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 * posixshmcontrol(1) allows users to inspect the state of the memory 40 * objects. Per-uid swap resource limit controls total amount of 41 * memory that user can consume for anonymous objects, including 42 * shared. 43 */ 44 45 #include <sys/cdefs.h> 46 __FBSDID("$FreeBSD$"); 47 48 #include "opt_capsicum.h" 49 #include "opt_ktrace.h" 50 51 #include <sys/param.h> 52 #include <sys/capsicum.h> 53 #include <sys/conf.h> 54 #include <sys/fcntl.h> 55 #include <sys/file.h> 56 #include <sys/filedesc.h> 57 #include <sys/filio.h> 58 #include <sys/fnv_hash.h> 59 #include <sys/kernel.h> 60 #include <sys/limits.h> 61 #include <sys/uio.h> 62 #include <sys/signal.h> 63 #include <sys/jail.h> 64 #include <sys/ktrace.h> 65 #include <sys/lock.h> 66 #include <sys/malloc.h> 67 #include <sys/mman.h> 68 #include <sys/mutex.h> 69 #include <sys/priv.h> 70 #include <sys/proc.h> 71 #include <sys/refcount.h> 72 #include <sys/resourcevar.h> 73 #include <sys/rwlock.h> 74 #include <sys/sbuf.h> 75 #include <sys/stat.h> 76 #include <sys/syscallsubr.h> 77 #include <sys/sysctl.h> 78 #include <sys/sysproto.h> 79 #include <sys/systm.h> 80 #include <sys/sx.h> 81 #include <sys/time.h> 82 #include <sys/vnode.h> 83 #include <sys/unistd.h> 84 #include <sys/user.h> 85 86 #include <security/audit/audit.h> 87 #include <security/mac/mac_framework.h> 88 89 #include <vm/vm.h> 90 #include <vm/vm_param.h> 91 #include <vm/pmap.h> 92 #include <vm/vm_extern.h> 93 #include <vm/vm_map.h> 94 #include <vm/vm_kern.h> 95 #include <vm/vm_object.h> 96 #include <vm/vm_page.h> 97 #include <vm/vm_pageout.h> 98 #include <vm/vm_pager.h> 99 #include <vm/swap_pager.h> 100 101 struct shm_mapping { 102 char *sm_path; 103 Fnv32_t sm_fnv; 104 struct shmfd *sm_shmfd; 105 LIST_ENTRY(shm_mapping) sm_link; 106 }; 107 108 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor"); 109 static LIST_HEAD(, shm_mapping) *shm_dictionary; 110 static struct sx shm_dict_lock; 111 static struct mtx shm_timestamp_lock; 112 static u_long shm_hash; 113 static struct unrhdr64 shm_ino_unr; 114 static dev_t shm_dev_ino; 115 116 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash]) 117 118 static void shm_init(void *arg); 119 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd); 120 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv); 121 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred); 122 123 static fo_rdwr_t shm_read; 124 static fo_rdwr_t shm_write; 125 static fo_truncate_t shm_truncate; 126 static fo_ioctl_t shm_ioctl; 127 static fo_stat_t shm_stat; 128 static fo_close_t shm_close; 129 static fo_chmod_t shm_chmod; 130 static fo_chown_t shm_chown; 131 static fo_seek_t shm_seek; 132 static fo_fill_kinfo_t shm_fill_kinfo; 133 static fo_mmap_t shm_mmap; 134 135 /* File descriptor operations. */ 136 struct fileops shm_ops = { 137 .fo_read = shm_read, 138 .fo_write = shm_write, 139 .fo_truncate = shm_truncate, 140 .fo_ioctl = shm_ioctl, 141 .fo_poll = invfo_poll, 142 .fo_kqfilter = invfo_kqfilter, 143 .fo_stat = shm_stat, 144 .fo_close = shm_close, 145 .fo_chmod = shm_chmod, 146 .fo_chown = shm_chown, 147 .fo_sendfile = vn_sendfile, 148 .fo_seek = shm_seek, 149 .fo_fill_kinfo = shm_fill_kinfo, 150 .fo_mmap = shm_mmap, 151 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE 152 }; 153 154 FEATURE(posix_shm, "POSIX shared memory"); 155 156 static int 157 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio) 158 { 159 vm_page_t m; 160 vm_pindex_t idx; 161 size_t tlen; 162 int error, offset, rv; 163 164 idx = OFF_TO_IDX(uio->uio_offset); 165 offset = uio->uio_offset & PAGE_MASK; 166 tlen = MIN(PAGE_SIZE - offset, len); 167 168 VM_OBJECT_WLOCK(obj); 169 170 /* 171 * Read I/O without either a corresponding resident page or swap 172 * page: use zero_region. This is intended to avoid instantiating 173 * pages on read from a sparse region. 