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  */
is_dx_dir(struct inode * inode)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  */
__ext4_check_dir_entry(const char * function,unsigned int line,struct inode * dir,struct file * filp,struct ext4_dir_entry_2 * de,struct buffer_head * bh,char * buf,int size,unsigned int offset)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(((char *) de - buf) + rlen >
81 			  size - EXT4_DIR_REC_LEN(1) &&
82 			  ((char *) de - buf) + rlen != size)) {
83 		error_msg = "directory entry too close to block end";
84 	}
85 	else if (unlikely(le32_to_cpu(de->inode) >
86 			le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
87 		error_msg = "inode out of bounds";
88 	else
89 		return 0;
90 
91 	if (filp)
92 		ext4_error_file(filp, function, line, bh->b_blocknr,
93 				"bad entry in directory: %s - offset=%u, "
94 				"inode=%u, rec_len=%d, name_len=%d, size=%d",
95 				error_msg, offset, le32_to_cpu(de->inode),
96 				rlen, de->name_len, size);
97 	else
98 		ext4_error_inode(dir, function, line, bh->b_blocknr,
99 				"bad entry in directory: %s - offset=%u, "
100 				"inode=%u, rec_len=%d, name_len=%d, size=%d",
101 				 error_msg, offset, le32_to_cpu(de->inode),
102 				 rlen, de->name_len, size);
103 
104 	return 1;
105 }
106 
ext4_readdir(struct file * file,struct dir_context * ctx)107 static int ext4_readdir(struct file *file, struct dir_context *ctx)
108 {
109 	unsigned int offset;
110 	int i;
111 	struct ext4_dir_entry_2 *de;
112 	int err;
113 	struct inode *inode = file_inode(file);
114 	struct super_block *sb = inode->i_sb;
115 	struct buffer_head *bh = NULL;
116 	struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
117 
118 	if (ext4_encrypted_inode(inode)) {
119 		err = fscrypt_get_encryption_info(inode);
120 		if (err && err != -ENOKEY)
121 			return err;
122 	}
123 
124 	if (is_dx_dir(inode)) {
125 		err = ext4_dx_readdir(file, ctx);
126 		if (err != ERR_BAD_DX_DIR) {
127 			return err;
128 		}
129 		/* Can we just clear INDEX flag to ignore htree information? */
130 		if (!ext4_has_metadata_csum(sb)) {
131 			/*
132 			 * We don't set the inode dirty flag since it's not
133 			 * critical that it gets flushed back to the disk.
134 			 */
135 			ext4_clear_inode_flag(inode, EXT4_INODE_INDEX);
136 		}
137 	}
138 
139 	if (ext4_has_inline_data(inode)) {
140 		int has_inline_data = 1;
141 		err = ext4_read_inline_dir(file, ctx,
142 					   &has_inline_data);
143 		if (has_inline_data)
144 			return err;
145 	}
146 
147 	if (ext4_encrypted_inode(inode)) {
148 		err = fscrypt_fname_alloc_buffer(inode, EXT4_NAME_LEN, &fstr);
149 		if (err < 0)
150 			return err;
151 	}
152 
153 	while (ctx->pos < inode->i_size) {
154 		struct ext4_map_blocks map;
155 
156 		if (fatal_signal_pending(current)) {
157 			err = -ERESTARTSYS;
158 			goto errout;
159 		}
160 		cond_resched();
161 		offset = ctx->pos & (sb->s_blocksize - 1);
162 		map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
163 		map.m_len = 1;
164 		err = ext4_map_blocks(NULL, inode, &map, 0);
165 		if (err == 0) {
166 			/* m_len should never be zero but let's avoid
167 			 * an infinite loop if it somehow is */
168 			if (map.m_len == 0)
169 				map.m_len = 1;
170 			ctx->pos += map.m_len * sb->s_blocksize;
171 			continue;
172 		}
173 		if (err > 0) {
174 			pgoff_t index = map.m_pblk >>
175 					(PAGE_SHIFT - inode->i_blkbits);
176 			if (!ra_has_index(&file->f_ra, index))
177 				page_cache_sync_readahead(
178 					sb->s_bdev->bd_inode->i_mapping,
179 					&file->f_ra, file,
180 					index, 1);
181 			file->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
182 			bh = ext4_bread(NULL, inode, map.m_lblk, 0);
183 			if (IS_ERR(bh)) {
184 				err = PTR_ERR(bh);
185 				bh = NULL;
186 				goto errout;
187 			}
188 		}
189 
190 		if (!bh) {
191 			/* corrupt size?  Maybe no more blocks to read */
