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/10.3/sys/kern/uipc_shm.c 325873 2017-11-15 22:45:13Z gordon $");
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/sysctl.h>
73 #include <sys/sysproto.h>
74 #include <sys/systm.h>
75 #include <sys/sx.h>
76 #include <sys/time.h>
77 #include <sys/vnode.h>
78 #include <sys/unistd.h>
79
80 #include <security/mac/mac_framework.h>
81
82 #include <vm/vm.h>
83 #include <vm/vm_param.h>
84 #include <vm/pmap.h>
85 #include <vm/vm_extern.h>
86 #include <vm/vm_map.h>
87 #include <vm/vm_kern.h>
88 #include <vm/vm_object.h>
89 #include <vm/vm_page.h>
90 #include <vm/vm_pageout.h>
91 #include <vm/vm_pager.h>
92 #include <vm/swap_pager.h>
93
94 struct shm_mapping {
95 char *sm_path;
96 Fnv32_t sm_fnv;
97 struct shmfd *sm_shmfd;
98 LIST_ENTRY(shm_mapping) sm_link;
99 };
100
101 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
102 static LIST_HEAD(, shm_mapping) *shm_dictionary;
103 static struct sx shm_dict_lock;
104 static struct mtx shm_timestamp_lock;
105 static u_long shm_hash;
106 static struct unrhdr *shm_ino_unr;
107 static dev_t shm_dev_ino;
108
109 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash])
110
111 static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
112 static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
113 static void shm_init(void *arg);
114 static void shm_drop(struct shmfd *shmfd);
115 static struct shmfd *shm_hold(struct shmfd *shmfd);
116 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
117 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
118 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
119 static int shm_dotruncate(struct shmfd *shmfd, off_t length);
120
121 static fo_rdwr_t shm_read;
122 static fo_rdwr_t shm_write;
123 static fo_truncate_t shm_truncate;
124 static fo_ioctl_t shm_ioctl;
125 static fo_poll_t shm_poll;
126 static fo_kqfilter_t shm_kqfilter;
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
133 /* File descriptor operations. */
134 static struct fileops shm_ops = {
135 .fo_read = shm_read,
136 .fo_write = shm_write,
137 .fo_truncate = shm_truncate,
138 .fo_ioctl = shm_ioctl,
139 .fo_poll = shm_poll,
140 .fo_kqfilter = shm_kqfilter,
141 .fo_stat = shm_stat,
142 .fo_close = shm_close,
143 .fo_chmod = shm_chmod,
144 .fo_chown = shm_chown,
145 .fo_sendfile = vn_sendfile,
146 .fo_seek = shm_seek,
147 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
148 };
149
150 FEATURE(posix_shm, "POSIX shared memory");
151
152 static int
153 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
154 {
155 vm_page_t m;
156 vm_pindex_t idx;
157 size_t tlen;
158 int error, offset, rv;
159
160 idx = OFF_TO_IDX(uio->uio_offset);
161 offset = uio->uio_offset & PAGE_MASK;
162 tlen = MIN(PAGE_SIZE - offset, len);
163
164 VM_OBJECT_WLOCK(obj);
165
166 /*
167 * Parallel reads of the page content from disk are prevented
168 * by exclusive busy.
169 *
170 * Although the tmpfs vnode lock is held here, it is
171 * nonetheless safe to sleep waiting for a free page. The
172 * pageout daemon does not need to acquire the tmpfs vnode
173 * lock to page out tobj's pages because tobj is a OBJT_SWAP
174 * type object.
