FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_shm.c
1 /*-
2 * Copyright (c) 2006, 2011 Robert N. M. Watson
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27 /*
28 * Support for shared swap-backed anonymous memory objects via
29 * shm_open(2) and shm_unlink(2). While most of the implementation is
30 * here, vm_mmap.c contains mapping logic changes.
31 *
32 * TODO:
33 *
34 * (1) Need to export data to a userland tool via a sysctl. Should ipcs(1)
35 * and ipcrm(1) be expanded or should new tools to manage both POSIX
36 * kernel semaphores and POSIX shared memory be written?
37 *
38 * (2) Add support for this file type to fstat(1).
39 *
40 * (3) Resource limits? Does this need its own resource limits or are the
41 * existing limits in mmap(2) sufficient?
42 */
43
44 #include <sys/cdefs.h>
45 __FBSDID("$FreeBSD: releng/11.0/sys/kern/uipc_shm.c 302151 2016-06-23 20:59:13Z jilles $");
46
47 #include "opt_capsicum.h"
48 #include "opt_ktrace.h"
49
50 #include <sys/param.h>
51 #include <sys/capsicum.h>
52 #include <sys/conf.h>
53 #include <sys/fcntl.h>
54 #include <sys/file.h>
55 #include <sys/filedesc.h>
56 #include <sys/fnv_hash.h>
57 #include <sys/kernel.h>
58 #include <sys/uio.h>
59 #include <sys/signal.h>
60 #include <sys/jail.h>
61 #include <sys/ktrace.h>
62 #include <sys/lock.h>
63 #include <sys/malloc.h>
64 #include <sys/mman.h>
65 #include <sys/mutex.h>
66 #include <sys/priv.h>
67 #include <sys/proc.h>
68 #include <sys/refcount.h>
69 #include <sys/resourcevar.h>
70 #include <sys/rwlock.h>
71 #include <sys/stat.h>
72 #include <sys/syscallsubr.h>
73 #include <sys/sysctl.h>
74 #include <sys/sysproto.h>
75 #include <sys/systm.h>
76 #include <sys/sx.h>
77 #include <sys/time.h>
78 #include <sys/vnode.h>
79 #include <sys/unistd.h>
80 #include <sys/user.h>
81
82 #include <security/mac/mac_framework.h>
83
84 #include <vm/vm.h>
85 #include <vm/vm_param.h>
86 #include <vm/pmap.h>
87 #include <vm/vm_extern.h>
88 #include <vm/vm_map.h>
89 #include <vm/vm_kern.h>
90 #include <vm/vm_object.h>
91 #include <vm/vm_page.h>
92 #include <vm/vm_pageout.h>
93 #include <vm/vm_pager.h>
94 #include <vm/swap_pager.h>
95
96 struct shm_mapping {
97 char *sm_path;
98 Fnv32_t sm_fnv;
99 struct shmfd *sm_shmfd;
100 LIST_ENTRY(shm_mapping) sm_link;
101 };
102
103 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
104 static LIST_HEAD(, shm_mapping) *shm_dictionary;
105 static struct sx shm_dict_lock;
106 static struct mtx shm_timestamp_lock;
107 static u_long shm_hash;
108 static struct unrhdr *shm_ino_unr;
109 static dev_t shm_dev_ino;
110
111 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash])
112
113 static void shm_init(void *arg);
114 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
115 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
116 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
117
118 static fo_rdwr_t shm_read;
119 static fo_rdwr_t shm_write;
120 static fo_truncate_t shm_truncate;
121 static fo_stat_t shm_stat;
122 static fo_close_t shm_close;
123 static fo_chmod_t shm_chmod;
124 static fo_chown_t shm_chown;
125 static fo_seek_t shm_seek;
126 static fo_fill_kinfo_t shm_fill_kinfo;
127 static fo_mmap_t shm_mmap;
128
129 /* File descriptor operations. */
130 struct fileops shm_ops = {
131 .fo_read = shm_read,
132 .fo_write = shm_write,
133 .fo_truncate = shm_truncate,
134 .fo_ioctl = invfo_ioctl,
135 .fo_poll = invfo_poll,
136 .fo_kqfilter = invfo_kqfilter,
137 .fo_stat = shm_stat,
138 .fo_close = shm_close,
139 .fo_chmod = shm_chmod,
140 .fo_chown = shm_chown,
141 .fo_sendfile = vn_sendfile,
142 .fo_seek = shm_seek,
143 .fo_fill_kinfo = shm_fill_kinfo,
144 .fo_mmap = shm_mmap,
145 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
146 };
147
148 FEATURE(posix_shm, "POSIX shared memory");
149
150 static int
151 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
152 {
153 vm_page_t m;
154 vm_pindex_t idx;
155 size_t tlen;
156 int error, offset, rv;
157
158 idx = OFF_TO_IDX(uio->uio_offset);
159 offset = uio->uio_offset & PAGE_MASK;
160 tlen = MIN(PAGE_SIZE - offset, len);
161
162 VM_OBJECT_WLOCK(obj);
163
164 /*
165 * Read I/O without either a corresponding resident page or swap
166 * page: use zero_region. This is intended to avoid instantiating
167 * pages on read from a sparse region.