192 			if (ctx->pos > inode->i_blocks << 9)
193 				break;
194 			ctx->pos += sb->s_blocksize - offset;
195 			continue;
196 		}
197 
198 		/* Check the checksum */
199 		if (!buffer_verified(bh) &&
200 		    !ext4_dirent_csum_verify(inode,
201 				(struct ext4_dir_entry *)bh->b_data)) {
202 			EXT4_ERROR_FILE(file, 0, "directory fails checksum "
203 					"at offset %llu",
204 					(unsigned long long)ctx->pos);
205 			ctx->pos += sb->s_blocksize - offset;
206 			brelse(bh);
207 			bh = NULL;
208 			continue;
209 		}
210 		set_buffer_verified(bh);
211 
212 		/* If the dir block has changed since the last call to
213 		 * readdir(2), then we might be pointing to an invalid
214 		 * dirent right now.  Scan from the start of the block
215 		 * to make sure. */
216 		if (!inode_eq_iversion(inode, file->f_version)) {
217 			for (i = 0; i < sb->s_blocksize && i < offset; ) {
218 				de = (struct ext4_dir_entry_2 *)
219 					(bh->b_data + i);
220 				/* It's too expensive to do a full
221 				 * dirent test each time round this
222 				 * loop, but we do have to test at
223 				 * least that it is non-zero.  A
224 				 * failure will be detected in the
225 				 * dirent test below. */
226 				if (ext4_rec_len_from_disk(de->rec_len,
227 					sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
228 					break;
229 				i += ext4_rec_len_from_disk(de->rec_len,
230 							    sb->s_blocksize);
231 			}
232 			offset = i;
233 			ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
234 				| offset;
235 			file->f_version = inode_query_iversion(inode);
236 		}
237 
238 		while (ctx->pos < inode->i_size
239 		       && offset < sb->s_blocksize) {
240 			de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
241 			if (ext4_check_dir_entry(inode, file, de, bh,
242 						 bh->b_data, bh->b_size,
243 						 offset)) {
244 				/*
245 				 * On error, skip to the next block
246 				 */
247 				ctx->pos = (ctx->pos |
248 						(sb->s_blocksize - 1)) + 1;
249 				break;
250 			}
251 			offset += ext4_rec_len_from_disk(de->rec_len,
252 					sb->s_blocksize);
253 			if (le32_to_cpu(de->inode)) {
254 				if (!ext4_encrypted_inode(inode)) {
255 					if (!dir_emit(ctx, de->name,
256 					    de->name_len,
257 					    le32_to_cpu(de->inode),
258 					    get_dtype(sb, de->file_type)))
259 						goto done;
260 				} else {
261 					int save_len = fstr.len;
262 					struct fscrypt_str de_name =
263 							FSTR_INIT(de->name,
264 								de->name_len);
265 
266 					/* Directory is encrypted */
267 					err = fscrypt_fname_disk_to_usr(inode,
268 						0, 0, &de_name, &fstr);
269 					de_name = fstr;
270 					fstr.len = save_len;
271 					if (err)
272 						goto errout;
273 					if (!dir_emit(ctx,
274 					    de_name.name, de_name.len,
275 					    le32_to_cpu(de->inode),
276 					    get_dtype(sb, de->file_type)))
277 						goto done;
278 				}
279 			}
280 			ctx->pos += ext4_rec_len_from_disk(de->rec_len,
281 						sb->s_blocksize);
282 		}
283 		if ((ctx->pos < inode->i_size) && !dir_relax_shared(inode))
284 			goto done;
285 		brelse(bh);
286 		bh = NULL;
287 		offset = 0;
288 	}
289 done:
290 	err = 0;
291 errout:
292 #ifdef CONFIG_EXT4_FS_ENCRYPTION
293 	fscrypt_fname_free_buffer(&fstr);
294 #endif
295 	brelse(bh);
296 	return err;
297 }
298 
is_32bit_api(void)299 static inline int is_32bit_api(void)
300 {
301 #ifdef CONFIG_COMPAT
302 	return in_compat_syscall();
303 #else
304 	return (BITS_PER_LONG == 32);
305 #endif
306 }
307 
308 /*
309  * These functions convert from the major/minor hash to an f_pos
310  * value for dx directories
311  *
312  * Upper layer (for example NFS) should specify FMODE_32BITHASH or
313  * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
314  * directly on both 32-bit and 64-bit nodes, under such case, neither
315  * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
316  */