175 */
176 m = vm_page_grab(obj, idx, VM_ALLOC_NORMAL);
177 if (m->valid != VM_PAGE_BITS_ALL) {
178 if (vm_pager_has_page(obj, idx, NULL, NULL)) {
179 rv = vm_pager_get_pages(obj, &m, 1, 0);
180 m = vm_page_lookup(obj, idx);
181 if (m == NULL) {
182 printf(
183 "uiomove_object: vm_obj %p idx %jd null lookup rv %d\n",
184 obj, idx, rv);
185 VM_OBJECT_WUNLOCK(obj);
186 return (EIO);
187 }
188 if (rv != VM_PAGER_OK) {
189 printf(
190 "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n",
191 obj, idx, m->valid, rv);
192 vm_page_lock(m);
193 vm_page_free(m);
194 vm_page_unlock(m);
195 VM_OBJECT_WUNLOCK(obj);
196 return (EIO);
197 }
198 } else
199 vm_page_zero_invalid(m, TRUE);
200 }
201 vm_page_xunbusy(m);
202 vm_page_lock(m);
203 vm_page_hold(m);
204 if (m->queue == PQ_NONE) {
205 vm_page_deactivate(m);
206 } else {
207 /* Requeue to maintain LRU ordering. */
208 vm_page_requeue(m);
209 }
210 vm_page_unlock(m);
211 VM_OBJECT_WUNLOCK(obj);
212 error = uiomove_fromphys(&m, offset, tlen, uio);
213 if (uio->uio_rw == UIO_WRITE && error == 0) {
214 VM_OBJECT_WLOCK(obj);
215 vm_page_dirty(m);
216 vm_pager_page_unswapped(m);
217 VM_OBJECT_WUNLOCK(obj);
218 }
219 vm_page_lock(m);
220 vm_page_unhold(m);
221 vm_page_unlock(m);
222
223 return (error);
224 }
225
226 int
227 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio)
228 {
229 ssize_t resid;
230 size_t len;
231 int error;
232
233 error = 0;
234 while ((resid = uio->uio_resid) > 0) {
235 if (obj_size <= uio->uio_offset)
236 break;
237 len = MIN(obj_size - uio->uio_offset, resid);
238 if (len == 0)
239 break;
240 error = uiomove_object_page(obj, len, uio);
241 if (error != 0 || resid == uio->uio_resid)
242 break;
243 }
244 return (error);
245 }
246
247 static int
248 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td)
249 {
250 struct shmfd *shmfd;
251 off_t foffset;
252 int error;
253
254 shmfd = fp->f_data;
255 foffset = foffset_lock(fp, 0);
256 error = 0;
257 switch (whence) {
258 case L_INCR:
259 if (foffset < 0 ||
260 (offset > 0 && foffset > OFF_MAX - offset)) {
261 error = EOVERFLOW;
262 break;
263 }
264 offset += foffset;
265 break;
266 case L_XTND:
267 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) {
268 error = EOVERFLOW;
269 break;
270 }
271 offset += shmfd->shm_size;
272 break;
273 case L_SET:
274 break;
275 default:
276 error = EINVAL;
277 }
278 if (error == 0) {
279 if (offset < 0 || offset > shmfd->shm_size)
280 error = EINVAL;
281 else
282 *(off_t *)(td->td_retval) = offset;
283 }
284 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
285 return (error);
286 }
287
288 static int
289 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
290 int flags, struct thread *td)
291 {
292 struct shmfd *shmfd;
293 void *rl_cookie;
294 int error;
295
296 shmfd = fp->f_data;
297 foffset_lock_uio(fp, uio, flags);
298 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
299 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
300 #ifdef MAC
301 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
302 if (error)
303 return (error);
304 #endif
305 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
306 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
307 foffset_unlock_uio(fp, uio, flags);
308 return (error);
309 }
310
311 static int
312 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
313 int flags, struct thread *td)
314 {
315 struct shmfd *shmfd;
316 void *rl_cookie;
