2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2006, 2011, 2016-2017 Robert N. M. Watson
7 * Portions of this software were developed by BAE Systems, the University of
8 * Cambridge Computer Laboratory, and Memorial University under DARPA/AFRL
9 * contract FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent
10 * Computing (TC) research program.
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * Support for shared swap-backed anonymous memory objects via
36 * shm_open(2), shm_rename(2), and shm_unlink(2).
37 * While most of the implementation is here, vm_mmap.c contains
38 * mapping logic changes.
40 * posixshmcontrol(1) allows users to inspect the state of the memory
41 * objects. Per-uid swap resource limit controls total amount of
42 * memory that user can consume for anonymous objects, including
46 #include <sys/cdefs.h>
47 __FBSDID("$FreeBSD$");
49 #include "opt_capsicum.h"
50 #include "opt_ktrace.h"
52 #include <sys/param.h>
53 #include <sys/capsicum.h>
55 #include <sys/fcntl.h>
57 #include <sys/filedesc.h>
58 #include <sys/filio.h>
59 #include <sys/fnv_hash.h>
60 #include <sys/kernel.h>
61 #include <sys/limits.h>
63 #include <sys/signal.h>
65 #include <sys/ktrace.h>
67 #include <sys/malloc.h>
69 #include <sys/mutex.h>
72 #include <sys/refcount.h>
73 #include <sys/resourcevar.h>
74 #include <sys/rwlock.h>
77 #include <sys/syscallsubr.h>
78 #include <sys/sysctl.h>
79 #include <sys/sysproto.h>
80 #include <sys/systm.h>
83 #include <sys/vnode.h>
84 #include <sys/unistd.h>
87 #include <security/audit/audit.h>
88 #include <security/mac/mac_framework.h>
91 #include <vm/vm_param.h>
93 #include <vm/vm_extern.h>
94 #include <vm/vm_map.h>
95 #include <vm/vm_kern.h>
96 #include <vm/vm_object.h>
97 #include <vm/vm_page.h>
98 #include <vm/vm_pageout.h>
99 #include <vm/vm_pager.h>
100 #include <vm/swap_pager.h>
105 struct shmfd *sm_shmfd;
106 LIST_ENTRY(shm_mapping) sm_link;
109 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
110 static LIST_HEAD(, shm_mapping) *shm_dictionary;
111 static struct sx shm_dict_lock;
112 static struct mtx shm_timestamp_lock;
113 static u_long shm_hash;
114 static struct unrhdr64 shm_ino_unr;
115 static dev_t shm_dev_ino;
117 #define SHM_HASH(fnv) (&shm_dictionary[(fnv) & shm_hash])
119 static void shm_init(void *arg);
120 static void shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
121 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
122 static int shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
123 static int shm_dotruncate_locked(struct shmfd *shmfd, off_t length,
126 static fo_rdwr_t shm_read;
127 static fo_rdwr_t shm_write;
128 static fo_truncate_t shm_truncate;
129 static fo_ioctl_t shm_ioctl;
130 static fo_stat_t shm_stat;
131 static fo_close_t shm_close;
132 static fo_chmod_t shm_chmod;
133 static fo_chown_t shm_chown;
134 static fo_seek_t shm_seek;
135 static fo_fill_kinfo_t shm_fill_kinfo;
136 static fo_mmap_t shm_mmap;
137 static fo_get_seals_t shm_get_seals;
138 static fo_add_seals_t shm_add_seals;
140 /* File descriptor operations. */
141 struct fileops shm_ops = {
143 .fo_write = shm_write,
144 .fo_truncate = shm_truncate,
145 .fo_ioctl = shm_ioctl,
146 .fo_poll = invfo_poll,
147 .fo_kqfilter = invfo_kqfilter,
149 .fo_close = shm_close,
150 .fo_chmod = shm_chmod,
151 .fo_chown = shm_chown,
152 .fo_sendfile = vn_sendfile,
154 .fo_fill_kinfo = shm_fill_kinfo,
156 .fo_get_seals = shm_get_seals,
157 .fo_add_seals = shm_add_seals,
158 .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
161 FEATURE(posix_shm, "POSIX shared memory");
164 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
169 int error, offset, rv;
171 idx = OFF_TO_IDX(uio->uio_offset);
172 offset = uio->uio_offset & PAGE_MASK;
173 tlen = MIN(PAGE_SIZE - offset, len);
175 VM_OBJECT_WLOCK(obj);
178 * Read I/O without either a corresponding resident page or swap
179 * page: use zero_region. This is intended to avoid instantiating
180 * pages on read from a sparse region.
