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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  * @flags:      lookup flags
 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 %pd in directory inode 0x%lx.",
115                         dent, 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 @d_inode(child_dent)->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 = d_inode(child_dent);
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 };
406 

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