168 */
169 if (uio->uio_rw == UIO_READ && vm_page_lookup(obj, idx) == NULL &&
170 !vm_pager_has_page(obj, idx, NULL, NULL)) {
171 VM_OBJECT_WUNLOCK(obj);
172 return (uiomove(__DECONST(void *, zero_region), tlen, uio));
173 }
174
175 /*
176 * Parallel reads of the page content from disk are prevented
177 * by exclusive busy.
178 *
179 * Although the tmpfs vnode lock is held here, it is
180 * nonetheless safe to sleep waiting for a free page. The
181 * pageout daemon does not need to acquire the tmpfs vnode
182 * lock to page out tobj's pages because tobj is a OBJT_SWAP
183 * type object.
184 */
185 m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL);
186 if (m->valid != VM_PAGE_BITS_ALL) {
187 if (vm_pager_has_page(obj, idx, NULL, NULL)) {
188 rv = vm_pager_get_pages(obj, &m, 1, NULL, NULL);
189 if (rv != VM_PAGER_OK) {
190 printf(
191 "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n",
192 obj, idx, m->valid, rv);
193 vm_page_lock(m);
194 vm_page_free(m);
195 vm_page_unlock(m);
196 VM_OBJECT_WUNLOCK(obj);
197 return (EIO);
198 }
199 } else
200 vm_page_zero_invalid(m, TRUE);
201 }
202 vm_page_xunbusy(m);
203 vm_page_lock(m);
204 vm_page_hold(m);
205 if (m->queue == PQ_NONE) {
206 vm_page_deactivate(m);
207 } else {
208 /* Requeue to maintain LRU ordering. */
209 vm_page_requeue(m);
210 }
211 vm_page_unlock(m);
212 VM_OBJECT_WUNLOCK(obj);
213 error = uiomove_fromphys(&m, offset, tlen, uio);
214 if (uio->uio_rw == UIO_WRITE && error == 0) {
215 VM_OBJECT_WLOCK(obj);
216 vm_page_dirty(m);
217 vm_pager_page_unswapped(m);
218 VM_OBJECT_WUNLOCK(obj);
219 }
220 vm_page_lock(m);
221 vm_page_unhold(m);
222 vm_page_unlock(m);
223
224 return (error);
225 }
226
227 int
228 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio)
229 {
230 ssize_t resid;
231 size_t len;
232 int error;
233
234 error = 0;
235 while ((resid = uio->uio_resid) > 0) {
236 if (obj_size <= uio->uio_offset)
237 break;
238 len = MIN(obj_size - uio->uio_offset, resid);
239 if (len == 0)
240 break;
241 error = uiomove_object_page(obj, len, uio);
242 if (error != 0 || resid == uio->uio_resid)
243 break;
244 }
245 return (error);
246 }
247
248 static int
249 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td)
250 {
251 struct shmfd *shmfd;
252 off_t foffset;
253 int error;
254
255 shmfd = fp->f_data;
256 foffset = foffset_lock(fp, 0);
257 error = 0;
258 switch (whence) {
259 case L_INCR:
260 if (foffset < 0 ||
261 (offset > 0 && foffset > OFF_MAX - offset)) {
262 error = EOVERFLOW;
263 break;
264 }
265 offset += foffset;
266 break;
267 case L_XTND:
268 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) {
269 error = EOVERFLOW;
270 break;
271 }
272 offset += shmfd->shm_size;
273 break;
274 case L_SET:
275 break;
276 default:
277 error = EINVAL;
278 }
279 if (error == 0) {
280 if (offset < 0 || offset > shmfd->shm_size)
281 error = EINVAL;
282 else
283 td->td_uretoff.tdu_off = offset;
284 }
285 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
286 return (error);
287 }
288
289 static int
290 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
291 int flags, struct thread *td)
292 {
293 struct shmfd *shmfd;
294 void *rl_cookie;
295 int error;
296
297 shmfd = fp->f_data;
298 #ifdef MAC
299 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
300 if (error)
301 return (error);
302 #endif
303 foffset_lock_uio(fp, uio, flags);
304 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
