fs/ntfs/namei.c

   1 /*
   2  * namei.c - NTFS kernel directory inode operations. Part of the Linux-NTFS
   3  *           project.
   4  *
   5  * Copyright (c) 2001-2004 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/security.h>
  25
  26 #include "attrib.h"
  27 #include "debug.h"
  28 #include "dir.h"
  29 #include "mft.h"
  30 #include "ntfs.h"
  31
  32 /**
  33  * ntfs_lookup - find the inode represented by a dentry in a directory inode
  34  * @dir_ino:    directory inode in which to look for the inode
  35  * @dent:       dentry representing the inode to look for
  36  * @nd:         lookup nameidata
  37  *
  38  * In short, ntfs_lookup() looks for the inode represented by the dentry @dent
  39  * in the directory inode @dir_ino and if found attaches the inode to the
  40  * dentry @dent.
  41  *
  42  * In more detail, the dentry @dent specifies which inode to look for by
  43  * supplying the name of the inode in @dent->d_name.name. ntfs_lookup()
  44  * converts the name to Unicode and walks the contents of the directory inode
  45  * @dir_ino looking for the converted Unicode name. If the name is found in the
  46  * directory, the corresponding inode is loaded by calling ntfs_iget() on its
  47  * inode number and the inode is associated with the dentry @dent via a call to
  48  * d_splice_alias().
  49  *
  50  * If the name is not found in the directory, a NULL inode is inserted into the
  51  * dentry @dent via a call to d_add(). The dentry is then termed a negative
  52  * dentry.
  53  *
  54  * Only if an actual error occurs, do we return an error via ERR_PTR().
  55  *
  56  * In order to handle the case insensitivity issues of NTFS with regards to the
  57  * dcache and the dcache requiring only one dentry per directory, we deal with
  58  * dentry aliases that only differ in case in ->ntfs_lookup() while maintaining
  59  * a case sensitive dcache. This means that we get the full benefit of dcache
  60  * speed when the file/directory is looked up with the same case as returned by
  61  * ->ntfs_readdir() but that a lookup for any other case (or for the short file
  62  * name) will not find anything in dcache and will enter ->ntfs_lookup()
  63  * instead, where we search the directory for a fully matching file name
  64  * (including case) and if that is not found, we search for a file name that
  65  * matches with different case and if that has non-POSIX semantics we return
  66  * that. We actually do only one search (case sensitive) and keep tabs on
  67  * whether we have found a case insensitive match in the process.
  68  *
  69  * To simplify matters for us, we do not treat the short vs long filenames as
  70  * two hard links but instead if the lookup matches a short filename, we
  71  * return the dentry for the corresponding long filename instead.
  72  *
  73  * There are three cases we need to distinguish here:
  74  *
  75  * 1) @dent perfectly matches (i.e. including case) a directory entry with a
  76  *    file name in the WIN32 or POSIX namespaces. In this case
  77  *    ntfs_lookup_inode_by_name() will return with name set to NULL and we
  78  *    just d_splice_alias() @dent.
  79  * 2) @dent matches (not including case) a directory entry with a file name in
  80  *    the WIN32 namespace. In this case ntfs_lookup_inode_by_name() will return
  81  *    with name set to point to a kmalloc()ed ntfs_name structure containing
  82  *    the properly cased little endian Unicode name. We convert the name to the
  83  *    current NLS code page, search if a dentry with this name already exists
  84  *    and if so return that instead of @dent.  At this point things are
  85  *    complicated by the possibility of 'disconnected' dentries due to NFS
  86  *    which we deal with appropriately (see the code comments).  The VFS will
  87  *    then destroy the old @dent and use the one we returned.  If a dentry is
  88  *    not found, we allocate a new one, d_splice_alias() it, and return it as
  89  *    above.
