1/*-
2 * Copyright (c) 2006 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 * (2) 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 * (3) Add support for this file type to fstat(1).
39 *
40 * (4) Resource limits? Does this need its own resource limits or are the
41 * existing limits in mmap(2) sufficient?
42 *
43 * (5) Partial page truncation. vnode_pager_setsize() will zero any parts
44 * of a partially mapped page as a result of ftruncate(2)/truncate(2).
45 * We can do the same (with the same pmap evil), but do we need to
46 * worry about the bits on disk if the page is swapped out or will the
47 * swapper zero the parts of a page that are invalid if the page is
48 * swapped back in for us?
49 *
50 * (6) Add MAC support in mac_biba(4) and mac_mls(4).
51 *
52 * (7) Add a MAC check_create() hook for creating new named objects.
53 */
54
55#include <sys/cdefs.h>
56__FBSDID("$FreeBSD: head/sys/kern/uipc_shm.c 193303 2009-06-02 08:02:27Z alc $");
57
58#include "opt_mac.h"
59
60#include <sys/param.h>
61#include <sys/fcntl.h>
62#include <sys/file.h>
63#include <sys/filedesc.h>
64#include <sys/fnv_hash.h>
65#include <sys/kernel.h>
66#include <sys/lock.h>
67#include <sys/malloc.h>
68#include <sys/mman.h>
69#include <sys/mutex.h>
70#include <sys/proc.h>
71#include <sys/refcount.h>
72#include <sys/resourcevar.h>
73#include <sys/stat.h>
74#include <sys/sysctl.h>
75#include <sys/sysproto.h>
76#include <sys/systm.h>
77#include <sys/sx.h>
78#include <sys/time.h>
79#include <sys/vnode.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_map.h>
87#include <vm/vm_object.h>
88#include <vm/vm_page.h>
89#include <vm/vm_pager.h>
90#include <vm/swap_pager.h>
91
92struct shm_mapping {
93 char *sm_path;
94 Fnv32_t sm_fnv;
95 struct shmfd *sm_shmfd;
96 LIST_ENTRY(shm_mapping) sm_link;
97};
98
99static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
100static LIST_HEAD(, shm_mapping) *shm_dictionary;
101static struct sx shm_dict_lock;
102static struct mtx shm_timestamp_lock;
103static u_long shm_hash;
104
105#define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash])
106
107static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
108static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
109static void shm_dict_init(void *arg);
110static void shm_drop(struct shmfd *shmfd);
111static struct shmfd *shm_hold(struct shmfd *shmfd);
112static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
113static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
114static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
115static void shm_dotruncate(struct shmfd *shmfd, off_t length);
116
117static fo_rdwr_t shm_read;
118static fo_rdwr_t shm_write;
119static fo_truncate_t shm_truncate;
120static fo_ioctl_t shm_ioctl;
121static fo_poll_t shm_poll;
122static fo_kqfilter_t shm_kqfilter;
123static fo_stat_t shm_stat;
124static fo_close_t shm_close;
125
126/* File descriptor operations. */
127static struct fileops shm_ops = {
128 .fo_read = shm_read,
129 .fo_write = shm_write,
130 .fo_truncate = shm_truncate,
131 .fo_ioctl = shm_ioctl,
132 .fo_poll = shm_poll,
133 .fo_kqfilter = shm_kqfilter,
134 .fo_stat = shm_stat,
135 .fo_close = shm_close,
136 .fo_flags = DFLAG_PASSABLE
137};
138
139FEATURE(posix_shm, "POSIX shared memory");
140
141static int
142shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
143 int flags, struct thread *td)
144{
145
146 return (EOPNOTSUPP);
147}
148
149static int
150shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
151 int flags, struct thread *td)
152{
153
154 return (EOPNOTSUPP);
155}
156
157static int
158shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
159 struct thread *td)
160{
161 struct shmfd *shmfd;
162#ifdef MAC
163 int error;
164#endif
165
166 shmfd = fp->f_data;
167#ifdef MAC
168 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
169 if (error)
170 return (error);
171#endif
172 shm_dotruncate(shmfd, length);
173 return (0);
174}
175
176static int
177shm_ioctl(struct file *fp, u_long com, void *data,
178 struct ucred *active_cred, struct thread *td)
179{
180
181 return (EOPNOTSUPP);
182}
183
184static int
185shm_poll(struct file *fp, int events, struct ucred *active_cred,
186 struct thread *td)
187{
188
189 return (EOPNOTSUPP);
190}
191
192static int
193shm_kqfilter(struct file *fp, struct knote *kn)
194{
195
196 return (EOPNOTSUPP);
197}
198
199static int
200shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
201 struct thread *td)
202{
203 struct shmfd *shmfd;
204#ifdef MAC
205 int error;
206#endif
207
208 shmfd = fp->f_data;
209
210#ifdef MAC
211 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
212 if (error)
213 return (error);
214#endif
215
216 /*
217 * Attempt to return sanish values for fstat() on a memory file
218 * descriptor.