317 int error;
318
319 shmfd = fp->f_data;
320 #ifdef MAC
321 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd);
322 if (error)
323 return (error);
324 #endif
325 foffset_lock_uio(fp, uio, flags);
326 if ((flags & FOF_OFFSET) == 0) {
327 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
328 &shmfd->shm_mtx);
329 } else {
330 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
331 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
332 }
333
334 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
335 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
336 foffset_unlock_uio(fp, uio, flags);
337 return (error);
338 }
339
340 static int
341 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
342 struct thread *td)
343 {
344 struct shmfd *shmfd;
345 #ifdef MAC
346 int error;
347 #endif
348
349 shmfd = fp->f_data;
350 #ifdef MAC
351 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
352 if (error)
353 return (error);
354 #endif
355 return (shm_dotruncate(shmfd, length));
356 }
357
358 static int
359 shm_ioctl(struct file *fp, u_long com, void *data,
360 struct ucred *active_cred, struct thread *td)
361 {
362
363 return (EOPNOTSUPP);
364 }
365
366 static int
367 shm_poll(struct file *fp, int events, struct ucred *active_cred,
368 struct thread *td)
369 {
370
371 return (EOPNOTSUPP);
372 }
373
374 static int
375 shm_kqfilter(struct file *fp, struct knote *kn)
376 {
377
378 return (EOPNOTSUPP);
379 }
380
381 static int
382 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
383 struct thread *td)
384 {
385 struct shmfd *shmfd;
386 #ifdef MAC
387 int error;
388 #endif
389
390 shmfd = fp->f_data;
391
392 #ifdef MAC
393 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
394 if (error)
395 return (error);
396 #endif
397
398 /*
399 * Attempt to return sanish values for fstat() on a memory file
400 * descriptor.
401 */
402 bzero(sb, sizeof(*sb));
403 sb->st_blksize = PAGE_SIZE;
404 sb->st_size = shmfd->shm_size;
405 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
406 mtx_lock(&shm_timestamp_lock);
407 sb->st_atim = shmfd->shm_atime;
408 sb->st_ctim = shmfd->shm_ctime;
409 sb->st_mtim = shmfd->shm_mtime;
410 sb->st_birthtim = shmfd->shm_birthtime;
411 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */
412 sb->st_uid = shmfd->shm_uid;
413 sb->st_gid = shmfd->shm_gid;
414 mtx_unlock(&shm_timestamp_lock);
415 sb->st_dev = shm_dev_ino;
416 sb->st_ino = shmfd->shm_ino;
417
418 return (0);
419 }
420
421 static int
422 shm_close(struct file *fp, struct thread *td)
423 {
424 struct shmfd *shmfd;
425
426 shmfd = fp->f_data;
427 fp->f_data = NULL;
428 shm_drop(shmfd);
429
430 return (0);
431 }
432
433 static int
434 shm_dotruncate(struct shmfd *shmfd, off_t length)
435 {
436 vm_object_t object;
437 vm_page_t m, ma[1];
438 vm_pindex_t idx, nobjsize;
439 vm_ooffset_t delta;
440 int base, rv;
441
442 object = shmfd->shm_object;
443 VM_OBJECT_WLOCK(object);
444 if (length == shmfd->shm_size) {
445 VM_OBJECT_WUNLOCK(object);
446 return (0);
447 }
448 nobjsize = OFF_TO_IDX(length + PAGE_MASK);
449
450 /* Are we shrinking? If so, trim the end. */
451 if (length < shmfd->shm_size) {
452 /*
453 * Disallow any requests to shrink the size if this
454 * object is mapped into the kernel.
455 */
456 if (shmfd->shm_kmappings > 0) {
457 VM_OBJECT_WUNLOCK(object);
458 return (EBUSY);
459 }
460
461 /*
462 * Zero the truncated part of the last page.
