fs/ntfs/namei.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * namei.c - NTFS kernel directory inode operations. Part of the Linux-NTFS
   4  *           project.
   5  *
   6  * Copyright (c) 2001-2006 Anton Altaparmakov
   7  */
   8
   9 #include <linux/dcache.h>
  10 #include <linux/exportfs.h>
  11 #include <linux/security.h>
  12 #include <linux/slab.h>
  13
  14 #include "attrib.h"
  15 #include "debug.h"
  16 #include "dir.h"
  17 #include "mft.h"
  18 #include "ntfs.h"
  19
  20 /**
  21  * ntfs_lookup - find the inode represented by a dentry in a directory inode
  22  * @dir_ino:    directory inode in which to look for the inode
  23  * @dent:       dentry representing the inode to look for
  24  * @flags:      lookup flags
  25  *
  26  * In short, ntfs_lookup() looks for the inode represented by the dentry @dent
  27  * in the directory inode @dir_ino and if found attaches the inode to the
  28  * dentry @dent.
  29  *
  30  * In more detail, the dentry @dent specifies which inode to look for by
  31  * supplying the name of the inode in @dent->d_name.name. ntfs_lookup()
  32  * converts the name to Unicode and walks the contents of the directory inode
  33  * @dir_ino looking for the converted Unicode name. If the name is found in the
  34  * directory, the corresponding inode is loaded by calling ntfs_iget() on its
  35  * inode number and the inode is associated with the dentry @dent via a call to
  36  * d_splice_alias().
  37  *
  38  * If the name is not found in the directory, a NULL inode is inserted into the
  39  * dentry @dent via a call to d_add(). The dentry is then termed a negative
  40  * dentry.
  41  *
  42  * Only if an actual error occurs, do we return an error via ERR_PTR().
  43  *
  44  * In order to handle the case insensitivity issues of NTFS with regards to the
  45  * dcache and the dcache requiring only one dentry per directory, we deal with
  46  * dentry aliases that only differ in case in ->ntfs_lookup() while maintaining
  47  * a case sensitive dcache. This means that we get the full benefit of dcache
  48  * speed when the file/directory is looked up with the same case as returned by
  49  * ->ntfs_readdir() but that a lookup for any other case (or for the short file
  50  * name) will not find anything in dcache and will enter ->ntfs_lookup()
  51  * instead, where we search the directory for a fully matching file name
  52  * (including case) and if that is not found, we search for a file name that
  53  * matches with different case and if that has non-POSIX semantics we return
  54  * that. We actually do only one search (case sensitive) and keep tabs on
  55  * whether we have found a case insensitive match in the process.
  56  *
  57  * To simplify matters for us, we do not treat the short vs long filenames as
  58  * two hard links but instead if the lookup matches a short filename, we
  59  * return the dentry for the corresponding long filename instead.
  60  *
  61  * There are three cases we need to distinguish here:
  62  *
  63  * 1) @dent perfectly matches (i.e. including case) a directory entry with a
  64  *    file name in the WIN32 or POSIX namespaces. In this case
  65  *    ntfs_lookup_inode_by_name() will return with name set to NULL and we
  66  *    just d_splice_alias() @dent.
  67  * 2) @dent matches (not including case) a directory entry with a file name in
  68  *    the WIN32 namespace. In this case ntfs_lookup_inode_by_name() will return
  69  *    with name set to point to a kmalloc()ed ntfs_name structure containing
  70  *    the properly cased little endian Unicode name. We convert the name to the
  71  *    current NLS code page, search if a dentry with this name already exists
  72  *    and if so return that instead of @dent.  At this point things are
  73  *    complicated by the possibility of 'disconnected' dentries due to NFS
  74  *    which we deal with appropriately (see the code comments).  The VFS will
  75  *    then destroy the old @dent and use the one we returned.  If a dentry is
  76  *    not found, we allocate a new one, d_splice_alias() it, and return it as
  77  *    above.
  78  * 3) @dent matches either perfectly or not (i.e. we don't care about case) a
  79  *    directory entry with a file name in the DOS namespace. In this case
  80  *    ntfs_lookup_inode_by_name() will return with name set to point to a
  81  *    kmalloc()ed ntfs_name structure containing the mft reference (cpu endian)
  82  *    of the inode. We use the mft reference to read the inode and to find the
  83  *    file name in the WIN32 namespace corresponding to the matched short file
  84  *    name. We then convert the name to the current NLS code page, and proceed
  85  *    searching for a dentry with this name, etc, as in case 2), above.
