linux/fs/ntfs/namei.c
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   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 */
 103static 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)
 176handle_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
 262eio_err_out:
 263        ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
 264        err = -EIO;
 265err_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 */
 279const 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 */
 300static 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        }
 322try_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
 351static 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
 367static 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
 374static 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 */
 400const 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};
 406
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