174 */ 175 if (uio->uio_rw == UIO_READ && vm_page_lookup(obj, idx) == NULL && 176 !vm_pager_has_page(obj, idx, NULL, NULL)) { 177 VM_OBJECT_WUNLOCK(obj); 178 return (uiomove(__DECONST(void *, zero_region), tlen, uio)); 179 } 180 181 /* 182 * Parallel reads of the page content from disk are prevented 183 * by exclusive busy. 184 * 185 * Although the tmpfs vnode lock is held here, it is 186 * nonetheless safe to sleep waiting for a free page. The 187 * pageout daemon does not need to acquire the tmpfs vnode 188 * lock to page out tobj's pages because tobj is a OBJT_SWAP 189 * type object. 190 */ 191 m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL | VM_ALLOC_NOBUSY); 192 if (m->valid != VM_PAGE_BITS_ALL) { 193 vm_page_xbusy(m); 194 if (vm_pager_has_page(obj, idx, NULL, NULL)) { 195 rv = vm_pager_get_pages(obj, &m, 1, NULL, NULL); 196 if (rv != VM_PAGER_OK) { 197 printf( 198 "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n", 199 obj, idx, m->valid, rv); 200 vm_page_lock(m); 201 vm_page_free(m); 202 vm_page_unlock(m); 203 VM_OBJECT_WUNLOCK(obj); 204 return (EIO); 205 } 206 } else 207 vm_page_zero_invalid(m, TRUE); 208 vm_page_xunbusy(m); 209 } 210 vm_page_lock(m); 211 vm_page_hold(m); 212 if (vm_page_active(m)) 213 vm_page_reference(m); 214 else 215 vm_page_activate(m); 216 vm_page_unlock(m); 217 VM_OBJECT_WUNLOCK(obj); 218 error = uiomove_fromphys(&m, offset, tlen, uio); 219 if (uio->uio_rw == UIO_WRITE && error == 0) { 220 VM_OBJECT_WLOCK(obj); 221 vm_page_dirty(m); 222 vm_pager_page_unswapped(m); 223 VM_OBJECT_WUNLOCK(obj); 224 } 225 vm_page_lock(m); 226 vm_page_unhold(m); 227 vm_page_unlock(m); 228 229 return (error); 230 } 231 232 int 233 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio) 234 { 235 ssize_t resid; 236 size_t len; 237 int error; 238 239 error = 0; 240 while ((resid = uio->uio_resid) > 0) { 241 if (obj_size <= uio->uio_offset) 242 break; 243 len = MIN(obj_size - uio->uio_offset, resid); 244 if (len == 0) 245 break; 246 error = uiomove_object_page(obj, len, uio); 247 if (error != 0 || resid == uio->uio_resid) 248 break; 249 } 250 return (error); 251 } 252 253 static int 254 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td) 255 { 256 struct shmfd *shmfd; 257 off_t foffset; 258 int error; 259 260 shmfd = fp->f_data; 261 foffset = foffset_lock(fp, 0); 262 error = 0; 263 switch (whence) { 264 case L_INCR: 265 if (foffset < 0 || 266 (offset > 0 && foffset > OFF_MAX - offset)) { 267 error = EOVERFLOW; 268 break; 269 } 270 offset += foffset; 271 break; 272 case L_XTND: 273 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) { 274 error = EOVERFLOW; 275 break; 276 } 277 offset += shmfd->shm_size; 278 break; 279 case L_SET: 280 break; 281 default: 282 error = EINVAL; 283 } 284 if (error == 0) { 285 if (offset < 0 || offset > shmfd->shm_size) 286 error = EINVAL; 287 else 288 td->td_uretoff.tdu_off = offset; 289 } 290 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0); 291 return (error); 292 } 293 294 static int 295 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred, 296 int flags, struct thread *td) 297 { 298 struct shmfd *shmfd; 299 void *rl_cookie; 300 int error; 301 302 shmfd = fp->f_data; 303 #ifdef MAC 304 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd); 305 if (error) 306 return (error); 307 #endif 308 foffset_lock_uio(fp, uio, flags); 309 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset, 310 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 311 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 312 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 313 foffset_unlock_uio(fp, uio, flags); 314 return (error); 315 } 316 317 static int 318 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred, 319 int flags, struct thread *td) 320 { 321 struct shmfd *shmfd; 322 void *rl_cookie; 323 int error; 324 325 shmfd = fp->f_data; 326 #ifdef MAC 327 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd); 328 if (error) 329 