hash2pos(struct file * filp,__u32 major,__u32 minor)317 static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
318 {
319 	if ((filp->f_mode & FMODE_32BITHASH) ||
320 	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
321 		return major >> 1;
322 	else
323 		return ((__u64)(major >> 1) << 32) | (__u64)minor;
324 }
325 
pos2maj_hash(struct file * filp,loff_t pos)326 static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
327 {
328 	if ((filp->f_mode & FMODE_32BITHASH) ||
329 	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
330 		return (pos << 1) & 0xffffffff;
331 	else
332 		return ((pos >> 32) << 1) & 0xffffffff;
333 }
334 
pos2min_hash(struct file * filp,loff_t pos)335 static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
336 {
337 	if ((filp->f_mode & FMODE_32BITHASH) ||
338 	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
339 		return 0;
340 	else
341 		return pos & 0xffffffff;
342 }
343 
344 /*
345  * Return 32- or 64-bit end-of-file for dx directories
346  */
ext4_get_htree_eof(struct file * filp)347 static inline loff_t ext4_get_htree_eof(struct file *filp)
348 {
349 	if ((filp->f_mode & FMODE_32BITHASH) ||
350 	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
351 		return EXT4_HTREE_EOF_32BIT;
352 	else
353 		return EXT4_HTREE_EOF_64BIT;
354 }
355 
356 
357 /*
358  * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
359  * directories, where the "offset" is in terms of the filename hash
360  * value instead of the byte offset.
361  *
362  * Because we may return a 64-bit hash that is well beyond offset limits,
363  * we need to pass the max hash as the maximum allowable offset in
364  * the htree directory case.
365  *
366  * For non-htree, ext4_llseek already chooses the proper max offset.
367  */
ext4_dir_llseek(struct file * file,loff_t offset,int whence)368 static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
369 {
370 	struct inode *inode = file->f_mapping->host;
371 	int dx_dir = is_dx_dir(inode);
372 	loff_t ret, htree_max = ext4_get_htree_eof(file);
373 
374 	if (likely(dx_dir))
375 		ret = generic_file_llseek_size(file, offset, whence,
376 						    htree_max, htree_max);
377 	else
378 		ret = ext4_llseek(file, offset, whence);
379 	file->f_version = inode_peek_iversion(inode) - 1;
380 	return ret;
381 }
382 
383 /*
384  * This structure holds the nodes of the red-black tree used to store
385  * the directory entry in hash order.
386  */
387 struct fname {
388 	__u32		hash;
389 	__u32		minor_hash;
390 	struct rb_node	rb_hash;
391 	struct fname	*next;
392 	__u32		inode;
393 	__u8		name_len;
394 	__u8		file_type;
395 	char		name[0];
396 };
397 
398 /*
399  * This functoin implements a non-recursive way of freeing all of the
400  * nodes in the red-black tree.
401  */
free_rb_tree_fname(struct rb_root * root)402 static void free_rb_tree_fname(struct rb_root *root)
403 {
404 	struct fname *fname, *next;
405 
406 	rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
407 		while (fname) {
408 			struct fname *old = fname;
409 			fname = fname->next;
410 			kfree(old);
411 		}
412 
413 	*root = RB_ROOT;
414 }
415 
416 
ext4_htree_create_dir_info(struct file * filp,loff_t pos)417 static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
418 							   loff_t pos)
419 {
420 	struct dir_private_info *p;
421 
422 	p = kzalloc(sizeof(*p), GFP_KERNEL);
423 	if (!p)
424 		return NULL;
425 	p->curr_hash = pos2maj_hash(filp, pos);
426 	p->curr_minor_hash = pos2min_hash(filp, pos);
427 	return p;
428 }
429 
ext4_htree_free_dir_info(struct dir_private_info * p)430 void ext4_htree_free_dir_info(struct dir_private_info *p)
431 {
432 	free_rb_tree_fname(&p->root);
433 	kfree(p);
434 }
435 
436 /*
437  * Given a directory entry, enter it into the fname rb tree.
438  *
439  * When filename encryption is enabled, the dirent will hold the
440  * encrypted filename, while the htree will hold decrypted filename.