  90  * 3) @dent matches either perfectly or not (i.e. we don't care about case) a
  91  *    directory entry with a file name in the DOS namespace. In this case
  92  *    ntfs_lookup_inode_by_name() will return with name set to point to a
  93  *    kmalloc()ed ntfs_name structure containing the mft reference (cpu endian)
  94  *    of the inode. We use the mft reference to read the inode and to find the
  95  *    file name in the WIN32 namespace corresponding to the matched short file
  96  *    name. We then convert the name to the current NLS code page, and proceed
  97  *    searching for a dentry with this name, etc, as in case 2), above.
  98  *
  99  * Locking: Caller must hold i_sem on the directory.
 100  */
 101 static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent,
 102                 struct nameidata *nd)
 103 {
 104         ntfs_volume *vol = NTFS_SB(dir_ino->i_sb);
 105         struct inode *dent_inode;
 106         ntfschar *uname;
 107         ntfs_name *name = NULL;
 108         MFT_REF mref;
 109         unsigned long dent_ino;
 110         int uname_len;
 111
 112         ntfs_debug("Looking up %s in directory inode 0x%lx.",
 113                         dent->d_name.name, dir_ino->i_ino);
 114         /* Convert the name of the dentry to Unicode. */
 115         uname_len = ntfs_nlstoucs(vol, dent->d_name.name, dent->d_name.len,
 116                         &uname);
 117         if (uname_len < 0) {
 118                 ntfs_error(vol->sb, "Failed to convert name to Unicode.");
 119                 return ERR_PTR(uname_len);
 120         }
 121         mref = ntfs_lookup_inode_by_name(NTFS_I(dir_ino), uname, uname_len,
 122                         &name);
 123         kmem_cache_free(ntfs_name_cache, uname);
 124         if (!IS_ERR_MREF(mref)) {
 125                 dent_ino = MREF(mref);
 126                 ntfs_debug("Found inode 0x%lx. Calling ntfs_iget.", dent_ino);
 127                 dent_inode = ntfs_iget(vol->sb, dent_ino);
 128                 if (likely(!IS_ERR(dent_inode))) {
 129                         /* Consistency check. */
 130                         if (is_bad_inode(dent_inode) || MSEQNO(mref) ==
 131                                         NTFS_I(dent_inode)->seq_no ||
 132                                         dent_ino == FILE_MFT) {
 133                                 /* Perfect WIN32/POSIX match. -- Case 1. */
 134                                 if (!name) {
 135                                         ntfs_debug("Done.  (Case 1.)");
 136                                         return d_splice_alias(dent_inode, dent);
 137                                 }
 138                                 /*
 139                                  * We are too indented.  Handle imperfect
 140                                  * matches and short file names further below.
 141                                  */
 142                                 goto handle_name;
 143                         }
 144                         ntfs_error(vol->sb, "Found stale reference to inode "
 145                                         "0x%lx (reference sequence number = "
 146                                         "0x%x, inode sequence number = 0x%x), "
 147                                         "returning -EIO. Run chkdsk.",
 148                                         dent_ino, MSEQNO(mref),
 149                                         NTFS_I(dent_inode)->seq_no);
 150                         iput(dent_inode);
 151                         dent_inode = ERR_PTR(-EIO);
 152                 } else
 153                         ntfs_error(vol->sb, "ntfs_iget(0x%lx) failed with "
 154                                         "error code %li.", dent_ino,
 155                                         PTR_ERR(dent_inode));
 156                 kfree(name);
 157                 /* Return the error code. */
 158                 return (struct dentry *)dent_inode;
 159         }
 160         /* It is guaranteed that name is no longer allocated at this point. */
 161         if (MREF_ERR(mref) == -ENOENT) {
 162                 ntfs_debug("Entry was not found, adding negative dentry.");
 163                 /* The dcache will handle negative entries. */
 164                 d_add(dent, NULL);
 165                 ntfs_debug("Done.");
 166                 return NULL;
 167         }
