fs/ntfs/namei.c

   1 /*
   2  * namei.c - NTFS kernel directory inode operations. Part of the Linux-NTFS
   3  *           project.
   4  *
   5  * Copyright (c) 2001-2006 Anton Altaparmakov
   6  *
   7  * This program/include file is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as published
   9  * by the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program/include file is distributed in the hope that it will be
  13  * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
  14  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program (in the main directory of the Linux-NTFS
  19  * distribution in the file COPYING); if not, write to the Free Software
  20  * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21  */
  22
  23 #include <linux/dcache.h>
  24 #include <linux/exportfs.h>
  25 #include <linux/security.h>
  26
  27 #include "attrib.h"
  28 #include "debug.h"
  29 #include "dir.h"
  30 #include "mft.h"
  31 #include "ntfs.h"
  32
  33 /**
  34  * ntfs_lookup - find the inode represented by a dentry in a directory inode
  35  * @dir_ino:    directory inode in which to look for the inode
  36  * @dent:       dentry representing the inode to look for
  37  * @nd:         lookup nameidata
  38  *
  39  * In short, ntfs_lookup() looks for the inode represented by the dentry @dent
  40  * in the directory inode @dir_ino and if found attaches the inode to the
  41  * dentry @dent.
  42  *
  43  * In more detail, the dentry @dent specifies which inode to look for by
  44  * supplying the name of the inode in @dent->d_name.name. ntfs_lookup()
  45  * converts the name to Unicode and walks the contents of the directory inode
  46  * @dir_ino looking for the converted Unicode name. If the name is found in the
  47  * directory, the corresponding inode is loaded by calling ntfs_iget() on its
  48  * inode number and the inode is associated with the dentry @dent via a call to
  49  * d_splice_alias().
  50  *
  51  * If the name is not found in the directory, a NULL inode is inserted into the
  52  * dentry @dent via a call to d_add(). The dentry is then termed a negative
  53  * dentry.
  54  *
  55  * Only if an actual error occurs, do we return an error via ERR_PTR().
  56  *
  57  * In order to handle the case insensitivity issues of NTFS with regards to the
  58  * dcache and the dcache requiring only one dentry per directory, we deal with
  59  * dentry aliases that only differ in case in ->ntfs_lookup() while maintaining
  60  * a case sensitive dcache. This means that we get the full benefit of dcache
  61  * speed when the file/directory is looked up with the same case as returned by
  62  * ->ntfs_readdir() but that a lookup for any other case (or for the short file
  63  * name) will not find anything in dcache and will enter ->ntfs_lookup()
  64  * instead, where we search the directory for a fully matching file name
  65  * (including case) and if that is not found, we search for a file name that
  66  * matches with different case and if that has non-POSIX semantics we return
  67  * that. We actually do only one search (case sensitive) and keep tabs on
  68  * whether we have found a case insensitive match in the process.
  69  *
  70  * To simplify matters for us, we do not treat the short vs long filenames as
  71  * two hard links but instead if the lookup matches a short filename, we
  72  * return the dentry for the corresponding long filename instead.
  73  *
  74  * There are three cases we need to distinguish here:
  75  *
  76  * 1) @dent perfectly matches (i.e. including case) a directory entry with a
  77  *    file name in the WIN32 or POSIX namespaces. In this case
  78  *    ntfs_lookup_inode_by_name() will return with name set to NULL and we
  79  *    just d_splice_alias() @dent.
  80  * 2) @dent matches (not including case) a directory entry with a file name in
  81  *    the WIN32 namespace. In this case ntfs_lookup_inode_by_name() will return
  82  *    with name set to point to a kmalloc()ed ntfs_name structure containing
  83  *    the properly cased little endian Unicode name. We convert the name to the
  84  *    current NLS code page, search if a dentry with this name already exists
  85  *    and if so return that instead of @dent.  At this point things are
  86  *    complicated by the possibility of 'disconnected' dentries due to NFS
  87  *    which we deal with appropriately (see the code comments).  The VFS will
  88  *    then destroy the old @dent and use the one we returned.  If a dentry is
  89  *    not found, we allocate a new one, d_splice_alias() it, and return it as
  90  *    above.
  91  * 3) @dent matches either perfectly or not (i.e. we don't care about case) a
  92  *    directory entry with a file name in the DOS namespace. In this case
  93  *    ntfs_lookup_inode_by_name() will return with name set to point to a
  94  *    kmalloc()ed ntfs_name structure containing the mft reference (cpu endian)
  95  *    of the inode. We use the mft reference to read the inode and to find the
  96  *    file name in the WIN32 namespace corresponding to the matched short file
  97  *    name. We then convert the name to the current NLS code page, and proceed
  98  *    searching for a dentry with this name, etc, as in case 2), above.
