if (IN_CAPABILITY_MODE(td) && (userpath != SHM_ANON)) 712 return (ECAPMODE); 713 #endif 714 715 AUDIT_ARG_FFLAGS(flags); 716 AUDIT_ARG_MODE(mode); 717 718 if ((flags & O_ACCMODE) != O_RDONLY && (flags & O_ACCMODE) != O_RDWR) 719 return (EINVAL); 720 721 if ((flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0) 722 return (EINVAL); 723 724 fdp = td->td_proc->p_fd; 725 cmode = (mode & ~fdp->fd_cmask) & ACCESSPERMS; 726 727 error = falloc_caps(td, &fp, &fd, O_CLOEXEC, fcaps); 728 if (error) 729 return (error); 730 731 /* A SHM_ANON path pointer creates an anonymous object. */ 732 if (userpath == SHM_ANON) { 733 /* A read-only anonymous object is pointless. */ 734 if ((flags & O_ACCMODE) == O_RDONLY) { 735 fdclose(td, fp, fd); 736 fdrop(fp, td); 737 return (EINVAL); 738 } 739 shmfd = shm_alloc(td->td_ucred, cmode); 740 } else { 741 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 742 pr_path = td->td_ucred->cr_prison->pr_path; 743 744 /* Construct a full pathname for jailed callers. */ 745 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0 746 : strlcpy(path, pr_path, MAXPATHLEN); 747 error = copyinstr(userpath, path + pr_pathlen, 748 MAXPATHLEN - pr_pathlen, NULL); 749 #ifdef KTRACE 750 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI)) 751 ktrnamei(path); 752 #endif 753 /* Require paths to start with a '/' character. */ 754 if (error == 0 && path[pr_pathlen] != '/') 755 error = EINVAL; 756 if (error) { 757 fdclose(td, fp, fd); 758 fdrop(fp, td); 759 free(path, M_SHMFD); 760 return (error); 761 } 762 763 AUDIT_ARG_UPATH1_CANON(path); 764 fnv = fnv_32_str(path, FNV1_32_INIT); 765 sx_xlock(&shm_dict_lock); 766 shmfd = shm_lookup(path, fnv); 767 if (shmfd == NULL) { 768 /* Object does not yet exist, create it if requested. */ 769 if (flags & O_CREAT) { 770 #ifdef MAC 771 error = mac_posixshm_check_create(td->td_ucred, 772 path); 773 if (error == 0) { 774 #endif 775 shmfd = shm_alloc(td->td_ucred, cmode); 776 shm_insert(path, fnv, shmfd); 777 #ifdef MAC 778 } 779 #endif 780 } else { 781 free(path, M_SHMFD); 782 error = ENOENT; 783 } 784 } else { 785 /* 786 * Object already exists, obtain a new 787 * reference if requested and permitted. 788 */ 789 free(path, M_SHMFD); 790 if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL)) 791 error = EEXIST; 792 else { 793 #ifdef MAC 794 error = mac_posixshm_check_open(td->td_ucred, 795 shmfd, FFLAGS(flags & O_ACCMODE)); 796 if (error == 0) 797 #endif 798 error = shm_access(shmfd, td->td_ucred, 799 FFLAGS(flags & O_ACCMODE)); 800 } 801 802 /* 803 * Truncate the file back to zero length if 804 * O_TRUNC was specified and the object was 805 * opened with read/write. 806 */ 807 if (error == 0 && 808 (flags & (O_ACCMODE | O_TRUNC)) == 809 (O_RDWR | O_TRUNC)) { 810 #ifdef MAC 811 error = mac_posixshm_check_truncate( 812 td->td_ucred, fp->f_cred, shmfd); 813 if (error == 0) 814 #endif 815 shm_dotruncate(shmfd, 0); 816 } 817 if (error == 0) 818 shm_hold(shmfd); 819 } 820 sx_xunlock(&shm_dict_lock); 821 822 if (error) { 823 fdclose(td, fp, fd); 824 fdrop(fp, td); 825 return (error); 826 } 827 } 828 829 finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 830 831 td->td_retval[0] = fd; 832 fdrop(fp, td); 833 834 return (0); 835 } 836 837 /* System calls. */ 838 int 839 sys_shm_open(struct thread *td, struct shm_open_args *uap) 840 { 841 842 return (kern_shm_open(td, uap->path, uap->flags, uap->mode, NULL)); 843 } 844 845 int 846 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap) 847 { 848 char *path; 849 const char *pr_path; 850 size_t pr_pathlen; 851 Fnv32_t fnv; 852 int error; 853 854 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 855 pr_path = td->td_ucred->cr_prison->pr_path; 856 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0 