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 #include <linux/slab.h>
  27
  28 #include "attrib.h"
  29 #include "debug.h"
  30 #include "dir.h"
  31 #include "mft.h"
  32 #include "ntfs.h"
  33
  34 /**
  35  * ntfs_lookup - find the inode represented by a dentry in a directory inode
  36  * @dir_ino:    directory inode in which to look for the inode
  37  * @dent:       dentry representing the inode to look for
  38  * @nd:         lookup nameidata
  39  *
  40  * In short, ntfs_lookup() looks for the inode represented by the dentry @dent
  41  * in the directory inode @dir_ino and if found attaches the inode to the
  42  * dentry @dent.
  43  *
  44  * In more detail, the dentry @dent specifies which inode to look for by
  45  * supplying the name of the inode in @dent->d_name.name. ntfs_lookup()
  46  * converts the name to Unicode and walks the contents of the directory inode
  47  * @dir_ino looking for the converted Unicode name. If the name is found in the
  48  * directory, the corresponding inode is loaded by calling ntfs_iget() on its
  49  * inode number and the inode is associated with the dentry @dent via a call to
  50  * d_splice_alias().
  51  *
  52  * If the name is not found in the directory, a NULL inode is inserted into the
  53  * dentry @dent via a call to d_add(). The dentry is then termed a negative
  54  * dentry.
  55  *
  56  * Only if an actual error occurs, do we return an error via ERR_PTR().
  57  *
  58  * In order to handle the case insensitivity issues of NTFS with regards to the
  59  * dcache and the dcache requiring only one dentry per directory, we deal with
  60  * dentry aliases that only differ in case in ->ntfs_lookup() while maintaining
  61  * a case sensitive dcache. This means that we get the full benefit of dcache
  62  * speed when the file/directory is looked up with the same case as returned by
  63  * ->ntfs_readdir() but that a lookup for any other case (or for the short file
  64  * name) will not find anything in dcache and will enter ->ntfs_lookup()
  65  * instead, where we search the directory for a fully matching file name
  66  * (including case) and if that is not found, we search for a file name that
  67  * matches with different case and if that has non-POSIX semantics we return
  68  * that. We actually do only one search (case sensitive) and keep tabs on
  69  * whether we have found a case insensitive match in the process.
  70  *
  71  * To simplify matters for us, we do not treat the short vs long filenames as
  72  * two hard links but instead if the lookup matches a short filename, we
  73  * return the dentry for the corresponding long filename instead.
  74  *
  75  * There are three cases we need to distinguish here:
  76  *
  77  * 1) @dent perfectly matches (i.e. including case) a directory entry with a
  78  *    file name in the WIN32 or POSIX namespaces. In this case
  79  *    ntfs_lookup_inode_by_name() will return with name set to NULL and we
  80  *    just d_splice_alias() @dent.
  81  * 2) @dent matches (not including case) a directory entry with a file name in
  82  *    the WIN32 namespace. In this case ntfs_lookup_inode_by_name() will return
  83  *    with name set to point to a kmalloc()ed ntfs_name structure containing
  84  *    the properly cased little endian Unicode name. We convert the name to the
  85  *    current NLS code page, search if a dentry with this name already exists
  86  *    and if so return that instead of @dent.  At this point things are
  87  *    complicated by the possibility of 'disconnected' dentries due to NFS
  88  *    which we deal with appropriately (see the code comments).  The VFS will
  89  *    then destroy the old @dent and use the one we returned.  If a dentry is
  90  *    not found, we allocate a new one, d_splice_alias() it, and return it as
  91  *    above.
  92  * 3) @dent matches either perfectly or not (i.e. we don't care about case) a
  93  *    directory entry with a file name in the DOS namespace. In this case
  94  *    ntfs_lookup_inode_by_name() will return with name set to point to a
  95  *    kmalloc()ed ntfs_name structure containing the mft reference (cpu endian)
  96  *    of the inode. We use the mft reference to read the inode and to find the
  97  *    file name in the WIN32 namespace corresponding to the matched short file
  98  *    name. We then convert the name to the current NLS code page, and proceed
  99  *    searching for a dentry with this name, etc, as in case 2), above.
 100  *
 101  * Locking: Caller must hold i_mutex on the directory.