  86  *
  87  * Locking: Caller must hold i_mutex on the directory.
  88  */
  89 static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent,
  90                 unsigned int flags)
  91 {
  92         ntfs_volume *vol = NTFS_SB(dir_ino->i_sb);
  93         struct inode *dent_inode;
  94         ntfschar *uname;
  95         ntfs_name *name = NULL;
  96         MFT_REF mref;
  97         unsigned long dent_ino;
  98         int uname_len;
  99
 100         ntfs_debug("Looking up %pd in directory inode 0x%lx.",
 101                         dent, dir_ino->i_ino);
 102         /* Convert the name of the dentry to Unicode. */
 103         uname_len = ntfs_nlstoucs(vol, dent->d_name.name, dent->d_name.len,
 104                         &uname);
 105         if (uname_len < 0) {
 106                 if (uname_len != -ENAMETOOLONG)
 107                         ntfs_error(vol->sb, "Failed to convert name to "
 108                                         "Unicode.");
 109                 return ERR_PTR(uname_len);
 110         }
 111         mref = ntfs_lookup_inode_by_name(NTFS_I(dir_ino), uname, uname_len,
 112                         &name);
 113         kmem_cache_free(ntfs_name_cache, uname);
 114         if (!IS_ERR_MREF(mref)) {
 115                 dent_ino = MREF(mref);
 116                 ntfs_debug("Found inode 0x%lx. Calling ntfs_iget.", dent_ino);
 117                 dent_inode = ntfs_iget(vol->sb, dent_ino);
 118                 if (!IS_ERR(dent_inode)) {
 119                         /* Consistency check. */
 120                         if (is_bad_inode(dent_inode) || MSEQNO(mref) ==
 121                                         NTFS_I(dent_inode)->seq_no ||
 122                                         dent_ino == FILE_MFT) {
 123                                 /* Perfect WIN32/POSIX match. -- Case 1. */
 124                                 if (!name) {
 125                                         ntfs_debug("Done.  (Case 1.)");
 126                                         return d_splice_alias(dent_inode, dent);
 127                                 }
 128                                 /*
 129                                  * We are too indented.  Handle imperfect
 130                                  * matches and short file names further below.
 131                                  */
 132                                 goto handle_name;
 133                         }
 134                         ntfs_error(vol->sb, "Found stale reference to inode "
 135                                         "0x%lx (reference sequence number = "
 136                                         "0x%x, inode sequence number = 0x%x), "
 137                                         "returning -EIO. Run chkdsk.",
 138                                         dent_ino, MSEQNO(mref),
 139                                         NTFS_I(dent_inode)->seq_no);
 140                         iput(dent_inode);
 141                         dent_inode = ERR_PTR(-EIO);
 142                 } else
 143                         ntfs_error(vol->sb, "ntfs_iget(0x%lx) failed with "
 144                                         "error code %li.", dent_ino,
 145                                         PTR_ERR(dent_inode));
 146                 kfree(name);
 147                 /* Return the error code. */
 148                 return ERR_CAST(dent_inode);
 149         }
 150         /* It is guaranteed that @name is no longer allocated at this point. */
 151         if (MREF_ERR(mref) == -ENOENT) {
 152                 ntfs_debug("Entry was not found, adding negative dentry.");
 153                 /* The dcache will handle negative entries. */
 154                 d_add(dent, NULL);
 155                 ntfs_debug("Done.");
 156                 return NULL;
 157         }
 158         ntfs_error(vol->sb, "ntfs_lookup_ino_by_name() failed with error "
 159                         "code %i.", -MREF_ERR(mref));
 160         return ERR_PTR(MREF_ERR(mref));
 161         // TODO: Consider moving this lot to a separate function! (AIA)
 162 handle_name:
 163    {
 164         MFT_RECORD *m;
 165         ntfs_attr_search_ctx *ctx;
 166         ntfs_inode *ni = NTFS_I(dent_inode);
 167         int err;
 168         struct qstr nls_name;
 169
 170         nls_name.name = NULL;
 171         if (name->type != FILE_NAME_DOS) {                      /* Case 2. */
 172                 ntfs_debug("Case 2.");
 173                 nls_name.len = (unsigned)ntfs_ucstonls(vol,
 174                                 (ntfschar*)&name->name, name->len,
 175                                 (unsigned char**)&nls_name.name, 0);
 176                 kfree(name);
 177         } else /* if (name->type == FILE_NAME_DOS) */ {         /* Case 3. */
 178                 FILE_NAME_ATTR *fn;
