bsd/hfs/hfs_lookup.c

   1 /*
   2  * Copyright (c) 1999-2007 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*
  29  * Copyright (c) 1989, 1993
  30  *      The Regents of the University of California.  All rights reserved.
  31  * (c) UNIX System Laboratories, Inc.
  32  * All or some portions of this file are derived from material licensed
  33  * to the University of California by American Telephone and Telegraph
  34  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
  35  * the permission of UNIX System Laboratories, Inc.
  36  *
  37  * Redistribution and use in source and binary forms, with or without
  38  * modification, are permitted provided that the following conditions
  39  * are met:
  40  * 1. Redistributions of source code must retain the above copyright
  41  *        notice, this list of conditions and the following disclaimer.
  42  * 2. Redistributions in binary form must reproduce the above copyright
  43  *        notice, this list of conditions and the following disclaimer in the
  44  *        documentation and/or other materials provided with the distribution.
  45  * 3. All advertising materials mentioning features or use of this software
  46  *        must display the following acknowledgement:
  47  *      This product includes software developed by the University of
  48  *      California, Berkeley and its contributors.
  49  * 4. Neither the name of the University nor the names of its contributors
  50  *        may be used to endorse or promote products derived from this software
  51  *        without specific prior written permission.
  52  *
  53  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  54  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  55  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  56  * ARE DISCLAIMED.      IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  57  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  58  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  59  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  60  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  61  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  62  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  63  * SUCH DAMAGE.
  64  *
  65  *      @(#)hfs_lookup.c        1.0
  66  *      derived from @(#)ufs_lookup.c   8.15 (Berkeley) 6/16/95
  67  *
  68  *      (c) 1998-1999   Apple Computer, Inc.     All Rights Reserved
  69  *      (c) 1990, 1992  NeXT Computer, Inc.     All Rights Reserved
  70  *
  71  *
  72  *      hfs_lookup.c -- code to handle directory traversal on HFS/HFS+ volume
  73  */
  74
  75 #include <sys/param.h>
  76 #include <sys/file.h>
  77 #include <sys/mount.h>
  78 #include <sys/vnode.h>
  79 #include <sys/malloc.h>
  80 #include <sys/kdebug.h>
  81 #include <sys/kauth.h>
  82 #include <sys/namei.h>
  83
  84 #include "hfs.h"
  85 #include "hfs_catalog.h"
  86 #include "hfs_cnode.h"
  87
  88
  89 /*
  90  * FROM FREEBSD 3.1
  91  * Convert a component of a pathname into a pointer to a locked cnode.
  92  * This is a very central and rather complicated routine.
  93  * If the file system is not maintained in a strict tree hierarchy,
  94  * this can result in a deadlock situation (see comments in code below).
  95  *
  96  * The cnp->cn_nameiop argument is LOOKUP, CREATE, RENAME, or DELETE depending
  97  * on whether the name is to be looked up, created, renamed, or deleted.
  98  * When CREATE, RENAME, or DELETE is specified, information usable in
  99  * creating, renaming, or deleting a directory entry may be calculated.
 100  * Notice that these are the only operations that can affect the directory of the target.
 101  *
 102  * LOCKPARENT and WANTPARENT actually refer to the parent of the last item,
 103  * so if ISLASTCN is not set, they should be ignored. Also they are mutually exclusive, or
 104  * WANTPARENT really implies DONTLOCKPARENT. Either of them set means that the calling
 105  * routine wants to access the parent of the target, locked or unlocked.
 106  *
 107  * Keeping the parent locked as long as possible protects from other processes
 108  * looking up the same item, so it has to be locked until the cnode is totally finished
 109  *
 110  * hfs_cache_lookup() performs the following for us:
 111  *      check that it is a directory
 112  *      check accessibility of directory
 113  *      check for modification attempts on read-only mounts
 114  *      if name found in cache
 115  *              if at end of path and deleting or creating
 116  *              drop it
 117  *               else
 118  *              return name.
 119  *      return hfs_lookup()
 120  *
 121  * Overall outline of hfs_lookup:
 122  *
 123  *      handle simple cases of . and ..
 124  *      search for name in directory, to found or notfound
 125  * notfound:
 126  *      if creating, return locked directory, leaving info on available slots
 127  *      else return error
 128  * found:
 129  *      if at end of path and deleting, return information to allow delete
 130  *      if at end of path and rewriting (RENAME and LOCKPARENT), lock target
 131  *        cnode and return info to allow rewrite
 132  *      if not at end, add name to cache; if at end and neither creating
 133  *        nor deleting, add name to cache
 134  */
 135
 136
 137 /*
 138  *      Lookup *cnp in directory *dvp, return it in *vpp.