219 */
220 bzero(sb, sizeof(*sb));
221 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */
222 sb->st_blksize = PAGE_SIZE;
223 sb->st_size = shmfd->shm_size;
224 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
225 sb->st_atimespec = shmfd->shm_atime;
226 sb->st_ctimespec = shmfd->shm_ctime;
227 sb->st_mtimespec = shmfd->shm_mtime;
228 sb->st_birthtimespec = shmfd->shm_birthtime;
229 sb->st_uid = shmfd->shm_uid;
230 sb->st_gid = shmfd->shm_gid;
231
232 return (0);
233}
234
235static int
236shm_close(struct file *fp, struct thread *td)
237{
238 struct shmfd *shmfd;
239
240 shmfd = fp->f_data;
241 fp->f_data = NULL;
242 shm_drop(shmfd);
243
244 return (0);
245}
246
247static void
248shm_dotruncate(struct shmfd *shmfd, off_t length)
249{
250 vm_object_t object;
251 vm_page_t m;
252 vm_pindex_t nobjsize;
253
254 object = shmfd->shm_object;
255 VM_OBJECT_LOCK(object);
256 if (length == shmfd->shm_size) {
257 VM_OBJECT_UNLOCK(object);
258 return;
259 }
260 nobjsize = OFF_TO_IDX(length + PAGE_MASK);
261
262 /* Are we shrinking? If so, trim the end. */
263 if (length < shmfd->shm_size) {
264 /* Toss in memory pages. */
265 if (nobjsize < object->size)
266 vm_object_page_remove(object, nobjsize, object->size,
267 FALSE);
268
269 /* Toss pages from swap. */
270 if (object->type == OBJT_SWAP)
271 swap_pager_freespace(object, nobjsize,
272 object->size - nobjsize);
273
274 /*
275 * If the last page is partially mapped, then zero out
276 * the garbage at the end of the page. See comments
277 * in vnode_pager_setsize() for more details.
278 *
279 * XXXJHB: This handles in memory pages, but what about
280 * a page swapped out to disk?
281 */
282 if ((length & PAGE_MASK) &&
283 (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL &&
284 m->valid != 0) {
285 int base = (int)length & PAGE_MASK;
286 int size = PAGE_SIZE - base;
287
288 pmap_zero_page_area(m, base, size);
289
290 /*
291 * Update the valid bits to reflect the blocks that
292 * have been zeroed. Some of these valid bits may
293 * have already been set.
294 */
295 vm_page_set_valid(m, base, size);
296
297 /*
298 * Round "base" to the next block boundary so that the
299 * dirty bit for a partially zeroed block is not
300 * cleared.
301 */
302 base = roundup2(base, DEV_BSIZE);
303
304 vm_page_lock_queues();
305 vm_page_clear_dirty(m, base, PAGE_SIZE - base);
306 vm_page_unlock_queues();
307 } else if ((length & PAGE_MASK) &&
308 __predict_false(object->cache != NULL)) {
309 vm_page_cache_free(object, OFF_TO_IDX(length),
310 nobjsize);
311 }
312 }
313 shmfd->shm_size = length;
314 mtx_lock(&shm_timestamp_lock);
315 vfs_timestamp(&shmfd->shm_ctime);
316 shmfd->shm_mtime = shmfd->shm_ctime;
317 mtx_unlock(&shm_timestamp_lock);
318 object->size = nobjsize;
319 VM_OBJECT_UNLOCK(object);
320}
321
322/*
323 * shmfd object management including creation and reference counting
324 * routines.