441  * The decrypted filename is passed in via ent_name.  parameter.
442  */
ext4_htree_store_dirent(struct file * dir_file,__u32 hash,__u32 minor_hash,struct ext4_dir_entry_2 * dirent,struct fscrypt_str * ent_name)443 int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
444 			     __u32 minor_hash,
445 			    struct ext4_dir_entry_2 *dirent,
446 			    struct fscrypt_str *ent_name)
447 {
448 	struct rb_node **p, *parent = NULL;
449 	struct fname *fname, *new_fn;
450 	struct dir_private_info *info;
451 	int len;
452 
453 	info = dir_file->private_data;
454 	p = &info->root.rb_node;
455 
456 	/* Create and allocate the fname structure */
457 	len = sizeof(struct fname) + ent_name->len + 1;
458 	new_fn = kzalloc(len, GFP_KERNEL);
459 	if (!new_fn)
460 		return -ENOMEM;
461 	new_fn->hash = hash;
462 	new_fn->minor_hash = minor_hash;
463 	new_fn->inode = le32_to_cpu(dirent->inode);
464 	new_fn->name_len = ent_name->len;
465 	new_fn->file_type = dirent->file_type;
466 	memcpy(new_fn->name, ent_name->name, ent_name->len);
467 	new_fn->name[ent_name->len] = 0;
468 
469 	while (*p) {
470 		parent = *p;
471 		fname = rb_entry(parent, struct fname, rb_hash);
472 
473 		/*
474 		 * If the hash and minor hash match up, then we put
475 		 * them on a linked list.  This rarely happens...
476 		 */
477 		if ((new_fn->hash == fname->hash) &&
478 		    (new_fn->minor_hash == fname->minor_hash)) {
479 			new_fn->next = fname->next;
480 			fname->next = new_fn;
481 			return 0;
482 		}
483 
484 		if (new_fn->hash < fname->hash)
485 			p = &(*p)->rb_left;
486 		else if (new_fn->hash > fname->hash)
487 			p = &(*p)->rb_right;
488 		else if (new_fn->minor_hash < fname->minor_hash)
489 			p = &(*p)->rb_left;
490 		else /* if (new_fn->minor_hash > fname->minor_hash) */
491 			p = &(*p)->rb_right;
492 	}
493 
494 	rb_link_node(&new_fn->rb_hash, parent, p);
495 	rb_insert_color(&new_fn->rb_hash, &info->root);
496 	return 0;
497 }
498 
499 
500 
501 /*
502  * This is a helper function for ext4_dx_readdir.  It calls filldir
503  * for all entres on the fname linked list.  (Normally there is only
504  * one entry on the linked list, unless there are 62 bit hash collisions.)
505  */
call_filldir(struct file * file,struct dir_context * ctx,struct fname * fname)506 static int call_filldir(struct file *file, struct dir_context *ctx,
507 			struct fname *fname)
508 {
509 	struct dir_private_info *info = file->private_data;
510 	struct inode *inode = file_inode(file);
511 	struct super_block *sb = inode->i_sb;
512 
513 	if (!fname) {
514 		ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
515 			 "called with null fname?!?", __func__, __LINE__,
516 			 inode->i_ino, current->comm);
517 		return 0;
518 	}
519 	ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
520 	while (fname) {
521 		if (!dir_emit(ctx, fname->name,
522 				fname->name_len,
523 				fname->inode,
524 				get_dtype(sb, fname->file_type))) {
525 			info->extra_fname = fname;
526 			return 1;
527 		}
528 		fname = fname->next;
529 	}
530 	return 0;
531 }
532 
ext4_dx_readdir(struct file * file,struct dir_context * ctx)533 static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
534 {
535 	struct dir_private_info *info = file->private_data;
536 	struct inode *inode = file_inode(file);
537 	struct fname *fname;
538 	int ret = 0;
539 
540 	if (!info) {
541 		info = ext4_htree_create_dir_info(file, ctx->pos);
542 		if (!info)
543 			return -ENOMEM;
544 		file->private_data = info;
545 	}
546 
547 	if (ctx->pos == ext4_get_htree_eof(file))
548 		return 0;	/* EOF */
549 
550 	/* Some one has messed with f_pos; reset the world */
551 	if (info->last_pos != ctx->pos) {
552 		free_rb_tree_fname(&info->root);
553 		info->curr_node = NULL;
554 		info->extra_fname = NULL;
555 		info->curr_hash = pos2maj_hash(file, ctx->pos);
556 		info->curr_minor_hash = pos2min_hash(file, ctx->pos);
557 	}
558 
559 	/*
560 	 * If there are any leftover names on the hash collision
561 	 * chain, return them first.