return (error); 330 #endif 331 foffset_lock_uio(fp, uio, flags); 332 if ((flags & FOF_OFFSET) == 0) { 333 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX, 334 &shmfd->shm_mtx); 335 } else { 336 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset, 337 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx); 338 } 339 340 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio); 341 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx); 342 foffset_unlock_uio(fp, uio, flags); 343 return (error); 344 } 345 346 static int 347 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred, 348 struct thread *td) 349 { 350 struct shmfd *shmfd; 351 #ifdef MAC 352 int error; 353 #endif 354 355 shmfd = fp->f_data; 356 #ifdef MAC 357 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd); 358 if (error) 359 return (error); 360 #endif 361 return (shm_dotruncate(shmfd, length)); 362 } 363 364 int 365 shm_ioctl(struct file *fp, u_long com, void *data, struct ucred *active_cred, 366 struct thread *td) 367 { 368 369 switch (com) { 370 case FIONBIO: 371 case FIOASYNC: 372 /* 373 * Allow fcntl(fd, F_SETFL, O_NONBLOCK) to work, 374 * just like it would on an unlinked regular file 375 */ 376 return (0); 377 default: 378 return (ENOTTY); 379 } 380 } 381 382 static int 383 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred, 384 struct thread *td) 385 { 386 struct shmfd *shmfd; 387 #ifdef MAC 388 int error; 389 #endif 390 391 shmfd = fp->f_data; 392 393 #ifdef MAC 394 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd); 395 if (error) 396 return (error); 397 #endif 398 399 /* 400 * Attempt to return sanish values for fstat() on a memory file 401 * descriptor. 402 */ 403 bzero(sb, sizeof(*sb)); 404 sb->st_blksize = PAGE_SIZE; 405 sb->st_size = shmfd->shm_size; 406 sb->st_blocks = howmany(sb->st_size, sb->st_blksize); 407 mtx_lock(&shm_timestamp_lock); 408 sb->st_atim = shmfd->shm_atime; 409 sb->st_ctim = shmfd->shm_ctime; 410 sb->st_mtim = shmfd->shm_mtime; 411 sb->st_birthtim = shmfd->shm_birthtime; 412 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */ 413 sb->st_uid = shmfd->shm_uid; 414 sb->st_gid = shmfd->shm_gid; 415 mtx_unlock(&shm_timestamp_lock); 416 sb->st_dev = shm_dev_ino; 417 sb->st_ino = shmfd->shm_ino; 418 sb->st_nlink = shmfd->shm_object->ref_count; 419 420 return (0); 421 } 422 423 static int 424 shm_close(struct file *fp, struct thread *td) 425 { 426 struct shmfd *shmfd; 427 428 shmfd = fp->f_data; 429 fp->f_data = NULL; 430 shm_drop(shmfd); 431 432 return (0); 433 } 434 435 int 436 shm_dotruncate(struct shmfd *shmfd, off_t length) 437 { 438 vm_object_t object; 439 vm_page_t m; 440 vm_pindex_t idx, nobjsize; 441 vm_ooffset_t delta; 442 int base, rv; 443 444 KASSERT(length >= 0, ("shm_dotruncate: length < 0")); 445 object = shmfd->shm_object; 446 VM_OBJECT_WLOCK(object); 447 if (length == shmfd->shm_size) { 448 VM_OBJECT_WUNLOCK(object); 449 return (0); 450 } 451 nobjsize = OFF_TO_IDX(length + PAGE_MASK); 452 453 /* Are we shrinking? If so, trim the end. */ 454 if (length < shmfd->shm_size) { 455 /* 456 * Disallow any requests to shrink the size if this 457 * object is mapped into the kernel. 458 */ 459 if (shmfd->shm_kmappings > 0) { 460 VM_OBJECT_WUNLOCK(object); 461 return (EBUSY); 462 } 463 464 /* 465 * Zero the truncated part of the last page. 466 */ 467 base = length & PAGE_MASK; 468 if (base != 0) { 469 idx = OFF_TO_IDX(length); 470 retry: 471 m = vm_page_lookup(object, idx); 472 if (m != NULL) { 473 if (vm_page_sleep_if_busy(m, "shmtrc")) 474 goto retry; 475 } else if (vm_pager_has_page(object, idx, NULL, NULL)) { 476 m = vm_page_alloc(object, idx, 477 VM_ALLOC_NORMAL | VM_ALLOC_WAITFAIL); 478 if (m == NULL) 479 goto retry; 480 rv = vm_pager_get_pages(object, &m, 1, NULL, 481 NULL); 482 vm_page_lock(m); 483 if (rv == VM_PAGER_OK) { 484 /* 485 * Since the page was not resident, 486 * and therefore not recently 487 * accessed, immediately enqueue it 488 * for asynchronous laundering. The 489 * current operation is not regarded 490 * as an access. 