182 if (uio->uio_rw == UIO_READ && vm_page_lookup(obj, idx) == NULL &&
183 !vm_pager_has_page(obj, idx, NULL, NULL)) {
184 VM_OBJECT_WUNLOCK(obj);
185 return (uiomove(__DECONST(void *, zero_region), tlen, uio));
189 * Parallel reads of the page content from disk are prevented
192 * Although the tmpfs vnode lock is held here, it is
193 * nonetheless safe to sleep waiting for a free page. The
194 * pageout daemon does not need to acquire the tmpfs vnode
195 * lock to page out tobj's pages because tobj is a OBJT_SWAP
198 rv = vm_page_grab_valid(&m, obj, idx,
199 VM_ALLOC_NORMAL | VM_ALLOC_WIRED | VM_ALLOC_NOBUSY);
200 if (rv != VM_PAGER_OK) {
201 VM_OBJECT_WUNLOCK(obj);
202 printf("uiomove_object: vm_obj %p idx %jd pager error %d\n",
206 VM_OBJECT_WUNLOCK(obj);
207 error = uiomove_fromphys(&m, offset, tlen, uio);
208 if (uio->uio_rw == UIO_WRITE && error == 0) {
209 VM_OBJECT_WLOCK(obj);
211 vm_pager_page_unswapped(m);
212 VM_OBJECT_WUNLOCK(obj);
214 vm_page_unwire(m, PQ_ACTIVE);
220 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio)
227 while ((resid = uio->uio_resid) > 0) {
228 if (obj_size <= uio->uio_offset)
230 len = MIN(obj_size - uio->uio_offset, resid);
233 error = uiomove_object_page(obj, len, uio);
234 if (error != 0 || resid == uio->uio_resid)
241 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td)
248 foffset = foffset_lock(fp, 0);
253 (offset > 0 && foffset > OFF_MAX - offset)) {
260 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) {
264 offset += shmfd->shm_size;
272 if (offset < 0 || offset > shmfd->shm_size)
275 td->td_uretoff.tdu_off = offset;
277 foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
282 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
283 int flags, struct thread *td)
291 error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
295 foffset_lock_uio(fp, uio, flags);
296 rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
297 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
298 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
299 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
300 foffset_unlock_uio(fp, uio, flags);
305 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
306 int flags, struct thread *td)
314 error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd);
318 foffset_lock_uio(fp, uio, flags);
319 if ((flags & FOF_OFFSET) == 0) {
320 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
323 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
324 uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
326 if ((shmfd->shm_seals & F_SEAL_WRITE) != 0)
329 error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
330 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
331 foffset_unlock_uio(fp, uio, flags);
336 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
346 error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
350 return (shm_dotruncate(shmfd, length));
354 shm_ioctl(struct file *fp, u_long com, void *data, struct ucred *active_cred,
362 * Allow fcntl(fd, F_SETFL, O_NONBLOCK) to work,
363 * just like it would on an unlinked regular file
372 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
383 error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
389 * Attempt to return sanish values for fstat() on a memory file
392 bzero(sb, sizeof(*sb));
393 sb->st_blksize = PAGE_SIZE;
394 sb->st_size = shmfd->shm_size;
395 sb->st_blocks = howmany(sb->st_size, sb->st_blksize);
396 mtx_lock(&shm_timestamp_lock);
397 sb->st_atim = shmfd->shm_atime;
398 sb->st_ctim = shmfd->shm_ctime;
399 sb->st_mtim = shmfd->shm_mtime;
400 sb->st_birthtim = shmfd->shm_birthtime;
401 sb->st_mode = S_IFREG | shmfd->shm_mode; /* XXX */
402 sb->st_uid = shmfd->shm_uid;
403 sb->st_gid = shmfd->shm_gid;
404 mtx_unlock(&shm_timestamp_lock);
405 sb->st_dev = shm_dev_ino;
406 sb->st_ino = shmfd->shm_ino;
407 sb->st_nlink = shmfd->shm_object->ref_count;
413 shm_close(struct file *fp, struct thread *td)
425 shm_dotruncate_locked(struct shmfd *shmfd, off_t length, void *rl_cookie)
429 vm_pindex_t idx, nobjsize;
433 KASSERT(length >= 0, ("shm_dotruncate: length < 0"));
434 object = shmfd->shm_object;
435 VM_OBJECT_ASSERT_WLOCKED(object);
436 rangelock_cookie_assert(rl_cookie, RA_WLOCKED);
437 if (length == shmfd->shm_size)
439 nobjsize = OFF_TO_IDX(length + PAGE_MASK);
441 /* Are we shrinking? If so, trim the end. */
442 if (length < shmfd->shm_size) {
443 if ((shmfd->shm_seals & F_SEAL_SHRINK) != 0)
447 * Disallow any requests to shrink the size if this
448 * object is mapped into the kernel.