 139  *      **vpp is held on exit.
 140  *      We create a cnode for the file, but we do NOT open the file here.
 141
 142 #% lookup       dvp L ? ?
 143 #% lookup       vpp - L -
 144
 145         IN struct vnode *dvp - Parent node of file;
 146         INOUT struct vnode **vpp - node of target file, its a new node if
 147                 the target vnode did not exist;
 148         IN struct componentname *cnp - Name of file;
 149
 150  *      When should we lock parent_hp in here ??
 151  */
 152 static int
 153 hfs_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp, int *cnode_locked)
 154 {
 155         struct cnode *dcp;      /* cnode for directory being searched */
 156         struct vnode *tvp;      /* target vnode */
 157         struct hfsmount *hfsmp;
 158         int flags;
 159         int nameiop;
 160         int retval = 0;
 161         int isDot;
 162         struct cat_desc desc;
 163         struct cat_desc cndesc;
 164         struct cat_attr attr;
 165         struct cat_fork fork;
 166         int lockflags;
 167
 168   retry:
 169         dcp = NULL;
 170         hfsmp = VTOHFS(dvp);
 171         *vpp = NULL;
 172         *cnode_locked = 0;
 173         isDot = FALSE;
 174         tvp = NULL;
 175         nameiop = cnp->cn_nameiop;
 176         flags = cnp->cn_flags;
 177         bzero(&desc, sizeof(desc));
 178
 179         /*
 180          * First check to see if it is a . or .., else look it up.
 181          */
 182         if (flags & ISDOTDOT) {         /* Wanting the parent */
 183                 cnp->cn_flags &= ~MAKEENTRY;
 184                 goto found;     /* .. is always defined */
 185         } else if ((cnp->cn_nameptr[0] == '.') && (cnp->cn_namelen == 1)) {
 186                 isDot = TRUE;
 187                 cnp->cn_flags &= ~MAKEENTRY;
 188                 goto found;     /* We always know who we are */
 189         } else {
 190                 if (hfs_lock(VTOC(dvp), HFS_EXCLUSIVE_LOCK) != 0) {
 191                         retval = ENOENT;  /* The parent no longer exists ? */
 192                         goto exit;
 193                 }
 194                 dcp = VTOC(dvp);
 195
 196                 if (dcp->c_flag & C_DIR_MODIFICATION) {
 197                     // XXXdbg - if we could msleep on a lck_rw_t then we would do that
 198                     //          but since we can't we have to unlock, delay for a bit
 199                     //          and then retry...
 200                     // msleep((caddr_t)&dcp->c_flag, &dcp->c_rwlock, PINOD, "hfs_vnop_lookup", 0);
 201                     hfs_unlock(dcp);
 202                     tsleep((caddr_t)dvp, PRIBIO, "hfs_lookup", 1);
 203
 204                     goto retry;
 205                 }
 206
 207                 /* No need to go to catalog if there are no children */
 208                 if (dcp->c_entries == 0) {
 209                         goto notfound;
 210                 }
 211
 212                 bzero(&cndesc, sizeof(cndesc));
 213                 cndesc.cd_nameptr = (const u_int8_t *)cnp->cn_nameptr;
 214                 cndesc.cd_namelen = cnp->cn_namelen;
 215                 cndesc.cd_parentcnid = dcp->c_fileid;
 216                 cndesc.cd_hint = dcp->c_childhint;
 217
 218                 lockflags = hfs_systemfile_lock(hfsmp, SFL_CATALOG, HFS_SHARED_LOCK);
 219
 220                 retval = cat_lookup(hfsmp, &cndesc, 0, &desc, &attr, &fork, NULL);
 221
 222                 hfs_systemfile_unlock(hfsmp, lockflags);
 223
 224                 if (retval == 0) {
 225                         dcp->c_childhint = desc.cd_hint;
 226                         /*
 227                          * Note: We must drop the parent lock here before calling
 228                          * hfs_getnewvnode (which takes the child lock).