 168         ntfs_error(vol->sb, "ntfs_lookup_ino_by_name() failed with error "
 169                         "code %i.", -MREF_ERR(mref));
 170         return ERR_PTR(MREF_ERR(mref));
 171
 172         // TODO: Consider moving this lot to a separate function! (AIA)
 173 handle_name:
 174    {
 175         struct dentry *real_dent, *new_dent;
 176         MFT_RECORD *m;
 177         ntfs_attr_search_ctx *ctx;
 178         ntfs_inode *ni = NTFS_I(dent_inode);
 179         int err;
 180         struct qstr nls_name;
 181
 182         nls_name.name = NULL;
 183         if (name->type != FILE_NAME_DOS) {                      /* Case 2. */
 184                 ntfs_debug("Case 2.");
 185                 nls_name.len = (unsigned)ntfs_ucstonls(vol,
 186                                 (ntfschar*)&name->name, name->len,
 187                                 (unsigned char**)&nls_name.name, 0);
 188                 kfree(name);
 189         } else /* if (name->type == FILE_NAME_DOS) */ {         /* Case 3. */
 190                 FILE_NAME_ATTR *fn;
 191
 192                 ntfs_debug("Case 3.");
 193                 kfree(name);
 194
 195                 /* Find the WIN32 name corresponding to the matched DOS name. */
 196                 ni = NTFS_I(dent_inode);
 197                 m = map_mft_record(ni);
 198                 if (IS_ERR(m)) {
 199                         err = PTR_ERR(m);
 200                         m = NULL;
 201                         ctx = NULL;
 202                         goto err_out;
 203                 }
 204                 ctx = ntfs_attr_get_search_ctx(ni, m);
 205                 if (unlikely(!ctx)) {
 206                         err = -ENOMEM;
 207                         goto err_out;
 208                 }
 209                 do {
 210                         ATTR_RECORD *a;
 211                         u32 val_len;
 212
 213                         err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, 0, 0,
 214                                         NULL, 0, ctx);
 215                         if (unlikely(err)) {
 216                                 ntfs_error(vol->sb, "Inode corrupt: No WIN32 "
 217                                                 "namespace counterpart to DOS "
 218                                                 "file name. Run chkdsk.");
 219                                 if (err == -ENOENT)
 220                                         err = -EIO;
 221                                 goto err_out;
 222                         }
 223                         /* Consistency checks. */
 224                         a = ctx->attr;
 225                         if (a->non_resident || a->flags)
 226                                 goto eio_err_out;
 227                         val_len = le32_to_cpu(a->data.resident.value_length);
 228                         if (le16_to_cpu(a->data.resident.value_offset) +
 229                                         val_len > le32_to_cpu(a->length))
 230                                 goto eio_err_out;
 231                         fn = (FILE_NAME_ATTR*)((u8*)ctx->attr + le16_to_cpu(
 232                                         ctx->attr->data.resident.value_offset));
 233                         if ((u32)(fn->file_name_length * sizeof(ntfschar) +
 234                                         sizeof(FILE_NAME_ATTR)) > val_len)
 235                                 goto eio_err_out;
 236                 } while (fn->file_name_type != FILE_NAME_WIN32);
 237
 238                 /* Convert the found WIN32 name to current NLS code page. */
 239                 nls_name.len = (unsigned)ntfs_ucstonls(vol,
 240                                 (ntfschar*)&fn->file_name, fn->file_name_length,
 241                                 (unsigned char**)&nls_name.name, 0);
 242
 243                 ntfs_attr_put_search_ctx(ctx);
 244                 unmap_mft_record(ni);
 245         }
 246         m = NULL;
 247         ctx = NULL;
 248
 249         /* Check if a conversion error occurred. */
 250         if ((signed)nls_name.len < 0) {
 251                 err = (signed)nls_name.len;
 252                 goto err_out;
 253         }
 254         nls_name.hash = full_name_hash(nls_name.name, nls_name.len);
 255
 256         /*
 257          * Note: No need for dent->d_lock lock as i_sem is held on the
 258          * parent inode.