450 if (shmfd->shm_kmappings > 0)
454 * Zero the truncated part of the last page.
456 base = length & PAGE_MASK;
458 idx = OFF_TO_IDX(length);
460 m = vm_page_grab(object, idx, VM_ALLOC_NOCREAT);
462 MPASS(vm_page_all_valid(m));
463 } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
464 m = vm_page_alloc(object, idx,
465 VM_ALLOC_NORMAL | VM_ALLOC_WAITFAIL);
468 rv = vm_pager_get_pages(object, &m, 1, NULL,
470 if (rv == VM_PAGER_OK) {
472 * Since the page was not resident,
473 * and therefore not recently
474 * accessed, immediately enqueue it
475 * for asynchronous laundering. The
476 * current operation is not regarded
482 VM_OBJECT_WUNLOCK(object);
487 pmap_zero_page_area(m, base, PAGE_SIZE - base);
488 KASSERT(vm_page_all_valid(m),
489 ("shm_dotruncate: page %p is invalid", m));
492 vm_pager_page_unswapped(m);
495 delta = IDX_TO_OFF(object->size - nobjsize);
497 /* Toss in memory pages. */
498 if (nobjsize < object->size)
499 vm_object_page_remove(object, nobjsize, object->size,
502 /* Toss pages from swap. */
503 if (object->type == OBJT_SWAP)
504 swap_pager_freespace(object, nobjsize, delta);
506 /* Free the swap accounted for shm */
507 swap_release_by_cred(delta, object->cred);
508 object->charge -= delta;
510 if ((shmfd->shm_seals & F_SEAL_GROW) != 0)
513 /* Try to reserve additional swap space. */
514 delta = IDX_TO_OFF(nobjsize - object->size);
515 if (!swap_reserve_by_cred(delta, object->cred))
517 object->charge += delta;
519 shmfd->shm_size = length;
520 mtx_lock(&shm_timestamp_lock);
521 vfs_timestamp(&shmfd->shm_ctime);
522 shmfd->shm_mtime = shmfd->shm_ctime;
523 mtx_unlock(&shm_timestamp_lock);
524 object->size = nobjsize;
529 shm_dotruncate(struct shmfd *shmfd, off_t length)
534 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
536 VM_OBJECT_WLOCK(shmfd->shm_object);
537 error = shm_dotruncate_locked(shmfd, length, rl_cookie);
538 VM_OBJECT_WUNLOCK(shmfd->shm_object);
539 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
544 * shmfd object management including creation and reference counting
548 shm_alloc(struct ucred *ucred, mode_t mode)
552 shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
554 shmfd->shm_uid = ucred->cr_uid;
555 shmfd->shm_gid = ucred->cr_gid;
556 shmfd->shm_mode = mode;
557 shmfd->shm_object = vm_pager_allocate(OBJT_SWAP, NULL,
558 shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
559 KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
560 shmfd->shm_object->pg_color = 0;
561 VM_OBJECT_WLOCK(shmfd->shm_object);
562 vm_object_clear_flag(shmfd->shm_object, OBJ_ONEMAPPING);
563 vm_object_set_flag(shmfd->shm_object, OBJ_COLORED | OBJ_NOSPLIT);
564 VM_OBJECT_WUNLOCK(shmfd->shm_object);
565 vfs_timestamp(&shmfd->shm_birthtime);
566 shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
567 shmfd->shm_birthtime;
568 shmfd->shm_ino = alloc_unr64(&shm_ino_unr);
569 refcount_init(&shmfd->shm_refs, 1);
570 mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF);
571 rangelock_init(&shmfd->shm_rl);
573 mac_posixshm_init(shmfd);
574 mac_posixshm_create(ucred, shmfd);
581 shm_hold(struct shmfd *shmfd)
584 refcount_acquire(&shmfd->shm_refs);
589 shm_drop(struct shmfd *shmfd)
592 if (refcount_release(&shmfd->shm_refs)) {
594 mac_posixshm_destroy(shmfd);
596 rangelock_destroy(&shmfd->shm_rl);
597 mtx_destroy(&shmfd->shm_mtx);
598 vm_object_deallocate(shmfd->shm_object);
599 free(shmfd, M_SHMFD);
604 * Determine if the credentials have sufficient permissions for a
605 * specified combination of FREAD and FWRITE.