  99  *
 100  * Locking: Caller must hold i_mutex on the directory.
 101  */
 102 static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent,
 103                 struct nameidata *nd)
 104 {
 105         ntfs_volume *vol = NTFS_SB(dir_ino->i_sb);
 106         struct inode *dent_inode;
 107         ntfschar *uname;
 108         ntfs_name *name = NULL;
 109         MFT_REF mref;
 110         unsigned long dent_ino;
 111         int uname_len;
 112
 113         ntfs_debug("Looking up %s in directory inode 0x%lx.",
 114                         dent->d_name.name, dir_ino->i_ino);
 115         /* Convert the name of the dentry to Unicode. */
 116         uname_len = ntfs_nlstoucs(vol, dent->d_name.name, dent->d_name.len,
 117                         &uname);
 118         if (uname_len < 0) {
 119                 if (uname_len != -ENAMETOOLONG)
 120                         ntfs_error(vol->sb, "Failed to convert name to "
 121                                         "Unicode.");
 122                 return ERR_PTR(uname_len);
 123         }
 124         mref = ntfs_lookup_inode_by_name(NTFS_I(dir_ino), uname, uname_len,
 125                         &name);
 126         kmem_cache_free(ntfs_name_cache, uname);
 127         if (!IS_ERR_MREF(mref)) {
 128                 dent_ino = MREF(mref);
 129                 ntfs_debug("Found inode 0x%lx. Calling ntfs_iget.", dent_ino);
 130                 dent_inode = ntfs_iget(vol->sb, dent_ino);
 131                 if (likely(!IS_ERR(dent_inode))) {
 132                         /* Consistency check. */
 133                         if (is_bad_inode(dent_inode) || MSEQNO(mref) ==
 134                                         NTFS_I(dent_inode)->seq_no ||
 135                                         dent_ino == FILE_MFT) {
 136                                 /* Perfect WIN32/POSIX match. -- Case 1. */
 137                                 if (!name) {
 138                                         ntfs_debug("Done.  (Case 1.)");
 139                                         return d_splice_alias(dent_inode, dent);
 140                                 }
 141                                 /*
 142                                  * We are too indented.  Handle imperfect
 143                                  * matches and short file names further below.
 144                                  */
 145                                 goto handle_name;
 146                         }
 147                         ntfs_error(vol->sb, "Found stale reference to inode "
 148                                         "0x%lx (reference sequence number = "
 149                                         "0x%x, inode sequence number = 0x%x), "
 150                                         "returning -EIO. Run chkdsk.",
 151                                         dent_ino, MSEQNO(mref),
 152                                         NTFS_I(dent_inode)->seq_no);
 153                         iput(dent_inode);
 154                         dent_inode = ERR_PTR(-EIO);
 155                 } else
 156                         ntfs_error(vol->sb, "ntfs_iget(0x%lx) failed with "
 157                                         "error code %li.", dent_ino,
 158                                         PTR_ERR(dent_inode));
 159                 kfree(name);
 160                 /* Return the error code. */
 161                 return (struct dentry *)dent_inode;
 162         }
 163         /* It is guaranteed that @name is no longer allocated at this point. */
 164         if (MREF_ERR(mref) == -ENOENT) {
 165                 ntfs_debug("Entry was not found, adding negative dentry.");
 166                 /* The dcache will handle negative entries. */
 167                 d_add(dent, NULL);
 168                 ntfs_debug("Done.");
 169                 return NULL;
 170         }
 171         ntfs_error(vol->sb, "ntfs_lookup_ino_by_name() failed with error "
 172                         "code %i.", -MREF_ERR(mref));
 173         return ERR_PTR(MREF_ERR(mref));
 174         // TODO: Consider moving this lot to a separate function! (AIA)
 175 handle_name:
 176    {
 177         struct dentry *real_dent, *new_dent;
 178         MFT_RECORD *m;
 179         ntfs_attr_search_ctx *ctx;
 180         ntfs_inode *ni = NTFS_I(dent_inode);
 181         int err;
 182         struct qstr nls_name;
 183
 184         nls_name.name = NULL;
 185         if (name->type != FILE_NAME_DOS) {                      /* Case 2. */
 186                 ntfs_debug("Case 2.");
 187                 nls_name.len = (unsigned)ntfs_ucstonls(vol,
 188                                 (ntfschar*)&name->name, name->len,
 189                                 (unsigned char**)&nls_name.name, 0);
 190                 kfree(name);
 191         } else /* if (name->type == FILE_NAME_DOS) */ {         /* Case 3. */
 192                 FILE_NAME_ATTR *fn;
 193
 194                 ntfs_debug("Case 3.");
 195                 kfree(name);