 259          */
 260
 261         /* Does a dentry matching the nls_name exist already? */
 262         real_dent = d_lookup(dent->d_parent, &nls_name);
 263         /* If not, create it now. */
 264         if (!real_dent) {
 265                 real_dent = d_alloc(dent->d_parent, &nls_name);
 266                 kfree(nls_name.name);
 267                 if (!real_dent) {
 268                         err = -ENOMEM;
 269                         goto err_out;
 270                 }
 271                 new_dent = d_splice_alias(dent_inode, real_dent);
 272                 if (new_dent)
 273                         dput(real_dent);
 274                 else
 275                         new_dent = real_dent;
 276                 ntfs_debug("Done.  (Created new dentry.)");
 277                 return new_dent;
 278         }
 279         kfree(nls_name.name);
 280         /* Matching dentry exists, check if it is negative. */
 281         if (real_dent->d_inode) {
 282                 if (unlikely(real_dent->d_inode != dent_inode)) {
 283                         /* This can happen because bad inodes are unhashed. */
 284                         BUG_ON(!is_bad_inode(dent_inode));
 285                         BUG_ON(!is_bad_inode(real_dent->d_inode));
 286                 }
 287                 /*
 288                  * Already have the inode and the dentry attached, decrement
 289                  * the reference count to balance the ntfs_iget() we did
 290                  * earlier on.  We found the dentry using d_lookup() so it
 291                  * cannot be disconnected and thus we do not need to worry
 292                  * about any NFS/disconnectedness issues here.
 293                  */
 294                 iput(dent_inode);
 295                 ntfs_debug("Done.  (Already had inode and dentry.)");
 296                 return real_dent;
 297         }
 298         /*
 299          * Negative dentry: instantiate it unless the inode is a directory and
 300          * has a 'disconnected' dentry (i.e. IS_ROOT and DCACHE_DISCONNECTED),
 301          * in which case d_move() that in place of the found dentry.
 302          */
 303         if (!S_ISDIR(dent_inode->i_mode)) {
 304                 /* Not a directory; everything is easy. */
 305                 d_instantiate(real_dent, dent_inode);
 306                 ntfs_debug("Done.  (Already had negative file dentry.)");
 307                 return real_dent;
 308         }
 309         spin_lock(&dcache_lock);
 310         if (list_empty(&dent_inode->i_dentry)) {
 311                 /*
 312                  * Directory without a 'disconnected' dentry; we need to do
 313                  * d_instantiate() by hand because it takes dcache_lock which
 314                  * we already hold.
 315                  */
 316                 list_add(&real_dent->d_alias, &dent_inode->i_dentry);
 317                 real_dent->d_inode = dent_inode;
 318                 spin_unlock(&dcache_lock);
 319                 security_d_instantiate(real_dent, dent_inode);
 320                 ntfs_debug("Done.  (Already had negative directory dentry.)");
 321                 return real_dent;
 322         }
 323         /*
 324          * Directory with a 'disconnected' dentry; get a reference to the
 325          * 'disconnected' dentry.
 326          */
 327         new_dent = list_entry(dent_inode->i_dentry.next, struct dentry,
 328                         d_alias);
 329         dget_locked(new_dent);
 330         spin_unlock(&dcache_lock);
 331         /* Do security vodoo. */
 332         security_d_instantiate(real_dent, dent_inode);
 333         /* Move new_dent in place of real_dent. */
 334         d_move(new_dent, real_dent);
 335         /* Balance the ntfs_iget() we did above. */
 336         iput(dent_inode);
 337         /* Throw away real_dent. */
 338         dput(real_dent);
 339         /* Use new_dent as the actual dentry. */
 340         ntfs_debug("Done.  (Already had negative, disconnected directory "
 341                         "dentry.)");
 342         return new_dent;
 343
 344 eio_err_out:
 345         ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
 346         err = -EIO;
 347 err_out:
 348         if (ctx)
 349                 ntfs_attr_put_search_ctx(ctx);
 350         if (m)
 351                 unmap_mft_record(ni);
 352         iput(dent_inode);
 353         ntfs_error(vol->sb, "Failed, returning error code %i.", err);
 354         return ERR_PTR(err);
 355    }
 356 }
 357
 358 /**
 359  * Inode operations for directories.