608 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
618 mtx_lock(&shm_timestamp_lock);
619 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
620 accmode, ucred, NULL);
621 mtx_unlock(&shm_timestamp_lock);
626 * Dictionary management. We maintain an in-kernel dictionary to map
627 * paths to shmfd objects. We use the FNV hash on the path to store
628 * the mappings in a hash table.
634 mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
635 sx_init(&shm_dict_lock, "shm dictionary");
636 shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
637 new_unrhdr64(&shm_ino_unr, 1);
638 shm_dev_ino = devfs_alloc_cdp_inode();
639 KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized"));
641 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL);
643 static struct shmfd *
644 shm_lookup(char *path, Fnv32_t fnv)
646 struct shm_mapping *map;
648 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
649 if (map->sm_fnv != fnv)
651 if (strcmp(map->sm_path, path) == 0)
652 return (map->sm_shmfd);
659 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
661 struct shm_mapping *map;
663 map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
666 map->sm_shmfd = shm_hold(shmfd);
667 shmfd->shm_path = path;
668 LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
672 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
674 struct shm_mapping *map;
677 LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
678 if (map->sm_fnv != fnv)
680 if (strcmp(map->sm_path, path) == 0) {
682 error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
686 error = shm_access(map->sm_shmfd, ucred,
690 map->sm_shmfd->shm_path = NULL;
691 LIST_REMOVE(map, sm_link);
692 shm_drop(map->sm_shmfd);
693 free(map->sm_path, M_SHMFD);
703 kern_shm_open(struct thread *td, const char *userpath, int flags, mode_t mode,
704 struct filecaps *fcaps, int initial_seals)
706 struct filedesc *fdp;
717 #ifdef CAPABILITY_MODE
719 * shm_open(2) is only allowed for anonymous objects.
721 if (IN_CAPABILITY_MODE(td) && (userpath != SHM_ANON))
725 AUDIT_ARG_FFLAGS(flags);
726 AUDIT_ARG_MODE(mode);
728 if ((flags & O_ACCMODE) != O_RDONLY && (flags & O_ACCMODE) != O_RDWR)
731 if ((flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0)
735 * Currently only F_SEAL_SEAL may be set when creating or opening shmfd.
736 * If the decision is made later to allow additional seals, care must be
737 * taken below to ensure that the seals are properly set if the shmfd
738 * already existed -- this currently assumes that only F_SEAL_SEAL can
739 * be set and doesn't take further precautions to ensure the validity of
740 * the seals being added with respect to current mappings.
742 if ((initial_seals & ~F_SEAL_SEAL) != 0)
745 fdp = td->td_proc->p_fd;
746 cmode = (mode & ~fdp->fd_cmask) & ACCESSPERMS;
749 * shm_open(2) created shm should always have O_CLOEXEC set, as mandated
750 * by POSIX. We allow it to be unset here so that an in-kernel
751 * interface may be written as a thin layer around shm, optionally not
752 * setting CLOEXEC. For shm_open(2), O_CLOEXEC is set unconditionally
753 * in sys_shm_open() to keep this implementation compliant.
755 error = falloc_caps(td, &fp, &fd, flags & O_CLOEXEC, fcaps);
759 /* A SHM_ANON path pointer creates an anonymous object. */
760 if (userpath == SHM_ANON) {
761 /* A read-only anonymous object is pointless. */
762 if ((flags & O_ACCMODE) == O_RDONLY) {
767 shmfd = shm_alloc(td->td_ucred, cmode);
768 shmfd->shm_seals = initial_seals;
770 path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
771 pr_path = td->td_ucred->cr_prison->pr_path;
773 /* Construct a full pathname for jailed callers. */
774 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0
775 : strlcpy(path, pr_path, MAXPATHLEN);
776 error = copyinstr(userpath, path + pr_pathlen,
777 MAXPATHLEN - pr_pathlen, NULL);
779 if (error == 0 && KTRPOINT(curthread, KTR_NAMEI))
782 /* Require paths to start with a '/' character. */
783 if (error == 0 && path[pr_pathlen] != '/')
792 AUDIT_ARG_UPATH1_CANON(path);
793 fnv = fnv_32_str(path, FNV1_32_INIT);
794 sx_xlock(&shm_dict_lock);
795 shmfd = shm_lookup(path, fnv);
797 /* Object does not yet exist, create it if requested. */
798 if (flags & O_CREAT) {
800 error = mac_posixshm_check_create(td->td_ucred,
804 shmfd = shm_alloc(td->td_ucred, cmode);
805 shmfd->shm_seals = initial_seals;
806 shm_insert(path, fnv, shmfd);
815 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
819 * kern_shm_open() likely shouldn't ever error out on
820 * trying to set a seal that already exists, unlike
821 * F_ADD_SEALS. This would break terribly as
822 * shm_open(2) actually sets F_SEAL_SEAL to maintain
823 * historical behavior where the underlying file could
826 initial_seals &= ~shmfd->shm_seals;
829 * Object already exists, obtain a new
830 * reference if requested and permitted.