325 */
326static struct shmfd *
327shm_alloc(struct ucred *ucred, mode_t mode)
328{
329 struct shmfd *shmfd;
330
331 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
332 shmfd->shm_size = 0;
333 shmfd->shm_uid = ucred->cr_uid;
334 shmfd->shm_gid = ucred->cr_gid;
335 shmfd->shm_mode = mode;
336 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
337 shmfd->shm_size, VM_PROT_DEFAULT, 0);
338 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
339 VM_OBJECT_LOCK(shmfd->shm_object);
340 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
341 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT);
342 VM_OBJECT_UNLOCK(shmfd->shm_object);
343 vfs_timestamp(&shmfd->shm_birthtime);
344 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
345 shmfd->shm_birthtime;
346 refcount_init(&shmfd->shm_refs, 1);
347#ifdef MAC
348 mac_posixshm_init(shmfd);
349 mac_posixshm_create(ucred, shmfd);
350#endif
351
352 return (shmfd);
353}
354
355static struct shmfd *
356shm_hold(struct shmfd *shmfd)
357{
358
359 refcount_acquire(&shmfd->shm_refs);
360 return (shmfd);
361}
362
363static void
364shm_drop(struct shmfd *shmfd)
365{
366
367 if (refcount_release(&shmfd->shm_refs)) {
368#ifdef MAC
369 mac_posixshm_destroy(shmfd);
370#endif
371 vm_object_deallocate(shmfd->shm_object);
372 free(shmfd, M_SHMFD);
373 }
374}
375
376/*
377 * Determine if the credentials have sufficient permissions for a
378 * specified combination of FREAD and FWRITE.
379 */
380static int
381shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
382{
383 accmode_t accmode;
384
385 accmode = 0;
386 if (flags & FREAD)
387 accmode |= VREAD;
388 if (flags & FWRITE)
389 accmode |= VWRITE;
390 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
391 accmode, ucred, NULL));
392}
393
394/*
395 * Dictionary management. We maintain an in-kernel dictionary to map
396 * paths to shmfd objects. We use the FNV hash on the path to store
397 * the mappings in a hash table.
398 */
399static void
400shm_dict_init(void *arg)
401{
402
403 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
404 sx_init(&shm_dict_lock, "shm dictionary");
405 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
406}
407SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL);
408
409static struct shmfd *
410shm_lookup(char *path, Fnv32_t fnv)
411{
412 struct shm_mapping *map;
413
414 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
415 if (map->sm_fnv != fnv)
416 continue;
417 if (strcmp(map->sm_path, path) == 0)
418 return (map->sm_shmfd);
419 }
420
421 return (NULL);
422}
423
424static void
425shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
426{
427 struct shm_mapping *map;
428
429 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
430 map->sm_path = path;
431 map->sm_fnv = fnv;
432 map->sm_shmfd = shm_hold(shmfd);
433 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
434}
435
436static int
437shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
438{
439 struct shm_mapping *map;
440 int error;
441
442 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
443 if (map->sm_fnv != fnv)
444 continue;
445 if (strcmp(map->sm_path, path) == 0) {
446#ifdef MAC
447 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
448 if (error)
449 return (error);
450#endif
451 error = shm_access(map->sm_shmfd, ucred,
452 FREAD | FWRITE);
453 if (error)
454 return (error);
455 LIST_REMOVE(map, sm_link);
456 shm_drop(map->sm_shmfd);
457 free(map->sm_path, M_SHMFD);
458 free(map, M_SHMFD);
459 return (0);
460 }
461 }
462
463 return (ENOENT);
464}
465
466/* System calls. */
467int
468shm_open(struct thread *td, struct shm_open_args *uap)
469{
470 struct filedesc *fdp;
471 struct shmfd *shmfd;
472 struct file *fp;
473 char *path;
474 Fnv32_t fnv;
475 mode_t cmode;
476 int fd, error;
477
478 if ((uap->flags & O_ACCMODE) != O_RDONLY &&
479 (uap->flags & O_ACCMODE) != O_RDWR)
480 return (EINVAL);
481
482 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0)
483 return (EINVAL);
484
485 fdp = td->td_proc->p_fd;
486 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;
487
488 error = falloc(td, &fp, &fd);
489 if (error)
490 return (error);
491
492 /* A SHM_ANON path pointer creates an anonymous object. */
493 if (uap->path == SHM_ANON) {
494 /* A read-only anonymous object is pointless. */
495 if ((uap->flags & O_ACCMODE) == O_RDONLY) {
496 fdclose(fdp, fp, fd, td);
497 fdrop(fp, td);
498 return (EINVAL);
499 }
500 shmfd = shm_alloc(td->td_ucred, cmode);
501 } else {
502 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
503 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
504
505 /* Require paths to start with a '/' character. */
506 if (error == 0 && path[0] != '/')
507 error = EINVAL;
508 if (error) {
509 fdclose(fdp, fp, fd, td);
510 fdrop(fp, td);
511 free(path, M_SHMFD);
512 return (error);
513 }
514
515 fnv = fnv_32_str(path, FNV1_32_INIT);
516 sx_xlock(&shm_dict_lock);
517 shmfd = shm_lookup(path, fnv);
518 if (shmfd == NULL) {
519 /* Object does not yet exist, create it if requested. */
520 if (uap->flags & O_CREAT) {
521 shmfd = shm_alloc(td->td_ucred, cmode);
522 shm_insert(path, fnv, shmfd);
523 } else {
524 free(path, M_SHMFD);
525 error = ENOENT;
526 }
527 } else {
528 /*
529 * Object already exists, obtain a new
530 * reference if requested and permitted.
