sys/kern/uipc_shm.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2006, 2011, 2016-2017 Robert N. M. Watson
   5  * Copyright 2020 The FreeBSD Foundation
   6  * All rights reserved.
   7  *
   8  * Portions of this software were developed by BAE Systems, the University of
   9  * Cambridge Computer Laboratory, and Memorial University under DARPA/AFRL
  10  * contract FA8650-15-C-7558 ("CADETS"), as part of the DARPA Transparent
  11  * Computing (TC) research program.
  12  *
  13  * Portions of this software were developed by Konstantin Belousov
  14  * under sponsorship from the FreeBSD Foundation.
  15  *
  16  * Redistribution and use in source and binary forms, with or without
  17  * modification, are permitted provided that the following conditions
  18  * are met:
  19  * 1. Redistributions of source code must retain the above copyright
  20  *    notice, this list of conditions and the following disclaimer.
  21  * 2. Redistributions in binary form must reproduce the above copyright
  22  *    notice, this list of conditions and the following disclaimer in the
  23  *    documentation and/or other materials provided with the distribution.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  35  * SUCH DAMAGE.
  36  */
  37
  38 /*
  39  * Support for shared swap-backed anonymous memory objects via
  40  * shm_open(2), shm_rename(2), and shm_unlink(2).
  41  * While most of the implementation is here, vm_mmap.c contains
  42  * mapping logic changes.
  43  *
  44  * posixshmcontrol(1) allows users to inspect the state of the memory
  45  * objects.  Per-uid swap resource limit controls total amount of
  46  * memory that user can consume for anonymous objects, including
  47  * shared.
  48  */
  49
  50 #include <sys/cdefs.h>
  51 __FBSDID("$FreeBSD$");
  52
  53 #include "opt_capsicum.h"
  54 #include "opt_ktrace.h"
  55
  56 #include <sys/param.h>
  57 #include <sys/capsicum.h>
  58 #include <sys/conf.h>
  59 #include <sys/fcntl.h>
  60 #include <sys/file.h>
  61 #include <sys/filedesc.h>
  62 #include <sys/filio.h>
  63 #include <sys/fnv_hash.h>
  64 #include <sys/kernel.h>
  65 #include <sys/limits.h>
  66 #include <sys/uio.h>
  67 #include <sys/signal.h>
  68 #include <sys/jail.h>
  69 #include <sys/ktrace.h>
  70 #include <sys/lock.h>
  71 #include <sys/malloc.h>
  72 #include <sys/mman.h>
  73 #include <sys/mutex.h>
  74 #include <sys/priv.h>
  75 #include <sys/proc.h>
  76 #include <sys/refcount.h>
  77 #include <sys/resourcevar.h>
  78 #include <sys/rwlock.h>
  79 #include <sys/sbuf.h>
  80 #include <sys/stat.h>
  81 #include <sys/syscallsubr.h>
  82 #include <sys/sysctl.h>
  83 #include <sys/sysproto.h>
  84 #include <sys/systm.h>
  85 #include <sys/sx.h>
  86 #include <sys/time.h>
  87 #include <sys/vmmeter.h>
  88 #include <sys/vnode.h>
  89 #include <sys/unistd.h>
  90 #include <sys/user.h>
  91
  92 #include <security/audit/audit.h>
  93 #include <security/mac/mac_framework.h>
  94
  95 #include <vm/vm.h>
  96 #include <vm/vm_param.h>
  97 #include <vm/pmap.h>
  98 #include <vm/vm_extern.h>
  99 #include <vm/vm_map.h>
 100 #include <vm/vm_kern.h>
 101 #include <vm/vm_object.h>
 102 #include <vm/vm_page.h>
 103 #include <vm/vm_pageout.h>
 104 #include <vm/vm_pager.h>
 105 #include <vm/swap_pager.h>
 106
 107 struct shm_mapping {
 108         char            *sm_path;
 109         Fnv32_t         sm_fnv;
 110         struct shmfd    *sm_shmfd;
 111         LIST_ENTRY(shm_mapping) sm_link;
 112 };
 113
 114 static MALLOC_DEFINE(M_SHMFD, "shmfd", "shared memory file descriptor");
 115 static LIST_HEAD(, shm_mapping) *shm_dictionary;
 116 static struct sx shm_dict_lock;
 117 static struct mtx shm_timestamp_lock;
 118 static u_long shm_hash;
 119 static struct unrhdr64 shm_ino_unr;
 120 static dev_t shm_dev_ino;
 121
 122 #define SHM_HASH(fnv)   (&shm_dictionary[(fnv) & shm_hash])
 123
 124 static void     shm_init(void *arg);
 125 static void     shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd);
 126 static struct shmfd *shm_lookup(char *path, Fnv32_t fnv);
 127 static int      shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred);
 128 static int      shm_dotruncate_cookie(struct shmfd *shmfd, off_t length,
 129     void *rl_cookie);
 130 static int      shm_dotruncate_locked(struct shmfd *shmfd, off_t length,
 131     void *rl_cookie);
 132 static int      shm_copyin_path(struct thread *td, const char *userpath_in,
 133     char **path_out);
 134
 135 static fo_rdwr_t        shm_read;
 136 static fo_rdwr_t        shm_write;
 137 static fo_truncate_t    shm_truncate;
 138 static fo_ioctl_t       shm_ioctl;
 139 static fo_stat_t        shm_stat;
 140 static fo_close_t       shm_close;
 141 static fo_chmod_t       shm_chmod;
 142 static fo_chown_t       shm_chown;
 143 static fo_seek_t        shm_seek;
 144 static fo_fill_kinfo_t  shm_fill_kinfo;
 145 static fo_mmap_t        shm_mmap;
 146 static fo_get_seals_t   shm_get_seals;
 147 static fo_add_seals_t   shm_add_seals;
 148 static fo_fallocate_t   shm_fallocate;
 149
 150 /* File descriptor operations. */
 151 struct fileops shm_ops = {
 152         .fo_read = shm_read,
 153         .fo_write = shm_write,
 154         .fo_truncate = shm_truncate,
 155         .fo_ioctl = shm_ioctl,
 156         .fo_poll = invfo_poll,
 157         .fo_kqfilter = invfo_kqfilter,
 158         .fo_stat = shm_stat,
 159         .fo_close = shm_close,
 160         .fo_chmod = shm_chmod,
 161         .fo_chown = shm_chown,
 162         .fo_sendfile = vn_sendfile,
 163         .fo_seek = shm_seek,
 164         .fo_fill_kinfo = shm_fill_kinfo,
 165         .fo_mmap = shm_mmap,
 166         .fo_get_seals = shm_get_seals,
 167         .fo_add_seals = shm_add_seals,
 168         .fo_fallocate = shm_fallocate,
 169         .fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE,
 170 };
 171
 172 FEATURE(posix_shm, "POSIX shared memory");
 173
 174 static SYSCTL_NODE(_vm, OID_AUTO, largepages, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
 175     "");
 176
 177 static int largepage_reclaim_tries = 1;
 178 SYSCTL_INT(_vm_largepages, OID_AUTO, reclaim_tries,
 179     CTLFLAG_RWTUN, &largepage_reclaim_tries, 0,
 180     "Number of contig reclaims before giving up for default alloc policy");
 181
 182 static int
 183 uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
 184 {
 185         vm_page_t m;
 186         vm_pindex_t idx;
 187         size_t tlen;
 188         int error, offset, rv;
 189
 190         idx = OFF_TO_IDX(uio->uio_offset);
 191         offset = uio->uio_offset & PAGE_MASK;
 192         tlen = MIN(PAGE_SIZE - offset, len);
 193
 194         rv = vm_page_grab_valid_unlocked(&m, obj, idx,
 195             VM_ALLOC_SBUSY | VM_ALLOC_IGN_SBUSY | VM_ALLOC_NOCREAT);
 196         if (rv == VM_PAGER_OK)
 197                 goto found;
 198
 199         /*
 200          * Read I/O without either a corresponding resident page or swap
 201          * page: use zero_region.  This is intended to avoid instantiating
 202          * pages on read from a sparse region.
 203          */
 204         VM_OBJECT_WLOCK(obj);
 205         m = vm_page_lookup(obj, idx);
 206         if (uio->uio_rw == UIO_READ && m == NULL &&
 207             !vm_pager_has_page(obj, idx, NULL, NULL)) {
 208                 VM_OBJECT_WUNLOCK(obj);
 209                 return (uiomove(__DECONST(void *, zero_region), tlen, uio));
 210         }
 211
 212         /*
 213          * Although the tmpfs vnode lock is held here, it is
 214          * nonetheless safe to sleep waiting for a free page.  The
 215          * pageout daemon does not need to acquire the tmpfs vnode
 216          * lock to page out tobj's pages because tobj is a OBJT_SWAP
 217          * type object.