835 * initial_seals can't set additional seals if we've
836 * already been set F_SEAL_SEAL. If F_SEAL_SEAL is set,
837 * then we've already removed that one from
838 * initial_seals. This is currently redundant as we
839 * only allow setting F_SEAL_SEAL at creation time, but
840 * it's cheap to check and decreases the effort required
841 * to allow additional seals.
843 if ((shmfd->shm_seals & F_SEAL_SEAL) != 0 &&
846 else if ((flags & (O_CREAT | O_EXCL)) ==
851 error = mac_posixshm_check_open(td->td_ucred,
852 shmfd, FFLAGS(flags & O_ACCMODE));
855 error = shm_access(shmfd, td->td_ucred,
856 FFLAGS(flags & O_ACCMODE));
860 * Truncate the file back to zero length if
861 * O_TRUNC was specified and the object was
862 * opened with read/write.
865 (flags & (O_ACCMODE | O_TRUNC)) ==
866 (O_RDWR | O_TRUNC)) {
867 VM_OBJECT_WLOCK(shmfd->shm_object);
869 error = mac_posixshm_check_truncate(
870 td->td_ucred, fp->f_cred, shmfd);
873 error = shm_dotruncate_locked(shmfd, 0,
875 VM_OBJECT_WUNLOCK(shmfd->shm_object);
879 * Currently we only allow F_SEAL_SEAL to be
880 * set initially. As noted above, this would
881 * need to be reworked should that change.
883 shmfd->shm_seals |= initial_seals;
886 rangelock_unlock(&shmfd->shm_rl, rl_cookie,
889 sx_xunlock(&shm_dict_lock);
898 finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
900 td->td_retval[0] = fd;
907 #ifdef COMPAT_FREEBSD12
909 freebsd12_shm_open(struct thread *td, struct freebsd12_shm_open_args *uap)
912 return (kern_shm_open(td, uap->path, uap->flags | O_CLOEXEC, uap->mode,
918 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
926 path = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
927 pr_path = td->td_ucred->cr_prison->pr_path;
928 pr_pathlen = strcmp(pr_path, "/") == 0 ? 0
929 : strlcpy(path, pr_path, MAXPATHLEN);
930 error = copyinstr(uap->path, path + pr_pathlen, MAXPATHLEN - pr_pathlen,
937 if (KTRPOINT(curthread, KTR_NAMEI))
940 AUDIT_ARG_UPATH1_CANON(path);
941 fnv = fnv_32_str(path, FNV1_32_INIT);
942 sx_xlock(&shm_dict_lock);
943 error = shm_remove(path, fnv, td->td_ucred);
944 sx_xunlock(&shm_dict_lock);
951 sys_shm_rename(struct thread *td, struct shm_rename_args *uap)
953 char *path_from = NULL, *path_to = NULL;
954 Fnv32_t fnv_from, fnv_to;
955 struct shmfd *fd_from;
963 * Make sure the user passed only valid flags.
964 * If you add a new flag, please add a new term here.
967 SHM_RENAME_NOREPLACE |
975 * EXCHANGE and NOREPLACE don't quite make sense together. Let's
976 * force the user to choose one or the other.
978 if ((flags & SHM_RENAME_NOREPLACE) != 0 &&
979 (flags & SHM_RENAME_EXCHANGE) != 0) {
985 * Malloc zone M_SHMFD, since this path may end up freed later from
986 * M_SHMFD if we end up doing an insert.