 360  */
 361 struct inode_operations ntfs_dir_inode_ops = {
 362         .lookup = ntfs_lookup,  /* VFS: Lookup directory. */
 363 };
 364
 365 /**
 366  * ntfs_get_parent - find the dentry of the parent of a given directory dentry
 367  * @child_dent:         dentry of the directory whose parent directory to find
 368  *
 369  * Find the dentry for the parent directory of the directory specified by the
 370  * dentry @child_dent.  This function is called from
 371  * fs/exportfs/expfs.c::find_exported_dentry() which in turn is called from the
 372  * default ->decode_fh() which is export_decode_fh() in the same file.
 373  *
 374  * The code is based on the ext3 ->get_parent() implementation found in
 375  * fs/ext3/namei.c::ext3_get_parent().
 376  *
 377  * Note: ntfs_get_parent() is called with @child_dent->d_inode->i_sem down.
 378  *
 379  * Return the dentry of the parent directory on success or the error code on
 380  * error (IS_ERR() is true).
 381  */
 382 static struct dentry *ntfs_get_parent(struct dentry *child_dent)
 383 {
 384         struct inode *vi = child_dent->d_inode;
 385         ntfs_inode *ni = NTFS_I(vi);
 386         MFT_RECORD *mrec;
 387         ntfs_attr_search_ctx *ctx;
 388         ATTR_RECORD *attr;
 389         FILE_NAME_ATTR *fn;
 390         struct inode *parent_vi;
 391         struct dentry *parent_dent;
 392         unsigned long parent_ino;
 393         int err;
 394
 395         ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
 396         /* Get the mft record of the inode belonging to the child dentry. */
 397         mrec = map_mft_record(ni);
 398         if (IS_ERR(mrec))
 399                 return (struct dentry *)mrec;
 400         /* Find the first file name attribute in the mft record. */
 401         ctx = ntfs_attr_get_search_ctx(ni, mrec);
 402         if (unlikely(!ctx)) {
 403                 unmap_mft_record(ni);
 404                 return ERR_PTR(-ENOMEM);
 405         }
 406 try_next:
 407         err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, CASE_SENSITIVE, 0, NULL,
 408                         0, ctx);
 409         if (unlikely(err)) {
 410                 ntfs_attr_put_search_ctx(ctx);
 411                 unmap_mft_record(ni);
 412                 if (err == -ENOENT)
 413                         ntfs_error(vi->i_sb, "Inode 0x%lx does not have a "
 414                                         "file name attribute.  Run chkdsk.",
 415                                         vi->i_ino);
 416                 return ERR_PTR(err);
 417         }
 418         attr = ctx->attr;
 419         if (unlikely(attr->non_resident))
 420                 goto try_next;
 421         fn = (FILE_NAME_ATTR *)((u8 *)attr +
 422                         le16_to_cpu(attr->data.resident.value_offset));
 423         if (unlikely((u8 *)fn + le32_to_cpu(attr->data.resident.value_length) >
 424                         (u8*)attr + le32_to_cpu(attr->length)))
 425                 goto try_next;
 426         /* Get the inode number of the parent directory. */
 427         parent_ino = MREF_LE(fn->parent_directory);
 428         /* Release the search context and the mft record of the child. */
 429         ntfs_attr_put_search_ctx(ctx);
 430         unmap_mft_record(ni);
 431         /* Get the inode of the parent directory. */
 432         parent_vi = ntfs_iget(vi->i_sb, parent_ino);
 433         if (IS_ERR(parent_vi) || unlikely(is_bad_inode(parent_vi))) {
 434                 if (!IS_ERR(parent_vi))
 435                         iput(parent_vi);
 436                 ntfs_error(vi->i_sb, "Failed to get parent directory inode "
 437                                 "0x%lx of child inode 0x%lx.", parent_ino,
 438                                 vi->i_ino);
 439                 return ERR_PTR(-EACCES);
 440         }
 441         /* Finally get a dentry for the parent directory and return it. */
 442         parent_dent = d_alloc_anon(parent_vi);
 443         if (unlikely(!parent_dent)) {
 444                 iput(parent_vi);
 445                 return ERR_PTR(-ENOMEM);
 446         }
 447         ntfs_debug("Done for inode 0x%lx.", vi->i_ino);
 448         return parent_dent;
 449 }
 450
 451 /**
 452  * ntfs_get_dentry - find a dentry for the inode from a file handle sub-fragment
 453  * @sb:         super block identifying the mounted ntfs volume
 454  * @fh:         the file handle sub-fragment
 455  *
 456  * Find a dentry for the inode given a file handle sub-fragment.  This function
 457  * is called from fs/exportfs/expfs.c::find_exported_dentry() which in turn is
 458  * called from the default ->decode_fh() which is export_decode_fh() in the
 459  * same file.  The code is closely based on the default ->get_dentry() helper
 460  * fs/exportfs/expfs.c::get_object().