 218          */
 219         rv = vm_page_grab_valid(&m, obj, idx,
 220             VM_ALLOC_NORMAL | VM_ALLOC_SBUSY | VM_ALLOC_IGN_SBUSY);
 221         if (rv != VM_PAGER_OK) {
 222                 VM_OBJECT_WUNLOCK(obj);
 223                 printf("uiomove_object: vm_obj %p idx %jd pager error %d\n",
 224                     obj, idx, rv);
 225                 return (EIO);
 226         }
 227         VM_OBJECT_WUNLOCK(obj);
 228
 229 found:
 230         error = uiomove_fromphys(&m, offset, tlen, uio);
 231         if (uio->uio_rw == UIO_WRITE && error == 0)
 232                 vm_page_set_dirty(m);
 233         vm_page_activate(m);
 234         vm_page_sunbusy(m);
 235
 236         return (error);
 237 }
 238
 239 int
 240 uiomove_object(vm_object_t obj, off_t obj_size, struct uio *uio)
 241 {
 242         ssize_t resid;
 243         size_t len;
 244         int error;
 245
 246         error = 0;
 247         while ((resid = uio->uio_resid) > 0) {
 248                 if (obj_size <= uio->uio_offset)
 249                         break;
 250                 len = MIN(obj_size - uio->uio_offset, resid);
 251                 if (len == 0)
 252                         break;
 253                 error = uiomove_object_page(obj, len, uio);
 254                 if (error != 0 || resid == uio->uio_resid)
 255                         break;
 256         }
 257         return (error);
 258 }
 259
 260 static u_long count_largepages[MAXPAGESIZES];
 261
 262 static int
 263 shm_largepage_phys_populate(vm_object_t object, vm_pindex_t pidx,
 264     int fault_type, vm_prot_t max_prot, vm_pindex_t *first, vm_pindex_t *last)
 265 {
 266         vm_page_t m;
 267         int psind;
 268
 269         psind = object->un_pager.phys.data_val;
 270         if (psind == 0 || pidx >= object->size)
 271                 return (VM_PAGER_FAIL);
 272         *first = rounddown2(pidx, pagesizes[psind] / PAGE_SIZE);
 273
 274         /*
 275          * We only busy the first page in the superpage run.  It is
 276          * useless to busy whole run since we only remove full
 277          * superpage, and it takes too long to busy e.g. 512 * 512 ==
 278          * 262144 pages constituing 1G amd64 superage.
 279          */
 280         m = vm_page_grab(object, *first, VM_ALLOC_NORMAL | VM_ALLOC_NOCREAT);
 281         MPASS(m != NULL);
 282
 283         *last = *first + atop(pagesizes[psind]) - 1;
 284         return (VM_PAGER_OK);
 285 }
 286
 287 static boolean_t
 288 shm_largepage_phys_haspage(vm_object_t object, vm_pindex_t pindex,
 289     int *before, int *after)
 290 {
 291         int psind;
 292
 293         psind = object->un_pager.phys.data_val;
 294         if (psind == 0 || pindex >= object->size)
 295                 return (FALSE);
 296         if (before != NULL) {
 297                 *before = pindex - rounddown2(pindex, pagesizes[psind] /
 298                     PAGE_SIZE);
 299         }
 300         if (after != NULL) {
 301                 *after = roundup2(pindex, pagesizes[psind] / PAGE_SIZE) -
 302                     pindex;
 303         }
 304         return (TRUE);
 305 }
 306
 307 static void
 308 shm_largepage_phys_ctor(vm_object_t object, vm_prot_t prot,
 309     vm_ooffset_t foff, struct ucred *cred)
 310 {
 311 }
 312
 313 static void
 314 shm_largepage_phys_dtor(vm_object_t object)
 315 {
 316         int psind;
 317
 318         psind = object->un_pager.phys.data_val;
 319         if (psind != 0) {
 320                 atomic_subtract_long(&count_largepages[psind],
 321                     object->size / (pagesizes[psind] / PAGE_SIZE));
 322                 vm_wire_sub(object->size);
 323         } else {
 324                 KASSERT(object->size == 0,
 325                     ("largepage phys obj %p not initialized bit size %#jx > 0",
 326                     object, (uintmax_t)object->size));
 327         }
 328 }
 329
 330 static struct phys_pager_ops shm_largepage_phys_ops = {
 331         .phys_pg_populate =     shm_largepage_phys_populate,
 332         .phys_pg_haspage =      shm_largepage_phys_haspage,
 333         .phys_pg_ctor =         shm_largepage_phys_ctor,
 334         .phys_pg_dtor =         shm_largepage_phys_dtor,
 335 };
 336
 337 bool
 338 shm_largepage(struct shmfd *shmfd)
 339 {
 340         return (shmfd->shm_object->type == OBJT_PHYS);
 341 }
 342
 343 static int
 344 shm_seek(struct file *fp, off_t offset, int whence, struct thread *td)
 345 {
 346         struct shmfd *shmfd;
 347         off_t foffset;
 348         int error;
 349
 350         shmfd = fp->f_data;
 351         foffset = foffset_lock(fp, 0);
 352         error = 0;
 353         switch (whence) {
 354         case L_INCR:
 355                 if (foffset < 0 ||
 356                     (offset > 0 && foffset > OFF_MAX - offset)) {
 357                         error = EOVERFLOW;
 358                         break;
 359                 }
 360                 offset += foffset;
 361                 break;
 362         case L_XTND:
 363                 if (offset > 0 && shmfd->shm_size > OFF_MAX - offset) {
 364                         error = EOVERFLOW;
 365                         break;
 366                 }
 367                 offset += shmfd->shm_size;
 368                 break;
 369         case L_SET:
 370                 break;
 371         default:
 372                 error = EINVAL;
 373         }
 374         if (error == 0) {
 375                 if (offset < 0 || offset > shmfd->shm_size)
 376                         error = EINVAL;
 377                 else
 378                         td->td_uretoff.tdu_off = offset;
 379         }
 380         foffset_unlock(fp, offset, error != 0 ? FOF_NOUPDATE : 0);
 381         return (error);
 382 }
 383
 384 static int
 385 shm_read(struct file *fp, struct uio *uio, struct ucred *active_cred,
 386     int flags, struct thread *td)
 387 {
 388         struct shmfd *shmfd;
 389         void *rl_cookie;
 390         int error;
 391
 392         shmfd = fp->f_data;
 393 #ifdef MAC
 394         error = mac_posixshm_check_read(active_cred, fp->f_cred, shmfd);
 395         if (error)
 396                 return (error);
 397 #endif
 398         foffset_lock_uio(fp, uio, flags);
 399         rl_cookie = rangelock_rlock(&shmfd->shm_rl, uio->uio_offset,
 400             uio->uio_offset + uio->uio_resid, &shmfd->shm_mtx);
 401         error = uiomove_object(shmfd->shm_object, shmfd->shm_size, uio);
 402         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 403         foffset_unlock_uio(fp, uio, flags);
 404         return (error);
 405 }
 406
 407 static int
 408 shm_write(struct file *fp, struct uio *uio, struct ucred *active_cred,
 409     int flags, struct thread *td)
 410 {
 411         struct shmfd *shmfd;
 412         void *rl_cookie;
 413         int error;
 414         off_t size;
 415
 416         shmfd = fp->f_data;
 417 #ifdef MAC
 418         error = mac_posixshm_check_write(active_cred, fp->f_cred, shmfd);
 419         if (error)
 420                 return (error);
 421 #endif
 422         if (shm_largepage(shmfd) && shmfd->shm_lp_psind == 0)
 423                 return (EINVAL);
 424         foffset_lock_uio(fp, uio, flags);
 425         if (uio->uio_resid > OFF_MAX - uio->uio_offset) {
 426                 /*
 427                  * Overflow is only an error if we're supposed to expand on
 428                  * write.  Otherwise, we'll just truncate the write to the
 429                  * size of the file, which can only grow up to OFF_MAX.
 430                  */
 431                 if ((shmfd->shm_flags & SHM_GROW_ON_WRITE) != 0) {
 432                         foffset_unlock_uio(fp, uio, flags);
 433                         return (EFBIG);
 434                 }
 435
 436                 size = shmfd->shm_size;
 437         } else {
 438                 size = uio->uio_offset + uio->uio_resid;
 439         }
 440         if ((flags & FOF_OFFSET) == 0) {
 441                 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
 442                     &shmfd->shm_mtx);
 443         } else {
 444                 rl_cookie = rangelock_wlock(&shmfd->shm_rl, uio->uio_offset,
 445                     size, &shmfd->shm_mtx);
 446         }
 447         if ((shmfd->shm_seals & F_SEAL_WRITE) != 0) {
 448                 error = EPERM;
 449         } else {
 450                 error = 0;
 451                 if ((shmfd->shm_flags & SHM_GROW_ON_WRITE) != 0 &&
 452                     size > shmfd->shm_size) {
 453                         VM_OBJECT_WLOCK(shmfd->shm_object);
 454                         error = shm_dotruncate_locked(shmfd, size, rl_cookie);
 455                         VM_OBJECT_WUNLOCK(shmfd->shm_object);
 456                 }
 457                 if (error == 0)
 458                         error = uiomove_object(shmfd->shm_object,
 459                             shmfd->shm_size, uio);
 460         }
 461         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 462         foffset_unlock_uio(fp, uio, flags);
 463         return (error);
 464 }
 465
 466 static int
 467 shm_truncate(struct file *fp, off_t length, struct ucred *active_cred,
 468     struct thread *td)
 469 {
 470         struct shmfd *shmfd;
 471 #ifdef MAC
 472         int error;
 473 #endif
 474
 475         shmfd = fp->f_data;
 476 #ifdef MAC
 477         error = mac_posixshm_check_truncate(active_cred, fp->f_cred, shmfd);
 478         if (error)
 479                 return (error);
 480 #endif
 481         return (shm_dotruncate(shmfd, length));
 482 }
 483
 484 int
 485 shm_ioctl(struct file *fp, u_long com, void *data, struct ucred *active_cred,
 486     struct thread *td)
 487 {
 488         struct shmfd *shmfd;
 489         struct shm_largepage_conf *conf;
 490         void *rl_cookie;
 491
 492         shmfd = fp->f_data;
 493         switch (com) {
 494         case FIONBIO:
 495         case FIOASYNC:
 496                 /*
 497                  * Allow fcntl(fd, F_SETFL, O_NONBLOCK) to work,
 498                  * just like it would on an unlinked regular file
 499                  */
 500                 return (0);
 501         case FIOSSHMLPGCNF:
 502                 if (!shm_largepage(shmfd))
 503                         return (ENOTTY);
 504                 conf = data;
 505                 if (shmfd->shm_lp_psind != 0 &&
 506                     conf->psind != shmfd->shm_lp_psind)
 507                         return (EINVAL);
 508                 if (conf->psind <= 0 || conf->psind >= MAXPAGESIZES ||
 509                     pagesizes[conf->psind] == 0)
 510                         return (EINVAL);
 511                 if (conf->alloc_policy != SHM_LARGEPAGE_ALLOC_DEFAULT &&
 512                     conf->alloc_policy != SHM_LARGEPAGE_ALLOC_NOWAIT &&
 513                     conf->alloc_policy != SHM_LARGEPAGE_ALLOC_HARD)
 514                         return (EINVAL);
 515
 516                 rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
 517                     &shmfd->shm_mtx);
 518                 shmfd->shm_lp_psind = conf->psind;
 519                 shmfd->shm_lp_alloc_policy = conf->alloc_policy;
 520                 shmfd->shm_object->un_pager.phys.data_val = conf->psind;
 521                 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 522                 return (0);
 523         case FIOGSHMLPGCNF:
 524                 if (!shm_largepage(shmfd))
 525                         return (ENOTTY);
 526                 conf = data;
 527                 rl_cookie = rangelock_rlock(&shmfd->shm_rl, 0, OFF_MAX,
 528                     &shmfd->shm_mtx);
 529                 conf->psind = shmfd->shm_lp_psind;
 530                 conf->alloc_policy = shmfd->shm_lp_alloc_policy;
 531                 rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 532                 return (0);
 533         default:
 534                 return (ENOTTY);
 535         }
 536 }
 537
 538 static int
 539 shm_stat(struct file *fp, struct stat *sb, struct ucred *active_cred,
 540     struct thread *td)
 541 {
 542         struct shmfd *shmfd;
 543 #ifdef MAC
 544         int error;
 545 #endif
 546
 547         shmfd = fp->f_data;
 548
 549 #ifdef MAC
 550         error = mac_posixshm_check_stat(active_cred, fp->f_cred, shmfd);
 551         if (error)
 552                 return (error);
 553 #endif
 554
 555         /*
 556          * Attempt to return sanish values for fstat() on a memory file
 557          * descriptor.