305 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
306 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
307 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
308 foffset_unlock_uio(fp, uio, flags);
309 return (error);
310 }
311
312 static int
313 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
314 int flags, struct thread *td)
315 {
316 struct shmfd *shmfd;
317 void *rl_cookie;
318 int error;
319
320 shmfd = fp->f_data;
321 #ifdef MAC
322 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd);
323 if (error)
324 return (error);
325 #endif
326 foffset_lock_uio(fp, uio, flags);
327 if ((flags & FOF_OFFSET) == 0) {
328 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
329 &shmfd->shm_mtx);
330 } else {
331 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
332 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
333 }
334
335 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
336 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
337 foffset_unlock_uio(fp, uio, flags);
338 return (error);
339 }
340
341 static int
342 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
343 struct thread *td)
344 {
345 struct shmfd *shmfd;
346 #ifdef MAC
347 int error;
348 #endif
349
350 shmfd = fp->f_data;
351 #ifdef MAC
352 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
353 if (error)
354 return (error);
355 #endif
356 return (shm_dotruncate(shmfd, length));
357 }
358
359 static int
360 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
361 struct thread *td)
362 {
363 struct shmfd *shmfd;
364 #ifdef MAC
365 int error;
366 #endif
367
368 shmfd = fp->f_data;
369
370 #ifdef MAC
371 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
372 if (error)
373 return (error);
374 #endif
375
376 /*
377 * Attempt to return sanish values for fstat() on a memory file
378 * descriptor.
379 */
380 bzero(sb, sizeof(*sb));
381 sb->st_blksize = PAGE_SIZE;
382 sb->st_size = shmfd->shm_size;
383 sb->st_blocks = howmany(sb->st_size, sb->st_blksize);
384 mtx_lock(&shm_timestamp_lock);
385 sb->st_atim = shmfd->shm_atime;
386 sb->st_ctim = shmfd->shm_ctime;
387 sb->st_mtim = shmfd->shm_mtime;
388 sb->st_birthtim = shmfd->shm_birthtime;
389 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */
390 sb->st_uid = shmfd->shm_uid;
391 sb->st_gid = shmfd->shm_gid;
392 mtx_unlock(&shm_timestamp_lock);
393 sb->st_dev = shm_dev_ino;
394 sb->st_ino = shmfd->shm_ino;
395
396 return (0);
397 }
398
399 static int
400 shm_close(struct file *fp, struct thread *td)
401 {
402 struct shmfd *shmfd;
403
404 shmfd = fp->f_data;
405 fp->f_data = NULL;
406 shm_drop(shmfd);
407
408 return (0);
409 }
410
411 int
412 shm_dotruncate(struct shmfd *shmfd, off_t length)
413 {
414 vm_object_t object;
415 vm_page_t m;
416 vm_pindex_t idx, nobjsize;
417 vm_ooffset_t delta;
418 int base, rv;
419
420 object = shmfd->shm_object;
421 VM_OBJECT_WLOCK(object);
422 if (length == shmfd->shm_size) {
423 VM_OBJECT_WUNLOCK(object);
424 return (0);
425 }
426 nobjsize = OFF_TO_IDX(length + PAGE_MASK);
427
428 /* Are we shrinking? If so, trim the end. */
429 if (length < shmfd->shm_size) {
430 /*
431 * Disallow any requests to shrink the size if this
432 * object is mapped into the kernel.
433 */
434 if (shmfd->shm_kmappings > 0) {
435 VM_OBJECT_WUNLOCK(object);
436 return (EBUSY);
437 }
438
439 /*
440 * Zero the truncated part of the last page.