988 path_from = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
989 error = copyinstr(uap->path_from, path_from, MAXPATHLEN, NULL);
993 path_to = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
994 error = copyinstr(uap->path_to, path_to, MAXPATHLEN, NULL);
998 /* Rename with from/to equal is a no-op */
999 if (strncmp(path_from, path_to, MAXPATHLEN) == 0)
1002 fnv_from = fnv_32_str(path_from, FNV1_32_INIT);
1003 fnv_to = fnv_32_str(path_to, FNV1_32_INIT);
1005 sx_xlock(&shm_dict_lock);
1007 fd_from = shm_lookup(path_from, fnv_from);
1008 if (fd_from == NULL) {
1009 sx_xunlock(&shm_dict_lock);
1014 fd_to = shm_lookup(path_to, fnv_to);
1015 if ((flags & SHM_RENAME_NOREPLACE) != 0 && fd_to != NULL) {
1016 sx_xunlock(&shm_dict_lock);
1022 * Unconditionally prevents shm_remove from invalidating the 'from'
1026 error = shm_remove(path_from, fnv_from, td->td_ucred);
1029 * One of my assumptions failed if ENOENT (e.g. locking didn't
1032 KASSERT(error != ENOENT, ("Our shm disappeared during shm_rename: %s",
1036 sx_xunlock(&shm_dict_lock);
1041 * If we are exchanging, we need to ensure the shm_remove below
1042 * doesn't invalidate the dest shm's state.
1044 if ((flags & SHM_RENAME_EXCHANGE) != 0 && fd_to != NULL)
1048 * NOTE: if path_to is not already in the hash, c'est la vie;
1049 * it simply means we have nothing already at path_to to unlink.
1050 * That is the ENOENT case.
1052 * If we somehow don't have access to unlink this guy, but
1053 * did for the shm at path_from, then relink the shm to path_from
1054 * and abort with EACCES.
1056 * All other errors: that is weird; let's relink and abort the
1059 error = shm_remove(path_to, fnv_to, td->td_ucred);
1060 if (error && error != ENOENT) {
1061 shm_insert(path_from, fnv_from, fd_from);
1063 /* Don't free path_from now, since the hash references it */
1065 sx_xunlock(&shm_dict_lock);
1069 shm_insert(path_to, fnv_to, fd_from);
1071 /* Don't free path_to now, since the hash references it */
1074 /* We kept a ref when we removed, and incremented again in insert */
1077 KASSERT(fd_from->shm_refs > 0, ("Expected >0 refs; got: %d\n",
1078 fd_from->shm_refs));
1081 if ((flags & SHM_RENAME_EXCHANGE) != 0 && fd_to != NULL) {
1082 shm_insert(path_from, fnv_from, fd_to);
1086 KASSERT(fd_to->shm_refs > 0, ("Expected >0 refs; got: %d\n",
1092 sx_xunlock(&shm_dict_lock);
1095 if (path_from != NULL)
1096 free(path_from, M_SHMFD);
1097 if (path_to != NULL)
1098 free(path_to, M_SHMFD);
1103 shm_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t objsize,
1104 vm_prot_t prot, vm_prot_t cap_maxprot, int flags,
1105 vm_ooffset_t foff, struct thread *td)
1107 struct shmfd *shmfd;
1114 maxprot = VM_PROT_NONE;
1116 rl_cookie = rangelock_rlock(&shmfd->shm_rl, 0, objsize,
1118 /* FREAD should always be set. */
1119 if ((fp->f_flag & FREAD) != 0)
1120 maxprot |= VM_PROT_EXECUTE | VM_PROT_READ;
1121 if ((fp->f_flag & FWRITE) != 0)
1122 maxprot |= VM_PROT_WRITE;
1124 writecnt = (flags & MAP_SHARED) != 0 && (prot & VM_PROT_WRITE) != 0;
1126 if (writecnt && (shmfd->shm_seals & F_SEAL_WRITE) != 0) {
1131 /* Don't permit shared writable mappings on read-only descriptors. */
1132 if (writecnt && (maxprot & VM_PROT_WRITE) == 0) {
1136 maxprot &= cap_maxprot;
1138 /* See comment in vn_mmap(). */
1141 objsize > OFF_MAX ||
1143 foff < 0 || foff > OFF_MAX - objsize) {
1149 error = mac_posixshm_check_mmap(td->td_ucred, shmfd, prot, flags);
1154 mtx_lock(&shm_timestamp_lock);
1155 vfs_timestamp(&shmfd->shm_atime);
1156 mtx_unlock(&shm_timestamp_lock);
1157 vm_object_reference(shmfd->shm_object);
1160 vm_pager_update_writecount(shmfd->shm_object, 0, objsize);
1161 error = vm_mmap_object(map, addr, objsize, prot, maxprot, flags,
1162 shmfd->shm_object, foff, writecnt, td);
1165 vm_pager_release_writecount(shmfd->shm_object, 0,
1167 vm_object_deallocate(shmfd->shm_object);
1170 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
1175 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
1178 struct shmfd *shmfd;
1183 mtx_lock(&shm_timestamp_lock);
1185 * SUSv4 says that x bits of permission need not be affected.