463 */
464 base = length & PAGE_MASK;
465 if (base != 0) {
466 idx = OFF_TO_IDX(length);
467 retry:
468 m = vm_page_lookup(object, idx);
469 if (m != NULL) {
470 if (vm_page_sleep_if_busy(m, "shmtrc"))
471 goto retry;
472 } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
473 m = vm_page_alloc(object, idx, VM_ALLOC_NORMAL);
474 if (m == NULL) {
475 VM_OBJECT_WUNLOCK(object);
476 VM_WAIT;
477 VM_OBJECT_WLOCK(object);
478 goto retry;
479 } else if (m->valid != VM_PAGE_BITS_ALL) {
480 ma[0] = m;
481 rv = vm_pager_get_pages(object, ma, 1,
482 0);
483 m = vm_page_lookup(object, idx);
484 } else
485 /* A cached page was reactivated. */
486 rv = VM_PAGER_OK;
487 vm_page_lock(m);
488 if (rv == VM_PAGER_OK) {
489 vm_page_deactivate(m);
490 vm_page_unlock(m);
491 vm_page_xunbusy(m);
492 } else {
493 vm_page_free(m);
494 vm_page_unlock(m);
495 VM_OBJECT_WUNLOCK(object);
496 return (EIO);
497 }
498 }
499 if (m != NULL) {
500 pmap_zero_page_area(m, base, PAGE_SIZE - base);
501 KASSERT(m->valid == VM_PAGE_BITS_ALL,
502 ("shm_dotruncate: page %p is invalid", m));
503 vm_page_dirty(m);
504 vm_pager_page_unswapped(m);
505 }
506 }
507 delta = ptoa(object->size - nobjsize);
508
509 /* Toss in memory pages. */
510 if (nobjsize < object->size)
511 vm_object_page_remove(object, nobjsize, object->size,
512 0);
513
514 /* Toss pages from swap. */
515 if (object->type == OBJT_SWAP)
516 swap_pager_freespace(object, nobjsize, delta);
517
518 /* Free the swap accounted for shm */
519 swap_release_by_cred(delta, object->cred);
520 object->charge -= delta;
521 } else {
522 /* Attempt to reserve the swap */
523 delta = ptoa(nobjsize - object->size);
524 if (!swap_reserve_by_cred(delta, object->cred)) {
525 VM_OBJECT_WUNLOCK(object);
526 return (ENOMEM);
527 }
528 object->charge += delta;
529 }
530 shmfd->shm_size = length;
531 mtx_lock(&shm_timestamp_lock);
532 vfs_timestamp(&shmfd->shm_ctime);
533 shmfd->shm_mtime = shmfd->shm_ctime;
534 mtx_unlock(&shm_timestamp_lock);
535 object->size = nobjsize;
536 VM_OBJECT_WUNLOCK(object);
537 return (0);
538 }
539
540 /*
541 * shmfd object management including creation and reference counting
542 * routines.
543 */
544 static struct shmfd *
545 shm_alloc(struct ucred *ucred, mode_t mode)
546 {
547 struct shmfd *shmfd;
548 int ino;
549
550 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
551 shmfd->shm_size = 0;
552 shmfd->shm_uid = ucred->cr_uid;
553 shmfd->shm_gid = ucred->cr_gid;
554 shmfd->shm_mode = mode;
555 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
556 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
557 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
558 shmfd->shm_object->pg_color = 0;
559 VM_OBJECT_WLOCK(shmfd->shm_object);
560 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
561 vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT);
562 VM_OBJECT_WUNLOCK(shmfd->shm_object);
563 vfs_timestamp(&shmfd->shm_birthtime);
564 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
565 shmfd->shm_birthtime;
566 ino = alloc_unr(shm_ino_unr);
567 if (ino == -1)
568 shmfd->shm_ino = 0;
569 else
570 shmfd->shm_ino = ino;
571 refcount_init(&shmfd->shm_refs, 1);
572 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF);
573 rangelock_init(&shmfd->shm_rl);
574 #ifdef MAC
575 mac_posixshm_init(shmfd);
576 mac_posixshm_create(ucred, shmfd);
577 #endif
578
579 return (shmfd);
580 }
581
582 static struct shmfd *
583 shm_hold(struct shmfd *shmfd)
584 {
585
586 refcount_acquire(&shmfd->shm_refs);
587 return (shmfd);
588 }
589
590 static void
591 shm_drop(struct shmfd *shmfd)
592 {
593
594 if (refcount_release(&shmfd->shm_refs)) {
595 #ifdef MAC
596 mac_posixshm_destroy(shmfd);
597 #endif
598 rangelock_destroy(&shmfd->shm_rl);
599 mtx_destroy(&shmfd->shm_mtx);
600 vm_object_deallocate(shmfd->shm_object);
601 if (shmfd->shm_ino != 0)
602 free_unr(shm_ino_unr, shmfd->shm_ino);
603 free(shmfd, M_SHMFD);
604 }
605 }
606
607 /*
608 * Determine if the credentials have sufficient permissions for a
609 * specified combination of FREAD and FWRITE.