441 */
442 base = length & PAGE_MASK;
443 if (base != 0) {
444 idx = OFF_TO_IDX(length);
445 retry:
446 m = vm_page_lookup(object, idx);
447 if (m != NULL) {
448 if (vm_page_sleep_if_busy(m, "shmtrc"))
449 goto retry;
450 } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
451 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL);
452 if (m == NULL) {
453 VM_OBJECT_WUNLOCK(object);
454 VM_WAIT;
455 VM_OBJECT_WLOCK(object);
456 goto retry;
457 } else if (m->valid != VM_PAGE_BITS_ALL)
458 rv = vm_pager_get_pages(object, &m, 1,
459 NULL, NULL);
460 else
461 /* A cached page was reactivated. */
462 rv = VM_PAGER_OK;
463 vm_page_lock(m);
464 if (rv == VM_PAGER_OK) {
465 vm_page_deactivate(m);
466 vm_page_unlock(m);
467 vm_page_xunbusy(m);
468 } else {
469 vm_page_free(m);
470 vm_page_unlock(m);
471 VM_OBJECT_WUNLOCK(object);
472 return (EIO);
473 }
474 }
475 if (m != NULL) {
476 pmap_zero_page_area(m, base, PAGE_SIZE - base);
477 KASSERT(m->valid == VM_PAGE_BITS_ALL,
478 ("shm_dotruncate: page %p is invalid", m));
479 vm_page_dirty(m);
480 vm_pager_page_unswapped(m);
481 }
482 }
483 delta = ptoa(object->size - nobjsize);
484
485 /* Toss in memory pages. */
486 if (nobjsize < object->size)
487 vm_object_page_remove(object, nobjsize, object->size,
488 0);
489
490 /* Toss pages from swap. */
491 if (object->type == OBJT_SWAP)
492 swap_pager_freespace(object, nobjsize, delta);
493
494 /* Free the swap accounted for shm */
495 swap_release_by_cred(delta, object->cred);
496 object->charge -= delta;
497 } else {
498 /* Attempt to reserve the swap */
499 delta = ptoa(nobjsize - object->size);
500 if (!swap_reserve_by_cred(delta, object->cred)) {
501 VM_OBJECT_WUNLOCK(object);
502 return (ENOMEM);
503 }
504 object->charge += delta;
505 }
506 shmfd->shm_size = length;
507 mtx_lock(&shm_timestamp_lock);
508 vfs_timestamp(&shmfd->shm_ctime);
509 shmfd->shm_mtime = shmfd->shm_ctime;
510 mtx_unlock(&shm_timestamp_lock);
511 object->size = nobjsize;
512 VM_OBJECT_WUNLOCK(object);
513 return (0);
514 }
515
516 /*
517 * shmfd object management including creation and reference counting
518 * routines.
519 */
520 struct shmfd *
521 shm_alloc(struct ucred *ucred, mode_t mode)
522 {
523 struct shmfd *shmfd;
524 int ino;
525
526 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
527 shmfd->shm_size = 0;
528 shmfd->shm_uid = ucred->cr_uid;
529 shmfd->shm_gid = ucred->cr_gid;
530 shmfd->shm_mode = mode;
531 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
532 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
533 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
534 shmfd->shm_object->pg_color = 0;
535 VM_OBJECT_WLOCK(shmfd->shm_object);
536 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
537 vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT);
538 VM_OBJECT_WUNLOCK(shmfd->shm_object);
539 vfs_timestamp(&shmfd->shm_birthtime);
540 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
541 shmfd->shm_birthtime;
542 ino = alloc_unr(shm_ino_unr);
543 if (ino == -1)
544 shmfd->shm_ino = 0;
545 else
546 shmfd->shm_ino = ino;
547 refcount_init(&shmfd->shm_refs, 1);
548 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF);
549 rangelock_init(&shmfd->shm_rl);
550 #ifdef MAC
551 mac_posixshm_init(shmfd);
552 mac_posixshm_create(ucred, shmfd);
553 #endif
554
555 return (shmfd);
556 }
557
558 struct shmfd *
559 shm_hold(struct shmfd *shmfd)
560 {
561
562 refcount_acquire(&shmfd->shm_refs);
563 return (shmfd);
564 }
565
566 void
567 shm_drop(struct shmfd *shmfd)
568 {
569
570 if (refcount_release(&shmfd->shm_refs)) {
571 #ifdef MAC
572 mac_posixshm_destroy(shmfd);
573 #endif
574 rangelock_destroy(&shmfd->shm_rl);
575 mtx_destroy(&shmfd->shm_mtx);
576 vm_object_deallocate(shmfd->shm_object);
577 if (shmfd->shm_ino != 0)
578 free_unr(shm_ino_unr, shmfd->shm_ino);
579 free(shmfd, M_SHMFD);
580 }
581 }
582
583 /*
584 * Determine if the credentials have sufficient permissions for a
585 * specified combination of FREAD and FWRITE.