 196
 197                 /* Find the WIN32 name corresponding to the matched DOS name. */
 198                 ni = NTFS_I(dent_inode);
 199                 m = map_mft_record(ni);
 200                 if (IS_ERR(m)) {
 201                         err = PTR_ERR(m);
 202                         m = NULL;
 203                         ctx = NULL;
 204                         goto err_out;
 205                 }
 206                 ctx = ntfs_attr_get_search_ctx(ni, m);
 207                 if (unlikely(!ctx)) {
 208                         err = -ENOMEM;
 209                         goto err_out;
 210                 }
 211                 do {
 212                         ATTR_RECORD *a;
 213                         u32 val_len;
 214
 215                         err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, 0, 0,
 216                                         NULL, 0, ctx);
 217                         if (unlikely(err)) {
 218                                 ntfs_error(vol->sb, "Inode corrupt: No WIN32 "
 219                                                 "namespace counterpart to DOS "
 220                                                 "file name. Run chkdsk.");
 221                                 if (err == -ENOENT)
 222                                         err = -EIO;
 223                                 goto err_out;
 224                         }
 225                         /* Consistency checks. */
 226                         a = ctx->attr;
 227                         if (a->non_resident || a->flags)
 228                                 goto eio_err_out;
 229                         val_len = le32_to_cpu(a->data.resident.value_length);
 230                         if (le16_to_cpu(a->data.resident.value_offset) +
 231                                         val_len > le32_to_cpu(a->length))
 232                                 goto eio_err_out;
 233                         fn = (FILE_NAME_ATTR*)((u8*)ctx->attr + le16_to_cpu(
 234                                         ctx->attr->data.resident.value_offset));
 235                         if ((u32)(fn->file_name_length * sizeof(ntfschar) +
 236                                         sizeof(FILE_NAME_ATTR)) > val_len)
 237                                 goto eio_err_out;
 238                 } while (fn->file_name_type != FILE_NAME_WIN32);
 239
 240                 /* Convert the found WIN32 name to current NLS code page. */
 241                 nls_name.len = (unsigned)ntfs_ucstonls(vol,
 242                                 (ntfschar*)&fn->file_name, fn->file_name_length,
 243                                 (unsigned char**)&nls_name.name, 0);
 244
 245                 ntfs_attr_put_search_ctx(ctx);
 246                 unmap_mft_record(ni);
 247         }
 248         m = NULL;
 249         ctx = NULL;
 250
 251         /* Check if a conversion error occurred. */
 252         if ((signed)nls_name.len < 0) {
 253                 err = (signed)nls_name.len;
 254                 goto err_out;
 255         }
 256         nls_name.hash = full_name_hash(nls_name.name, nls_name.len);
 257
 258         /*
 259          * Note: No need for dent->d_lock lock as i_mutex is held on the
 260          * parent inode.
 261          */
 262
 263         /* Does a dentry matching the nls_name exist already? */
 264         real_dent = d_lookup(dent->d_parent, &nls_name);
 265         /* If not, create it now. */
 266         if (!real_dent) {
 267                 real_dent = d_alloc(dent->d_parent, &nls_name);
 268                 kfree(nls_name.name);
 269                 if (!real_dent) {
 270                         err = -ENOMEM;
 271                         goto err_out;
 272                 }
 273                 new_dent = d_splice_alias(dent_inode, real_dent);
 274                 if (new_dent)
 275                         dput(real_dent);
 276                 else
 277                         new_dent = real_dent;
 278                 ntfs_debug("Done.  (Created new dentry.)");
 279                 return new_dent;
 280         }
 281         kfree(nls_name.name);
 282         /* Matching dentry exists, check if it is negative. */
 283         if (real_dent->d_inode) {
 284                 if (unlikely(real_dent->d_inode != dent_inode)) {
 285                         /* This can happen because bad inodes are unhashed. */
 286                         BUG_ON(!is_bad_inode(dent_inode));
 287                         BUG_ON(!is_bad_inode(real_dent->d_inode));
 288                 }
 289                 /*
 290                  * Already have the inode and the dentry attached, decrement
 291                  * the reference count to balance the ntfs_iget() we did
 292                  * earlier on.  We found the dentry using d_lookup() so it
 293                  * cannot be disconnected and thus we do not need to worry
 294                  * about any NFS/disconnectedness issues here.