 558          */
 559         bzero(sb, sizeof(*sb));
 560         sb->st_blksize = PAGE_SIZE;
 561         sb->st_size = shmfd->shm_size;
 562         sb->st_blocks = howmany(sb->st_size, sb->st_blksize);
 563         mtx_lock(&shm_timestamp_lock);
 564         sb->st_atim = shmfd->shm_atime;
 565         sb->st_ctim = shmfd->shm_ctime;
 566         sb->st_mtim = shmfd->shm_mtime;
 567         sb->st_birthtim = shmfd->shm_birthtime;
 568         sb->st_mode = S_IFREG | shmfd->shm_mode;                /* XXX */
 569         sb->st_uid = shmfd->shm_uid;
 570         sb->st_gid = shmfd->shm_gid;
 571         mtx_unlock(&shm_timestamp_lock);
 572         sb->st_dev = shm_dev_ino;
 573         sb->st_ino = shmfd->shm_ino;
 574         sb->st_nlink = shmfd->shm_object->ref_count;
 575         sb->st_blocks = shmfd->shm_object->size /
 576             (pagesizes[shmfd->shm_lp_psind] >> PAGE_SHIFT);
 577
 578         return (0);
 579 }
 580
 581 static int
 582 shm_close(struct file *fp, struct thread *td)
 583 {
 584         struct shmfd *shmfd;
 585
 586         shmfd = fp->f_data;
 587         fp->f_data = NULL;
 588         shm_drop(shmfd);
 589
 590         return (0);
 591 }
 592
 593 static int
 594 shm_copyin_path(struct thread *td, const char *userpath_in, char **path_out) {
 595         int error;
 596         char *path;
 597         const char *pr_path;
 598         size_t pr_pathlen;
 599
 600         path = malloc(MAXPATHLEN, M_SHMFD, M_WAITOK);
 601         pr_path = td->td_ucred->cr_prison->pr_path;
 602
 603         /* Construct a full pathname for jailed callers. */
 604         pr_pathlen = strcmp(pr_path, "/") ==
 605             0 ? 0 : strlcpy(path, pr_path, MAXPATHLEN);
 606         error = copyinstr(userpath_in, path + pr_pathlen,
 607             MAXPATHLEN - pr_pathlen, NULL);
 608         if (error != 0)
 609                 goto out;
 610
 611 #ifdef KTRACE
 612         if (KTRPOINT(curthread, KTR_NAMEI))
 613                 ktrnamei(path);
 614 #endif
 615
 616         /* Require paths to start with a '/' character. */
 617         if (path[pr_pathlen] != '/') {
 618                 error = EINVAL;
 619                 goto out;
 620         }
 621
 622         *path_out = path;
 623
 624 out:
 625         if (error != 0)
 626                 free(path, M_SHMFD);
 627
 628         return (error);
 629 }
 630
 631 static int
 632 shm_dotruncate_locked(struct shmfd *shmfd, off_t length, void *rl_cookie)
 633 {
 634         vm_object_t object;
 635         vm_page_t m;
 636         vm_pindex_t idx, nobjsize;
 637         vm_ooffset_t delta;
 638         int base, rv;
 639
 640         KASSERT(length >= 0, ("shm_dotruncate: length < 0"));
 641         object = shmfd->shm_object;
 642         VM_OBJECT_ASSERT_WLOCKED(object);
 643         rangelock_cookie_assert(rl_cookie, RA_WLOCKED);
 644         if (length == shmfd->shm_size)
 645                 return (0);
 646         nobjsize = OFF_TO_IDX(length + PAGE_MASK);
 647
 648         /* Are we shrinking?  If so, trim the end. */
 649         if (length < shmfd->shm_size) {
 650                 if ((shmfd->shm_seals & F_SEAL_SHRINK) != 0)
 651                         return (EPERM);
 652
 653                 /*
 654                  * Disallow any requests to shrink the size if this
 655                  * object is mapped into the kernel.
 656                  */
 657                 if (shmfd->shm_kmappings > 0)
 658                         return (EBUSY);
 659
 660                 /*
 661                  * Zero the truncated part of the last page.
 662                  */
 663                 base = length & PAGE_MASK;
 664                 if (base != 0) {
 665                         idx = OFF_TO_IDX(length);
 666 retry:
 667                         m = vm_page_grab(object, idx, VM_ALLOC_NOCREAT);
 668                         if (m != NULL) {
 669                                 MPASS(vm_page_all_valid(m));
 670                         } else if (vm_pager_has_page(object, idx, NULL, NULL)) {
 671                                 m = vm_page_alloc(object, idx,
 672                                     VM_ALLOC_NORMAL | VM_ALLOC_WAITFAIL);
 673                                 if (m == NULL)
 674                                         goto retry;
 675                                 vm_object_pip_add(object, 1);
 676                                 VM_OBJECT_WUNLOCK(object);
 677                                 rv = vm_pager_get_pages(object, &m, 1, NULL,
 678                                     NULL);
 679                                 VM_OBJECT_WLOCK(object);
 680                                 vm_object_pip_wakeup(object);
 681                                 if (rv == VM_PAGER_OK) {
 682                                         /*
 683                                          * Since the page was not resident,
 684                                          * and therefore not recently
 685                                          * accessed, immediately enqueue it
 686                                          * for asynchronous laundering.  The
 687                                          * current operation is not regarded
 688                                          * as an access.
 689                                          */
 690                                         vm_page_launder(m);
 691                                 } else {
 692                                         vm_page_free(m);
 693                                         VM_OBJECT_WUNLOCK(object);
 694                                         return (EIO);
 695                                 }
 696                         }
 697                         if (m != NULL) {
 698                                 pmap_zero_page_area(m, base, PAGE_SIZE - base);
 699                                 KASSERT(vm_page_all_valid(m),
 700                                     ("shm_dotruncate: page %p is invalid", m));
 701                                 vm_page_set_dirty(m);
 702                                 vm_page_xunbusy(m);
 703                         }
 704                 }
 705                 delta = IDX_TO_OFF(object->size - nobjsize);
 706
 707                 if (nobjsize < object->size)
 708                         vm_object_page_remove(object, nobjsize, object->size,
 709                             0);
 710
 711                 /* Free the swap accounted for shm */
 712                 swap_release_by_cred(delta, object->cred);
 713                 object->charge -= delta;
 714         } else {
 715                 if ((shmfd->shm_seals & F_SEAL_GROW) != 0)
 716                         return (EPERM);
 717
 718                 /* Try to reserve additional swap space. */
 719                 delta = IDX_TO_OFF(nobjsize - object->size);
 720                 if (!swap_reserve_by_cred(delta, object->cred))
 721                         return (ENOMEM);
 722                 object->charge += delta;
 723         }
 724         shmfd->shm_size = length;
 725         mtx_lock(&shm_timestamp_lock);
 726         vfs_timestamp(&shmfd->shm_ctime);
 727         shmfd->shm_mtime = shmfd->shm_ctime;
 728         mtx_unlock(&shm_timestamp_lock);
 729         object->size = nobjsize;
 730         return (0);
 731 }
 732
 733 static int
 734 shm_dotruncate_largepage(struct shmfd *shmfd, off_t length, void *rl_cookie)
 735 {
 736         vm_object_t object;
 737         vm_page_t m;
 738         vm_pindex_t newobjsz, oldobjsz;
 739         int aflags, error, i, psind, try;
 740
 741         KASSERT(length >= 0, ("shm_dotruncate: length < 0"));
 742         object = shmfd->shm_object;
 743         VM_OBJECT_ASSERT_WLOCKED(object);
 744         rangelock_cookie_assert(rl_cookie, RA_WLOCKED);
 745
 746         oldobjsz = object->size;
 747         newobjsz = OFF_TO_IDX(length);
 748         if (length == shmfd->shm_size)
 749                 return (0);
 750         psind = shmfd->shm_lp_psind;
 751         if (psind == 0 && length != 0)
 752                 return (EINVAL);
 753         if ((length & (pagesizes[psind] - 1)) != 0)
 754                 return (EINVAL);
 755
 756         if (length < shmfd->shm_size) {
 757                 if ((shmfd->shm_seals & F_SEAL_SHRINK) != 0)
 758                         return (EPERM);
 759                 if (shmfd->shm_kmappings > 0)
 760                         return (EBUSY);
 761                 return (ENOTSUP);       /* Pages are unmanaged. */
 762 #if 0
 763                 vm_object_page_remove(object, newobjsz, oldobjsz, 0);
 764                 object->size = newobjsz;
 765                 shmfd->shm_size = length;
 766                 return (0);
 767 #endif
 768         }
 769
 770         aflags = VM_ALLOC_NORMAL | VM_ALLOC_ZERO;
 771         if (shmfd->shm_lp_alloc_policy == SHM_LARGEPAGE_ALLOC_NOWAIT)
 772                 aflags |= VM_ALLOC_WAITFAIL;
 773         try = 0;
 774
 775         /*
 776          * Extend shmfd and object, keeping all already fully
 777          * allocated large pages intact even on error, because dropped
 778          * object lock might allowed mapping of them.