586 */
587 int
588 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
589 {
590 accmode_t accmode;
591 int error;
592
593 accmode = 0;
594 if (flags & FREAD)
595 accmode |= VREAD;
596 if (flags & FWRITE)
597 accmode |= VWRITE;
598 mtx_lock(&shm_timestamp_lock);
599 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
600 accmode, ucred, NULL);
601 mtx_unlock(&shm_timestamp_lock);
602 return (error);
603 }
604
605 /*
606 * Dictionary management. We maintain an in-kernel dictionary to map
607 * paths to shmfd objects. We use the FNV hash on the path to store
608 * the mappings in a hash table.
609 */
610 static void
611 shm_init(void *arg)
612 {
613
614 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
615 sx_init(&shm_dict_lock, "shm dictionary");
616 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
617 shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL);
618 KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized"));
619 shm_dev_ino = devfs_alloc_cdp_inode();
620 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized"));
621 }
622 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL);
623
624 static struct shmfd *
625 shm_lookup(char *path, Fnv32_t fnv)
626 {
627 struct shm_mapping *map;
628
629 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
630 if (map->sm_fnv != fnv)
631 continue;
632 if (strcmp(map->sm_path, path) == 0)
633 return (map->sm_shmfd);
634 }
635
636 return (NULL);
637 }
638
639 static void
640 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
641 {
642 struct shm_mapping *map;
643
644 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
645 map->sm_path = path;
646 map->sm_fnv = fnv;
647 map->sm_shmfd = shm_hold(shmfd);
648 shmfd->shm_path = path;
649 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
650 }
651
652 static int
653 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
654 {
655 struct shm_mapping *map;
656 int error;
657
658 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
659 if (map->sm_fnv != fnv)
660 continue;
661 if (strcmp(map->sm_path, path) == 0) {
662 #ifdef MAC
663 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
664 if (error)
665 return (error);
666 #endif
667 error = shm_access(map->sm_shmfd, ucred,
668 FREAD | FWRITE);
669 if (error)
670 return (error);
671 map->sm_shmfd->shm_path = NULL;
672 LIST_REMOVE(map, sm_link);
673 shm_drop(map->sm_shmfd);
674 free(map->sm_path, M_SHMFD);
675 free(map, M_SHMFD);
676 return (0);
677 }
678 }
679
680 return (ENOENT);
681 }
682
683 int
684 kern_shm_open(struct thread *td, const char *userpath, int flags, mode_t mode,
685 struct filecaps *fcaps)
686 {
687 struct filedesc *fdp;
688 struct shmfd *shmfd;
689 struct file *fp;
690 char *path;
691 const char *pr_path;
692 size_t pr_pathlen;
693 Fnv32_t fnv;
694 mode_t cmode;
695 int fd, error;
696
697 #ifdef CAPABILITY_MODE
698 /*
699 * shm_open(2) is only allowed for anonymous objects.
