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 <linux/unicode.h>
30#include "ext4.h"
31#include "xattr.h"
32
33static int ext4_dx_readdir(struct file *, struct dir_context *);
34
35/**
36 * is_dx_dir() - check if a directory is using htree indexing
37 * @inode: directory inode
38 *
39 * Check if the given dir-inode refers to an htree-indexed directory
40 * (or a directory which could potentially get converted to use htree
41 * indexing).
42 *
43 * Return 1 if it is a dx dir, 0 if not
44 */
45static int is_dx_dir(struct inode *inode)
46{
47	struct super_block *sb = inode->i_sb;
48
49	if (ext4_has_feature_dir_index(inode->i_sb) &&
50	    ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
51	     ((inode->i_size >> sb->s_blocksize_bits) == 1) ||
52	     ext4_has_inline_data(inode)))
53		return 1;
54
55	return 0;
56}
57
58static bool is_fake_dir_entry(struct ext4_dir_entry_2 *de)
59{
60	/* Check if . or .. , or skip if namelen is 0 */
61	if ((de->name_len > 0) && (de->name_len <= 2) && (de->name[0] == '.') &&
62	    (de->name[1] == '.' || de->name[1] == '\0'))
63		return true;
64	/* Check if this is a csum entry */
65	if (de->file_type == EXT4_FT_DIR_CSUM)
66		return true;
67	return false;
68}
69
70/*
71 * Return 0 if the directory entry is OK, and 1 if there is a problem
72 *
73 * Note: this is the opposite of what ext2 and ext3 historically returned...
74 *
75 * bh passed here can be an inode block or a dir data block, depending
76 * on the inode inline data flag.
77 */
78int __ext4_check_dir_entry(const char *function, unsigned int line,
79			   struct inode *dir, struct file *filp,
80			   struct ext4_dir_entry_2 *de,
81			   struct buffer_head *bh, char *buf, int size,
82			   unsigned int offset)
83{
84	const char *error_msg = NULL;
85	const int rlen = ext4_rec_len_from_disk(de->rec_len,
86						dir->i_sb->s_blocksize);
87	const int next_offset = ((char *) de - buf) + rlen;
88	bool fake = is_fake_dir_entry(de);
89	bool has_csum = ext4_has_metadata_csum(dir->i_sb);
90
91	if (unlikely(rlen < ext4_dir_rec_len(1, fake ? NULL : dir)))
92		error_msg = "rec_len is smaller than minimal";
93	else if (unlikely(rlen % 4 != 0))
94		error_msg = "rec_len % 4 != 0";
95	else if (unlikely(rlen < ext4_dir_rec_len(de->name_len,
96							fake ? NULL : dir)))
97		error_msg = "rec_len is too small for name_len";
98	else if (unlikely(next_offset > size))
99		error_msg = "directory entry overrun";
100	else if (unlikely(next_offset > size - ext4_dir_rec_len(1,
101						  has_csum ? NULL : dir) &&
102			  next_offset != size))
103		error_msg = "directory entry too close to block end";
104	else if (unlikely(le32_to_cpu(de->inode) >
105			le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
106		error_msg = "inode out of bounds";
107	else
108		return 0;
109
110	if (filp)
111		ext4_error_file(filp, function, line, bh->b_blocknr,
112				"bad entry in directory: %s - offset=%u, "
113				"inode=%u, rec_len=%d, size=%d fake=%d",
114				error_msg, offset, le32_to_cpu(de->inode),
115				rlen, size, fake);
116	else
117		ext4_error_inode(dir, function, line, bh->b_blocknr,
118				"bad entry in directory: %s - offset=%u, "
119				"inode=%u, rec_len=%d, size=%d fake=%d",
120				 error_msg, offset, le32_to_cpu(de->inode),
121				 rlen, size, fake);
122
123	return 1;
124}
125
126static int ext4_readdir(struct file *file, struct dir_context *ctx)
127{
128	unsigned int offset;
129	int i;
130	struct ext4_dir_entry_2 *de;
131	int err;
132	struct inode *inode = file_inode(file);
133	struct super_block *sb = inode->i_sb;
134	struct buffer_head *bh = NULL;
135	struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
136
137	err = fscrypt_prepare_readdir(inode);
138	if (err)
139		return err;
140
141	if (is_dx_dir(inode)) {
142		err = ext4_dx_readdir(file, ctx);
143		if (err != ERR_BAD_DX_DIR)
144			return err;
145
146		/* Can we just clear INDEX flag to ignore htree information? */
147		if (!ext4_has_metadata_csum(sb)) {
148			/*
149			 * We don't set the inode dirty flag since it's not
150			 * critical that it gets flushed back to the disk.