491 */ 492 vm_page_launder(m); 493 vm_page_unlock(m); 494 vm_page_xunbusy(m); 495 } else { 496 vm_page_free(m); 497 vm_page_unlock(m); 498 VM_OBJECT_WUNLOCK(object); 499 return (EIO); 500 } 501 } 502 if (m != NULL) { 503 pmap_zero_page_area(m, base, PAGE_SIZE - base); 504 KASSERT(m->valid == VM_PAGE_BITS_ALL, 505 ("shm_dotruncate: page %p is invalid", m)); 506 vm_page_dirty(m); 507 vm_pager_page_unswapped(m); 508 } 509 } 510 delta = IDX_TO_OFF(object->size - nobjsize); 511 512 /* Toss in memory pages. */ 513 if (nobjsize < object->size) 514 vm_object_page_remove(object, nobjsize, object->size, 515 0); 516 517 /* Toss pages from swap. */ 518 if (object->type == OBJT_SWAP) 519 swap_pager_freespace(object, nobjsize, delta); 520 521 /* Free the swap accounted for shm */ 522 swap_release_by_cred(delta, object->cred); 523 object->charge -= delta; 524 } else { 525 /* Try to reserve additional swap space. */ 526 delta = IDX_TO_OFF(nobjsize - object->size); 527 if (!swap_reserve_by_cred(delta, object->cred)) { 528 VM_OBJECT_WUNLOCK(object); 529 return (ENOMEM); 530 } 531 object->charge += delta; 532 } 533 shmfd->shm_size = length; 534 shmfd->shm_oldsize = (size_t)length; 535 mtx_lock(&shm_timestamp_lock); 536 vfs_timestamp(&shmfd->shm_ctime); 537 shmfd->shm_mtime = shmfd->shm_ctime; 538 mtx_unlock(&shm_timestamp_lock); 539 object->size = nobjsize; 540 VM_OBJECT_WUNLOCK(object); 541 return (0); 542 } 543 544 /* 545 * shmfd object management including creation and reference counting 546 * routines. 547 */ 548 struct shmfd * 549 shm_alloc(struct ucred *ucred, mode_t mode) 550 { 551 struct shmfd *shmfd; 552 553 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO); 554 shmfd->shm_size = 0; 555 shmfd->shm_uid = ucred->cr_uid; 556 shmfd->shm_gid = ucred->cr_gid; 557 shmfd->shm_mode = mode; 558 shmfd->shm_object = vm_pager_allocate(OBJT_SWAP, NULL, 559 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred); 560 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate")); 561 shmfd->shm_object->pg_color = 0; 562 VM_OBJECT_WLOCK(shmfd->shm_object); 563 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING); 564 vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT); 565 VM_OBJECT_WUNLOCK(shmfd->shm_object); 566 vfs_timestamp(&shmfd->shm_birthtime); 567 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime = 568 shmfd->shm_birthtime; 569 shmfd->shm_ino = alloc_unr64(&shm_ino_unr); 570 refcount_init(&shmfd->shm_refs, 1); 571 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF); 572 rangelock_init(&shmfd->shm_rl); 573 #ifdef MAC 574 mac_posixshm_init(shmfd); 575 mac_posixshm_create(ucred, shmfd); 576 #endif 577 578 return (shmfd); 579 } 580 581 struct shmfd * 582 shm_hold(struct shmfd *shmfd) 583 { 584 585 refcount_acquire(&shmfd->shm_refs); 586 return (shmfd); 587 } 588 589 void 590 shm_drop(struct shmfd *shmfd) 591 { 592 593 if (refcount_release(&shmfd->shm_refs)) { 594 #ifdef MAC 595 mac_posixshm_destroy(shmfd); 596 #endif 597 rangelock_destroy(&shmfd->shm_rl); 598 mtx_destroy(&shmfd->shm_mtx); 599 vm_object_deallocate(shmfd->shm_object); 600 free(shmfd, M_SHMFD); 601 } 602 } 603 604 /* 605 * Determine if the credentials have sufficient permissions for a 606 * specified combination of FREAD and FWRITE. 607 */ 608 int 609 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags) 610 { 611 accmode_t accmode; 612 int error; 613 614 accmode = 0; 615 if (flags & FREAD) 616 accmode |= VREAD; 617 if (flags & FWRITE) 618 accmode |= VWRITE; 619 mtx_lock(&shm_timestamp_lock); 620 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid, 621 accmode, ucred, NULL); 622 mtx_unlock(&shm_timestamp_lock); 623 return (error); 624 } 625 626 static void 627 shm_init(void *arg) 628 { 629 630 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF); 631 sx_init(&shm_dict_lock, "shm dictionary"); 632 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash); 633 new_unrhdr64(&shm_ino_unr, 1); 634 shm_dev_ino = devfs_alloc_cdp_inode(); 635 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized")); 636 } 637 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL); 638 639 /* 640 * Dictionary management. We maintain an in-kernel dictionary to map 641 * paths to shmfd objects. We use the FNV hash on the path to store 642 * the mappings in a hash table. 