610 */
611 static int
612 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
613 {
614 accmode_t accmode;
615 int error;
616
617 accmode = 0;
618 if (flags & FREAD)
619 accmode |= VREAD;
620 if (flags & FWRITE)
621 accmode |= VWRITE;
622 mtx_lock(&shm_timestamp_lock);
623 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
624 accmode, ucred, NULL);
625 mtx_unlock(&shm_timestamp_lock);
626 return (error);
627 }
628
629 /*
630 * Dictionary management. We maintain an in-kernel dictionary to map
631 * paths to shmfd objects. We use the FNV hash on the path to store
632 * the mappings in a hash table.
633 */
634 static void
635 shm_init(void *arg)
636 {
637
638 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
639 sx_init(&shm_dict_lock, "shm dictionary");
640 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
641 shm_ino_unr = new_unrhdr(1, INT32_MAX, NULL);
642 KASSERT(shm_ino_unr != NULL, ("shm fake inodes not initialized"));
643 shm_dev_ino = devfs_alloc_cdp_inode();
644 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized"));
645 }
646 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL);
647
648 static struct shmfd *
649 shm_lookup(char *path, Fnv32_t fnv)
650 {
651 struct shm_mapping *map;
652
653 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
654 if (map->sm_fnv != fnv)
655 continue;
656 if (strcmp(map->sm_path, path) == 0)
657 return (map->sm_shmfd);
658 }
659
660 return (NULL);
661 }
662
663 static void
664 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
665 {
666 struct shm_mapping *map;
667
668 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
669 map->sm_path = path;
670 map->sm_fnv = fnv;
671 map->sm_shmfd = shm_hold(shmfd);
672 shmfd->shm_path = path;
673 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
674 }
675
676 static int
677 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
678 {
679 struct shm_mapping *map;
680 int error;
681
682 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
683 if (map->sm_fnv != fnv)
684 continue;
685 if (strcmp(map->sm_path, path) == 0) {
686 #ifdef MAC
687 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
688 if (error)
689 return (error);
690 #endif
691 error = shm_access(map->sm_shmfd, ucred,
692 FREAD | FWRITE);
693 if (error)
694 return (error);
695 map->sm_shmfd->shm_path = NULL;
696 LIST_REMOVE(map, sm_link);
697 shm_drop(map->sm_shmfd);
698 free(map->sm_path, M_SHMFD);
699 free(map, M_SHMFD);
700 return (0);
701 }
702 }
703
704 return (ENOENT);
705 }
706
707 /* System calls. */
708 int
709 sys_shm_open(struct thread *td, struct shm_open_args *uap)
710 {
711 struct filedesc *fdp;
712 struct shmfd *shmfd;
713 struct file *fp;
714 char *path;
715 const char *pr_path;
716 size_t pr_pathlen;
717 Fnv32_t fnv;
718 mode_t cmode;
719 int fd, error;
720
721 #ifdef CAPABILITY_MODE
722 /*
723 * shm_open(2) is only allowed for anonymous objects.