 295                  */
 296                 iput(dent_inode);
 297                 ntfs_debug("Done.  (Already had inode and dentry.)");
 298                 return real_dent;
 299         }
 300         /*
 301          * Negative dentry: instantiate it unless the inode is a directory and
 302          * has a 'disconnected' dentry (i.e. IS_ROOT and DCACHE_DISCONNECTED),
 303          * in which case d_move() that in place of the found dentry.
 304          */
 305         if (!S_ISDIR(dent_inode->i_mode)) {
 306                 /* Not a directory; everything is easy. */
 307                 d_instantiate(real_dent, dent_inode);
 308                 ntfs_debug("Done.  (Already had negative file dentry.)");
 309                 return real_dent;
 310         }
 311         spin_lock(&dcache_lock);
 312         if (list_empty(&dent_inode->i_dentry)) {
 313                 /*
 314                  * Directory without a 'disconnected' dentry; we need to do
 315                  * d_instantiate() by hand because it takes dcache_lock which
 316                  * we already hold.
 317                  */
 318                 list_add(&real_dent->d_alias, &dent_inode->i_dentry);
 319                 real_dent->d_inode = dent_inode;
 320                 spin_unlock(&dcache_lock);
 321                 security_d_instantiate(real_dent, dent_inode);
 322                 ntfs_debug("Done.  (Already had negative directory dentry.)");
 323                 return real_dent;
 324         }
 325         /*
 326          * Directory with a 'disconnected' dentry; get a reference to the
 327          * 'disconnected' dentry.
 328          */
 329         new_dent = list_entry(dent_inode->i_dentry.next, struct dentry,
 330                         d_alias);
 331         dget_locked(new_dent);
 332         spin_unlock(&dcache_lock);
 333         /* Do security vodoo. */
 334         security_d_instantiate(real_dent, dent_inode);
 335         /* Move new_dent in place of real_dent. */
 336         d_move(new_dent, real_dent);
 337         /* Balance the ntfs_iget() we did above. */
 338         iput(dent_inode);
 339         /* Throw away real_dent. */
 340         dput(real_dent);
 341         /* Use new_dent as the actual dentry. */
 342         ntfs_debug("Done.  (Already had negative, disconnected directory "
 343                         "dentry.)");
 344         return new_dent;
 345
 346 eio_err_out:
 347         ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
 348         err = -EIO;
 349 err_out:
 350         if (ctx)
 351                 ntfs_attr_put_search_ctx(ctx);
 352         if (m)
 353                 unmap_mft_record(ni);
 354         iput(dent_inode);
 355         ntfs_error(vol->sb, "Failed, returning error code %i.", err);
 356         return ERR_PTR(err);
 357    }
 358 }
 359
 360 /**
 361  * Inode operations for directories.
 362  */
 363 const struct inode_operations ntfs_dir_inode_ops = {
 364         .lookup = ntfs_lookup,  /* VFS: Lookup directory. */
 365 };
 366
 367 /**
 368  * ntfs_get_parent - find the dentry of the parent of a given directory dentry
 369  * @child_dent:         dentry of the directory whose parent directory to find
 370  *
 371  * Find the dentry for the parent directory of the directory specified by the
 372  * dentry @child_dent.  This function is called from
 373  * fs/exportfs/expfs.c::find_exported_dentry() which in turn is called from the
 374  * default ->decode_fh() which is export_decode_fh() in the same file.
 375  *
 376  * The code is based on the ext3 ->get_parent() implementation found in
 377  * fs/ext3/namei.c::ext3_get_parent().
 378  *
 379  * Note: ntfs_get_parent() is called with @child_dent->d_inode->i_mutex down.
 380  *
 381  * Return the dentry of the parent directory on success or the error code on
 382  * error (IS_ERR() is true).