 461  *
 462  * The @fh contains two 32-bit unsigned values, the first one is the inode
 463  * number and the second one is the inode generation.
 464  *
 465  * Return the dentry on success or the error code on error (IS_ERR() is true).
 466  */
 467 static struct dentry *ntfs_get_dentry(struct super_block *sb, void *fh)
 468 {
 469         struct inode *vi;
 470         struct dentry *dent;
 471         unsigned long ino = ((u32 *)fh)[0];
 472         u32 gen = ((u32 *)fh)[1];
 473
 474         ntfs_debug("Entering for inode 0x%lx, generation 0x%x.", ino, gen);
 475         vi = ntfs_iget(sb, ino);
 476         if (IS_ERR(vi)) {
 477                 ntfs_error(sb, "Failed to get inode 0x%lx.", ino);
 478                 return (struct dentry *)vi;
 479         }
 480         if (unlikely(is_bad_inode(vi) || vi->i_generation != gen)) {
 481                 /* We didn't find the right inode. */
 482                 ntfs_error(sb, "Inode 0x%lx, bad count: %d %d or version 0x%x "
 483                                 "0x%x.", vi->i_ino, vi->i_nlink,
 484                                 atomic_read(&vi->i_count), vi->i_generation,
 485                                 gen);
 486                 iput(vi);
 487                 return ERR_PTR(-ESTALE);
 488         }
 489         /* Now find a dentry.  If possible, get a well-connected one. */
 490         dent = d_alloc_anon(vi);
 491         if (unlikely(!dent)) {
 492                 iput(vi);
 493                 return ERR_PTR(-ENOMEM);
 494         }
 495         ntfs_debug("Done for inode 0x%lx, generation 0x%x.", ino, gen);
 496         return dent;
 497 }
 498
 499 /**
 500  * Export operations allowing NFS exporting of mounted NTFS partitions.
 501  *
 502  * We use the default ->decode_fh() and ->encode_fh() for now.  Note that they
 503  * use 32 bits to store the inode number which is an unsigned long so on 64-bit
 504  * architectures is usually 64 bits so it would all fail horribly on huge
 505  * volumes.  I guess we need to define our own encode and decode fh functions
 506  * that store 64-bit inode numbers at some point but for now we will ignore the
 507  * problem...
 508  *
 509  * We also use the default ->get_name() helper (used by ->decode_fh() via
 510  * fs/exportfs/expfs.c::find_exported_dentry()) as that is completely fs
 511  * independent.
 512  *
 513  * The default ->get_parent() just returns -EACCES so we have to provide our
 514  * own and the default ->get_dentry() is incompatible with NTFS due to not
 515  * allowing the inode number 0 which is used in NTFS for the system file $MFT
 516  * and due to using iget() whereas NTFS needs ntfs_iget().
 517  */
 518 struct export_operations ntfs_export_ops = {
 519         .get_parent     = ntfs_get_parent,      /* Find the parent of a given
 520                                                    directory. */
 521         .get_dentry     = ntfs_get_dentry,      /* Find a dentry for the inode
 522                                                    given a file handle
 523                                                    sub-fragment. */
 524 };