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