531 */
532 free(path, M_SHMFD);
533 if ((uap->flags & (O_CREAT | O_EXCL)) ==
534 (O_CREAT | O_EXCL))
535 error = EEXIST;
536 else {
537#ifdef MAC
538 error = mac_posixshm_check_open(td->td_ucred,
539 shmfd);
540 if (error == 0)
541#endif
542 error = shm_access(shmfd, td->td_ucred,
543 FFLAGS(uap->flags & O_ACCMODE));
544 }
545
546 /*
547 * Truncate the file back to zero length if
548 * O_TRUNC was specified and the object was
549 * opened with read/write.
550 */
551 if (error == 0 &&
552 (uap->flags & (O_ACCMODE | O_TRUNC)) ==
553 (O_RDWR | O_TRUNC)) {
554#ifdef MAC
555 error = mac_posixshm_check_truncate(
556 td->td_ucred, fp->f_cred, shmfd);
557 if (error == 0)
558#endif
559 shm_dotruncate(shmfd, 0);
560 }
561 if (error == 0)
562 shm_hold(shmfd);
563 }
564 sx_xunlock(&shm_dict_lock);
565
566 if (error) {
567 fdclose(fdp, fp, fd, td);
568 fdrop(fp, td);
569 return (error);
570 }
571 }
572
573 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
574
575 FILEDESC_XLOCK(fdp);
576 if (fdp->fd_ofiles[fd] == fp)
577 fdp->fd_ofileflags[fd] |= UF_EXCLOSE;
578 FILEDESC_XUNLOCK(fdp);
579 td->td_retval[0] = fd;
580 fdrop(fp, td);
581
582 return (0);
583}
584
585int
586shm_unlink(struct thread *td, struct shm_unlink_args *uap)
587{
588 char *path;
589 Fnv32_t fnv;
590 int error;
591
592 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
593 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
594 if (error) {
595 free(path, M_TEMP);
596 return (error);
597 }
598
599 fnv = fnv_32_str(path, FNV1_32_INIT);
600 sx_xlock(&shm_dict_lock);
601 error = shm_remove(path, fnv, td->td_ucred);
602 sx_xunlock(&shm_dict_lock);
603 free(path, M_TEMP);
604
605 return (error);
606}
607
608/*
609 * mmap() helper to validate mmap() requests against shm object state
610 * and give mmap() the vm_object to use for the mapping.
611 */
612int
613shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
614 vm_object_t *obj)
615{
616
617 /*
618 * XXXRW: This validation is probably insufficient, and subject to
619 * sign errors. It should be fixed.
620 */
621 if (foff >= shmfd->shm_size ||
622 foff + objsize > round_page(shmfd->shm_size))
623 return (EINVAL);
624
625 mtx_lock(&shm_timestamp_lock);
626 vfs_timestamp(&shmfd->shm_atime);
627 mtx_unlock(&shm_timestamp_lock);
628 vm_object_reference(shmfd->shm_object);
629 *obj = shmfd->shm_object;
630 return (0);
631}
2 * Copyright (c) 2006 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 * (2) 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 * (3) Add support for this file type to fstat(1).
39 *
40 * (4) Resource limits? Does this need its own resource limits or are the
41 * existing limits in mmap(2) sufficient?
42 *
43 * (5) Partial page truncation. vnode_pager_setsize() will zero any parts
44 * of a partially mapped page as a result of ftruncate(2)/truncate(2).