 779          */
 780         while (object->size < newobjsz) {
 781                 m = vm_page_alloc_contig(object, object->size, aflags,
 782                     pagesizes[psind] / PAGE_SIZE, 0, ~0,
 783                     pagesizes[psind], 0,
 784                     VM_MEMATTR_DEFAULT);
 785                 if (m == NULL) {
 786                         VM_OBJECT_WUNLOCK(object);
 787                         if (shmfd->shm_lp_alloc_policy ==
 788                             SHM_LARGEPAGE_ALLOC_NOWAIT ||
 789                             (shmfd->shm_lp_alloc_policy ==
 790                             SHM_LARGEPAGE_ALLOC_DEFAULT &&
 791                             try >= largepage_reclaim_tries)) {
 792                                 VM_OBJECT_WLOCK(object);
 793                                 return (ENOMEM);
 794                         }
 795                         error = vm_page_reclaim_contig(aflags,
 796                             pagesizes[psind] / PAGE_SIZE, 0, ~0,
 797                             pagesizes[psind], 0) ? 0 :
 798                             vm_wait_intr(object);
 799                         if (error != 0) {
 800                                 VM_OBJECT_WLOCK(object);
 801                                 return (error);
 802                         }
 803                         try++;
 804                         VM_OBJECT_WLOCK(object);
 805                         continue;
 806                 }
 807                 try = 0;
 808                 for (i = 0; i < pagesizes[psind] / PAGE_SIZE; i++) {
 809                         if ((m[i].flags & PG_ZERO) == 0)
 810                                 pmap_zero_page(&m[i]);
 811                         vm_page_valid(&m[i]);
 812                         vm_page_xunbusy(&m[i]);
 813                 }
 814                 object->size += OFF_TO_IDX(pagesizes[psind]);
 815                 shmfd->shm_size += pagesizes[psind];
 816                 atomic_add_long(&count_largepages[psind], 1);
 817                 vm_wire_add(atop(pagesizes[psind]));
 818         }
 819         return (0);
 820 }
 821
 822 static int
 823 shm_dotruncate_cookie(struct shmfd *shmfd, off_t length, void *rl_cookie)
 824 {
 825         int error;
 826
 827         VM_OBJECT_WLOCK(shmfd->shm_object);
 828         error = shm_largepage(shmfd) ? shm_dotruncate_largepage(shmfd,
 829             length, rl_cookie) : shm_dotruncate_locked(shmfd, length,
 830             rl_cookie);
 831         VM_OBJECT_WUNLOCK(shmfd->shm_object);
 832         return (error);
 833 }
 834
 835 int
 836 shm_dotruncate(struct shmfd *shmfd, off_t length)
 837 {
 838         void *rl_cookie;
 839         int error;
 840
 841         rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
 842             &shmfd->shm_mtx);
 843         error = shm_dotruncate_cookie(shmfd, length, rl_cookie);
 844         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
 845         return (error);
 846 }
 847
 848 /*
 849  * shmfd object management including creation and reference counting
 850  * routines.
 851  */
 852 struct shmfd *
 853 shm_alloc(struct ucred *ucred, mode_t mode, bool largepage)
 854 {
 855         struct shmfd *shmfd;
 856
 857         shmfd = malloc(sizeof(*shmfd), M_SHMFD, M_WAITOK | M_ZERO);
 858         shmfd->shm_size = 0;
 859         shmfd->shm_uid = ucred->cr_uid;
 860         shmfd->shm_gid = ucred->cr_gid;
 861         shmfd->shm_mode = mode;
 862         if (largepage) {
 863                 shmfd->shm_object = phys_pager_allocate(NULL,
 864                     &shm_largepage_phys_ops, NULL, shmfd->shm_size,
 865                     VM_PROT_DEFAULT, 0, ucred);
 866                 shmfd->shm_lp_alloc_policy = SHM_LARGEPAGE_ALLOC_DEFAULT;
 867         } else {
 868                 shmfd->shm_object = vm_pager_allocate(OBJT_SWAP, NULL,
 869                     shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
 870         }
 871         KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
 872         vfs_timestamp(&shmfd->shm_birthtime);
 873         shmfd->shm_atime = shmfd->shm_mtime = shmfd->shm_ctime =
 874             shmfd->shm_birthtime;
 875         shmfd->shm_ino = alloc_unr64(&shm_ino_unr);
 876         refcount_init(&shmfd->shm_refs, 1);
 877         mtx_init(&shmfd->shm_mtx, "shmrl", NULL, MTX_DEF);
 878         rangelock_init(&shmfd->shm_rl);
 879 #ifdef MAC
 880         mac_posixshm_init(shmfd);
 881         mac_posixshm_create(ucred, shmfd);
 882 #endif
 883
 884         return (shmfd);
 885 }
 886
 887 struct shmfd *
 888 shm_hold(struct shmfd *shmfd)
 889 {
 890
 891         refcount_acquire(&shmfd->shm_refs);
 892         return (shmfd);
 893 }
 894
 895 void
 896 shm_drop(struct shmfd *shmfd)
 897 {
 898
 899         if (refcount_release(&shmfd->shm_refs)) {
 900 #ifdef MAC
 901                 mac_posixshm_destroy(shmfd);
 902 #endif
 903                 rangelock_destroy(&shmfd->shm_rl);
 904                 mtx_destroy(&shmfd->shm_mtx);
 905                 vm_object_deallocate(shmfd->shm_object);
 906                 free(shmfd, M_SHMFD);
 907         }
 908 }
 909
 910 /*
 911  * Determine if the credentials have sufficient permissions for a
 912  * specified combination of FREAD and FWRITE.
 913  */
 914 int
 915 shm_access(struct shmfd *shmfd, struct ucred *ucred, int flags)
 916 {
 917         accmode_t accmode;
 918         int error;
 919
 920         accmode = 0;
 921         if (flags & FREAD)
 922                 accmode |= VREAD;
 923         if (flags & FWRITE)
 924                 accmode |= VWRITE;
 925         mtx_lock(&shm_timestamp_lock);
 926         error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
 927             accmode, ucred);
 928         mtx_unlock(&shm_timestamp_lock);
 929         return (error);
 930 }
 931
 932 static void
 933 shm_init(void *arg)
 934 {
 935         char name[32];
 936         int i;
 937
 938         mtx_init(&shm_timestamp_lock, "shm timestamps", NULL, MTX_DEF);
 939         sx_init(&shm_dict_lock, "shm dictionary");
 940         shm_dictionary = hashinit(1024, M_SHMFD, &shm_hash);
 941         new_unrhdr64(&shm_ino_unr, 1);
 942         shm_dev_ino = devfs_alloc_cdp_inode();
 943         KASSERT(shm_dev_ino > 0, ("shm dev inode not initialized"));
 944
 945         for (i = 1; i < MAXPAGESIZES; i++) {
 946                 if (pagesizes[i] == 0)
 947                         break;
 948 #define M       (1024 * 1024)
 949 #define G       (1024 * M)
 950                 if (pagesizes[i] >= G)
 951                         snprintf(name, sizeof(name), "%luG", pagesizes[i] / G);
 952                 else if (pagesizes[i] >= M)
 953                         snprintf(name, sizeof(name), "%luM", pagesizes[i] / M);
 954                 else
 955                         snprintf(name, sizeof(name), "%lu", pagesizes[i]);
 956 #undef G
 957 #undef M
 958                 SYSCTL_ADD_ULONG(NULL, SYSCTL_STATIC_CHILDREN(_vm_largepages),
 959                     OID_AUTO, name, CTLFLAG_RD, &count_largepages[i],
 960                     "number of non-transient largepages allocated");
 961         }
 962 }
 963 SYSINIT(shm_init, SI_SUB_SYSV_SHM, SI_ORDER_ANY, shm_init, NULL);
 964
 965 /*
 966  * Dictionary management.  We maintain an in-kernel dictionary to map
 967  * paths to shmfd objects.  We use the FNV hash on the path to store
 968  * the mappings in a hash table.