724 */
725 if (IN_CAPABILITY_MODE(td) && (uap->path != SHM_ANON))
726 return (ECAPMODE);
727 #endif
728
729 if ((uap->flags & O_ACCMODE) != O_RDONLY &&
730 (uap->flags & O_ACCMODE) != O_RDWR)
731 return (EINVAL);
732
733 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0)
734 return (EINVAL);
735
736 fdp = td->td_proc->p_fd;
737 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;
738
739 error = falloc(td, &fp, &fd, O_CLOEXEC);
740 if (error)
741 return (error);
742
743 /* A SHM_ANON path pointer creates an anonymous object. */
744 if (uap->path == SHM_ANON) {
745 /* A read-only anonymous object is pointless. */
746 if ((uap->flags & O_ACCMODE) == O_RDONLY) {
747 fdclose(fdp, fp, fd, td);
748 fdrop(fp, td);
749 return (EINVAL);
750 }
751 shmfd = shm_alloc(td->td_ucred, cmode);
752 } else {
753 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
754 pr_path = td->td_ucred->cr_prison->pr_path;
755
756 /* Construct a full pathname for jailed callers. */
757 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0
758 : strlcpy(path, pr_path, MAXPATHLEN);
759 error = copyinstr(uap->path, path + pr_pathlen,
760 MAXPATHLEN - pr_pathlen, NULL);
761 #ifdef KTRACE
762 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI))
763 ktrnamei(path);
764 #endif
765 /* Require paths to start with a '/' character. */
766 if (error == 0 && path[pr_pathlen] != '/')
767 error = EINVAL;
768 if (error) {
769 fdclose(fdp, fp, fd, td);
770 fdrop(fp, td);
771 free(path, M_SHMFD);
772 return (error);
773 }
774
775 fnv = fnv_32_str(path, FNV1_32_INIT);
776 sx_xlock(&shm_dict_lock);
777 shmfd = shm_lookup(path, fnv);
778 if (shmfd == NULL) {
779 /* Object does not yet exist, create it if requested. */
780 if (uap->flags & O_CREAT) {
781 #ifdef MAC
782 error = mac_posixshm_check_create(td->td_ucred,
783 path);
784 if (error == 0) {
785 #endif
786 shmfd = shm_alloc(td->td_ucred, cmode);
787 shm_insert(path, fnv, shmfd);
788 #ifdef MAC
789 }
790 #endif
791 } else {
792 free(path, M_SHMFD);
793 error = ENOENT;
794 }
795 } else {
796 /*
797 * Object already exists, obtain a new
798 * reference if requested and permitted.
799 */
800 free(path, M_SHMFD);
801 if ((uap->flags & (O_CREAT | O_EXCL)) ==
802 (O_CREAT | O_EXCL))
803 error = EEXIST;
804 else {
805 #ifdef MAC
806 error = mac_posixshm_check_open(td->td_ucred,
807 shmfd, FFLAGS(uap->flags & O_ACCMODE));
808 if (error == 0)
809 #endif
810 error = shm_access(shmfd, td->td_ucred,
811 FFLAGS(uap->flags & O_ACCMODE));
812 }
813
814 /*
815 * Truncate the file back to zero length if
816 * O_TRUNC was specified and the object was
817 * opened with read/write.