 229                          */
 230                         hfs_unlock(dcp);
 231                         dcp = NULL;
 232                         goto found;
 233                 }
 234 notfound:
 235                 /*
 236                  * ENAMETOOLONG supersedes other errors
 237                  *
 238                  * For a CREATE or RENAME operation on the last component
 239                  * the ENAMETOOLONG will be handled in the next VNOP.
 240                  */
 241                 if ((retval != ENAMETOOLONG) &&
 242                     (cnp->cn_namelen > kHFSPlusMaxFileNameChars) &&
 243                     (((flags & ISLASTCN) == 0) || ((nameiop != CREATE) && (nameiop != RENAME)))) {
 244                         retval = ENAMETOOLONG;
 245                 } else if (retval == 0) {
 246                         retval = ENOENT;
 247                 }
 248                 if (retval != ENOENT)
 249                         goto exit;
 250                 /*
 251                  * This is a non-existing entry
 252                  *
 253                  * If creating, and at end of pathname and current
 254                  * directory has not been removed, then can consider
 255                  * allowing file to be created.
 256                  */
 257                 if ((nameiop == CREATE || nameiop == RENAME ||
 258                     (nameiop == DELETE &&
 259                     (cnp->cn_flags & DOWHITEOUT) &&
 260                     (cnp->cn_flags & ISWHITEOUT))) &&
 261                     (flags & ISLASTCN) &&
 262                     !(ISSET(dcp->c_flag, C_DELETED | C_NOEXISTS))) {
 263                         retval = EJUSTRETURN;
 264                         goto exit;
 265                 }
 266                 /*
 267                  * Insert name into the name cache (as non-existent).
 268                  */
 269                 if ((hfsmp->hfs_flags & HFS_STANDARD) == 0 &&
 270                     (cnp->cn_flags & MAKEENTRY) &&
 271                     (nameiop != CREATE)) {
 272                         cache_enter(dvp, NULL, cnp);
 273                         dcp->c_flag |= C_NEG_ENTRIES;
 274                 }
 275                 goto exit;
 276         }
 277
 278 found:
 279         if (flags & ISLASTCN) {
 280                 switch(nameiop) {
 281                 case DELETE:
 282                         cnp->cn_flags &= ~MAKEENTRY;
 283                         break;
 284
 285                 case RENAME:
 286                         cnp->cn_flags &= ~MAKEENTRY;
 287                         if (isDot) {
 288                                 retval = EISDIR;
 289                                 goto exit;
 290                         }
 291                         break;
 292                 }
 293         }
 294
 295         if (isDot) {
 296                 if ((retval = vnode_get(dvp)))
 297                         goto exit;
 298                 *vpp = dvp;
 299         } else if (flags & ISDOTDOT) {
 300                 /*
 301                  * Directory hard links can have multiple parents so
 302                  * find the appropriate parent for the current thread.
 303                  */
 304                 if ((retval = hfs_vget(hfsmp, hfs_currentparent(VTOC(dvp)), &tvp, 0))) {
 305                         goto exit;
 306                 }
 307                 *cnode_locked = 1;
 308                 *vpp = tvp;
 309         } else {
 310                 int type = (attr.ca_mode & S_IFMT);
 311 #if NAMEDRSRCFORK
 312                 int rsrc_warn = 0;
 313
 314                 /*
 315                  * Check if caller wants the resource fork but utilized
 316                  * the legacy "file/rsrc" access path.
 317                  *
 318                  * This is deprecated behavior and support for it will not
 319                  * be allowed beyond case insensitive HFS+ and even that
 320                  * support will be removed in the next major OS release.
 321                  */
 322                 if ((type == S_IFREG) &&
 323                     ((flags & ISLASTCN) == 0) &&
 324                     (cnp->cn_nameptr[cnp->cn_namelen] == '/') &&
 325                     (bcmp(&cnp->cn_nameptr[cnp->cn_namelen+1], "rsrc", 5) == 0) &&
 326                     ((hfsmp->hfs_flags & (HFS_STANDARD | HFS_CASE_SENSITIVE)) == 0)) {
 327
 328                         cnp->cn_consume = 5;
 329                         cnp->cn_flags |= CN_WANTSRSRCFORK | ISLASTCN | NOCACHE;
 330                         cnp->cn_flags &= ~MAKEENTRY;
 331                         flags |= ISLASTCN;
 332                         rsrc_warn = 1;
 333                 }
 334 #endif
 335                 if (!(flags & ISLASTCN) && (type != S_IFDIR) && (type != S_IFLNK)) {
 336                         retval = ENOTDIR;
 337                         goto exit;
 338                 }
 339                 /* Don't cache directory hardlink names. */
 340                 if (attr.ca_recflags & kHFSHasLinkChainMask) {
 341                         cnp->cn_flags &= ~MAKEENTRY;
 342                 }
 343                 /* Names with composed chars are not cached. */
 344                 if (cnp->cn_namelen != desc.cd_namelen)
 345                         cnp->cn_flags &= ~MAKEENTRY;
 346
 347                 retval = hfs_getnewvnode(hfsmp, dvp, cnp, &desc, 0, &attr, &fork, &tvp);
 348
 349                 if (retval) {
 350                         /*
 351                          * If this was a create operation lookup and another
 352                          * process removed the object before we had a chance
 353                          * to create the vnode, then just treat it as the not
 354                          * found case above and return EJUSTRETURN.