 102  */
 103 static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent,
 104                 unsigned int flags)
 105 {
 106         ntfs_volume *vol = NTFS_SB(dir_ino->i_sb);
 107         struct inode *dent_inode;
 108         ntfschar *uname;
 109         ntfs_name *name = NULL;
 110         MFT_REF mref;
 111         unsigned long dent_ino;
 112         int uname_len;
 113
 114         ntfs_debug("Looking up %s in directory inode 0x%lx.",
 115                         dent->d_name.name, dir_ino->i_ino);
 116         /* Convert the name of the dentry to Unicode. */
 117         uname_len = ntfs_nlstoucs(vol, dent->d_name.name, dent->d_name.len,
 118                         &uname);
 119         if (uname_len < 0) {
 120                 if (uname_len != -ENAMETOOLONG)
 121                         ntfs_error(vol->sb, "Failed to convert name to "
 122                                         "Unicode.");
 123                 return ERR_PTR(uname_len);
 124         }
 125         mref = ntfs_lookup_inode_by_name(NTFS_I(dir_ino), uname, uname_len,
 126                         &name);
 127         kmem_cache_free(ntfs_name_cache, uname);
 128         if (!IS_ERR_MREF(mref)) {
 129                 dent_ino = MREF(mref);
 130                 ntfs_debug("Found inode 0x%lx. Calling ntfs_iget.", dent_ino);
 131                 dent_inode = ntfs_iget(vol->sb, dent_ino);
 132                 if (likely(!IS_ERR(dent_inode))) {
 133                         /* Consistency check. */
 134                         if (is_bad_inode(dent_inode) || MSEQNO(mref) ==
 135                                         NTFS_I(dent_inode)->seq_no ||
 136                                         dent_ino == FILE_MFT) {
 137                                 /* Perfect WIN32/POSIX match. -- Case 1. */
 138                                 if (!name) {
 139                                         ntfs_debug("Done.  (Case 1.)");
 140                                         return d_splice_alias(dent_inode, dent);
 141                                 }
 142                                 /*
 143                                  * We are too indented.  Handle imperfect
 144                                  * matches and short file names further below.
 145                                  */
 146                                 goto handle_name;
 147                         }
 148                         ntfs_error(vol->sb, "Found stale reference to inode "
 149                                         "0x%lx (reference sequence number = "
 150                                         "0x%x, inode sequence number = 0x%x), "
 151                                         "returning -EIO. Run chkdsk.",
 152                                         dent_ino, MSEQNO(mref),
 153                                         NTFS_I(dent_inode)->seq_no);
 154                         iput(dent_inode);
 155                         dent_inode = ERR_PTR(-EIO);
 156                 } else
 157                         ntfs_error(vol->sb, "ntfs_iget(0x%lx) failed with "
 158                                         "error code %li.", dent_ino,
 159                                         PTR_ERR(dent_inode));
 160                 kfree(name);
 161                 /* Return the error code. */
 162                 return (struct dentry *)dent_inode;
 163         }
 164         /* It is guaranteed that @name is no longer allocated at this point. */
 165         if (MREF_ERR(mref) == -ENOENT) {
 166                 ntfs_debug("Entry was not found, adding negative dentry.");
 167                 /* The dcache will handle negative entries. */
 168                 d_add(dent, NULL);
 169                 ntfs_debug("Done.");
 170                 return NULL;
 171         }
 172         ntfs_error(vol->sb, "ntfs_lookup_ino_by_name() failed with error "
 173                         "code %i.", -MREF_ERR(mref));
 174         return ERR_PTR(MREF_ERR(mref));
 175         // TODO: Consider moving this lot to a separate function! (AIA)
 176 handle_name:
 177    {
 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         dent = d_add_ci(dent, dent_inode, &nls_name);
 259         kfree(nls_name.name);
 260         return dent;
 261
 262 eio_err_out:
 263         ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
 264         err = -EIO;
 265 err_out:
 266         if (ctx)
 267                 ntfs_attr_put_search_ctx(ctx);
 268         if (m)
 269                 unmap_mft_record(ni);
 270         iput(dent_inode);
 271         ntfs_error(vol->sb, "Failed, returning error code %i.", err);
 272         return ERR_PTR(err);
 273    }
 274 }
 275
 276 /**
 277  * Inode operations for directories.
 278  */
 279 const struct inode_operations ntfs_dir_inode_ops = {
 280         .lookup = ntfs_lookup,  /* VFS: Lookup directory. */
 281 };
 282
 283 /**
 284  * ntfs_get_parent - find the dentry of the parent of a given directory dentry
 285  * @child_dent:         dentry of the directory whose parent directory to find
 286  *
 287  * Find the dentry for the parent directory of the directory specified by the
 288  * dentry @child_dent.  This function is called from
 289  * fs/exportfs/expfs.c::find_exported_dentry() which in turn is called from the
 290  * default ->decode_fh() which is export_decode_fh() in the same file.
 291  *
 292  * The code is based on the ext3 ->get_parent() implementation found in
 293  * fs/ext3/namei.c::ext3_get_parent().
 294  *
 295  * Note: ntfs_get_parent() is called with @child_dent->d_inode->i_mutex down.