45 * We can do the same (with the same pmap evil), but do we need to
46 * worry about the bits on disk if the page is swapped out or will the
47 * swapper zero the parts of a page that are invalid if the page is
48 * swapped back in for us?
49 *
50 * (6) Add MAC support in mac_biba(4) and mac_mls(4).
51 *
52 * (7) Add a MAC check_create() hook for creating new named objects.
53 */
54
55#include <sys/cdefs.h>
56__FBSDID("$FreeBSD: head/sys/kern/uipc_shm.c 193303 2009-06-02 08:02:27Z alc $");
57
58#include "opt_mac.h"
59
60#include <sys/param.h>
61#include <sys/fcntl.h>
62#include <sys/file.h>
63#include <sys/filedesc.h>
64#include <sys/fnv_hash.h>
65#include <sys/kernel.h>
66#include <sys/lock.h>
67#include <sys/malloc.h>
68#include <sys/mman.h>
69#include <sys/mutex.h>
70#include <sys/proc.h>
71#include <sys/refcount.h>
72#include <sys/resourcevar.h>
73#include <sys/stat.h>
74#include <sys/sysctl.h>
75#include <sys/sysproto.h>
76#include <sys/systm.h>
77#include <sys/sx.h>
78#include <sys/time.h>
79#include <sys/vnode.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_map.h>
87#include <vm/vm_object.h>
88#include <vm/vm_page.h>
89#include <vm/vm_pager.h>
90#include <vm/swap_pager.h>
91
92struct shm_mapping {
93 char *sm_path;
94 Fnv32_t sm_fnv;
95 struct shmfd *sm_shmfd;
96 LIST_ENTRY(shm_mapping) sm_link;
97};
98
99static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
100static LIST_HEAD(, shm_mapping) *shm_dictionary;
101static struct sx shm_dict_lock;
102static struct mtx shm_timestamp_lock;
103static u_long shm_hash;
104
105#define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash])
106
107static int shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags);
108static struct shmfd *shm_alloc(struct ucred *ucred, mode_t mode);
109static void shm_dict_init(void *arg);
110static void shm_drop(struct shmfd *shmfd);
111static struct shmfd *shm_hold(struct shmfd *shmfd);
112static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
113static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
114static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
115static void shm_dotruncate(struct shmfd *shmfd, off_t length);
116
117static fo_rdwr_t shm_read;
118static fo_rdwr_t shm_write;
119static fo_truncate_t shm_truncate;
120static fo_ioctl_t shm_ioctl;
121static fo_poll_t shm_poll;
122static fo_kqfilter_t shm_kqfilter;
123static fo_stat_t shm_stat;
124static fo_close_t shm_close;
125
126/* File descriptor operations. */
127static struct fileops shm_ops = {
128 .fo_read = shm_read,
129 .fo_write = shm_write,
130 .fo_truncate = shm_truncate,
131 .fo_ioctl = shm_ioctl,
132 .fo_poll = shm_poll,
133 .fo_kqfilter = shm_kqfilter,
134 .fo_stat = shm_stat,
135 .fo_close = shm_close,
136 .fo_flags = DFLAG_PASSABLE
137};
138
139FEATURE(posix_shm, "POSIX shared memory");
140
141static int
142shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
143 int flags, struct thread *td)
144{
145
146 return (EOPNOTSUPP);
147}
148
149static int
150shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
151 int flags, struct thread *td)
152{
153
154 return (EOPNOTSUPP);
155}
156
157static int
158shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
159 struct thread *td)
160{
161 struct shmfd *shmfd;
162#ifdef MAC
163 int error;
164#endif
165
166 shmfd = fp->f_data;
167#ifdef MAC
168 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
169 if (error)
170 return (error);
171#endif
172 shm_dotruncate(shmfd, length);
173 return (0);
174}
175
176static int
177shm_ioctl(struct file *fp, u_long com, void *data,
178 struct ucred *active_cred, struct thread *td)
179{
180
181 return (EOPNOTSUPP);
182}
183
184static int
185shm_poll(struct file *fp, int events, struct ucred *active_cred,
186 struct thread *td)
187{
188
189 return (EOPNOTSUPP);
190}
191
192static int
193shm_kqfilter(struct file *fp, struct knote *kn)
194{
195
196 return (EOPNOTSUPP);
197}
198
199static int
200shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
201 struct thread *td)
202{
203 struct shmfd *shmfd;
204#ifdef MAC
205 int error;
206#endif
207
208 shmfd = fp->f_data;
209
210#ifdef MAC
211 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
212 if (error)
213 return (error);
214#endif
215
216 /*
217 * Attempt to return sanish values for fstat() on a memory file
218 * descriptor.