700 */
701 if (IN_CAPABILITY_MODE(td) && (userpath != SHM_ANON))
702 return (ECAPMODE);
703 #endif
704
705 if ((flags & O_ACCMODE) != O_RDONLY && (flags & O_ACCMODE) != O_RDWR)
706 return (EINVAL);
707
708 if ((flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0)
709 return (EINVAL);
710
711 fdp = td->td_proc->p_fd;
712 cmode = (mode & ~fdp->fd_cmask) & ACCESSPERMS;
713
714 error = falloc_caps(td, &fp, &fd, O_CLOEXEC, fcaps);
715 if (error)
716 return (error);
717
718 /* A SHM_ANON path pointer creates an anonymous object. */
719 if (userpath == SHM_ANON) {
720 /* A read-only anonymous object is pointless. */
721 if ((flags & O_ACCMODE) == O_RDONLY) {
722 fdclose(td, fp, fd);
723 fdrop(fp, td);
724 return (EINVAL);
725 }
726 shmfd = shm_alloc(td->td_ucred, cmode);
727 } else {
728 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
729 pr_path = td->td_ucred->cr_prison->pr_path;
730
731 /* Construct a full pathname for jailed callers. */
732 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0
733 : strlcpy(path, pr_path, MAXPATHLEN);
734 error = copyinstr(userpath, path + pr_pathlen,
735 MAXPATHLEN - pr_pathlen, NULL);
736 #ifdef KTRACE
737 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI))
738 ktrnamei(path);
739 #endif
740 /* Require paths to start with a '/' character. */
741 if (error == 0 && path[pr_pathlen] != '/')
742 error = EINVAL;
743 if (error) {
744 fdclose(td, fp, fd);
745 fdrop(fp, td);
746 free(path, M_SHMFD);
747 return (error);
748 }
749
750 fnv = fnv_32_str(path, FNV1_32_INIT);
751 sx_xlock(&shm_dict_lock);
752 shmfd = shm_lookup(path, fnv);
753 if (shmfd == NULL) {
754 /* Object does not yet exist, create it if requested. */
755 if (flags & O_CREAT) {
756 #ifdef MAC
757 error = mac_posixshm_check_create(td->td_ucred,
758 path);
759 if (error == 0) {
760 #endif
761 shmfd = shm_alloc(td->td_ucred, cmode);
762 shm_insert(path, fnv, shmfd);
763 #ifdef MAC
764 }
765 #endif
766 } else {
767 free(path, M_SHMFD);
768 error = ENOENT;
769 }
770 } else {
771 /*
772 * Object already exists, obtain a new
773 * reference if requested and permitted.
774 */
775 free(path, M_SHMFD);
776 if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
777 error = EEXIST;
778 else {
779 #ifdef MAC
780 error = mac_posixshm_check_open(td->td_ucred,
781 shmfd, FFLAGS(flags & O_ACCMODE));
782 if (error == 0)
783 #endif
784 error = shm_access(shmfd, td->td_ucred,
785 FFLAGS(flags & O_ACCMODE));
786 }
787
788 /*
789 * Truncate the file back to zero length if
790 * O_TRUNC was specified and the object was
791 * opened with read/write.
792 */
793 if (error == 0 &&
794 (flags & (O_ACCMODE | O_TRUNC)) ==
795 (O_RDWR | O_TRUNC)) {
796 #ifdef MAC
797 error = mac_posixshm_check_truncate(
798 td->td_ucred, fp->f_cred, shmfd);
799 if (error == 0)
800 #endif
801 shm_dotruncate(shmfd, 0);
802 }
803 if (error == 0)
804 shm_hold(shmfd);
805 }
806 sx_xunlock(&shm_dict_lock);
807
808 if (error) {
809 fdclose(td, fp, fd);
810 fdrop(fp, td);
811 return (error);
812 }
813 }
814
815 finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
816
817 td->td_retval[0] = fd;
818 fdrop(fp, td);
819
820 return (0);
821 }
822
823 /* System calls. */
824 int
825 sys_shm_open(struct thread *td, struct shm_open_args *uap)
826 {
827
828 return (kern_shm_open(td, uap->path, uap->flags, uap->mode, NULL));
829 }
830
831 int
832 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
833 {
834 char *path;
835 const char *pr_path;
836 size_t pr_pathlen;
837 Fnv32_t fnv;
838 int error;
839
840 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
841 pr_path = td->td_ucred->cr_prison->pr_path;
842 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0
843 : strlcpy(path, pr_path, MAXPATHLEN);
844 error = copyinstr(uap->path, path + pr_pathlen, MAXPATHLEN - pr_pathlen,
845 NULL);
846 if (error) {
847 free(path, M_TEMP);
848 return (error);
849 }
850 #ifdef KTRACE
851 if (KTRPOINT(curthread, KTR_NAMEI))
852 ktrnamei(path);
853 #endif
854 fnv = fnv_32_str(path, FNV1_32_INIT);
855 sx_xlock(&shm_dict_lock);
856 error = shm_remove(path, fnv, td->td_ucred);
857 sx_xunlock(&shm_dict_lock);
858 free(path, M_TEMP);
859
860 return (error);
861 }
862
863 int
864 shm_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t objsize,
865 vm_prot_t prot, vm_prot_t cap_maxprot, int flags,
866 vm_ooffset_t foff, struct thread *td)
867 {
868 struct shmfd *shmfd;
869 vm_prot_t maxprot;
870 int error;
871
872 shmfd = fp->f_data;
873 maxprot = VM_PROT_NONE;
874
875 /* FREAD should always be set. */
876 if ((fp->f_flag & FREAD) != 0)
877 maxprot |= VM_PROT_EXECUTE | VM_PROT_READ;
878 if ((fp->f_flag & FWRITE) != 0)
879 maxprot |= VM_PROT_WRITE;
880
881 /* Don't permit shared writable mappings on read-only descriptors. */
882 if ((flags & MAP_SHARED) != 0 &&
883 (maxprot & VM_PROT_WRITE) == 0 &&
884 (prot & VM_PROT_WRITE) != 0)
885 return (EACCES);
886 maxprot &= cap_maxprot;
887
888 #ifdef MAC
889 error = mac_posixshm_check_mmap(td->td_ucred, shmfd, prot, flags);
890 if (error != 0)
891 return (error);
892 #endif
893
894 /*
895 * XXXRW: This validation is probably insufficient, and subject to
896 * sign errors. It should be fixed.