562 	 */
563 	if (info->extra_fname) {
564 		if (call_filldir(file, ctx, info->extra_fname))
565 			goto finished;
566 		info->extra_fname = NULL;
567 		goto next_node;
568 	} else if (!info->curr_node)
569 		info->curr_node = rb_first(&info->root);
570 
571 	while (1) {
572 		/*
573 		 * Fill the rbtree if we have no more entries,
574 		 * or the inode has changed since we last read in the
575 		 * cached entries.
576 		 */
577 		if ((!info->curr_node) ||
578 		    !inode_eq_iversion(inode, file->f_version)) {
579 			info->curr_node = NULL;
580 			free_rb_tree_fname(&info->root);
581 			file->f_version = inode_query_iversion(inode);
582 			ret = ext4_htree_fill_tree(file, info->curr_hash,
583 						   info->curr_minor_hash,
584 						   &info->next_hash);
585 			if (ret < 0)
586 				goto finished;
587 			if (ret == 0) {
588 				ctx->pos = ext4_get_htree_eof(file);
589 				break;
590 			}
591 			info->curr_node = rb_first(&info->root);
592 		}
593 
594 		fname = rb_entry(info->curr_node, struct fname, rb_hash);
595 		info->curr_hash = fname->hash;
596 		info->curr_minor_hash = fname->minor_hash;
597 		if (call_filldir(file, ctx, fname))
598 			break;
599 	next_node:
600 		info->curr_node = rb_next(info->curr_node);
601 		if (info->curr_node) {
602 			fname = rb_entry(info->curr_node, struct fname,
603 					 rb_hash);
604 			info->curr_hash = fname->hash;
605 			info->curr_minor_hash = fname->minor_hash;
606 		} else {
607 			if (info->next_hash == ~0) {
608 				ctx->pos = ext4_get_htree_eof(file);
609 				break;
610 			}
611 			info->curr_hash = info->next_hash;
612 			info->curr_minor_hash = 0;
613 		}
614 	}
615 finished:
616 	info->last_pos = ctx->pos;
617 	return ret < 0 ? ret : 0;
618 }
619 
ext4_dir_open(struct inode * inode,struct file * filp)620 static int ext4_dir_open(struct inode * inode, struct file * filp)
621 {
622 	if (ext4_encrypted_inode(inode))
623 		return fscrypt_get_encryption_info(inode) ? -EACCES : 0;
624 	return 0;
625 }
626 
ext4_release_dir(struct inode * inode,struct file * filp)627 static int ext4_release_dir(struct inode *inode, struct file *filp)
628 {
629 	if (filp->private_data)
630 		ext4_htree_free_dir_info(filp->private_data);
631 
632 	return 0;
633 }
634 
ext4_check_all_de(struct inode * dir,struct buffer_head * bh,void * buf,int buf_size)635 int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
636 		      int buf_size)
637 {
638 	struct ext4_dir_entry_2 *de;
639 	int rlen;
640 	unsigned int offset = 0;
641 	char *top;
642 
643 	de = (struct ext4_dir_entry_2 *)buf;
644 	top = buf + buf_size;
645 	while ((char *) de < top) {
646 		if (ext4_check_dir_entry(dir, NULL, de, bh,
647 					 buf, buf_size, offset))
648 			return -EFSCORRUPTED;
649 		rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
650 		de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
651 		offset += rlen;
652 	}
653 	if ((char *) de > top)
654 		return -EFSCORRUPTED;
655 
656 	return 0;
657 }
658 
659 const struct file_operations ext4_dir_operations = {
660 	.llseek		= ext4_dir_llseek,
661 	.read		= generic_read_dir,
662 	.iterate_shared	= ext4_readdir,
663 	.unlocked_ioctl = ext4_ioctl,
664 #ifdef CONFIG_COMPAT
665 	.compat_ioctl	= ext4_compat_ioctl,
666 #endif
667 	.fsync		= ext4_sync_file,
668 	.open		= ext4_dir_open,
669 	.release	= ext4_release_dir,
670 };
671