 355                          */
 356                         if ((retval == ENOENT) &&
 357                             (cnp->cn_nameiop == CREATE) &&
 358                             (flags & ISLASTCN)) {
 359                                 retval = EJUSTRETURN;
 360                         }
 361                         goto exit;
 362                 }
 363
 364                 /*
 365                  * Save the origin info for file and directory hardlinks.  Directory hardlinks
 366                  * need the origin for '..' lookups, and file hardlinks need it to ensure that
 367                  * competing lookups do not cause us to vend different hardlinks than the ones requested.
 368                  * We want to restrict saving the cache entries to LOOKUP namei operations, since
 369                  * we're really doing this to protect getattr.
 370                  */
 371                 if ((cnp->cn_nameiop == LOOKUP) && (VTOC(tvp)->c_flag & C_HARDLINK)) {
 372                         hfs_savelinkorigin(VTOC(tvp), VTOC(dvp)->c_fileid);
 373                 }
 374                 *cnode_locked = 1;
 375                 *vpp = tvp;
 376 #if NAMEDRSRCFORK
 377                 if (rsrc_warn) {
 378                         if ((VTOC(tvp)->c_flag & C_WARNED_RSRC) == 0) {
 379                                 VTOC(tvp)->c_flag |= C_WARNED_RSRC;
 380                                 printf("%.200s: file access by '/rsrc' was deprecated in 10.4\n",
 381                                        cnp->cn_nameptr);
 382                         }
 383                 }
 384 #endif
 385         }
 386 exit:
 387         if (dcp) {
 388                 hfs_unlock(dcp);
 389         }
 390         cat_releasedesc(&desc);
 391         return (retval);
 392 }
 393
 394
 395
 396 /*
 397  * Name caching works as follows:
 398  *
 399  * Names found by directory scans are retained in a cache
 400  * for future reference.  It is managed LRU, so frequently
 401  * used names will hang around.  Cache is indexed by hash value
 402  * obtained from (vp, name) where vp refers to the directory
 403  * containing name.
 404  *
 405  * If it is a "negative" entry, (i.e. for a name that is known NOT to
 406  * exist) the vnode pointer will be NULL.
 407  *
 408  * Upon reaching the last segment of a path, if the reference
 409  * is for DELETE, or NOCACHE is set (rewrite), and the
 410  * name is located in the cache, it will be dropped.
 411  *
 412  */
 413
 414 #define S_IXALL 0000111
 415
 416 __private_extern__
 417 int
 418 hfs_vnop_lookup(struct vnop_lookup_args *ap)
 419 {
 420         struct vnode *dvp = ap->a_dvp;
 421         struct vnode *vp;
 422         struct cnode *cp;
 423         struct cnode *dcp;
 424         int error;
 425         struct vnode **vpp = ap->a_vpp;
 426         struct componentname *cnp = ap->a_cnp;
 427         int flags = cnp->cn_flags;
 428         int cnode_locked;
 429
 430         *vpp = NULL;
 431         dcp = VTOC(dvp);
 432
 433         /*
 434          * Lookup an entry in the cache
 435          *
 436          * If the lookup succeeds, the vnode is returned in *vpp,
 437          * and a status of -1 is returned.
 438          *
 439          * If the lookup determines that the name does not exist
 440          * (negative cacheing), a status of ENOENT is returned.
 441          *
 442          * If the lookup fails, a status of zero is returned.