1186 * Be consistent with our shm_open there.
1189 error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
1193 error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid,
1194 shmfd->shm_gid, VADMIN, active_cred, NULL);
1197 shmfd->shm_mode = mode & ACCESSPERMS;
1199 mtx_unlock(&shm_timestamp_lock);
1204 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
1207 struct shmfd *shmfd;
1212 mtx_lock(&shm_timestamp_lock);
1214 error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
1218 if (uid == (uid_t)-1)
1219 uid = shmfd->shm_uid;
1220 if (gid == (gid_t)-1)
1221 gid = shmfd->shm_gid;
1222 if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
1223 (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
1224 (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN)))
1226 shmfd->shm_uid = uid;
1227 shmfd->shm_gid = gid;
1229 mtx_unlock(&shm_timestamp_lock);
1234 * Helper routines to allow the backing object of a shared memory file
1235 * descriptor to be mapped in the kernel.
1238 shm_map(struct file *fp, size_t size, off_t offset, void **memp)
1240 struct shmfd *shmfd;
1241 vm_offset_t kva, ofs;
1245 if (fp->f_type != DTYPE_SHM)
1248 obj = shmfd->shm_object;
1249 VM_OBJECT_WLOCK(obj);
1251 * XXXRW: This validation is probably insufficient, and subject to
1252 * sign errors. It should be fixed.
1254 if (offset >= shmfd->shm_size ||
1255 offset + size > round_page(shmfd->shm_size)) {
1256 VM_OBJECT_WUNLOCK(obj);
1260 shmfd->shm_kmappings++;
1261 vm_object_reference_locked(obj);
1262 VM_OBJECT_WUNLOCK(obj);
1264 /* Map the object into the kernel_map and wire it. */
1265 kva = vm_map_min(kernel_map);
1266 ofs = offset & PAGE_MASK;
1267 offset = trunc_page(offset);
1268 size = round_page(size + ofs);
1269 rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0,
1270 VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
1271 VM_PROT_READ | VM_PROT_WRITE, 0);
1272 if (rv == KERN_SUCCESS) {
1273 rv = vm_map_wire(kernel_map, kva, kva + size,
1274 VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
1275 if (rv == KERN_SUCCESS) {
1276 *memp = (void *)(kva + ofs);
1279 vm_map_remove(kernel_map, kva, kva + size);
1281 vm_object_deallocate(obj);
1283 /* On failure, drop our mapping reference. */
1284 VM_OBJECT_WLOCK(obj);
1285 shmfd->shm_kmappings--;
1286 VM_OBJECT_WUNLOCK(obj);
1288 return (vm_mmap_to_errno(rv));
1292 * We require the caller to unmap the entire entry. This allows us to
1293 * safely decrement shm_kmappings when a mapping is removed.
1296 shm_unmap(struct file *fp, void *mem, size_t size)
1298 struct shmfd *shmfd;
1299 vm_map_entry_t entry;
1300 vm_offset_t kva, ofs;
1308 if (fp->f_type != DTYPE_SHM)
1311 kva = (vm_offset_t)mem;
1312 ofs = kva & PAGE_MASK;
1313 kva = trunc_page(kva);
1314 size = round_page(size + ofs);
1316 rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
1317 &obj, &pindex, &prot, &wired);
1318 if (rv != KERN_SUCCESS)
1320 if (entry->start != kva || entry->end != kva + size) {
1321 vm_map_lookup_done(map, entry);
1324 vm_map_lookup_done(map, entry);
1325 if (obj != shmfd->shm_object)
1327 vm_map_remove(map, kva, kva + size);
1328 VM_OBJECT_WLOCK(obj);
1329 KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
1330 shmfd->shm_kmappings--;
1331 VM_OBJECT_WUNLOCK(obj);
1336 shm_fill_kinfo_locked(struct shmfd *shmfd, struct kinfo_file *kif, bool list)
1338 const char *path, *pr_path;
1342 sx_assert(&shm_dict_lock, SA_LOCKED);
1343 kif->kf_type = KF_TYPE_SHM;
1344 kif->kf_un.kf_file.kf_file_mode = S_IFREG | shmfd->shm_mode;
1345 kif->kf_un.kf_file.kf_file_size = shmfd->shm_size;
1346 if (shmfd->shm_path != NULL) {