219 */
220 bzero(sb, sizeof(*sb));
221 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */
222 sb->st_blksize = PAGE_SIZE;
223 sb->st_size = shmfd->shm_size;
224 sb->st_blocks = (sb->st_size + sb->st_blksize - 1) / sb->st_blksize;
225 sb->st_atimespec = shmfd->shm_atime;
226 sb->st_ctimespec = shmfd->shm_ctime;
227 sb->st_mtimespec = shmfd->shm_mtime;
228 sb->st_birthtimespec = shmfd->shm_birthtime;
229 sb->st_uid = shmfd->shm_uid;
230 sb->st_gid = shmfd->shm_gid;
231
232 return (0);
233}
234
235static int
236shm_close(struct file *fp, struct thread *td)
237{
238 struct shmfd *shmfd;
239
240 shmfd = fp->f_data;
241 fp->f_data = NULL;
242 shm_drop(shmfd);
243
244 return (0);
245}
246
247static void
248shm_dotruncate(struct shmfd *shmfd, off_t length)
249{
250 vm_object_t object;
251 vm_page_t m;
252 vm_pindex_t nobjsize;
253
254 object = shmfd->shm_object;
255 VM_OBJECT_LOCK(object);
256 if (length == shmfd->shm_size) {
257 VM_OBJECT_UNLOCK(object);
258 return;
259 }
260 nobjsize = OFF_TO_IDX(length + PAGE_MASK);
261
262 /* Are we shrinking? If so, trim the end. */
263 if (length < shmfd->shm_size) {
264 /* Toss in memory pages. */
265 if (nobjsize < object->size)
266 vm_object_page_remove(object, nobjsize, object->size,
267 FALSE);
268
269 /* Toss pages from swap. */
270 if (object->type == OBJT_SWAP)
271 swap_pager_freespace(object, nobjsize,
272 object->size - nobjsize);
273
274 /*
275 * If the last page is partially mapped, then zero out
276 * the garbage at the end of the page. See comments
277 * in vnode_pager_setsize() for more details.
278 *
279 * XXXJHB: This handles in memory pages, but what about
280 * a page swapped out to disk?
281 */
282 if ((length & PAGE_MASK) &&
283 (m = vm_page_lookup(object, OFF_TO_IDX(length))) != NULL &&
284 m->valid != 0) {
285 int base = (int)length & PAGE_MASK;
286 int size = PAGE_SIZE - base;
287
288 pmap_zero_page_area(m, base, size);
289
290 /*
291 * Update the valid bits to reflect the blocks that
292 * have been zeroed. Some of these valid bits may
293 * have already been set.
294 */
295 vm_page_set_valid(m, base, size);
296
297 /*
298 * Round "base" to the next block boundary so that the
299 * dirty bit for a partially zeroed block is not
300 * cleared.
301 */
302 base = roundup2(base, DEV_BSIZE);
303
304 vm_page_lock_queues();
305 vm_page_clear_dirty(m, base, PAGE_SIZE - base);
306 vm_page_unlock_queues();
307 } else if ((length & PAGE_MASK) &&
308 __predict_false(object->cache != NULL)) {
309 vm_page_cache_free(object, OFF_TO_IDX(length),
310 nobjsize);
311 }
312 }
313 shmfd->shm_size = length;
314 mtx_lock(&shm_timestamp_lock);
315 vfs_timestamp(&shmfd->shm_ctime);
316 shmfd->shm_mtime = shmfd->shm_ctime;
317 mtx_unlock(&shm_timestamp_lock);
318 object->size = nobjsize;
319 VM_OBJECT_UNLOCK(object);
320}
321
322/*
323 * shmfd object management including creation and reference counting
324 * routines.