643 */ 644 static struct shmfd * 645 shm_lookup(char *path, Fnv32_t fnv) 646 { 647 struct shm_mapping *map; 648 649 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 650 if (map->sm_fnv != fnv) 651 continue; 652 if (strcmp(map->sm_path, path) == 0) 653 return (map->sm_shmfd); 654 } 655 656 return (NULL); 657 } 658 659 static void 660 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd) 661 { 662 struct shm_mapping *map; 663 664 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK); 665 map->sm_path = path; 666 map->sm_fnv = fnv; 667 map->sm_shmfd = shm_hold(shmfd); 668 shmfd->shm_path = path; 669 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link); 670 } 671 672 static int 673 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred) 674 { 675 struct shm_mapping *map; 676 int error; 677 678 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) { 679 if (map->sm_fnv != fnv) 680 continue; 681 if (strcmp(map->sm_path, path) == 0) { 682 #ifdef MAC 683 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd); 684 if (error) 685 return (error); 686 #endif 687 error = shm_access(map->sm_shmfd, ucred, 688 FREAD | FWRITE); 689 if (error) 690 return (error); 691 map->sm_shmfd->shm_path = NULL; 692 LIST_REMOVE(map, sm_link); 693 shm_drop(map->sm_shmfd); 694 free(map->sm_path, M_SHMFD); 695 free(map, M_SHMFD); 696 return (0); 697 } 698 } 699 700 return (ENOENT); 701 } 702 703 int 704 kern_shm_open(struct thread *td, const char *userpath, int flags, mode_t mode, 705 struct filecaps *fcaps) 706 { 707 struct filedesc *fdp; 708 struct shmfd *shmfd; 709 struct file *fp; 710 char *path; 711 const char *pr_path; 712 size_t pr_pathlen; 713 Fnv32_t fnv; 714 mode_t cmode; 715 int fd, error; 716 717 #ifdef CAPABILITY_MODE 718 /* 719 * shm_open(2) is only allowed for anonymous objects. 720 */ 721 if (IN_CAPABILITY_MODE(td) && (userpath != SHM_ANON)) 722 return (ECAPMODE); 723 #endif 724 725 AUDIT_ARG_FFLAGS(flags); 726 AUDIT_ARG_MODE(mode); 727 728 if ((flags & O_ACCMODE) != O_RDONLY && (flags & O_ACCMODE) != O_RDWR) 729 return (EINVAL); 730 731 if ((flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0) 732 return (EINVAL); 733 734 fdp = td->td_proc->p_fd; 735 cmode = (mode & ~fdp->fd_cmask) & ACCESSPERMS; 736 737 /* 738 * shm_open(2) created shm should always have O_CLOEXEC set, as mandated 739 * by POSIX. We allow it to be unset here so that an in-kernel 740 * interface may be written as a thin layer around shm, optionally not 741 * setting CLOEXEC. For shm_open(2), O_CLOEXEC is set unconditionally 742 * in sys_shm_open() to keep this implementation compliant. 743 */ 744 error = falloc_caps(td, &fp, &fd, flags & O_CLOEXEC, fcaps); 745 if (error) 746 return (error); 747 748 /* A SHM_ANON path pointer creates an anonymous object. */ 749 if (userpath == SHM_ANON) { 750 /* A read-only anonymous object is pointless. */ 751 if ((flags & O_ACCMODE) == O_RDONLY) { 752 fdclose(td, fp, fd); 753 fdrop(fp, td); 754 return (EINVAL); 755 } 756 shmfd = shm_alloc(td->td_ucred, cmode); 757 } else { 758 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK); 759 pr_path = td->td_ucred->cr_prison->pr_path; 760 761 /* Construct a full pathname for jailed callers. */ 762 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0 763 : strlcpy(path, pr_path, MAXPATHLEN); 764 error = copyinstr(userpath, path + pr_pathlen, 765 MAXPATHLEN - pr_pathlen, NULL); 766 #ifdef KTRACE 767 