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TOMOYO Linux Cross Reference
Linux/fs/ext4/dir.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  *  linux/fs/ext4/dir.c
  4  *
  5  * Copyright (C) 1992, 1993, 1994, 1995
  6  * Remy Card (card@masi.ibp.fr)
  7  * Laboratoire MASI - Institut Blaise Pascal
  8  * Universite Pierre et Marie Curie (Paris VI)
  9  *
 10  *  from
 11  *
 12  *  linux/fs/minix/dir.c
 13  *
 14  *  Copyright (C) 1991, 1992  Linus Torvalds
 15  *
 16  *  ext4 directory handling functions
 17  *
 18  *  Big-endian to little-endian byte-swapping/bitmaps by
 19  *        David S. Miller (davem@caip.rutgers.edu), 1995
 20  *
 21  * Hash Tree Directory indexing (c) 2001  Daniel Phillips
 22  *
 23  */
 24 
 25 #include <linux/fs.h>
 26 #include <linux/buffer_head.h>
 27 #include <linux/slab.h>
 28 #include <linux/iversion.h>
 29 #include "ext4.h"
 30 #include "xattr.h"
 31 
 32 static int ext4_dx_readdir(struct file *, struct dir_context *);
 33 
 34 /**
 35  * Check if the given dir-inode refers to an htree-indexed directory
 36  * (or a directory which could potentially get converted to use htree
 37  * indexing).
 38  *
 39  * Return 1 if it is a dx dir, 0 if not
 40  */
 41 static int is_dx_dir(struct inode *inode)
 42 {
 43         struct super_block *sb = inode->i_sb;
 44 
 45         if (ext4_has_feature_dir_index(inode->i_sb) &&
 46             ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
 47              ((inode->i_size >> sb->s_blocksize_bits) == 1) ||
 48              ext4_has_inline_data(inode)))
 49                 return 1;
 50 
 51         return 0;
 52 }
 53 
 54 /*
 55  * Return 0 if the directory entry is OK, and 1 if there is a problem
 56  *
 57  * Note: this is the opposite of what ext2 and ext3 historically returned...
 58  *
 59  * bh passed here can be an inode block or a dir data block, depending
 60  * on the inode inline data flag.
 61  */
 62 int __ext4_check_dir_entry(const char *function, unsigned int line,
 63                            struct inode *dir, struct file *filp,
 64                            struct ext4_dir_entry_2 *de,
 65                            struct buffer_head *bh, char *buf, int size,
 66                            unsigned int offset)
 67 {
 68         const char *error_msg = NULL;
 69         const int rlen = ext4_rec_len_from_disk(de->rec_len,
 70                                                 dir->i_sb->s_blocksize);
 71 
 72         if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
 73                 error_msg = "rec_len is smaller than minimal";
 74         else if (unlikely(rlen % 4 != 0))
 75                 error_msg = "rec_len % 4 != 0";
 76         else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
 77                 error_msg = "rec_len is too small for name_len";
 78         else if (unlikely(((char *) de - buf) + rlen > size))
 79                 error_msg = "directory entry overrun";
 80         else if (unlikely(le32_to_cpu(de->inode) >
 81                         le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
 82                 error_msg = "inode out of bounds";
 83         else
 84                 return 0;
 85 
 86         if (filp)
 87                 ext4_error_file(filp, function, line, bh->b_blocknr,
 88                                 "bad entry in directory: %s - offset=%u, "
 89                                 "inode=%u, rec_len=%d, name_len=%d, size=%d",
 90                                 error_msg, offset, le32_to_cpu(de->inode),
 91                                 rlen, de->name_len, size);
 92         else
 93                 ext4_error_inode(dir, function, line, bh->b_blocknr,
 94                                 "bad entry in directory: %s - offset=%u, "
 95                                 "inode=%u, rec_len=%d, name_len=%d, size=%d",
 96                                  error_msg, offset, le32_to_cpu(de->inode),
 97                                  rlen, de->name_len, size);
 98 
 99         return 1;
100 }
101 
102 static int ext4_readdir(struct file *file, struct dir_context *ctx)
103 {
104         unsigned int offset;
105         int i;
106         struct ext4_dir_entry_2 *de;
107         int err;
108         struct inode *inode = file_inode(file);
109         struct super_block *sb = inode->i_sb;
110         struct buffer_head *bh = NULL;
111         int dir_has_error = 0;
112         struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
113 
114         if (ext4_encrypted_inode(inode)) {
115                 err = fscrypt_get_encryption_info(inode);
116                 if (err && err != -ENOKEY)
117                         return err;
118         }
119 
120         if (is_dx_dir(inode)) {
121                 err = ext4_dx_readdir(file, ctx);
122                 if (err != ERR_BAD_DX_DIR) {
123                         return err;
124                 }
125                 /*
126                  * We don't set the inode dirty flag since it's not
127                  * critical that it get flushed back to the disk.