897 */
898 if (foff >= shmfd->shm_size ||
899 foff + objsize > round_page(shmfd->shm_size))
900 return (EINVAL);
901
902 mtx_lock(&shm_timestamp_lock);
903 vfs_timestamp(&shmfd->shm_atime);
904 mtx_unlock(&shm_timestamp_lock);
905 vm_object_reference(shmfd->shm_object);
906
907 error = vm_mmap_object(map, addr, objsize, prot, maxprot, flags,
908 shmfd->shm_object, foff, FALSE, td);
909 if (error != 0)
910 vm_object_deallocate(shmfd->shm_object);
911 return (0);
912 }
913
914 static int
915 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
916 struct thread *td)
917 {
918 struct shmfd *shmfd;
919 int error;
920
921 error = 0;
922 shmfd = fp->f_data;
923 mtx_lock(&shm_timestamp_lock);
924 /*
925 * SUSv4 says that x bits of permission need not be affected.
926 * Be consistent with our shm_open there.
927 */
928 #ifdef MAC
929 error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
930 if (error != 0)
931 goto out;
932 #endif
933 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid,
934 shmfd->shm_gid, VADMIN, active_cred, NULL);
935 if (error != 0)
936 goto out;
937 shmfd->shm_mode = mode & ACCESSPERMS;
938 out:
939 mtx_unlock(&shm_timestamp_lock);
940 return (error);
941 }
942
943 static int
944 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
945 struct thread *td)
946 {
947 struct shmfd *shmfd;
948 int error;
949
950 error = 0;
951 shmfd = fp->f_data;
952 mtx_lock(&shm_timestamp_lock);
953 #ifdef MAC
954 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
955 if (error != 0)
956 goto out;
957 #endif
958 if (uid == (uid_t)-1)
959 uid = shmfd->shm_uid;
960 if (gid == (gid_t)-1)
961 gid = shmfd->shm_gid;
962 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
963 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
964 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
965 goto out;
966 shmfd->shm_uid = uid;
967 shmfd->shm_gid = gid;
968 out:
969 mtx_unlock(&shm_timestamp_lock);
970 return (error);
971 }
972
973 /*
974 * Helper routines to allow the backing object of a shared memory file
975 * descriptor to be mapped in the kernel.
976 */
977 int
978 shm_map(struct file *fp, size_t size, off_t offset, void **memp)
979 {
980 struct shmfd *shmfd;
981 vm_offset_t kva, ofs;
982 vm_object_t obj;
983 int rv;
984
985 if (fp->f_type != DTYPE_SHM)
986 return (EINVAL);
987 shmfd = fp->f_data;
988 obj = shmfd->shm_object;
989 VM_OBJECT_WLOCK(obj);
990 /*
991 * XXXRW: This validation is probably insufficient, and subject to
992 * sign errors. It should be fixed.