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI)) 768 ktrnamei(path); 769 #endif 770 /* Require paths to start with a '/' character. */ 771 if (error == 0 && path[pr_pathlen] != '/') 772 error = EINVAL; 773 if (error) { 774 fdclose(td, fp, fd); 775 fdrop(fp, td); 776 free(path, M_SHMFD); 777 return (error); 778 } 779 780 AUDIT_ARG_UPATH1_CANON(path); 781 fnv = fnv_32_str(path, FNV1_32_INIT); 782 sx_xlock(&shm_dict_lock); 783 shmfd = shm_lookup(path, fnv); 784 if (shmfd == NULL) { 785 /* Object does not yet exist, create it if requested. */ 786 if (flags & O_CREAT) { 787 #ifdef MAC 788 error = mac_posixshm_check_create(td->td_ucred, 789 path); 790 if (error == 0) { 791 #endif 792 shmfd = shm_alloc(td->td_ucred, cmode); 793 shm_insert(path, fnv, shmfd); 794 #ifdef MAC 795 } 796 #endif 797 } else { 798 free(path, M_SHMFD); 799 error = ENOENT; 800 } 801 } else { 802 /* 803 * Object already exists, obtain a new 804 * reference if requested and permitted. 805 */ 806 free(path, M_SHMFD); 807 if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL)) 808 error = EEXIST; 809 else { 810 #ifdef MAC 811 error = mac_posixshm_check_open(td->td_ucred, 812 shmfd, FFLAGS(flags & O_ACCMODE)); 813 if (error == 0) 814 #endif 815 error = shm_access(shmfd, td->td_ucred, 816 FFLAGS(flags & O_ACCMODE)); 817 } 818 819 /* 820 * Truncate the file back to zero length if 821 * O_TRUNC was specified and the object was 822 * opened with read/write. 823 */ 824 if (error == 0 && 825 (flags & (O_ACCMODE | O_TRUNC)) == 826 (O_RDWR | O_TRUNC)) { 827 #ifdef MAC 828 error = mac_posixshm_check_truncate( 829 td->td_ucred, fp->f_cred, shmfd); 830 if (error == 0) 831 #endif 832 shm_dotruncate(shmfd, 0); 833 } 834 if (error == 0) 835 shm_hold(shmfd); 836 } 837 sx_xunlock(&shm_dict_lock); 838 839 if (error) { 840 fdclose(td, fp, fd); 841 fdrop(fp, td); 842 return (error); 843 } 844 } 845 846 finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops); 847 848 td->td_retval[0] = fd; 849 fdrop(fp, td); 850 851 return (0); 852 } 853 854 /* System calls. */ 855 int 856 sys_shm_open(struct thread *td, struct shm_open_args *uap) 857 { 858 859 return (kern_shm_open(td, uap->path, uap->flags | O_CLOEXEC, uap->mode, 860 NULL)); 861 } 862 863 int 864 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap) 865 { 866 char *path; 867 const char *pr_path; 868 size_t pr_pathlen; 869 Fnv32_t fnv; 870 int error; 871 872 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK); 873 pr_path = td->td_ucred->cr_prison->pr_path; 874 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0 875 : strlcpy(path, pr_path, MAXPATHLEN); 876 error = copyinstr(uap->path, path + pr_pathlen, MAXPATHLEN - pr_pathlen, 877 NULL); 878 if (error) { 879 free(path, M_TEMP); 880 return (error); 881 } 882 #ifdef KTRACE 883 if (KTRPOINT(curthread, KTR_NAMEI)) 884 ktrnamei(path); 885 #endif 886 AUDIT_ARG_UPATH1_CANON(path); 887 fnv = fnv_32_str(path, FNV1_32_INIT); 888 sx_xlock(&shm_dict_lock); 889 error = shm_remove(path, fnv, td->td_ucred); 890 sx_xunlock(&shm_dict_lock); 891 free(path, M_TEMP); 892 893 return (error); 894 } 895 896 int 897 shm_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t objsize, 898 vm_prot_t prot, vm_prot_t cap_maxprot, int flags, 899 vm_ooffset_t foff, struct thread *td) 900 { 901 struct shmfd *shmfd; 902 vm_prot_t maxprot; 903 int error; 904 bool writecnt; 905 906 shmfd = fp->f_data; 907 maxprot = VM_PROT_NONE; 908 909 /* FREAD should always be set. */ 910 if ((fp->f_flag & FREAD) != 0) 911 maxprot |= VM_PROT_EXECUTE | VM_PROT_READ; 912 if ((fp->f_flag & FWRITE) != 0) 913 maxprot |= VM_PROT_WRITE; 914 915 writecnt = (flags & MAP_SHARED) != 0 && (prot & VM_PROT_WRITE) != 0; 916 917 /* Don't permit shared writable mappings on read-only descriptors. */ 918 if (writecnt && (maxprot & VM_PROT_WRITE) == 0) 919 return (EACCES); 920 maxprot &= cap_maxprot; 921 922 /* See comment in vn_mmap(). */ 923 if ( 924 #ifdef _LP64 