1347 if (shmfd->shm_path != NULL) {
1348 path = shmfd->shm_path;
1349 pr_path = curthread->td_ucred->cr_prison->pr_path;
1350 if (strcmp(pr_path, "/") != 0) {
1351 /* Return the jail-rooted pathname. */
1352 pr_pathlen = strlen(pr_path);
1353 visible = strncmp(path, pr_path, pr_pathlen)
1354 == 0 && path[pr_pathlen] == '/';
1355 if (list && !visible)
1360 strlcpy(kif->kf_path, path, sizeof(kif->kf_path));
1367 shm_fill_kinfo(struct file *fp, struct kinfo_file *kif,
1368 struct filedesc *fdp __unused)
1372 sx_slock(&shm_dict_lock);
1373 res = shm_fill_kinfo_locked(fp->f_data, kif, false);
1374 sx_sunlock(&shm_dict_lock);
1379 shm_add_seals(struct file *fp, int seals)
1381 struct shmfd *shmfd;
1383 vm_ooffset_t writemappings;
1388 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
1391 /* Even already-set seals should result in EPERM. */
1392 if ((shmfd->shm_seals & F_SEAL_SEAL) != 0) {
1396 nseals = seals & ~shmfd->shm_seals;
1397 if ((nseals & F_SEAL_WRITE) != 0) {
1399 * The rangelock above prevents writable mappings from being
1400 * added after we've started applying seals. The RLOCK here
1401 * is to avoid torn reads on ILP32 arches as unmapping/reducing
1402 * writemappings will be done without a rangelock.
1404 VM_OBJECT_RLOCK(shmfd->shm_object);
1405 writemappings = shmfd->shm_object->un_pager.swp.writemappings;
1406 VM_OBJECT_RUNLOCK(shmfd->shm_object);
1407 /* kmappings are also writable */
1408 if (writemappings > 0) {
1413 shmfd->shm_seals |= nseals;
1415 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
1420 shm_get_seals(struct file *fp, int *seals)
1422 struct shmfd *shmfd;
1425 *seals = shmfd->shm_seals;
1430 sysctl_posix_shm_list(SYSCTL_HANDLER_ARGS)
1432 struct shm_mapping *shmm;
1434 struct kinfo_file kif;
1439 sbuf_new_for_sysctl(&sb, NULL, sizeof(struct kinfo_file) * 5, req);
1440 sbuf_clear_flags(&sb, SBUF_INCLUDENUL);
1443 sx_slock(&shm_dict_lock);
1444 for (i = 0; i < shm_hash + 1; i++) {
1445 LIST_FOREACH(shmm, &shm_dictionary[i], sm_link) {
1446 error = shm_fill_kinfo_locked(shmm->sm_shmfd,
1453 if (req->oldptr != NULL &&
1454 kif.kf_structsize + curlen > req->oldlen)
1456 error = sbuf_bcat(&sb, &kif, kif.kf_structsize) == 0 ?
1460 curlen += kif.kf_structsize;
1463 sx_sunlock(&shm_dict_lock);
1464 error2 = sbuf_finish(&sb);
1466 return (error != 0 ? error : error2);
1469 SYSCTL_PROC(_kern_ipc, OID_AUTO, posix_shm_list,
1470 CTLFLAG_RD | CTLFLAG_MPSAFE | CTLTYPE_OPAQUE,
1471 NULL, 0, sysctl_posix_shm_list, "",
1475 kern_shm_open2(struct thread *td, const char *path, int flags, mode_t mode,
1476 int shmflags, const char *name __unused)
1480 if ((shmflags & ~SHM_ALLOW_SEALING) != 0)
1483 initial_seals = F_SEAL_SEAL;
1484 if ((shmflags & SHM_ALLOW_SEALING) != 0)
1485 initial_seals &= ~F_SEAL_SEAL;
1486 return (kern_shm_open(td, path, flags, mode, NULL, initial_seals));
1490 * This version of the shm_open() interface leaves CLOEXEC behavior up to the
1491 * caller, and libc will enforce it for the traditional shm_open() call. This
1492 * allows other consumers, like memfd_create(), to opt-in for CLOEXEC. This
1493 * interface also includes a 'name' argument that is currently unused, but could
1494 * potentially be exported later via some interface for debugging purposes.
1495 * From the kernel's perspective, it is optional. Individual consumers like
1496 * memfd_create() may require it in order to be compatible with other systems
1497 * implementing the same function.
1500 sys_shm_open2(struct thread *td, struct shm_open2_args *uap)
1503 return (kern_shm_open2(td, uap->path, uap->flags, uap->mode,
1504 uap->shmflags, uap->name));