128                  */
129                 ext4_clear_inode_flag(file_inode(file),
130                                       EXT4_INODE_INDEX);
131         }
132 
133         if (ext4_has_inline_data(inode)) {
134                 int has_inline_data = 1;
135                 err = ext4_read_inline_dir(file, ctx,
136                                            &has_inline_data);
137                 if (has_inline_data)
138                         return err;
139         }
140 
141         if (ext4_encrypted_inode(inode)) {
142                 err = fscrypt_fname_alloc_buffer(inode, EXT4_NAME_LEN, &fstr);
143                 if (err < 0)
144                         return err;
145         }
146 
147         offset = ctx->pos & (sb->s_blocksize - 1);
148 
149         while (ctx->pos < inode->i_size) {
150                 struct ext4_map_blocks map;
151 
152                 if (fatal_signal_pending(current)) {
153                         err = -ERESTARTSYS;
154                         goto errout;
155                 }
156                 cond_resched();
157                 map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
158                 map.m_len = 1;
159                 err = ext4_map_blocks(NULL, inode, &map, 0);
160                 if (err > 0) {
161                         pgoff_t index = map.m_pblk >>
162                                         (PAGE_SHIFT - inode->i_blkbits);
163                         if (!ra_has_index(&file->f_ra, index))
164                                 page_cache_sync_readahead(
165                                         sb->s_bdev->bd_inode->i_mapping,
166                                         &file->f_ra, file,
167                                         index, 1);
168                         file->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
169                         bh = ext4_bread(NULL, inode, map.m_lblk, 0);
170                         if (IS_ERR(bh)) {
171                                 err = PTR_ERR(bh);
172                                 bh = NULL;
173                                 goto errout;
174                         }
175                 }
176 
177                 if (!bh) {
178                         if (!dir_has_error) {
179                                 EXT4_ERROR_FILE(file, 0,
180                                                 "directory contains a "
181                                                 "hole at offset %llu",
182                                            (unsigned long long) ctx->pos);
183                                 dir_has_error = 1;
184                         }
185                         /* corrupt size?  Maybe no more blocks to read */
186                         if (ctx->pos > inode->i_blocks << 9)
187                                 break;
188                         ctx->pos += sb->s_blocksize - offset;
189                         continue;
190                 }
191 
192                 /* Check the checksum */
193                 if (!buffer_verified(bh) &&
194                     !ext4_dirent_csum_verify(inode,
195                                 (struct ext4_dir_entry *)bh->b_data)) {
196                         EXT4_ERROR_FILE(file, 0, "directory fails checksum "
197                                         "at offset %llu",
198                                         (unsigned long long)ctx->pos);
199                         ctx->pos += sb->s_blocksize - offset;
200                         brelse(bh);
201                         bh = NULL;
202                         continue;
203                 }
204                 set_buffer_verified(bh);
205 
206                 /* If the dir block has changed since the last call to
207                  * readdir(2), then we might be pointing to an invalid
208                  * dirent right now.  Scan from the start of the block
209                  * to make sure. */
210                 if (!inode_eq_iversion(inode, file->f_version)) {
211                         for (i = 0; i < sb->s_blocksize && i < offset; ) {
212                                 de = (struct ext4_dir_entry_2 *)
213                                         (bh->b_data + i);
214                                 /* It's too expensive to do a full
215                                  * dirent test each time round this
216                                  * loop, but we do have to test at
217                                  * least that it is non-zero.  A
218                                  * failure will be detected in the
219                                  * dirent test below. */
220                                 if (ext4_rec_len_from_disk(de->rec_len,
221                                         sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
222                                         break;
223                                 i += ext4_rec_len_from_disk(de->rec_len,
224                                                             sb->s_blocksize);
225                         }
226                         offset = i;
227                         ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
228                                 | offset;
229                         file->f_version = inode_query_iversion(inode);
230                 }
231 
232                 while (ctx->pos < inode->i_size
233                        && offset < sb->s_blocksize) {
234                         de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
235                         if (ext4_check_dir_entry(inode, file, de, bh,
236                                                  bh->b_data, bh->b_size,
237                                                  offset)) {
238                                 /*
239                                  * On error, skip to the next block