925 objsize > OFF_MAX || 926 #endif 927 foff < 0 || foff > OFF_MAX - objsize) 928 return (EINVAL); 929 930 #ifdef MAC 931 error = mac_posixshm_check_mmap(td->td_ucred, shmfd, prot, flags); 932 if (error != 0) 933 return (error); 934 #endif 935 936 mtx_lock(&shm_timestamp_lock); 937 vfs_timestamp(&shmfd->shm_atime); 938 mtx_unlock(&shm_timestamp_lock); 939 vm_object_reference(shmfd->shm_object); 940 941 if (writecnt) 942 vm_pager_update_writecount(shmfd->shm_object, 0, objsize); 943 error = vm_mmap_object(map, addr, objsize, prot, maxprot, flags, 944 shmfd->shm_object, foff, writecnt, td); 945 if (error != 0) { 946 if (writecnt) 947 vm_pager_release_writecount(shmfd->shm_object, 0, 948 objsize); 949 vm_object_deallocate(shmfd->shm_object); 950 } 951 return (error); 952 } 953 954 static int 955 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred, 956 struct thread *td) 957 { 958 struct shmfd *shmfd; 959 int error; 960 961 error = 0; 962 shmfd = fp->f_data; 963 mtx_lock(&shm_timestamp_lock); 964 /* 965 * SUSv4 says that x bits of permission need not be affected. 966 * Be consistent with our shm_open there. 967 */ 968 #ifdef MAC 969 error = mac_posixshm_check_setmode(active_cred, shmfd, mode); 970 if (error != 0) 971 goto out; 972 #endif 973 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, 974 shmfd->shm_gid, VADMIN, active_cred, NULL); 975 if (error != 0) 976 goto out; 977 shmfd->shm_mode = mode & ACCESSPERMS; 978 out: 979 mtx_unlock(&shm_timestamp_lock); 980 return (error); 981 } 982 983 static int 984 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred, 985 struct thread *td) 986 { 987 struct shmfd *shmfd; 988 int error; 989 990 error = 0; 991 shmfd = fp->f_data; 992 mtx_lock(&shm_timestamp_lock); 993 #ifdef MAC 994 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid); 995 if (error != 0) 996 goto out; 997 #endif 998 if (uid == (uid_t)-1) 999 uid = shmfd->shm_uid; 1000 if (gid == (gid_t)-1) 1001 gid = shmfd->shm_gid; 1002 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) || 1003 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) && 1004 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0))) 1005 goto out; 1006 shmfd->shm_uid = uid; 1007 shmfd->shm_gid = gid; 1008 out: 1009 mtx_unlock(&shm_timestamp_lock); 1010 return (error); 1011 } 1012 1013 /* 1014 * Helper routines to allow the backing object of a shared memory file 1015 * descriptor to be mapped in the kernel. 1016 */ 1017 int 1018 shm_map(struct file *fp, size_t size, off_t offset, void **memp) 1019 { 1020 struct shmfd *shmfd; 1021 vm_offset_t kva, ofs; 1022 vm_object_t obj; 1023 int rv; 1024 1025 if (fp->f_type != DTYPE_SHM) 1026 return (EINVAL); 1027 shmfd = fp->f_data; 1028 obj = shmfd->shm_object; 1029 VM_OBJECT_WLOCK(obj); 1030 /* 1031 * XXXRW: This validation is probably insufficient, and subject to 1032 * sign errors. It should be fixed. 1033 */ 1034 if (offset >= shmfd->shm_size || 1035 offset + size > round_page(shmfd->shm_size)) { 1036 VM_OBJECT_WUNLOCK(obj); 1037 return (EINVAL); 1038 } 1039 1040 shmfd->shm_kmappings++; 1041 vm_object_reference_locked(obj); 1042 VM_OBJECT_WUNLOCK(obj); 1043 1044 /* Map the object into the kernel_map and wire it. */ 1045 kva = vm_map_min(kernel_map); 1046 ofs = offset & PAGE_MASK; 1047 offset = trunc_page(offset); 1048 size = round_page(size + ofs); 1049 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0, 1050 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE, 1051 VM_PROT_READ | VM_PROT_WRITE, 0); 1052 if (rv == KERN_SUCCESS) { 1053 rv = vm_map_wire(kernel_map, kva, kva + size, 1054 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES); 1055 if (rv == KERN_SUCCESS) { 1056 *memp = (void *)(kva + ofs); 1057 return (0); 1058 } 1059 vm_map_remove(kernel_map, kva, kva + size); 1060 } else 1061 vm_object_deallocate(obj); 1062 1063 /* On failure, drop our mapping reference. */ 1064 VM_OBJECT_WLOCK(obj); 1065 shmfd->shm_kmappings--; 1066 VM_OBJECT_WUNLOCK(obj); 1067 1068 return (vm_mmap_to_errno(rv)); 1069 } 1070 1071 /* 1072 * We require the caller to unmap the entire entry. This allows us to 1073 * safely decrement shm_kmappings when a mapping is removed. 