325 */
326static struct shmfd *
327shm_alloc(struct ucred *ucred, mode_t mode)
328{
329 struct shmfd *shmfd;
330
331 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
332 shmfd->shm_size = 0;
333 shmfd->shm_uid = ucred->cr_uid;
334 shmfd->shm_gid = ucred->cr_gid;
335 shmfd->shm_mode = mode;
336 shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
337 shmfd->shm_size, VM_PROT_DEFAULT, 0);
338 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
339 VM_OBJECT_LOCK(shmfd->shm_object);
340 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
341 vm_object_set_flag(shmfd->shm_object, OBJ_NOSPLIT);
342 VM_OBJECT_UNLOCK(shmfd->shm_object);
343 vfs_timestamp(&shmfd->shm_birthtime);
344 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
345 shmfd->shm_birthtime;
346 refcount_init(&shmfd->shm_refs, 1);
347#ifdef MAC
348 mac_posixshm_init(shmfd);
349 mac_posixshm_create(ucred, shmfd);
350#endif
351
352 return (shmfd);
353}
354
355static struct shmfd *
356shm_hold(struct shmfd *shmfd)
357{
358
359 refcount_acquire(&shmfd->shm_refs);
360 return (shmfd);
361}
362
363static void
364shm_drop(struct shmfd *shmfd)
365{
366
367 if (refcount_release(&shmfd->shm_refs)) {
368#ifdef MAC
369 mac_posixshm_destroy(shmfd);
370#endif
371 vm_object_deallocate(shmfd->shm_object);
372 free(shmfd, M_SHMFD);
373 }
374}
375
376/*
377 * Determine if the credentials have sufficient permissions for a
378 * specified combination of FREAD and FWRITE.
379 */
380static int
381shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
382{
383 accmode_t accmode;
384
385 accmode = 0;
386 if (flags & FREAD)
387 accmode |= VREAD;
388 if (flags & FWRITE)
389 accmode |= VWRITE;
390 return (vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
391 accmode, ucred, NULL));
392}
393
394/*
395 * Dictionary management. We maintain an in-kernel dictionary to map
396 * paths to shmfd objects. We use the FNV hash on the path to store
397 * the mappings in a hash table.
398 */
399static void
400shm_dict_init(void *arg)
401{
402
403 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
404 sx_init(&shm_dict_lock, "shm dictionary");
405 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
406}
407SYSINIT(shm_dict_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_dict_init, NULL);
408
409static struct shmfd *
410shm_lookup(char *path, Fnv32_t fnv)
411{
412 struct shm_mapping *map;
413
414 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
415 if (map->sm_fnv != fnv)
416 continue;
417 if (strcmp(map->sm_path, path) == 0)
418 return (map->sm_shmfd);
419 }
420
421 return (NULL);
422}
423
424static void
425shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
426{
427 struct shm_mapping *map;
428
429 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
430 map->sm_path = path;
431 map->sm_fnv = fnv;
432 map->sm_shmfd = shm_hold(shmfd);
433 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
434}
435
436static int
437shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
438{
439 struct shm_mapping *map;
440 int error;
441
442 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
443 if (map->sm_fnv != fnv)
444 continue;
445 if (strcmp(map->sm_path, path) == 0) {
446#ifdef MAC
447 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
448 if (error)
449 return (error);
450#endif
451 error = shm_access(map->sm_shmfd, ucred,
452 FREAD | FWRITE);
453 if (error)
454 return (error);
455 LIST_REMOVE(map, sm_link);
456 shm_drop(map->sm_shmfd);
457 free(map->sm_path, M_SHMFD);
458 free(map, M_SHMFD);
459 return (0);
460 }
461 }
462
463 return (ENOENT);
464}
465
466/* System calls. */
467int
468shm_open(struct thread *td, struct shm_open_args *uap)
469{
470 struct filedesc *fdp;
471 struct shmfd *shmfd;
472 struct file *fp;
473 char *path;
474 Fnv32_t fnv;
475 mode_t cmode;
476 int fd, error;
477
478 if ((uap->flags & O_ACCMODE) != O_RDONLY &&
479 (uap->flags & O_ACCMODE) != O_RDWR)
480 return (EINVAL);
481
482 if ((uap->flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC)) != 0)
483 return (EINVAL);
484
485 fdp = td->td_proc->p_fd;
486 cmode = (uap->mode & ~fdp->fd_cmask) & ACCESSPERMS;
487
488 error = falloc(td, &fp, &fd);
489 if (error)
490 return (error);
491
492 /* A SHM_ANON path pointer creates an anonymous object. */
493 if (uap->path == SHM_ANON) {
494 /* A read-only anonymous object is pointless. */
495 if ((uap->flags & O_ACCMODE) == O_RDONLY) {
496 fdclose(fdp, fp, fd, td);
497 fdrop(fp, td);
498 return (EINVAL);
499 }
500 shmfd = shm_alloc(td->td_ucred, cmode);
501 } else {
502 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
503 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
504
505 /* Require paths to start with a '/' character. */
506 if (error == 0 && path[0] != '/')
507 error = EINVAL;
508 if (error) {
509 fdclose(fdp, fp, fd, td);
510 fdrop(fp, td);
511 free(path, M_SHMFD);
512 return (error);
513 }
514
515 fnv = fnv_32_str(path, FNV1_32_INIT);
516 sx_xlock(&shm_dict_lock);
517 shmfd = shm_lookup(path, fnv);
518 if (shmfd == NULL) {
519 /* Object does not yet exist, create it if requested. */
520 if (uap->flags & O_CREAT) {
521 shmfd = shm_alloc(td->td_ucred, cmode);
522 shm_insert(path, fnv, shmfd);
523 } else {
524 free(path, M_SHMFD);
525 error = ENOENT;
526 }
527 } else {
528 /*
529 * Object already exists, obtain a new
530 * reference if requested and permitted.
