FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_shm.c
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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