857 : strlcpy(path, pr_path, MAXPATHLEN); 858 error = copyinstr(uap->path, path + pr_pathlen, MAXPATHLEN - pr_pathlen, 859 NULL); 860 if (error) { 861 free(path, M_TEMP); 862 return (error); 863 } 864 #ifdef KTRACE 865 if (KTRPOINT(curthread, KTR_NAMEI)) 866 ktrnamei(path); 867 #endif 868 AUDIT_ARG_UPATH1_CANON(path); 869 fnv = fnv_32_str(path, FNV1_32_INIT); 870 sx_xlock(&shm_dict_lock); 871 error = shm_remove(path, fnv, td->td_ucred); 872 sx_xunlock(&shm_dict_lock); 873 free(path, M_TEMP); 874 875 return (error); 876 } 877 878 int 879 shm_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t objsize, 880 vm_prot_t prot, vm_prot_t cap_maxprot, int flags, 881 vm_ooffset_t foff, struct thread *td) 882 { 883 struct shmfd *shmfd; 884 vm_prot_t maxprot; 885 int error; 886 887 shmfd = fp->f_data; 888 maxprot = VM_PROT_NONE; 889 890 /* FREAD should always be set. */ 891 if ((fp->f_flag & FREAD) != 0) 892 maxprot |= VM_PROT_EXECUTE | VM_PROT_READ; 893 if ((fp->f_flag & FWRITE) != 0) 894 maxprot |= VM_PROT_WRITE; 895 896 /* Don't permit shared writable mappings on read-only descriptors. */ 897 if ((flags & MAP_SHARED) != 0 && 898 (maxprot & VM_PROT_WRITE) == 0 && 899 (prot & VM_PROT_WRITE) != 0) 900 return (EACCES); 901 maxprot &= cap_maxprot; 902 903 /* See comment in vn_mmap(). */ 904 if ( 905 #ifdef _LP64 906 objsize > OFF_MAX || 907 #endif 908 foff < 0 || foff > OFF_MAX - objsize) 909 return (EINVAL); 910 911 #ifdef MAC 912 error = mac_posixshm_check_mmap(td->td_ucred, shmfd, prot, flags); 913 if (error != 0) 914 return (error); 915 #endif 916 917 mtx_lock(&shm_timestamp_lock); 918 vfs_timestamp(&shmfd->shm_atime); 919 mtx_unlock(&shm_timestamp_lock); 920 vm_object_reference(shmfd->shm_object); 921 922 error = vm_mmap_object(map, addr, objsize, prot, maxprot, flags, 923 shmfd->shm_object, foff, FALSE, td); 924 if (error != 0) 925 vm_object_deallocate(shmfd->shm_object); 926 return (error); 927 } 928 929 static int 930 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 931 struct thread *td) 932 { 933 struct shmfd *shmfd; 934 int error; 935 936 error = 0; 937 shmfd = fp->f_data; 938 mtx_lock(&shm_timestamp_lock); 939 /* 940 * SUSv4 says that x bits of permission need not be affected. 941 * Be consistent with our shm_open there. 942 */ 943 #ifdef MAC 944 error = mac_posixshm_check_setmode(active_cred, shmfd, mode); 945 if (error != 0) 946 goto out; 947 #endif 948 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, 949 shmfd->shm_gid, VADMIN, active_cred, NULL); 950 if (error != 0) 951 goto out; 952 shmfd->shm_mode = mode & ACCESSPERMS; 953 out: 954 mtx_unlock(&shm_timestamp_lock); 955 return (error); 956 } 957 958 static int 959 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 960 struct thread *td) 961 { 962 struct shmfd *shmfd; 963 int error; 964 965 error = 0; 966 shmfd = fp->f_data; 967 mtx_lock(&shm_timestamp_lock); 968 #ifdef MAC 969 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid); 970 if (error != 0) 971 goto out; 972 #endif 973 if (uid == (uid_t)-1) 974 uid = shmfd->shm_uid; 975 if (gid == (gid_t)-1) 976 gid = shmfd->shm_gid; 977 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) || 978 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) && 979 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0))) 980 goto out; 981 shmfd->shm_uid = uid; 982 shmfd->shm_gid = gid; 983 out: 984 mtx_unlock(&shm_timestamp_lock); 985 return (error); 986 } 987 988 /* 989 * Helper routines to allow the backing object of a shared memory file 990 * descriptor to be mapped in the kernel. 