818 */
819 if (error == 0 &&
820 (uap->flags & (O_ACCMODE | O_TRUNC)) ==
821 (O_RDWR | O_TRUNC)) {
822 #ifdef MAC
823 error = mac_posixshm_check_truncate(
824 td->td_ucred, fp->f_cred, shmfd);
825 if (error == 0)
826 #endif
827 shm_dotruncate(shmfd, 0);
828 }
829 if (error == 0)
830 shm_hold(shmfd);
831 }
832 sx_xunlock(&shm_dict_lock);
833
834 if (error) {
835 fdclose(fdp, fp, fd, td);
836 fdrop(fp, td);
837 return (error);
838 }
839 }
840
841 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
842
843 td->td_retval[0] = fd;
844 fdrop(fp, td);
845
846 return (0);
847 }
848
849 int
850 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
851 {
852 char *path;
853 const char *pr_path;
854 size_t pr_pathlen;
855 Fnv32_t fnv;
856 int error;
857
858 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
859 pr_path = td->td_ucred->cr_prison->pr_path;
860 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0
861 : strlcpy(path, pr_path, MAXPATHLEN);
862 error = copyinstr(uap->path, path + pr_pathlen, MAXPATHLEN - pr_pathlen,
863 NULL);
864 if (error) {
865 free(path, M_TEMP);
866 return (error);
867 }
868 #ifdef KTRACE
869 if (KTRPOINT(curthread, KTR_NAMEI))
870 ktrnamei(path);
871 #endif
872 fnv = fnv_32_str(path, FNV1_32_INIT);
873 sx_xlock(&shm_dict_lock);
874 error = shm_remove(path, fnv, td->td_ucred);
875 sx_xunlock(&shm_dict_lock);
876 free(path, M_TEMP);
877
878 return (error);
879 }
880
881 /*
882 * mmap() helper to validate mmap() requests against shm object state
883 * and give mmap() the vm_object to use for the mapping.
884 */
885 int
886 shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
887 vm_object_t *obj)
888 {
889
890 /*
891 * XXXRW: This validation is probably insufficient, and subject to
892 * sign errors. It should be fixed.
893 */
894 if (foff >= shmfd->shm_size ||
895 foff + objsize > round_page(shmfd->shm_size))
896 return (EINVAL);
897
898 mtx_lock(&shm_timestamp_lock);
899 vfs_timestamp(&shmfd->shm_atime);
900 mtx_unlock(&shm_timestamp_lock);
901 vm_object_reference(shmfd->shm_object);
902 *obj = shmfd->shm_object;
903 return (0);
904 }
905
906 static int
907 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
908 struct thread *td)
909 {
910 struct shmfd *shmfd;
911 int error;
912
913 error = 0;
914 shmfd = fp->f_data;
915 mtx_lock(&shm_timestamp_lock);
916 /*
917 * SUSv4 says that x bits of permission need not be affected.
918 * Be consistent with our shm_open there.
919 */
920 #ifdef MAC
921 error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
922 if (error != 0)
923 goto out;
924 #endif
925 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid,
926 shmfd->shm_gid, VADMIN, active_cred, NULL);
927 if (error != 0)
928 goto out;
929 shmfd->shm_mode = mode & ACCESSPERMS;
930 out:
931 mtx_unlock(&shm_timestamp_lock);
932 return (error);
933 }
934
935 static int
936 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
937 struct thread *td)
938 {
939 struct shmfd *shmfd;
940 int error;
941
942 error = 0;
943 shmfd = fp->f_data;
944 mtx_lock(&shm_timestamp_lock);
945 #ifdef MAC
946 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
947 if (error != 0)
948 goto out;
949 #endif
950 if (uid == (uid_t)-1)
951 uid = shmfd->shm_uid;
952 if (gid == (gid_t)-1)
953 gid = shmfd->shm_gid;
954 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
955 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
956 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN, 0)))
957 goto out;
958 shmfd->shm_uid = uid;
959 shmfd->shm_gid = gid;
960 out:
961 mtx_unlock(&shm_timestamp_lock);
962 return (error);
963 }
964
965 /*
966 * Helper routines to allow the backing object of a shared memory file
967 * descriptor to be mapped in the kernel.
968 */
969 int
970 shm_map(struct file *fp, size_t size, off_t offset, void **memp)
971 {
972 struct shmfd *shmfd;
973 vm_offset_t kva, ofs;
974 vm_object_t obj;
975 int rv;
976
977 if (fp->f_type != DTYPE_SHM)
978 return (EINVAL);
979 shmfd = fp->f_data;
980 obj = shmfd->shm_object;
981 VM_OBJECT_WLOCK(obj);
982 /*
983 * XXXRW: This validation is probably insufficient, and subject to
984 * sign errors. It should be fixed.