240                                  */
241                                 ctx->pos = (ctx->pos |
242                                                 (sb->s_blocksize - 1)) + 1;
243                                 break;
244                         }
245                         offset += ext4_rec_len_from_disk(de->rec_len,
246                                         sb->s_blocksize);
247                         if (le32_to_cpu(de->inode)) {
248                                 if (!ext4_encrypted_inode(inode)) {
249                                         if (!dir_emit(ctx, de->name,
250                                             de->name_len,
251                                             le32_to_cpu(de->inode),
252                                             get_dtype(sb, de->file_type)))
253                                                 goto done;
254                                 } else {
255                                         int save_len = fstr.len;
256                                         struct fscrypt_str de_name =
257                                                         FSTR_INIT(de->name,
258                                                                 de->name_len);
259 
260                                         /* Directory is encrypted */
261                                         err = fscrypt_fname_disk_to_usr(inode,
262                                                 0, 0, &de_name, &fstr);
263                                         de_name = fstr;
264                                         fstr.len = save_len;
265                                         if (err)
266                                                 goto errout;
267                                         if (!dir_emit(ctx,
268                                             de_name.name, de_name.len,
269                                             le32_to_cpu(de->inode),
270                                             get_dtype(sb, de->file_type)))
271                                                 goto done;
272                                 }
273                         }
274                         ctx->pos += ext4_rec_len_from_disk(de->rec_len,
275                                                 sb->s_blocksize);
276                 }
277                 if ((ctx->pos < inode->i_size) && !dir_relax_shared(inode))
278                         goto done;
279                 brelse(bh);
280                 bh = NULL;
281                 offset = 0;
282         }
283 done:
284         err = 0;
285 errout:
286 #ifdef CONFIG_EXT4_FS_ENCRYPTION
287         fscrypt_fname_free_buffer(&fstr);
288 #endif
289         brelse(bh);
290         return err;
291 }
292 
293 static inline int is_32bit_api(void)
294 {
295 #ifdef CONFIG_COMPAT
296         return in_compat_syscall();
297 #else
298         return (BITS_PER_LONG == 32);
299 #endif
300 }
301 
302 /*
303  * These functions convert from the major/minor hash to an f_pos
304  * value for dx directories
305  *
306  * Upper layer (for example NFS) should specify FMODE_32BITHASH or
307  * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
308  * directly on both 32-bit and 64-bit nodes, under such case, neither
309  * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
310  */
311 static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
312 {
313         if ((filp->f_mode & FMODE_32BITHASH) ||
314             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
315                 return major >> 1;
316         else
317                 return ((__u64)(major >> 1) << 32) | (__u64)minor;
318 }
319 
320 static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
321 {
322         if ((filp->f_mode & FMODE_32BITHASH) ||
323             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
324                 return (pos << 1) & 0xffffffff;
325         else
326                 return ((pos >> 32) << 1) & 0xffffffff;
327 }
328 
329 static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
330 {
331         if ((filp->f_mode & FMODE_32BITHASH) ||
332             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
333                 return 0;
334         else
335                 return pos & 0xffffffff;
336 }
337 
338 /*
339  * Return 32- or 64-bit end-of-file for dx directories
340  */
341 static inline loff_t ext4_get_htree_eof(struct file *filp)
342 {
343         if ((filp->f_mode & FMODE_32BITHASH) ||
344             (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
345                 return EXT4_HTREE_EOF_32BIT;
346         else
347                 return EXT4_HTREE_EOF_64BIT;
348 }
349 
350 
351 /*
352  * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
353  * directories, where the "offset" is in terms of the filename hash
354  * value instead of the byte offset.
355  *
356  * Because we may return a 64-bit hash that is well beyond offset limits,
357  * we need to pass the max hash as the maximum allowable offset in
358  * the htree directory case.
359  *
360  * For non-htree, ext4_llseek already chooses the proper max offset.
361  */
362 static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
363 {
364         struct inode *inode = file->f_mapping->host;
365         int dx_dir = is_dx_dir(inode);
366         loff_t ret, htree_max = ext4_get_htree_eof(file);
367 
368         if (likely(dx_dir))
369                 ret = generic_file_llseek_size(file, offset, whence,
370                                                     htree_max, htree_max);
371         else
372                 ret = ext4_llseek(file, offset, whence);
373         file->f_version = inode_peek_iversion(inode) - 1;
374         return ret;
375 }
376 
377 /*
378  * This structure holds the nodes of the red-black tree used to store
379  * the directory entry in hash order.