 443          */
 444         error = cache_lookup(dvp, vpp, cnp);
 445         if (error != -1) {
 446                 if ((error == ENOENT) && (cnp->cn_nameiop != CREATE))
 447                         goto exit;      /* found a negative cache entry */
 448                 goto lookup;            /* did not find it in the cache */
 449         }
 450         /*
 451          * We have a name that matched
 452          * cache_lookup returns the vp with an iocount reference already taken
 453          */
 454         error = 0;
 455         vp = *vpp;
 456
 457         /*
 458          * If this is a hard-link vnode then we need to update
 459          * the name (of the link), the parent ID, the cnid, the
 460          * text encoding and the catalog hint.  This enables
 461          * getattrlist calls to return the correct link info.
 462          */
 463         cp = VTOC(vp);
 464
 465         if ((flags & ISLASTCN) && (cp->c_flag & C_HARDLINK)) {
 466                 hfs_lock(cp, HFS_FORCE_LOCK);
 467                 if ((cp->c_parentcnid != dcp->c_cnid) ||
 468                     (bcmp(cnp->cn_nameptr, cp->c_desc.cd_nameptr, cp->c_desc.cd_namelen) != 0)) {
 469                         struct cat_desc desc;
 470                         int lockflags;
 471
 472                         /*
 473                          * Get an updated descriptor
 474                          */
 475                         desc.cd_nameptr = (const u_int8_t *)cnp->cn_nameptr;
 476                         desc.cd_namelen = cnp->cn_namelen;
 477                         desc.cd_parentcnid = dcp->c_fileid;
 478                         desc.cd_hint = dcp->c_childhint;
 479                         desc.cd_encoding = 0;
 480                         desc.cd_cnid = 0;
 481                         desc.cd_flags = S_ISDIR(cp->c_mode) ? CD_ISDIR : 0;
 482
 483                         lockflags = hfs_systemfile_lock(VTOHFS(dvp), SFL_CATALOG, HFS_SHARED_LOCK);
 484                         if (cat_lookup(VTOHFS(vp), &desc, 0, &desc, NULL, NULL, NULL) == 0)
 485                                 replace_desc(cp, &desc);
 486                         hfs_systemfile_unlock(VTOHFS(dvp), lockflags);
 487                 }
 488
 489                 /* Save the lookup result in the origin list for future lookups, but
 490                  * only if it was through a LOOKUP nameiop
 491                  */
 492                 if (cnp->cn_nameiop == LOOKUP) {
 493                         hfs_savelinkorigin(cp, dcp->c_fileid);
 494                 }
 495
 496                 hfs_unlock(cp);
 497         }
 498 #if NAMEDRSRCFORK
 499         /*
 500          * Check if caller wants the resource fork but utilized
 501          * the legacy "file/rsrc" access path.
 502          *
 503          * This is deprecated behavior and support for it will not
 504          * be allowed beyond case insensitive HFS+ and even that
 505          * support will be removed in the next major OS release.
 506          */
 507         if ((dvp != vp) &&
 508             ((flags & ISLASTCN) == 0) &&
 509             vnode_isreg(vp) &&
 510             (cnp->cn_nameptr[cnp->cn_namelen] == '/') &&
 511             (bcmp(&cnp->cn_nameptr[cnp->cn_namelen+1], "rsrc", 5) == 0) &&
 512             ((VTOHFS(vp)->hfs_flags & (HFS_STANDARD | HFS_CASE_SENSITIVE)) == 0)) {
 513                 cnp->cn_consume = 5;
 514                 cnp->cn_flags |= CN_WANTSRSRCFORK | ISLASTCN | NOCACHE;
 515                 cnp->cn_flags &= ~MAKEENTRY;
 516
 517                 hfs_lock(cp, HFS_FORCE_LOCK);
 518                 if ((cp->c_flag & C_WARNED_RSRC) == 0) {
 519                         cp->c_flag |= C_WARNED_RSRC;
 520                         printf("%.200s: file access by '/rsrc' was deprecated in 10.4\n", cnp->cn_nameptr);
 521                 }
 522                 hfs_unlock(cp);
 523         }
 524 #endif
 525         return (error);
 526
 527 lookup:
 528         /*
 529          * The vnode was not in the name cache or it was stale.
 530          *
 531          * So we need to do a real lookup.
 532          */
 533         cnode_locked = 0;
 534
 535         error = hfs_lookup(dvp, vpp, cnp, &cnode_locked);
 536
 537         if (cnode_locked)
 538                 hfs_unlock(VTOC(*vpp));
 539 exit:
 540         return (error);
 541 }
 542
 543