985 */
986 if (offset >= shmfd->shm_size ||
987 offset + size > round_page(shmfd->shm_size)) {
988 VM_OBJECT_WUNLOCK(obj);
989 return (EINVAL);
990 }
991
992 shmfd->shm_kmappings++;
993 vm_object_reference_locked(obj);
994 VM_OBJECT_WUNLOCK(obj);
995
996 /* Map the object into the kernel_map and wire it. */
997 kva = vm_map_min(kernel_map);
998 ofs = offset & PAGE_MASK;
999 offset = trunc_page(offset);
1000 size = round_page(size + ofs);
1001 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0,
1002 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
1003 VM_PROT_READ | VM_PROT_WRITE, 0);
1004 if (rv == KERN_SUCCESS) {
1005 rv = vm_map_wire(kernel_map, kva, kva + size,
1006 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
1007 if (rv == KERN_SUCCESS) {
1008 *memp = (void *)(kva + ofs);
1009 return (0);
1010 }
1011 vm_map_remove(kernel_map, kva, kva + size);
1012 } else
1013 vm_object_deallocate(obj);
1014
1015 /* On failure, drop our mapping reference. */
1016 VM_OBJECT_WLOCK(obj);
1017 shmfd->shm_kmappings--;
1018 VM_OBJECT_WUNLOCK(obj);
1019
1020 return (vm_mmap_to_errno(rv));
1021 }
1022
1023 /*
1024 * We require the caller to unmap the entire entry. This allows us to
1025 * safely decrement shm_kmappings when a mapping is removed.
1026 */
1027 int
1028 shm_unmap(struct file *fp, void *mem, size_t size)
1029 {
1030 struct shmfd *shmfd;
1031 vm_map_entry_t entry;
1032 vm_offset_t kva, ofs;
1033 vm_object_t obj;
1034 vm_pindex_t pindex;
1035 vm_prot_t prot;
1036 boolean_t wired;
1037 vm_map_t map;
1038 int rv;
1039
1040 if (fp->f_type != DTYPE_SHM)
1041 return (EINVAL);
1042 shmfd = fp->f_data;
1043 kva = (vm_offset_t)mem;
1044 ofs = kva & PAGE_MASK;
1045 kva = trunc_page(kva);
1046 size = round_page(size + ofs);
1047 map = kernel_map;
1048 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
1049 &obj, &pindex, &prot, &wired);
1050 if (rv != KERN_SUCCESS)
1051 return (EINVAL);
1052 if (entry->start != kva || entry->end != kva + size) {
1053 vm_map_lookup_done(map, entry);
1054 return (EINVAL);
1055 }
1056 vm_map_lookup_done(map, entry);
1057 if (obj != shmfd->shm_object)
1058 return (EINVAL);
1059 vm_map_remove(map, kva, kva + size);
1060 VM_OBJECT_WLOCK(obj);
1061 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
1062 shmfd->shm_kmappings--;
1063 VM_OBJECT_WUNLOCK(obj);
1064 return (0);
1065 }
1066
1067 void
1068 shm_path(struct shmfd *shmfd, char *path, size_t size)
1069 {
1070 const char *shm_path, *pr_path;
1071 size_t pr_pathlen;
1072
1073 if (shmfd->shm_path == NULL)
1074 return;
1075 sx_slock(&shm_dict_lock);
1076 shm_path = shmfd->shm_path;
1077 if (shm_path != NULL) {
1078 pr_path = curthread->td_ucred->cr_prison->pr_path;
1079 if (strcmp(pr_path, "/") != 0) {
1080 /* Return the jail-rooted pathname. */
1081 pr_pathlen = strlen(pr_path);
1082 if (strncmp(shm_path, pr_path, pr_pathlen) == 0 &&
1083 shm_path[pr_pathlen] == '/')
1084 shm_path += pr_pathlen;
1085 }
1086 strlcpy(path, shm_path, size);
1087 }
1088 sx_sunlock(&shm_dict_lock);
1089 }
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