 179
 180                 ntfs_debug("Case 3.");
 181                 kfree(name);
 182
 183                 /* Find the WIN32 name corresponding to the matched DOS name. */
 184                 ni = NTFS_I(dent_inode);
 185                 m = map_mft_record(ni);
 186                 if (IS_ERR(m)) {
 187                         err = PTR_ERR(m);
 188                         m = NULL;
 189                         ctx = NULL;
 190                         goto err_out;
 191                 }
 192                 ctx = ntfs_attr_get_search_ctx(ni, m);
 193                 if (unlikely(!ctx)) {
 194                         err = -ENOMEM;
 195                         goto err_out;
 196                 }
 197                 do {
 198                         ATTR_RECORD *a;
 199                         u32 val_len;
 200
 201                         err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, 0, 0,
 202                                         NULL, 0, ctx);
 203                         if (unlikely(err)) {
 204                                 ntfs_error(vol->sb, "Inode corrupt: No WIN32 "
 205                                                 "namespace counterpart to DOS "
 206                                                 "file name. Run chkdsk.");
 207                                 if (err == -ENOENT)
 208                                         err = -EIO;
 209                                 goto err_out;
 210                         }
 211                         /* Consistency checks. */
 212                         a = ctx->attr;
 213                         if (a->non_resident || a->flags)
 214                                 goto eio_err_out;
 215                         val_len = le32_to_cpu(a->data.resident.value_length);
 216                         if (le16_to_cpu(a->data.resident.value_offset) +
 217                                         val_len > le32_to_cpu(a->length))
 218                                 goto eio_err_out;
 219                         fn = (FILE_NAME_ATTR*)((u8*)ctx->attr + le16_to_cpu(
 220                                         ctx->attr->data.resident.value_offset));
 221                         if ((u32)(fn->file_name_length * sizeof(ntfschar) +
 222                                         sizeof(FILE_NAME_ATTR)) > val_len)
 223                                 goto eio_err_out;
 224                 } while (fn->file_name_type != FILE_NAME_WIN32);
 225
 226                 /* Convert the found WIN32 name to current NLS code page. */
 227                 nls_name.len = (unsigned)ntfs_ucstonls(vol,
 228                                 (ntfschar*)&fn->file_name, fn->file_name_length,
 229                                 (unsigned char**)&nls_name.name, 0);
 230
 231                 ntfs_attr_put_search_ctx(ctx);
 232                 unmap_mft_record(ni);
 233         }
 234         m = NULL;
 235         ctx = NULL;
 236
 237         /* Check if a conversion error occurred. */
 238         if ((signed)nls_name.len < 0) {
 239                 err = (signed)nls_name.len;
 240                 goto err_out;
 241         }
 242         nls_name.hash = full_name_hash(dent, nls_name.name, nls_name.len);
 243
 244         dent = d_add_ci(dent, dent_inode, &nls_name);
 245         kfree(nls_name.name);
 246         return dent;
 247
 248 eio_err_out:
 249         ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
 250         err = -EIO;
 251 err_out:
 252         if (ctx)
 253                 ntfs_attr_put_search_ctx(ctx);
 254         if (m)
 255                 unmap_mft_record(ni);
 256         iput(dent_inode);
 257         ntfs_error(vol->sb, "Failed, returning error code %i.", err);
 258         return ERR_PTR(err);
 259    }
 260 }
 261
 262 /**
 263  * Inode operations for directories.
 264  */
 265 const struct inode_operations ntfs_dir_inode_ops = {
 266         .lookup = ntfs_lookup,  /* VFS: Lookup directory. */
 267 };
 268
 269 /**
 270  * ntfs_get_parent - find the dentry of the parent of a given directory dentry
 271  * @child_dent:         dentry of the directory whose parent directory to find
 272  *
 273  * Find the dentry for the parent directory of the directory specified by the
 274  * dentry @child_dent.  This function is called from
 275  * fs/exportfs/expfs.c::find_exported_dentry() which in turn is called from the
 276  * default ->decode_fh() which is export_decode_fh() in the same file.
 277  *
 278  * The code is based on the ext3 ->get_parent() implementation found in
 279  * fs/ext3/namei.c::ext3_get_parent().
 280  *
 281  * Note: ntfs_get_parent() is called with @d_inode(child_dent)->i_mutex down.
 282  *
 283  * Return the dentry of the parent directory on success or the error code on
 284  * error (IS_ERR() is true).