380  */
381 struct fname {
382         __u32           hash;
383         __u32           minor_hash;
384         struct rb_node  rb_hash;
385         struct fname    *next;
386         __u32           inode;
387         __u8            name_len;
388         __u8            file_type;
389         char            name[0];
390 };
391 
392 /*
393  * This functoin implements a non-recursive way of freeing all of the
394  * nodes in the red-black tree.
395  */
396 static void free_rb_tree_fname(struct rb_root *root)
397 {
398         struct fname *fname, *next;
399 
400         rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
401                 while (fname) {
402                         struct fname *old = fname;
403                         fname = fname->next;
404                         kfree(old);
405                 }
406 
407         *root = RB_ROOT;
408 }
409 
410 
411 static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
412                                                            loff_t pos)
413 {
414         struct dir_private_info *p;
415 
416         p = kzalloc(sizeof(*p), GFP_KERNEL);
417         if (!p)
418                 return NULL;
419         p->curr_hash = pos2maj_hash(filp, pos);
420         p->curr_minor_hash = pos2min_hash(filp, pos);
421         return p;
422 }
423 
424 void ext4_htree_free_dir_info(struct dir_private_info *p)
425 {
426         free_rb_tree_fname(&p->root);
427         kfree(p);
428 }
429 
430 /*
431  * Given a directory entry, enter it into the fname rb tree.
432  *
433  * When filename encryption is enabled, the dirent will hold the
434  * encrypted filename, while the htree will hold decrypted filename.
435  * The decrypted filename is passed in via ent_name.  parameter.
436  */
437 int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
438                              __u32 minor_hash,
439                             struct ext4_dir_entry_2 *dirent,
440                             struct fscrypt_str *ent_name)
441 {
442         struct rb_node **p, *parent = NULL;
443         struct fname *fname, *new_fn;
444         struct dir_private_info *info;
445         int len;
446 
447         info = dir_file->private_data;
448         p = &info->root.rb_node;
449 
450         /* Create and allocate the fname structure */
451         len = sizeof(struct fname) + ent_name->len + 1;
452         new_fn = kzalloc(len, GFP_KERNEL);
453         if (!new_fn)
454                 return -ENOMEM;
455         new_fn->hash = hash;
456         new_fn->minor_hash = minor_hash;
457         new_fn->inode = le32_to_cpu(dirent->inode);
458         new_fn->name_len = ent_name->len;
459         new_fn->file_type = dirent->file_type;
460         memcpy(new_fn->name, ent_name->name, ent_name->len);
461         new_fn->name[ent_name->len] = 0;
462 
463         while (*p) {
464                 parent = *p;
465                 fname = rb_entry(parent, struct fname, rb_hash);
466 
467                 /*
468                  * If the hash and minor hash match up, then we put
469                  * them on a linked list.  This rarely happens...
470                  */
471                 if ((new_fn->hash == fname->hash) &&
472                     (new_fn->minor_hash == fname->minor_hash)) {
473                         new_fn->next = fname->next;
474                         fname->next = new_fn;
475                         return 0;
476                 }
477 
478                 if (new_fn->hash < fname->hash)
479                         p = &(*p)->rb_left;
480                 else if (new_fn->hash > fname->hash)
481                         p = &(*p)->rb_right;
482                 else if (new_fn->minor_hash < fname->minor_hash)
483                         p = &(*p)->rb_left;
484                 else /* if (new_fn->minor_hash > fname->minor_hash) */
485                         p = &(*p)->rb_right;
486         }
487 
488         rb_link_node(&new_fn->rb_hash, parent, p);
489         rb_insert_color(&new_fn->rb_hash, &info->root);
490         return 0;
491 }
492 
493 
494 
495 /*
496  * This is a helper function for ext4_dx_readdir.  It calls filldir
497  * for all entres on the fname linked list.  (Normally there is only
498  * one entry on the linked list, unless there are 62 bit hash collisions.)