993 */
994 if (offset >= shmfd->shm_size ||
995 offset + size > round_page(shmfd->shm_size)) {
996 VM_OBJECT_WUNLOCK(obj);
997 return (EINVAL);
998 }
999
1000 shmfd->shm_kmappings++;
1001 vm_object_reference_locked(obj);
1002 VM_OBJECT_WUNLOCK(obj);
1003
1004 /* Map the object into the kernel_map and wire it. */
1005 kva = vm_map_min(kernel_map);
1006 ofs = offset & PAGE_MASK;
1007 offset = trunc_page(offset);
1008 size = round_page(size + ofs);
1009 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0,
1010 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
1011 VM_PROT_READ | VM_PROT_WRITE, 0);
1012 if (rv == KERN_SUCCESS) {
1013 rv = vm_map_wire(kernel_map, kva, kva + size,
1014 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
1015 if (rv == KERN_SUCCESS) {
1016 *memp = (void *)(kva + ofs);
1017 return (0);
1018 }
1019 vm_map_remove(kernel_map, kva, kva + size);
1020 } else
1021 vm_object_deallocate(obj);
1022
1023 /* On failure, drop our mapping reference. */
1024 VM_OBJECT_WLOCK(obj);
1025 shmfd->shm_kmappings--;
1026 VM_OBJECT_WUNLOCK(obj);
1027
1028 return (vm_mmap_to_errno(rv));
1029 }
1030
1031 /*
1032 * We require the caller to unmap the entire entry. This allows us to
1033 * safely decrement shm_kmappings when a mapping is removed.
1034 */
1035 int
1036 shm_unmap(struct file *fp, void *mem, size_t size)
1037 {
1038 struct shmfd *shmfd;
1039 vm_map_entry_t entry;
1040 vm_offset_t kva, ofs;
1041 vm_object_t obj;
1042 vm_pindex_t pindex;
1043 vm_prot_t prot;
1044 boolean_t wired;
1045 vm_map_t map;
1046 int rv;
1047
1048 if (fp->f_type != DTYPE_SHM)
1049 return (EINVAL);
1050 shmfd = fp->f_data;
1051 kva = (vm_offset_t)mem;
1052 ofs = kva & PAGE_MASK;
1053 kva = trunc_page(kva);
1054 size = round_page(size + ofs);
1055 map = kernel_map;
1056 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
1057 &obj, &pindex, &prot, &wired);
1058 if (rv != KERN_SUCCESS)
1059 return (EINVAL);
1060 if (entry->start != kva || entry->end != kva + size) {
1061 vm_map_lookup_done(map, entry);
1062 return (EINVAL);
1063 }
1064 vm_map_lookup_done(map, entry);
1065 if (obj != shmfd->shm_object)
1066 return (EINVAL);
1067 vm_map_remove(map, kva, kva + size);
1068 VM_OBJECT_WLOCK(obj);
1069 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
1070 shmfd->shm_kmappings--;
1071 VM_OBJECT_WUNLOCK(obj);
1072 return (0);
1073 }
1074
1075 static int
1076 shm_fill_kinfo(struct file *fp, struct kinfo_file *kif, struct filedesc *fdp)
1077 {
1078 const char *path, *pr_path;
1079 struct shmfd *shmfd;
1080 size_t pr_pathlen;
1081
1082 kif->kf_type = KF_TYPE_SHM;
1083 shmfd = fp->f_data;
1084
1085 mtx_lock(&shm_timestamp_lock);
1086 kif->kf_un.kf_file.kf_file_mode = S_IFREG | shmfd->shm_mode; /* XXX */
1087 mtx_unlock(&shm_timestamp_lock);
1088 kif->kf_un.kf_file.kf_file_size = shmfd->shm_size;
1089 if (shmfd->shm_path != NULL) {
1090 sx_slock(&shm_dict_lock);
1091 if (shmfd->shm_path != NULL) {
1092 path = shmfd->shm_path;
1093 pr_path = curthread->td_ucred->cr_prison->pr_path;
1094 if (strcmp(pr_path, "/") != 0) {
1095 /* Return the jail-rooted pathname. */
1096 pr_pathlen = strlen(pr_path);
1097 if (strncmp(path, pr_path, pr_pathlen) == 0 &&
1098 path[pr_pathlen] == '/')
1099 path += pr_pathlen;
1100 }
1101 strlcpy(kif->kf_path, path, sizeof(kif->kf_path));
1102 }
1103 sx_sunlock(&shm_dict_lock);
1104 }
1105 return (0);
1106 }
Cache object: 1be55dfe0dd57f5a168249bb2b159787
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