 383  */
 384 static struct dentry *ntfs_get_parent(struct dentry *child_dent)
 385 {
 386         struct inode *vi = child_dent->d_inode;
 387         ntfs_inode *ni = NTFS_I(vi);
 388         MFT_RECORD *mrec;
 389         ntfs_attr_search_ctx *ctx;
 390         ATTR_RECORD *attr;
 391         FILE_NAME_ATTR *fn;
 392         struct inode *parent_vi;
 393         struct dentry *parent_dent;
 394         unsigned long parent_ino;
 395         int err;
 396
 397         ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
 398         /* Get the mft record of the inode belonging to the child dentry. */
 399         mrec = map_mft_record(ni);
 400         if (IS_ERR(mrec))
 401                 return (struct dentry *)mrec;
 402         /* Find the first file name attribute in the mft record. */
 403         ctx = ntfs_attr_get_search_ctx(ni, mrec);
 404         if (unlikely(!ctx)) {
 405                 unmap_mft_record(ni);
 406                 return ERR_PTR(-ENOMEM);
 407         }
 408 try_next:
 409         err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, CASE_SENSITIVE, 0, NULL,
 410                         0, ctx);
 411         if (unlikely(err)) {
 412                 ntfs_attr_put_search_ctx(ctx);
 413                 unmap_mft_record(ni);
 414                 if (err == -ENOENT)
 415                         ntfs_error(vi->i_sb, "Inode 0x%lx does not have a "
 416                                         "file name attribute.  Run chkdsk.",
 417                                         vi->i_ino);
 418                 return ERR_PTR(err);
 419         }
 420         attr = ctx->attr;
 421         if (unlikely(attr->non_resident))
 422                 goto try_next;
 423         fn = (FILE_NAME_ATTR *)((u8 *)attr +
 424                         le16_to_cpu(attr->data.resident.value_offset));
 425         if (unlikely((u8 *)fn + le32_to_cpu(attr->data.resident.value_length) >
 426                         (u8*)attr + le32_to_cpu(attr->length)))
 427                 goto try_next;
 428         /* Get the inode number of the parent directory. */
 429         parent_ino = MREF_LE(fn->parent_directory);
 430         /* Release the search context and the mft record of the child. */
 431         ntfs_attr_put_search_ctx(ctx);
 432         unmap_mft_record(ni);
 433         /* Get the inode of the parent directory. */
 434         parent_vi = ntfs_iget(vi->i_sb, parent_ino);
 435         if (IS_ERR(parent_vi) || unlikely(is_bad_inode(parent_vi))) {
 436                 if (!IS_ERR(parent_vi))
 437                         iput(parent_vi);
 438                 ntfs_error(vi->i_sb, "Failed to get parent directory inode "
 439                                 "0x%lx of child inode 0x%lx.", parent_ino,
 440                                 vi->i_ino);
 441                 return ERR_PTR(-EACCES);
 442         }
 443         /* Finally get a dentry for the parent directory and return it. */
 444         parent_dent = d_alloc_anon(parent_vi);
 445         if (unlikely(!parent_dent)) {
 446                 iput(parent_vi);
 447                 return ERR_PTR(-ENOMEM);
 448         }
 449         ntfs_debug("Done for inode 0x%lx.", vi->i_ino);
 450         return parent_dent;
 451 }
 452
 453 static struct inode *ntfs_nfs_get_inode(struct super_block *sb,
 454                 u64 ino, u32 generation)
 455 {
 456         struct inode *inode;
 457
 458         inode = ntfs_iget(sb, ino);
 459         if (!IS_ERR(inode)) {
 460                 if (is_bad_inode(inode) || inode->i_generation != generation) {
 461                         iput(inode);
 462                         inode = ERR_PTR(-ESTALE);
 463                 }
 464         }
 465
 466         return inode;
 467 }
 468
 469 static struct dentry *ntfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
 470                 int fh_len, int fh_type)
 471 {
 472         return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
 473                                     ntfs_nfs_get_inode);
 474 }
 475
 476 static struct dentry *ntfs_fh_to_parent(struct super_block *sb, struct fid *fid,
 477                 int fh_len, int fh_type)
 478 {
 479         return generic_fh_to_parent(sb, fid, fh_len, fh_type,
 480                                     ntfs_nfs_get_inode);
 481 }
 482
 483 /**
 484  * Export operations allowing NFS exporting of mounted NTFS partitions.
 485  *
 486  * We use the default ->encode_fh() for now.  Note that they
 487  * use 32 bits to store the inode number which is an unsigned long so on 64-bit
 488  * architectures is usually 64 bits so it would all fail horribly on huge
 489  * volumes.  I guess we need to define our own encode and decode fh functions
 490  * that store 64-bit inode numbers at some point but for now we will ignore the
 491  * problem...
 492  *
 493  * We also use the default ->get_name() helper (used by ->decode_fh() via
 494  * fs/exportfs/expfs.c::find_exported_dentry()) as that is completely fs
 495  * independent.
 496  *
 497  * The default ->get_parent() just returns -EACCES so we have to provide our
 498  * own and the default ->get_dentry() is incompatible with NTFS due to not
 499  * allowing the inode number 0 which is used in NTFS for the system file $MFT
 500  * and due to using iget() whereas NTFS needs ntfs_iget().
 501  */
 502 const struct export_operations ntfs_export_ops = {
 503         .get_parent     = ntfs_get_parent,      /* Find the parent of a given
 504                                                    directory. */
 505         .fh_to_dentry   = ntfs_fh_to_dentry,
 506         .fh_to_parent   = ntfs_fh_to_parent,
 507 };