 969  */
 970 static struct shmfd *
 971 shm_lookup(char *path, Fnv32_t fnv)
 972 {
 973         struct shm_mapping *map;
 974
 975         LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
 976                 if (map->sm_fnv != fnv)
 977                         continue;
 978                 if (strcmp(map->sm_path, path) == 0)
 979                         return (map->sm_shmfd);
 980         }
 981
 982         return (NULL);
 983 }
 984
 985 static void
 986 shm_insert(char *path, Fnv32_t fnv, struct shmfd *shmfd)
 987 {
 988         struct shm_mapping *map;
 989
 990         map = malloc(sizeof(struct shm_mapping), M_SHMFD, M_WAITOK);
 991         map->sm_path = path;
 992         map->sm_fnv = fnv;
 993         map->sm_shmfd = shm_hold(shmfd);
 994         shmfd->shm_path = path;
 995         LIST_INSERT_HEAD(SHM_HASH(fnv), map, sm_link);
 996 }
 997
 998 static int
 999 shm_remove(char *path, Fnv32_t fnv, struct ucred *ucred)
1000 {
1001         struct shm_mapping *map;
1002         int error;
1003
1004         LIST_FOREACH(map, SHM_HASH(fnv), sm_link) {
1005                 if (map->sm_fnv != fnv)
1006                         continue;
1007                 if (strcmp(map->sm_path, path) == 0) {
1008 #ifdef MAC
1009                         error = mac_posixshm_check_unlink(ucred, map->sm_shmfd);
1010                         if (error)
1011                                 return (error);
1012 #endif
1013                         error = shm_access(map->sm_shmfd, ucred,
1014                             FREAD | FWRITE);
1015                         if (error)
1016                                 return (error);
1017                         map->sm_shmfd->shm_path = NULL;
1018                         LIST_REMOVE(map, sm_link);
1019                         shm_drop(map->sm_shmfd);
1020                         free(map->sm_path, M_SHMFD);
1021                         free(map, M_SHMFD);
1022                         return (0);
1023                 }
1024         }
1025
1026         return (ENOENT);
1027 }
1028
1029 int
1030 kern_shm_open2(struct thread *td, const char *userpath, int flags, mode_t mode,
1031     int shmflags, struct filecaps *fcaps, const char *name __unused)
1032 {
1033         struct filedesc *fdp;
1034         struct shmfd *shmfd;
1035         struct file *fp;
1036         char *path;
1037         void *rl_cookie;
1038         Fnv32_t fnv;
1039         mode_t cmode;
1040         int error, fd, initial_seals;
1041         bool largepage;
1042
1043         if ((shmflags & ~(SHM_ALLOW_SEALING | SHM_GROW_ON_WRITE |
1044             SHM_LARGEPAGE)) != 0)
1045                 return (EINVAL);
1046
1047         initial_seals = F_SEAL_SEAL;
1048         if ((shmflags & SHM_ALLOW_SEALING) != 0)
1049                 initial_seals &= ~F_SEAL_SEAL;
1050
1051 #ifdef CAPABILITY_MODE
1052         /*
1053          * shm_open(2) is only allowed for anonymous objects.
1054          */
1055         if (IN_CAPABILITY_MODE(td) && (userpath != SHM_ANON))
1056                 return (ECAPMODE);
1057 #endif
1058
1059         AUDIT_ARG_FFLAGS(flags);
1060         AUDIT_ARG_MODE(mode);
1061
1062         if ((flags & O_ACCMODE) != O_RDONLY && (flags & O_ACCMODE) != O_RDWR)
1063                 return (EINVAL);
1064
1065         if ((flags & ~(O_ACCMODE | O_CREAT | O_EXCL | O_TRUNC | O_CLOEXEC)) != 0)
1066                 return (EINVAL);
1067
1068         largepage = (shmflags & SHM_LARGEPAGE) != 0;
1069 #if !defined(__amd64__)
1070         if (largepage)
1071                 return (ENOTTY);
1072 #endif
1073
1074         /*
1075          * Currently only F_SEAL_SEAL may be set when creating or opening shmfd.
1076          * If the decision is made later to allow additional seals, care must be
1077          * taken below to ensure that the seals are properly set if the shmfd
1078          * already existed -- this currently assumes that only F_SEAL_SEAL can
1079          * be set and doesn't take further precautions to ensure the validity of
1080          * the seals being added with respect to current mappings.
1081          */
1082         if ((initial_seals & ~F_SEAL_SEAL) != 0)
1083                 return (EINVAL);
1084
1085         fdp = td->td_proc->p_fd;
1086         cmode = (mode & ~fdp->fd_cmask) & ACCESSPERMS;
1087
1088         /*
1089          * shm_open(2) created shm should always have O_CLOEXEC set, as mandated
1090          * by POSIX.  We allow it to be unset here so that an in-kernel
1091          * interface may be written as a thin layer around shm, optionally not
1092          * setting CLOEXEC.  For shm_open(2), O_CLOEXEC is set unconditionally
1093          * in sys_shm_open() to keep this implementation compliant.
1094          */
1095         error = falloc_caps(td, &fp, &fd, flags & O_CLOEXEC, fcaps);
1096         if (error)
1097                 return (error);
1098
1099         /* A SHM_ANON path pointer creates an anonymous object. */
1100         if (userpath == SHM_ANON) {
1101                 /* A read-only anonymous object is pointless. */
1102                 if ((flags & O_ACCMODE) == O_RDONLY) {
1103                         fdclose(td, fp, fd);
1104                         fdrop(fp, td);
1105                         return (EINVAL);
1106                 }
1107                 shmfd = shm_alloc(td->td_ucred, cmode, largepage);
1108                 shmfd->shm_seals = initial_seals;
1109                 shmfd->shm_flags = shmflags;
1110         } else {
1111                 error = shm_copyin_path(td, userpath, &path);
1112                 if (error != 0) {
1113                         fdclose(td, fp, fd);
1114                         fdrop(fp, td);
1115                         return (error);
1116                 }
1117
1118                 AUDIT_ARG_UPATH1_CANON(path);
1119                 fnv = fnv_32_str(path, FNV1_32_INIT);
1120                 sx_xlock(&shm_dict_lock);
1121                 shmfd = shm_lookup(path, fnv);
1122                 if (shmfd == NULL) {
1123                         /* Object does not yet exist, create it if requested. */
1124                         if (flags & O_CREAT) {
1125 #ifdef MAC
1126                                 error = mac_posixshm_check_create(td->td_ucred,
1127                                     path);
1128                                 if (error == 0) {
1129 #endif
1130                                         shmfd = shm_alloc(td->td_ucred, cmode,
1131                                             largepage);
1132                                         shmfd->shm_seals = initial_seals;
1133                                         shmfd->shm_flags = shmflags;
1134                                         shm_insert(path, fnv, shmfd);
1135 #ifdef MAC
1136                                 }
1137 #endif
1138                         } else {
1139                                 free(path, M_SHMFD);
1140                                 error = ENOENT;
1141                         }
1142                 } else {
1143                         rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
1144                             &shmfd->shm_mtx);
1145
1146                         /*
1147                          * kern_shm_open() likely shouldn't ever error out on
1148                          * trying to set a seal that already exists, unlike
1149                          * F_ADD_SEALS.  This would break terribly as
1150                          * shm_open(2) actually sets F_SEAL_SEAL to maintain
1151                          * historical behavior where the underlying file could
1152                          * not be sealed.
1153                          */
1154                         initial_seals &= ~shmfd->shm_seals;
1155
1156                         /*
1157                          * Object already exists, obtain a new
1158                          * reference if requested and permitted.
1159                          */
1160                         free(path, M_SHMFD);
1161
1162                         /*
1163                          * initial_seals can't set additional seals if we've
1164                          * already been set F_SEAL_SEAL.  If F_SEAL_SEAL is set,
1165                          * then we've already removed that one from
1166                          * initial_seals.  This is currently redundant as we
1167                          * only allow setting F_SEAL_SEAL at creation time, but
1168                          * it's cheap to check and decreases the effort required
1169                          * to allow additional seals.
1170                          */
1171                         if ((shmfd->shm_seals & F_SEAL_SEAL) != 0 &&
1172                             initial_seals != 0)
1173                                 error = EPERM;
1174                         else if ((flags & (O_CREAT | O_EXCL)) ==
1175                             (O_CREAT | O_EXCL))
1176                                 error = EEXIST;
1177                         else if (shmflags != 0 && shmflags != shmfd->shm_flags)
1178                                 error = EINVAL;
1179                         else {
1180 #ifdef MAC
1181                                 error = mac_posixshm_check_open(td->td_ucred,
1182                                     shmfd, FFLAGS(flags & O_ACCMODE));
1183                                 if (error == 0)
1184 #endif
1185                                 error = shm_access(shmfd, td->td_ucred,
1186                                     FFLAGS(flags & O_ACCMODE));
1187                         }
1188
1189                         /*
1190                          * Truncate the file back to zero length if
1191                          * O_TRUNC was specified and the object was
1192                          * opened with read/write.
1193                          */
1194                         if (error == 0 &&
1195                             (flags & (O_ACCMODE | O_TRUNC)) ==
1196                             (O_RDWR | O_TRUNC)) {
1197                                 VM_OBJECT_WLOCK(shmfd->shm_object);
1198 #ifdef MAC
1199                                 error = mac_posixshm_check_truncate(
1200                                         td->td_ucred, fp->f_cred, shmfd);
1201                                 if (error == 0)
1202 #endif
1203                                         error = shm_dotruncate_locked(shmfd, 0,
1204                                             rl_cookie);
1205                                 VM_OBJECT_WUNLOCK(shmfd->shm_object);
1206                         }
1207                         if (error == 0) {
1208                                 /*
1209                                  * Currently we only allow F_SEAL_SEAL to be
1210                                  * set initially.  As noted above, this would
1211                                  * need to be reworked should that change.