 296  *
 297  * Return the dentry of the parent directory on success or the error code on
 298  * error (IS_ERR() is true).
 299  */
 300 static struct dentry *ntfs_get_parent(struct dentry *child_dent)
 301 {
 302         struct inode *vi = child_dent->d_inode;
 303         ntfs_inode *ni = NTFS_I(vi);
 304         MFT_RECORD *mrec;
 305         ntfs_attr_search_ctx *ctx;
 306         ATTR_RECORD *attr;
 307         FILE_NAME_ATTR *fn;
 308         unsigned long parent_ino;
 309         int err;
 310
 311         ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
 312         /* Get the mft record of the inode belonging to the child dentry. */
 313         mrec = map_mft_record(ni);
 314         if (IS_ERR(mrec))
 315                 return (struct dentry *)mrec;
 316         /* Find the first file name attribute in the mft record. */
 317         ctx = ntfs_attr_get_search_ctx(ni, mrec);
 318         if (unlikely(!ctx)) {
 319                 unmap_mft_record(ni);
 320                 return ERR_PTR(-ENOMEM);
 321         }
 322 try_next:
 323         err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, CASE_SENSITIVE, 0, NULL,
 324                         0, ctx);
 325         if (unlikely(err)) {
 326                 ntfs_attr_put_search_ctx(ctx);
 327                 unmap_mft_record(ni);
 328                 if (err == -ENOENT)
 329                         ntfs_error(vi->i_sb, "Inode 0x%lx does not have a "
 330                                         "file name attribute.  Run chkdsk.",
 331                                         vi->i_ino);
 332                 return ERR_PTR(err);
 333         }
 334         attr = ctx->attr;
 335         if (unlikely(attr->non_resident))
 336                 goto try_next;
 337         fn = (FILE_NAME_ATTR *)((u8 *)attr +
 338                         le16_to_cpu(attr->data.resident.value_offset));
 339         if (unlikely((u8 *)fn + le32_to_cpu(attr->data.resident.value_length) >
 340                         (u8*)attr + le32_to_cpu(attr->length)))
 341                 goto try_next;
 342         /* Get the inode number of the parent directory. */
 343         parent_ino = MREF_LE(fn->parent_directory);
 344         /* Release the search context and the mft record of the child. */
 345         ntfs_attr_put_search_ctx(ctx);
 346         unmap_mft_record(ni);
 347
 348         return d_obtain_alias(ntfs_iget(vi->i_sb, parent_ino));
 349 }
 350
 351 static struct inode *ntfs_nfs_get_inode(struct super_block *sb,
 352                 u64 ino, u32 generation)
 353 {
 354         struct inode *inode;
 355
 356         inode = ntfs_iget(sb, ino);
 357         if (!IS_ERR(inode)) {
 358                 if (is_bad_inode(inode) || inode->i_generation != generation) {
 359                         iput(inode);
 360                         inode = ERR_PTR(-ESTALE);
 361                 }
 362         }
 363
 364         return inode;
 365 }
 366
 367 static struct dentry *ntfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
 368                 int fh_len, int fh_type)
 369 {
 370         return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
 371                                     ntfs_nfs_get_inode);
 372 }
 373
 374 static struct dentry *ntfs_fh_to_parent(struct super_block *sb, struct fid *fid,
 375                 int fh_len, int fh_type)
 376 {
 377         return generic_fh_to_parent(sb, fid, fh_len, fh_type,
 378                                     ntfs_nfs_get_inode);
 379 }
 380
 381 /**
 382  * Export operations allowing NFS exporting of mounted NTFS partitions.
 383  *
 384  * We use the default ->encode_fh() for now.  Note that they
 385  * use 32 bits to store the inode number which is an unsigned long so on 64-bit
 386  * architectures is usually 64 bits so it would all fail horribly on huge
 387  * volumes.  I guess we need to define our own encode and decode fh functions
 388  * that store 64-bit inode numbers at some point but for now we will ignore the
 389  * problem...
 390  *
 391  * We also use the default ->get_name() helper (used by ->decode_fh() via
 392  * fs/exportfs/expfs.c::find_exported_dentry()) as that is completely fs
 393  * independent.
 394  *
 395  * The default ->get_parent() just returns -EACCES so we have to provide our
 396  * own and the default ->get_dentry() is incompatible with NTFS due to not
 397  * allowing the inode number 0 which is used in NTFS for the system file $MFT
 398  * and due to using iget() whereas NTFS needs ntfs_iget().
 399  */
 400 const struct export_operations ntfs_export_ops = {
 401         .get_parent     = ntfs_get_parent,      /* Find the parent of a given
 402                                                    directory. */
 403         .fh_to_dentry   = ntfs_fh_to_dentry,
 404         .fh_to_parent   = ntfs_fh_to_parent,
 405 };