531 */
532 free(path, M_SHMFD);
533 if ((uap->flags & (O_CREAT | O_EXCL)) ==
534 (O_CREAT | O_EXCL))
535 error = EEXIST;
536 else {
537#ifdef MAC
538 error = mac_posixshm_check_open(td->td_ucred,
539 shmfd);
540 if (error == 0)
541#endif
542 error = shm_access(shmfd, td->td_ucred,
543 FFLAGS(uap->flags & O_ACCMODE));
544 }
545
546 /*
547 * Truncate the file back to zero length if
548 * O_TRUNC was specified and the object was
549 * opened with read/write.
550 */
551 if (error == 0 &&
552 (uap->flags & (O_ACCMODE | O_TRUNC)) ==
553 (O_RDWR | O_TRUNC)) {
554#ifdef MAC
555 error = mac_posixshm_check_truncate(
556 td->td_ucred, fp->f_cred, shmfd);
557 if (error == 0)
558#endif
559 shm_dotruncate(shmfd, 0);
560 }
561 if (error == 0)
562 shm_hold(shmfd);
563 }
564 sx_xunlock(&shm_dict_lock);
565
566 if (error) {
567 fdclose(fdp, fp, fd, td);
568 fdrop(fp, td);
569 return (error);
570 }
571 }
572
573 finit(fp, FFLAGS(uap->flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
574
575 FILEDESC_XLOCK(fdp);
576 if (fdp->fd_ofiles[fd] == fp)
577 fdp->fd_ofileflags[fd] |= UF_EXCLOSE;
578 FILEDESC_XUNLOCK(fdp);
579 td->td_retval[0] = fd;
580 fdrop(fp, td);
581
582 return (0);
583}
584
585int
586shm_unlink(struct thread *td, struct shm_unlink_args *uap)
587{
588 char *path;
589 Fnv32_t fnv;
590 int error;
591
592 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
593 error = copyinstr(uap->path, path, MAXPATHLEN, NULL);
594 if (error) {
595 free(path, M_TEMP);
596 return (error);
597 }
598
599 fnv = fnv_32_str(path, FNV1_32_INIT);
600 sx_xlock(&shm_dict_lock);
601 error = shm_remove(path, fnv, td->td_ucred);
602 sx_xunlock(&shm_dict_lock);
603 free(path, M_TEMP);
604
605 return (error);
606}
607
608/*
609 * mmap() helper to validate mmap() requests against shm object state
610 * and give mmap() the vm_object to use for the mapping.
611 */
612int
613shm_mmap(struct shmfd *shmfd, vm_size_t objsize, vm_ooffset_t foff,
614 vm_object_t *obj)
615{
616
617 /*
618 * XXXRW: This validation is probably insufficient, and subject to
619 * sign errors. It should be fixed.
620 */
621 if (foff >= shmfd->shm_size ||
622 foff + objsize > round_page(shmfd->shm_size))
623 return (EINVAL);
624
625 mtx_lock(&shm_timestamp_lock);
626 vfs_timestamp(&shmfd->shm_atime);
627 mtx_unlock(&shm_timestamp_lock);
628 vm_object_reference(shmfd->shm_object);
629 *obj = shmfd->shm_object;
630 return (0);
631}