1212                                  */
1213                                 shmfd->shm_seals |= initial_seals;
1214                                 shm_hold(shmfd);
1215                         }
1216                         rangelock_unlock(&shmfd->shm_rl, rl_cookie,
1217                             &shmfd->shm_mtx);
1218                 }
1219                 sx_xunlock(&shm_dict_lock);
1220
1221                 if (error) {
1222                         fdclose(td, fp, fd);
1223                         fdrop(fp, td);
1224                         return (error);
1225                 }
1226         }
1227
1228         finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
1229
1230         td->td_retval[0] = fd;
1231         fdrop(fp, td);
1232
1233         return (0);
1234 }
1235
1236 /* System calls. */
1237 #ifdef COMPAT_FREEBSD12
1238 int
1239 freebsd12_shm_open(struct thread *td, struct freebsd12_shm_open_args *uap)
1240 {
1241
1242         return (kern_shm_open(td, uap->path, uap->flags | O_CLOEXEC,
1243             uap->mode, NULL));
1244 }
1245 #endif
1246
1247 int
1248 sys_shm_unlink(struct thread *td, struct shm_unlink_args *uap)
1249 {
1250         char *path;
1251         Fnv32_t fnv;
1252         int error;
1253
1254         error = shm_copyin_path(td, uap->path, &path);
1255         if (error != 0)
1256                 return (error);
1257
1258         AUDIT_ARG_UPATH1_CANON(path);
1259         fnv = fnv_32_str(path, FNV1_32_INIT);
1260         sx_xlock(&shm_dict_lock);
1261         error = shm_remove(path, fnv, td->td_ucred);
1262         sx_xunlock(&shm_dict_lock);
1263         free(path, M_SHMFD);
1264
1265         return (error);
1266 }
1267
1268 int
1269 sys_shm_rename(struct thread *td, struct shm_rename_args *uap)
1270 {
1271         char *path_from = NULL, *path_to = NULL;
1272         Fnv32_t fnv_from, fnv_to;
1273         struct shmfd *fd_from;
1274         struct shmfd *fd_to;
1275         int error;
1276         int flags;
1277
1278         flags = uap->flags;
1279         AUDIT_ARG_FFLAGS(flags);
1280
1281         /*
1282          * Make sure the user passed only valid flags.
1283          * If you add a new flag, please add a new term here.
1284          */
1285         if ((flags & ~(
1286             SHM_RENAME_NOREPLACE |
1287             SHM_RENAME_EXCHANGE
1288             )) != 0) {
1289                 error = EINVAL;
1290                 goto out;
1291         }
1292
1293         /*
1294          * EXCHANGE and NOREPLACE don't quite make sense together. Let's
1295          * force the user to choose one or the other.
1296          */
1297         if ((flags & SHM_RENAME_NOREPLACE) != 0 &&
1298             (flags & SHM_RENAME_EXCHANGE) != 0) {
1299                 error = EINVAL;
1300                 goto out;
1301         }
1302
1303         /* Renaming to or from anonymous makes no sense */
1304         if (uap->path_from == SHM_ANON || uap->path_to == SHM_ANON) {
1305                 error = EINVAL;
1306                 goto out;
1307         }
1308
1309         error = shm_copyin_path(td, uap->path_from, &path_from);
1310         if (error != 0)
1311                 goto out;
1312
1313         error = shm_copyin_path(td, uap->path_to, &path_to);
1314         if (error != 0)
1315                 goto out;
1316
1317         AUDIT_ARG_UPATH1_CANON(path_from);
1318         AUDIT_ARG_UPATH2_CANON(path_to);
1319
1320         /* Rename with from/to equal is a no-op */
1321         if (strcmp(path_from, path_to) == 0)
1322                 goto out;
1323
1324         fnv_from = fnv_32_str(path_from, FNV1_32_INIT);
1325         fnv_to = fnv_32_str(path_to, FNV1_32_INIT);
1326
1327         sx_xlock(&shm_dict_lock);
1328
1329         fd_from = shm_lookup(path_from, fnv_from);
1330         if (fd_from == NULL) {
1331                 error = ENOENT;
1332                 goto out_locked;
1333         }
1334
1335         fd_to = shm_lookup(path_to, fnv_to);
1336         if ((flags & SHM_RENAME_NOREPLACE) != 0 && fd_to != NULL) {
1337                 error = EEXIST;
1338                 goto out_locked;
1339         }
1340
1341         /*
1342          * Unconditionally prevents shm_remove from invalidating the 'from'
1343          * shm's state.
1344          */
1345         shm_hold(fd_from);
1346         error = shm_remove(path_from, fnv_from, td->td_ucred);
1347
1348         /*
1349          * One of my assumptions failed if ENOENT (e.g. locking didn't
1350          * protect us)
1351          */
1352         KASSERT(error != ENOENT, ("Our shm disappeared during shm_rename: %s",
1353             path_from));
1354         if (error != 0) {
1355                 shm_drop(fd_from);
1356                 goto out_locked;
1357         }
1358
1359         /*
1360          * If we are exchanging, we need to ensure the shm_remove below
1361          * doesn't invalidate the dest shm's state.
1362          */
1363         if ((flags & SHM_RENAME_EXCHANGE) != 0 && fd_to != NULL)
1364                 shm_hold(fd_to);
1365
1366         /*
1367          * NOTE: if path_to is not already in the hash, c'est la vie;
1368          * it simply means we have nothing already at path_to to unlink.
1369          * That is the ENOENT case.
1370          *
1371          * If we somehow don't have access to unlink this guy, but
1372          * did for the shm at path_from, then relink the shm to path_from
1373          * and abort with EACCES.
1374          *
1375          * All other errors: that is weird; let's relink and abort the
1376          * operation.
1377          */
1378         error = shm_remove(path_to, fnv_to, td->td_ucred);
1379         if (error != 0 && error != ENOENT) {
1380                 shm_insert(path_from, fnv_from, fd_from);
1381                 shm_drop(fd_from);
1382                 /* Don't free path_from now, since the hash references it */
1383                 path_from = NULL;
1384                 goto out_locked;
1385         }
1386
1387         error = 0;
1388
1389         shm_insert(path_to, fnv_to, fd_from);
1390
1391         /* Don't free path_to now, since the hash references it */
1392         path_to = NULL;
1393
1394         /* We kept a ref when we removed, and incremented again in insert */
1395         shm_drop(fd_from);
1396         KASSERT(fd_from->shm_refs > 0, ("Expected >0 refs; got: %d\n",
1397             fd_from->shm_refs));
1398
1399         if ((flags & SHM_RENAME_EXCHANGE) != 0 && fd_to != NULL) {
1400                 shm_insert(path_from, fnv_from, fd_to);
1401                 path_from = NULL;
1402                 shm_drop(fd_to);
1403                 KASSERT(fd_to->shm_refs > 0, ("Expected >0 refs; got: %d\n",
1404                     fd_to->shm_refs));
1405         }
1406
1407 out_locked:
1408         sx_xunlock(&shm_dict_lock);
1409
1410 out:
1411         free(path_from, M_SHMFD);
1412         free(path_to, M_SHMFD);
1413         return (error);
1414 }
1415
1416 static int
1417 shm_mmap_large(struct shmfd *shmfd, vm_map_t map, vm_offset_t *addr,
1418     vm_size_t size, vm_prot_t prot, vm_prot_t max_prot, int flags,
1419     vm_ooffset_t foff, bool writecounted, struct thread *td)
1420 {
1421         struct vmspace *vms;
1422         vm_map_entry_t next_entry, prev_entry;
1423         vm_offset_t align, mask, maxaddr;
1424         int docow, error, rv, try;
1425         bool curmap;
1426
1427         if (shmfd->shm_lp_psind == 0)
1428                 return (EINVAL);
1429
1430         /* MAP_PRIVATE is disabled */
1431         if ((flags & ~(MAP_SHARED | MAP_FIXED | MAP_EXCL |
1432             MAP_NOCORE |
1433 #ifdef MAP_32BIT
1434             MAP_32BIT |
1435 #endif
1436             MAP_ALIGNMENT_MASK)) != 0)
1437                 return (EINVAL);
1438
1439         vms = td->td_proc->p_vmspace;
1440         curmap = map == &vms->vm_map;
1441         if (curmap) {
1442                 error = kern_mmap_racct_check(td, map, size);
1443                 if (error != 0)
1444                         return (error);
1445         }
1446
1447         docow = shmfd->shm_lp_psind << MAP_SPLIT_BOUNDARY_SHIFT;
1448         docow |= MAP_INHERIT_SHARE;
1449         if ((flags & MAP_NOCORE) != 0)
1450                 docow |= MAP_DISABLE_COREDUMP;
1451         if (writecounted)
1452                 docow |= MAP_WRITECOUNT;
1453
1454         mask = pagesizes[shmfd->shm_lp_psind] - 1;
1455         if ((foff & mask) != 0)
1456                 return (EINVAL);
1457         maxaddr = vm_map_max(map);
1458 #ifdef MAP_32BIT
1459         if ((flags & MAP_32BIT) != 0 && maxaddr > MAP_32BIT_MAX_ADDR)
1460                 maxaddr = MAP_32BIT_MAX_ADDR;
1461 #endif
1462         if (size == 0 || (size & mask) != 0 ||
1463             (*addr != 0 && ((*addr & mask) != 0 ||
1464             *addr + size < *addr || *addr + size > maxaddr)))
1465                 return (EINVAL);
1466
1467         align = flags & MAP_ALIGNMENT_MASK;
1468         if (align == 0) {
1469                 align = pagesizes[shmfd->shm_lp_psind];
1470         } else if (align == MAP_ALIGNED_SUPER) {
1471                 if (shmfd->shm_lp_psind != 1)
1472                         return (EINVAL);
1473                 align = pagesizes[1];
1474         } else {
1475                 align >>= MAP_ALIGNMENT_SHIFT;
1476                 align = 1ULL << align;
1477                 /* Also handles overflow. */
1478                 if (align < pagesizes[shmfd->shm_lp_psind])
1479                         return (EINVAL);
1480         }
1481
1482         vm_map_lock(map);
1483         if ((flags & MAP_FIXED) == 0) {
1484                 try = 1;
1485                 if (curmap && (*addr == 0 ||
1486                     (*addr >= round_page((vm_offset_t)vms->vm_taddr) &&
1487                     *addr < round_page((vm_offset_t)vms->vm_daddr +
1488                     lim_max(td, RLIMIT_DATA))))) {
1489                         *addr = roundup2((vm_offset_t)vms->vm_daddr +
1490                             lim_max(td, RLIMIT_DATA),
1491                             pagesizes[shmfd->shm_lp_psind]);
1492                 }
1493 again:
1494                 rv = vm_map_find_aligned(map, addr, size, maxaddr, align);
1495                 if (rv != KERN_SUCCESS) {
1496                         if (try == 1) {
1497                                 try = 2;
1498                                 *addr = vm_map_min(map);
1499                                 if ((*addr & mask) != 0)
1500                                         *addr = (*addr + mask) & mask;
1501                                 goto again;
1502                         }
1503                         goto fail1;
1504                 }
1505         } else if ((flags & MAP_EXCL) == 0) {
1506                 rv = vm_map_delete(map, *addr, *addr + size);
1507                 if (rv != KERN_SUCCESS)
1508                         goto fail1;
1509         } else {
1510                 error = ENOSPC;
1511                 if (vm_map_lookup_entry(map, *addr, &prev_entry))
1512                         goto fail;
1513                 next_entry = vm_map_entry_succ(prev_entry);
1514                 if (next_entry->start < *addr + size)
1515                         goto fail;
1516         }
1517
1518         rv = vm_map_insert(map, shmfd->shm_object, foff, *addr, *addr + size,
1519             prot, max_prot, docow);
1520 fail1:
1521         error = vm_mmap_to_errno(rv);
1522 fail:
1523         vm_map_unlock(map);
1524         return (error);
1525 }
1526
1527 static int
1528 shm_mmap(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t objsize,
1529     vm_prot_t prot, vm_prot_t cap_maxprot, int flags,
1530     vm_ooffset_t foff, struct thread *td)
1531 {
1532         struct shmfd *shmfd;
1533         vm_prot_t maxprot;
1534         int error;
1535         bool writecnt;
1536         void *rl_cookie;
1537
1538         shmfd = fp->f_data;
1539         maxprot = VM_PROT_NONE;
1540
1541         rl_cookie = rangelock_rlock(&shmfd->shm_rl, 0, objsize,
1542             &shmfd->shm_mtx);
1543         /* FREAD should always be set. */
1544         if ((fp->f_flag & FREAD) != 0)
1545                 maxprot |= VM_PROT_EXECUTE | VM_PROT_READ;
1546
1547         /*
1548          * If FWRITE's set, we can allow VM_PROT_WRITE unless it's a shared
1549          * mapping with a write seal applied.  Private mappings are always
1550          * writeable.