991 */ 992 int 993 shm_map(struct file *fp, size_t size, off_t offset, void **memp) 994 { 995 struct shmfd *shmfd; 996 vm_offset_t kva, ofs; 997 vm_object_t obj; 998 int rv; 999 1000 if (fp->f_type != DTYPE_SHM) 1001 return (EINVAL); 1002 shmfd = fp->f_data; 1003 obj = shmfd->shm_object; 1004 VM_OBJECT_WLOCK(obj); 1005 /* 1006 * XXXRW: This validation is probably insufficient, and subject to 1007 * sign errors. It should be fixed. 1008 */ 1009 if (offset >= shmfd->shm_size || 1010 offset + size > round_page(shmfd->shm_size)) { 1011 VM_OBJECT_WUNLOCK(obj); 1012 return (EINVAL); 1013 } 1014 1015 shmfd->shm_kmappings++; 1016 vm_object_reference_locked(obj); 1017 VM_OBJECT_WUNLOCK(obj); 1018 1019 /* Map the object into the kernel_map and wire it. */ 1020 kva = vm_map_min(kernel_map); 1021 ofs = offset & PAGE_MASK; 1022 offset = trunc_page(offset); 1023 size = round_page(size + ofs); 1024 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0, 1025 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE, 1026 VM_PROT_READ | VM_PROT_WRITE, 0); 1027 if (rv == KERN_SUCCESS) { 1028 rv = vm_map_wire(kernel_map, kva, kva + size, 1029 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 1030 if (rv == KERN_SUCCESS) { 1031 *memp = (void *)(kva + ofs); 1032 return (0); 1033 } 1034 vm_map_remove(kernel_map, kva, kva + size); 1035 } else 1036 vm_object_deallocate(obj); 1037 1038 /* On failure, drop our mapping reference. */ 1039 VM_OBJECT_WLOCK(obj); 1040 shmfd->shm_kmappings--; 1041 VM_OBJECT_WUNLOCK(obj); 1042 1043 return (vm_mmap_to_errno(rv)); 1044 } 1045 1046 /* 1047 * We require the caller to unmap the entire entry. This allows us to 1048 * safely decrement shm_kmappings when a mapping is removed. 1049 */ 1050 int 1051 shm_unmap(struct file *fp, void *mem, size_t size) 1052 { 1053 struct shmfd *shmfd; 1054 vm_map_entry_t entry; 1055 vm_offset_t kva, ofs; 1056 vm_object_t obj; 1057 vm_pindex_t pindex; 1058 vm_prot_t prot; 1059 boolean_t wired; 1060 vm_map_t map; 1061 int rv; 1062 1063 if (fp->f_type != DTYPE_SHM) 1064 return (EINVAL); 1065 shmfd = fp->f_data; 1066 kva = (vm_offset_t)mem; 1067 ofs = kva & PAGE_MASK; 1068 kva = trunc_page(kva); 1069 size = round_page(size + ofs); 1070 map = kernel_map; 1071 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 1072 &obj, &pindex, &prot, &wired); 1073 if (rv != KERN_SUCCESS) 1074 return (EINVAL); 1075 if (entry->start != kva || entry->end != kva + size) { 1076 vm_map_lookup_done(map, entry); 1077 return (EINVAL); 1078 } 1079 vm_map_lookup_done(map, entry); 1080 if (obj != shmfd->shm_object) 1081 return (EINVAL); 1082 vm_map_remove(map, kva, kva + size); 1083 VM_OBJECT_WLOCK(obj); 1084 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 1085 shmfd->shm_kmappings--; 1086 VM_OBJECT_WUNLOCK(obj); 1087 return (0); 1088 } 1089 1090 static int 1091 shm_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp) 1092 { 1093 const char *path, *pr_path; 1094 struct shmfd *shmfd; 1095 size_t pr_pathlen; 1096 1097 kif->kf_type = KF_TYPE_SHM; 1098 shmfd = fp->f_data; 1099 1100 mtx_lock(&shm_timestamp_lock); 1101 kif->kf_un.kf_file.kf_file_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 1102 mtx_unlock(&shm_timestamp_lock); 1103 kif->kf_un.kf_file.kf_file_size = shmfd->shm_size; 1104 if (shmfd->shm_path != NULL) { 1105 sx_slock(&shm_dict_lock); 1106 if (shmfd->shm_path != NULL) { 1107 path = shmfd->shm_path; 1108 pr_path = curthread->td_ucred->cr_prison->pr_path; 1109 if (strcmp(pr_path, "/") != 0) { 1110 /* Return the jail-rooted pathname. */ 1111 pr_pathlen = strlen(pr_path); 1112 if (strncmp(path, pr_path, pr_pathlen) == 0 && 1113 path[pr_pathlen] == '/') 1114 path += pr_pathlen; 1115 } 1116 strlcpy(kif->kf_path, path, sizeof(kif->kf_path)); 1117 } 1118 sx_sunlock(&shm_dict_lock); 1119 } 1120 return (0); 1121 }
Cache object: 93f339f033430178d686b2f8692705e7
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