1074 */ 1075 int 1076 shm_unmap(struct file *fp, void *mem, size_t size) 1077 { 1078 struct shmfd *shmfd; 1079 vm_map_entry_t entry; 1080 vm_offset_t kva, ofs; 1081 vm_object_t obj; 1082 vm_pindex_t pindex; 1083 vm_prot_t prot; 1084 boolean_t wired; 1085 vm_map_t map; 1086 int rv; 1087 1088 if (fp->f_type != DTYPE_SHM) 1089 return (EINVAL); 1090 shmfd = fp->f_data; 1091 kva = (vm_offset_t)mem; 1092 ofs = kva & PAGE_MASK; 1093 kva = trunc_page(kva); 1094 size = round_page(size + ofs); 1095 map = kernel_map; 1096 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry, 1097 &obj, &pindex, &prot, &wired); 1098 if (rv != KERN_SUCCESS) 1099 return (EINVAL); 1100 if (entry->start != kva || entry->end != kva + size) { 1101 vm_map_lookup_done(map, entry); 1102 return (EINVAL); 1103 } 1104 vm_map_lookup_done(map, entry); 1105 if (obj != shmfd->shm_object) 1106 return (EINVAL); 1107 vm_map_remove(map, kva, kva + size); 1108 VM_OBJECT_WLOCK(obj); 1109 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped")); 1110 shmfd->shm_kmappings--; 1111 VM_OBJECT_WUNLOCK(obj); 1112 return (0); 1113 } 1114 1115 static int 1116 shm_fill_kinfo_locked(struct shmfd *shmfd, struct kinfo_file *kif, bool list) 1117 { 1118 const char *path, *pr_path; 1119 size_t pr_pathlen; 1120 bool visible; 1121 1122 sx_assert(&shm_dict_lock, SA_LOCKED); 1123 kif->kf_type = KF_TYPE_SHM; 1124 kif->kf_un.kf_file.kf_file_mode = S_IFREG | shmfd->shm_mode; 1125 kif->kf_un.kf_file.kf_file_size = shmfd->shm_size; 1126 if (shmfd->shm_path != NULL) { 1127 if (shmfd->shm_path != NULL) { 1128 path = shmfd->shm_path; 1129 pr_path = curthread->td_ucred->cr_prison->pr_path; 1130 if (strcmp(pr_path, "/") != 0) { 1131 /* Return the jail-rooted pathname. */ 1132 pr_pathlen = strlen(pr_path); 1133 visible = strncmp(path, pr_path, pr_pathlen) 1134 == 0 && path[pr_pathlen] == '/'; 1135 if (list && !visible) 1136 return (EPERM); 1137 if (visible) 1138 path += pr_pathlen; 1139 } 1140 strlcpy(kif->kf_path, path, sizeof(kif->kf_path)); 1141 } 1142 } 1143 return (0); 1144 } 1145 1146 static int 1147 shm_fill_kinfo(struct file *fp, struct kinfo_file *kif, 1148 struct filedesc *fdp __unused) 1149 { 1150 int res; 1151 1152 sx_slock(&shm_dict_lock); 1153 res = shm_fill_kinfo_locked(fp->f_data, kif, false); 1154 sx_sunlock(&shm_dict_lock); 1155 return (res); 1156 } 1157 1158 static int 1159 sysctl_posix_shm_list(SYSCTL_HANDLER_ARGS) 1160 { 1161 struct shm_mapping *shmm; 1162 struct sbuf sb; 1163 struct kinfo_file kif; 1164 u_long i; 1165 ssize_t curlen; 1166 int error, error2; 1167 1168 sbuf_new_for_sysctl(&sb, NULL, sizeof(struct kinfo_file) * 5, req); 1169 sbuf_clear_flags(&sb, SBUF_INCLUDENUL); 1170 curlen = 0; 1171 error = 0; 1172 sx_slock(&shm_dict_lock); 1173 for (i = 0; i < shm_hash + 1; i++) { 1174 LIST_FOREACH(shmm, &shm_dictionary[i], sm_link) { 1175 error = shm_fill_kinfo_locked(shmm->sm_shmfd, 1176 &kif, true); 1177 if (error == EPERM) { 1178 error = 0; 1179 continue; 1180 } 1181 if (error != 0) 1182 break; 1183 pack_kinfo(&kif); 1184 if (req->oldptr != NULL && 1185 kif.kf_structsize + curlen > req->oldlen) 1186 break; 1187 error = sbuf_bcat(&sb, &kif, kif.kf_structsize) == 0 ? 1188 0 : ENOMEM; 1189 if (error != 0) 1190 break; 1191 curlen += kif.kf_structsize; 1192 } 1193 } 1194 sx_sunlock(&shm_dict_lock); 1195 error2 = sbuf_finish(&sb); 1196 sbuf_delete(&sb); 1197 return (error != 0 ? error : error2); 1198 } 1199 1200 SYSCTL_PROC(_kern_ipc, OID_AUTO, posix_shm_list, 1201 CTLFLAG_RD | CTLFLAG_MPSAFE | CTLTYPE_OPAQUE, 1202 NULL, 0, sysctl_posix_shm_list, "", 1203 "POSIX SHM list");
Cache object: 7d4c35861e6b693e58c41f44b60a5828
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