1551          */
1552         if ((flags & MAP_SHARED) == 0) {
1553                 cap_maxprot |= VM_PROT_WRITE;
1554                 maxprot |= VM_PROT_WRITE;
1555                 writecnt = false;
1556         } else {
1557                 if ((fp->f_flag & FWRITE) != 0 &&
1558                     (shmfd->shm_seals & F_SEAL_WRITE) == 0)
1559                         maxprot |= VM_PROT_WRITE;
1560
1561                 /*
1562                  * Any mappings from a writable descriptor may be upgraded to
1563                  * VM_PROT_WRITE with mprotect(2), unless a write-seal was
1564                  * applied between the open and subsequent mmap(2).  We want to
1565                  * reject application of a write seal as long as any such
1566                  * mapping exists so that the seal cannot be trivially bypassed.
1567                  */
1568                 writecnt = (maxprot & VM_PROT_WRITE) != 0;
1569                 if (!writecnt && (prot & VM_PROT_WRITE) != 0) {
1570                         error = EACCES;
1571                         goto out;
1572                 }
1573         }
1574         maxprot &= cap_maxprot;
1575
1576         /* See comment in vn_mmap(). */
1577         if (
1578 #ifdef _LP64
1579             objsize > OFF_MAX ||
1580 #endif
1581             foff < 0 || foff > OFF_MAX - objsize) {
1582                 error = EINVAL;
1583                 goto out;
1584         }
1585
1586 #ifdef MAC
1587         error = mac_posixshm_check_mmap(td->td_ucred, shmfd, prot, flags);
1588         if (error != 0)
1589                 goto out;
1590 #endif
1591
1592         mtx_lock(&shm_timestamp_lock);
1593         vfs_timestamp(&shmfd->shm_atime);
1594         mtx_unlock(&shm_timestamp_lock);
1595         vm_object_reference(shmfd->shm_object);
1596
1597         if (writecnt)
1598                 vm_pager_update_writecount(shmfd->shm_object, 0, objsize);
1599         if (shm_largepage(shmfd)) {
1600                 error = shm_mmap_large(shmfd, map, addr, objsize, prot,
1601                     maxprot, flags, foff, writecnt, td);
1602         } else {
1603                 error = vm_mmap_object(map, addr, objsize, prot, maxprot, flags,
1604                     shmfd->shm_object, foff, writecnt, td);
1605         }
1606         if (error != 0) {
1607                 if (writecnt)
1608                         vm_pager_release_writecount(shmfd->shm_object, 0,
1609                             objsize);
1610                 vm_object_deallocate(shmfd->shm_object);
1611         }
1612 out:
1613         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
1614         return (error);
1615 }
1616
1617 static int
1618 shm_chmod(struct file *fp, mode_t mode, struct ucred *active_cred,
1619     struct thread *td)
1620 {
1621         struct shmfd *shmfd;
1622         int error;
1623
1624         error = 0;
1625         shmfd = fp->f_data;
1626         mtx_lock(&shm_timestamp_lock);
1627         /*
1628          * SUSv4 says that x bits of permission need not be affected.
1629          * Be consistent with our shm_open there.
1630          */
1631 #ifdef MAC
1632         error = mac_posixshm_check_setmode(active_cred, shmfd, mode);
1633         if (error != 0)
1634                 goto out;
1635 #endif
1636         error = vaccess(VREG, shmfd->shm_mode, shmfd->shm_uid, shmfd->shm_gid,
1637             VADMIN, active_cred);
1638         if (error != 0)
1639                 goto out;
1640         shmfd->shm_mode = mode & ACCESSPERMS;
1641 out:
1642         mtx_unlock(&shm_timestamp_lock);
1643         return (error);
1644 }
1645
1646 static int
1647 shm_chown(struct file *fp, uid_t uid, gid_t gid, struct ucred *active_cred,
1648     struct thread *td)
1649 {
1650         struct shmfd *shmfd;
1651         int error;
1652
1653         error = 0;
1654         shmfd = fp->f_data;
1655         mtx_lock(&shm_timestamp_lock);
1656 #ifdef MAC
1657         error = mac_posixshm_check_setowner(active_cred, shmfd, uid, gid);
1658         if (error != 0)
1659                 goto out;
1660 #endif
1661         if (uid == (uid_t)-1)
1662                 uid = shmfd->shm_uid;
1663         if (gid == (gid_t)-1)
1664                  gid = shmfd->shm_gid;
1665         if (((uid != shmfd->shm_uid && uid != active_cred->cr_uid) ||
1666             (gid != shmfd->shm_gid && !groupmember(gid, active_cred))) &&
1667             (error = priv_check_cred(active_cred, PRIV_VFS_CHOWN)))
1668                 goto out;
1669         shmfd->shm_uid = uid;
1670         shmfd->shm_gid = gid;
1671 out:
1672         mtx_unlock(&shm_timestamp_lock);
1673         return (error);
1674 }
1675
1676 /*
1677  * Helper routines to allow the backing object of a shared memory file
1678  * descriptor to be mapped in the kernel.
1679  */
1680 int
1681 shm_map(struct file *fp, size_t size, off_t offset, void **memp)
1682 {
1683         struct shmfd *shmfd;
1684         vm_offset_t kva, ofs;
1685         vm_object_t obj;
1686         int rv;
1687
1688         if (fp->f_type != DTYPE_SHM)
1689                 return (EINVAL);
1690         shmfd = fp->f_data;
1691         obj = shmfd->shm_object;
1692         VM_OBJECT_WLOCK(obj);
1693         /*
1694          * XXXRW: This validation is probably insufficient, and subject to
1695          * sign errors.  It should be fixed.
1696          */
1697         if (offset >= shmfd->shm_size ||
1698             offset + size > round_page(shmfd->shm_size)) {
1699                 VM_OBJECT_WUNLOCK(obj);
1700                 return (EINVAL);
1701         }
1702
1703         shmfd->shm_kmappings++;
1704         vm_object_reference_locked(obj);
1705         VM_OBJECT_WUNLOCK(obj);
1706
1707         /* Map the object into the kernel_map and wire it. */
1708         kva = vm_map_min(kernel_map);
1709         ofs = offset & PAGE_MASK;
1710         offset = trunc_page(offset);
1711         size = round_page(size + ofs);
1712         rv = vm_map_find(kernel_map, obj, offset, &kva, size, 0,
1713             VMFS_OPTIMAL_SPACE, VM_PROT_READ | VM_PROT_WRITE,
1714             VM_PROT_READ | VM_PROT_WRITE, 0);
1715         if (rv == KERN_SUCCESS) {
1716                 rv = vm_map_wire(kernel_map, kva, kva + size,
1717                     VM_MAP_WIRE_SYSTEM | VM_MAP_WIRE_NOHOLES);
1718                 if (rv == KERN_SUCCESS) {
1719                         *memp = (void *)(kva + ofs);
1720                         return (0);
1721                 }
1722                 vm_map_remove(kernel_map, kva, kva + size);
1723         } else
1724                 vm_object_deallocate(obj);
1725
1726         /* On failure, drop our mapping reference. */
1727         VM_OBJECT_WLOCK(obj);
1728         shmfd->shm_kmappings--;
1729         VM_OBJECT_WUNLOCK(obj);
1730
1731         return (vm_mmap_to_errno(rv));
1732 }
1733
1734 /*
1735  * We require the caller to unmap the entire entry.  This allows us to
1736  * safely decrement shm_kmappings when a mapping is removed.