499  */
500 static int call_filldir(struct file *file, struct dir_context *ctx,
501                         struct fname *fname)
502 {
503         struct dir_private_info *info = file->private_data;
504         struct inode *inode = file_inode(file);
505         struct super_block *sb = inode->i_sb;
506 
507         if (!fname) {
508                 ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
509                          "called with null fname?!?", __func__, __LINE__,
510                          inode->i_ino, current->comm);
511                 return 0;
512         }
513         ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
514         while (fname) {
515                 if (!dir_emit(ctx, fname->name,
516                                 fname->name_len,
517                                 fname->inode,
518                                 get_dtype(sb, fname->file_type))) {
519                         info->extra_fname = fname;
520                         return 1;
521                 }
522                 fname = fname->next;
523         }
524         return 0;
525 }
526 
527 static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
528 {
529         struct dir_private_info *info = file->private_data;
530         struct inode *inode = file_inode(file);
531         struct fname *fname;
532         int     ret;
533 
534         if (!info) {
535                 info = ext4_htree_create_dir_info(file, ctx->pos);
536                 if (!info)
537                         return -ENOMEM;
538                 file->private_data = info;
539         }
540 
541         if (ctx->pos == ext4_get_htree_eof(file))
542                 return 0;       /* EOF */
543 
544         /* Some one has messed with f_pos; reset the world */
545         if (info->last_pos != ctx->pos) {
546                 free_rb_tree_fname(&info->root);
547                 info->curr_node = NULL;
548                 info->extra_fname = NULL;
549                 info->curr_hash = pos2maj_hash(file, ctx->pos);
550                 info->curr_minor_hash = pos2min_hash(file, ctx->pos);
551         }
552 
553         /*
554          * If there are any leftover names on the hash collision
555          * chain, return them first.
556          */
557         if (info->extra_fname) {
558                 if (call_filldir(file, ctx, info->extra_fname))
559                         goto finished;
560                 info->extra_fname = NULL;
561                 goto next_node;
562         } else if (!info->curr_node)
563                 info->curr_node = rb_first(&info->root);
564 
565         while (1) {
566                 /*
567                  * Fill the rbtree if we have no more entries,
568                  * or the inode has changed since we last read in the
569                  * cached entries.
570                  */
571                 if ((!info->curr_node) ||
572                     !inode_eq_iversion(inode, file->f_version)) {
573                         info->curr_node = NULL;
574                         free_rb_tree_fname(&info->root);
575                         file->f_version = inode_query_iversion(inode);
576                         ret = ext4_htree_fill_tree(file, info->curr_hash,
577                                                    info->curr_minor_hash,
578                                                    &info->next_hash);
579                         if (ret < 0)
580                                 return ret;
581                         if (ret == 0) {
582                                 ctx->pos = ext4_get_htree_eof(file);
583                                 break;
584                         }
585                         info->curr_node = rb_first(&info->root);
586                 }
587 
588                 fname = rb_entry(info->curr_node, struct fname, rb_hash);
589                 info->curr_hash = fname->hash;
590                 info->curr_minor_hash = fname->minor_hash;
591                 if (call_filldir(file, ctx, fname))
592                         break;
593         next_node:
594                 info->curr_node = rb_next(info->curr_node);
595                 if (info->curr_node) {
596                         fname = rb_entry(info->curr_node, struct fname,
597                                          rb_hash);
598                         info->curr_hash = fname->hash;
599                         info->curr_minor_hash = fname->minor_hash;
600                 } else {
601                         if (info->next_hash == ~0) {
602                                 ctx->pos = ext4_get_htree_eof(file);
603                                 break;
604                         }
605                         info->curr_hash = info->next_hash;
606                         info->curr_minor_hash = 0;
607                 }
608         }
609 finished:
610         info->last_pos = ctx->pos;
611         return 0;
612 }
613 
614 static int ext4_dir_open(struct inode * inode, struct file * filp)
615 {
616         if (ext4_encrypted_inode(inode))
617                 return fscrypt_get_encryption_info(inode) ? -EACCES : 0;
618         return 0;
619 }
620 
621 static int ext4_release_dir(struct inode *inode, struct file *filp)
622 {
623         if (filp->private_data)
624                 ext4_htree_free_dir_info(filp->private_data);
625 
626         return 0;
627 }
628 
629 int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
630                       int buf_size)
631 {
632         struct ext4_dir_entry_2 *de;
633         int rlen;
634         unsigned int offset = 0;
635         char *top;
636 
637         de = (struct ext4_dir_entry_2 *)buf;
638         top = buf + buf_size;
639         while ((char *) de < top) {
640                 if (ext4_check_dir_entry(dir, NULL, de, bh,
641                                          buf, buf_size, offset))
642                         return -EFSCORRUPTED;
643                 rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
644                 de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
645                 offset += rlen;
646         }
647         if ((char *) de > top)
648                 return -EFSCORRUPTED;
649 
650         return 0;
651 }
652 
653 const struct file_operations ext4_dir_operations = {
654         .llseek         = ext4_dir_llseek,
655         .read           = generic_read_dir,
656         .iterate_shared = ext4_readdir,
657         .unlocked_ioctl = ext4_ioctl,
658 #ifdef CONFIG_COMPAT
659         .compat_ioctl   = ext4_compat_ioctl,
660 #endif
661         .fsync          = ext4_sync_file,
662         .open           = ext4_dir_open,
663         .release        = ext4_release_dir,
664 };
665 

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