 285  */
 286 static struct dentry *ntfs_get_parent(struct dentry *child_dent)
 287 {
 288         struct inode *vi = d_inode(child_dent);
 289         ntfs_inode *ni = NTFS_I(vi);
 290         MFT_RECORD *mrec;
 291         ntfs_attr_search_ctx *ctx;
 292         ATTR_RECORD *attr;
 293         FILE_NAME_ATTR *fn;
 294         unsigned long parent_ino;
 295         int err;
 296
 297         ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
 298         /* Get the mft record of the inode belonging to the child dentry. */
 299         mrec = map_mft_record(ni);
 300         if (IS_ERR(mrec))
 301                 return ERR_CAST(mrec);
 302         /* Find the first file name attribute in the mft record. */
 303         ctx = ntfs_attr_get_search_ctx(ni, mrec);
 304         if (unlikely(!ctx)) {
 305                 unmap_mft_record(ni);
 306                 return ERR_PTR(-ENOMEM);
 307         }
 308 try_next:
 309         err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, CASE_SENSITIVE, 0, NULL,
 310                         0, ctx);
 311         if (unlikely(err)) {
 312                 ntfs_attr_put_search_ctx(ctx);
 313                 unmap_mft_record(ni);
 314                 if (err == -ENOENT)
 315                         ntfs_error(vi->i_sb, "Inode 0x%lx does not have a "
 316                                         "file name attribute.  Run chkdsk.",
 317                                         vi->i_ino);
 318                 return ERR_PTR(err);
 319         }
 320         attr = ctx->attr;
 321         if (unlikely(attr->non_resident))
 322                 goto try_next;
 323         fn = (FILE_NAME_ATTR *)((u8 *)attr +
 324                         le16_to_cpu(attr->data.resident.value_offset));
 325         if (unlikely((u8 *)fn + le32_to_cpu(attr->data.resident.value_length) >
 326                         (u8*)attr + le32_to_cpu(attr->length)))
 327                 goto try_next;
 328         /* Get the inode number of the parent directory. */
 329         parent_ino = MREF_LE(fn->parent_directory);
 330         /* Release the search context and the mft record of the child. */
 331         ntfs_attr_put_search_ctx(ctx);
 332         unmap_mft_record(ni);
 333
 334         return d_obtain_alias(ntfs_iget(vi->i_sb, parent_ino));
 335 }
 336
 337 static struct inode *ntfs_nfs_get_inode(struct super_block *sb,
 338                 u64 ino, u32 generation)
 339 {
 340         struct inode *inode;
 341
 342         inode = ntfs_iget(sb, ino);
 343         if (!IS_ERR(inode)) {
 344                 if (is_bad_inode(inode) || inode->i_generation != generation) {
 345                         iput(inode);
 346                         inode = ERR_PTR(-ESTALE);
 347                 }
 348         }
 349
 350         return inode;
 351 }
 352
 353 static struct dentry *ntfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
 354                 int fh_len, int fh_type)
 355 {
 356         return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
 357                                     ntfs_nfs_get_inode);
 358 }
 359
 360 static struct dentry *ntfs_fh_to_parent(struct super_block *sb, struct fid *fid,
 361                 int fh_len, int fh_type)
 362 {
 363         return generic_fh_to_parent(sb, fid, fh_len, fh_type,
 364                                     ntfs_nfs_get_inode);
 365 }
 366
 367 /**
 368  * Export operations allowing NFS exporting of mounted NTFS partitions.
 369  *
 370  * We use the default ->encode_fh() for now.  Note that they
 371  * use 32 bits to store the inode number which is an unsigned long so on 64-bit
 372  * architectures is usually 64 bits so it would all fail horribly on huge
 373  * volumes.  I guess we need to define our own encode and decode fh functions
 374  * that store 64-bit inode numbers at some point but for now we will ignore the
 375  * problem...
 376  *
 377  * We also use the default ->get_name() helper (used by ->decode_fh() via
 378  * fs/exportfs/expfs.c::find_exported_dentry()) as that is completely fs
 379  * independent.
 380  *
 381  * The default ->get_parent() just returns -EACCES so we have to provide our
 382  * own and the default ->get_dentry() is incompatible with NTFS due to not
 383  * allowing the inode number 0 which is used in NTFS for the system file $MFT
 384  * and due to using iget() whereas NTFS needs ntfs_iget().
 385  */
 386 const struct export_operations ntfs_export_ops = {
 387         .get_parent     = ntfs_get_parent,      /* Find the parent of a given
 388                                                    directory. */
 389         .fh_to_dentry   = ntfs_fh_to_dentry,
 390         .fh_to_parent   = ntfs_fh_to_parent,
 391 };