1737  */
1738 int
1739 shm_unmap(struct file *fp, void *mem, size_t size)
1740 {
1741         struct shmfd *shmfd;
1742         vm_map_entry_t entry;
1743         vm_offset_t kva, ofs;
1744         vm_object_t obj;
1745         vm_pindex_t pindex;
1746         vm_prot_t prot;
1747         boolean_t wired;
1748         vm_map_t map;
1749         int rv;
1750
1751         if (fp->f_type != DTYPE_SHM)
1752                 return (EINVAL);
1753         shmfd = fp->f_data;
1754         kva = (vm_offset_t)mem;
1755         ofs = kva & PAGE_MASK;
1756         kva = trunc_page(kva);
1757         size = round_page(size + ofs);
1758         map = kernel_map;
1759         rv = vm_map_lookup(&map, kva, VM_PROT_READ | VM_PROT_WRITE, &entry,
1760             &obj, &pindex, &prot, &wired);
1761         if (rv != KERN_SUCCESS)
1762                 return (EINVAL);
1763         if (entry->start != kva || entry->end != kva + size) {
1764                 vm_map_lookup_done(map, entry);
1765                 return (EINVAL);
1766         }
1767         vm_map_lookup_done(map, entry);
1768         if (obj != shmfd->shm_object)
1769                 return (EINVAL);
1770         vm_map_remove(map, kva, kva + size);
1771         VM_OBJECT_WLOCK(obj);
1772         KASSERT(shmfd->shm_kmappings > 0, ("shm_unmap: object not mapped"));
1773         shmfd->shm_kmappings--;
1774         VM_OBJECT_WUNLOCK(obj);
1775         return (0);
1776 }
1777
1778 static int
1779 shm_fill_kinfo_locked(struct shmfd *shmfd, struct kinfo_file *kif, bool list)
1780 {
1781         const char *path, *pr_path;
1782         size_t pr_pathlen;
1783         bool visible;
1784
1785         sx_assert(&shm_dict_lock, SA_LOCKED);
1786         kif->kf_type = KF_TYPE_SHM;
1787         kif->kf_un.kf_file.kf_file_mode = S_IFREG | shmfd->shm_mode;
1788         kif->kf_un.kf_file.kf_file_size = shmfd->shm_size;
1789         if (shmfd->shm_path != NULL) {
1790                 if (shmfd->shm_path != NULL) {
1791                         path = shmfd->shm_path;
1792                         pr_path = curthread->td_ucred->cr_prison->pr_path;
1793                         if (strcmp(pr_path, "/") != 0) {
1794                                 /* Return the jail-rooted pathname. */
1795                                 pr_pathlen = strlen(pr_path);
1796                                 visible = strncmp(path, pr_path, pr_pathlen)
1797                                     == 0 && path[pr_pathlen] == '/';
1798                                 if (list && !visible)
1799                                         return (EPERM);
1800                                 if (visible)
1801                                         path += pr_pathlen;
1802                         }
1803                         strlcpy(kif->kf_path, path, sizeof(kif->kf_path));
1804                 }
1805         }
1806         return (0);
1807 }
1808
1809 static int
1810 shm_fill_kinfo(struct file *fp, struct kinfo_file *kif,
1811     struct filedesc *fdp __unused)
1812 {
1813         int res;
1814
1815         sx_slock(&shm_dict_lock);
1816         res = shm_fill_kinfo_locked(fp->f_data, kif, false);
1817         sx_sunlock(&shm_dict_lock);
1818         return (res);
1819 }
1820
1821 static int
1822 shm_add_seals(struct file *fp, int seals)
1823 {
1824         struct shmfd *shmfd;
1825         void *rl_cookie;
1826         vm_ooffset_t writemappings;
1827         int error, nseals;
1828
1829         error = 0;
1830         shmfd = fp->f_data;
1831         rl_cookie = rangelock_wlock(&shmfd->shm_rl, 0, OFF_MAX,
1832             &shmfd->shm_mtx);
1833
1834         /* Even already-set seals should result in EPERM. */
1835         if ((shmfd->shm_seals & F_SEAL_SEAL) != 0) {
1836                 error = EPERM;
1837                 goto out;
1838         }
1839         nseals = seals & ~shmfd->shm_seals;
1840         if ((nseals & F_SEAL_WRITE) != 0) {
1841                 /*
1842                  * The rangelock above prevents writable mappings from being
1843                  * added after we've started applying seals.  The RLOCK here
1844                  * is to avoid torn reads on ILP32 arches as unmapping/reducing
1845                  * writemappings will be done without a rangelock.
1846                  */
1847                 VM_OBJECT_RLOCK(shmfd->shm_object);
1848                 writemappings = shmfd->shm_object->un_pager.swp.writemappings;
1849                 VM_OBJECT_RUNLOCK(shmfd->shm_object);
1850                 /* kmappings are also writable */
1851                 if (writemappings > 0) {
1852                         error = EBUSY;
1853                         goto out;
1854                 }
1855         }
1856         shmfd->shm_seals |= nseals;
1857 out:
1858         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
1859         return (error);
1860 }
1861
1862 static int
1863 shm_get_seals(struct file *fp, int *seals)
1864 {
1865         struct shmfd *shmfd;
1866
1867         shmfd = fp->f_data;
1868         *seals = shmfd->shm_seals;
1869         return (0);
1870 }
1871
1872 static int
1873 shm_fallocate(struct file *fp, off_t offset, off_t len, struct thread *td)
1874 {
1875         void *rl_cookie;
1876         struct shmfd *shmfd;
1877         size_t size;
1878         int error;
1879
1880         /* This assumes that the caller already checked for overflow. */
1881         error = 0;
1882         shmfd = fp->f_data;
1883         size = offset + len;
1884
1885         /*
1886          * Just grab the rangelock for the range that we may be attempting to
1887          * grow, rather than blocking read/write for regions we won't be
1888          * touching while this (potential) resize is in progress.  Other
1889          * attempts to resize the shmfd will have to take a write lock from 0 to
1890          * OFF_MAX, so this being potentially beyond the current usable range of
1891          * the shmfd is not necessarily a concern.  If other mechanisms are
1892          * added to grow a shmfd, this may need to be re-evaluated.
1893          */
1894         rl_cookie = rangelock_wlock(&shmfd->shm_rl, offset, size,
1895             &shmfd->shm_mtx);
1896         if (size > shmfd->shm_size)
1897                 error = shm_dotruncate_cookie(shmfd, size, rl_cookie);
1898         rangelock_unlock(&shmfd->shm_rl, rl_cookie, &shmfd->shm_mtx);
1899         /* Translate to posix_fallocate(2) return value as needed. */
1900         if (error == ENOMEM)
1901                 error = ENOSPC;
1902         return (error);
1903 }
1904
1905 static int
1906 sysctl_posix_shm_list(SYSCTL_HANDLER_ARGS)
1907 {
1908         struct shm_mapping *shmm;
1909         struct sbuf sb;
1910         struct kinfo_file kif;
1911         u_long i;
1912         ssize_t curlen;
1913         int error, error2;
1914
1915         sbuf_new_for_sysctl(&sb, NULL, sizeof(struct kinfo_file) * 5, req);
1916         sbuf_clear_flags(&sb, SBUF_INCLUDENUL);
1917         curlen = 0;
1918         error = 0;
1919         sx_slock(&shm_dict_lock);
1920         for (i = 0; i < shm_hash + 1; i++) {
1921                 LIST_FOREACH(shmm, &shm_dictionary[i], sm_link) {
1922                         error = shm_fill_kinfo_locked(shmm->sm_shmfd,
1923                             &kif, true);
1924                         if (error == EPERM)
1925                                 continue;
1926                         if (error != 0)
1927                                 break;
1928                         pack_kinfo(&kif);
1929                         if (req->oldptr != NULL &&
1930                             kif.kf_structsize + curlen > req->oldlen)
1931                                 break;
1932                         error = sbuf_bcat(&sb, &kif, kif.kf_structsize) == 0 ?
1933                             0 : ENOMEM;
1934                         if (error != 0)
1935                                 break;
1936                         curlen += kif.kf_structsize;
1937                 }
1938         }
1939         sx_sunlock(&shm_dict_lock);
1940         error2 = sbuf_finish(&sb);
1941         sbuf_delete(&sb);
1942         return (error != 0 ? error : error2);
1943 }
1944
1945 SYSCTL_PROC(_kern_ipc, OID_AUTO, posix_shm_list,
1946     CTLFLAG_RD | CTLFLAG_MPSAFE | CTLTYPE_OPAQUE,
1947     NULL, 0, sysctl_posix_shm_list, "",
1948     "POSIX SHM list");
1949
1950 int
1951 kern_shm_open(struct thread *td, const char *path, int flags, mode_t mode,
1952     struct filecaps *caps)
1953 {
1954
1955         return (kern_shm_open2(td, path, flags, mode, 0, caps, NULL));
1956 }
1957
1958 /*
1959  * This version of the shm_open() interface leaves CLOEXEC behavior up to the
1960  * caller, and libc will enforce it for the traditional shm_open() call.  This
1961  * allows other consumers, like memfd_create(), to opt-in for CLOEXEC.  This
1962  * interface also includes a 'name' argument that is currently unused, but could
1963  * potentially be exported later via some interface for debugging purposes.
1964  * From the kernel's perspective, it is optional.  Individual consumers like
1965  * memfd_create() may require it in order to be compatible with other systems
1966  * implementing the same function.
1967  */
1968 int
1969 sys_shm_open2(struct thread *td, struct shm_open2_args *uap)
1970 {
1971
1972         return (kern_shm_open2(td, uap->path, uap->flags, uap->mode,
1973             uap->shmflags, NULL, uap->name));
1974 }