151			 */
152			ext4_clear_inode_flag(inode, EXT4_INODE_INDEX);
153		}
154	}
155
156	if (ext4_has_inline_data(inode)) {
157		int has_inline_data = 1;
158		err = ext4_read_inline_dir(file, ctx,
159					   &has_inline_data);
160		if (has_inline_data)
161			return err;
162	}
163
164	if (IS_ENCRYPTED(inode)) {
165		err = fscrypt_fname_alloc_buffer(EXT4_NAME_LEN, &fstr);
166		if (err < 0)
167			return err;
168	}
169
170	while (ctx->pos < inode->i_size) {
171		struct ext4_map_blocks map;
172
173		if (fatal_signal_pending(current)) {
174			err = -ERESTARTSYS;
175			goto errout;
176		}
177		cond_resched();
178		offset = ctx->pos & (sb->s_blocksize - 1);
179		map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
180		map.m_len = 1;
181		err = ext4_map_blocks(NULL, inode, &map, 0);
182		if (err == 0) {
183			/* m_len should never be zero but let's avoid
184			 * an infinite loop if it somehow is */
185			if (map.m_len == 0)
186				map.m_len = 1;
187			ctx->pos += map.m_len * sb->s_blocksize;
188			continue;
189		}
190		if (err > 0) {
191			pgoff_t index = map.m_pblk >>
192					(PAGE_SHIFT - inode->i_blkbits);
193			if (!ra_has_index(&file->f_ra, index))
194				page_cache_sync_readahead(
195					sb->s_bdev->bd_inode->i_mapping,
196					&file->f_ra, file,
197					index, 1);
198			file->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
199			bh = ext4_bread(NULL, inode, map.m_lblk, 0);
200			if (IS_ERR(bh)) {
201				err = PTR_ERR(bh);
202				bh = NULL;
203				goto errout;
204			}
205		}
206
207		if (!bh) {
208			/* corrupt size?  Maybe no more blocks to read */
209			if (ctx->pos > inode->i_blocks << 9)
210				break;
211			ctx->pos += sb->s_blocksize - offset;
212			continue;
213		}
214
215		/* Check the checksum */
216		if (!buffer_verified(bh) &&
217		    !ext4_dirblock_csum_verify(inode, bh)) {
218			EXT4_ERROR_FILE(file, 0, "directory fails checksum "
219					"at offset %llu",
220					(unsigned long long)ctx->pos);
221			ctx->pos += sb->s_blocksize - offset;
222			brelse(bh);
223			bh = NULL;
224			continue;
225		}
226		set_buffer_verified(bh);
227
228		/* If the dir block has changed since the last call to
229		 * readdir(2), then we might be pointing to an invalid
230		 * dirent right now.  Scan from the start of the block
231		 * to make sure. */
232		if (!inode_eq_iversion(inode, file->f_version)) {
233			for (i = 0; i < sb->s_blocksize && i < offset; ) {
234				de = (struct ext4_dir_entry_2 *)
235					(bh->b_data + i);
236				/* It's too expensive to do a full
237				 * dirent test each time round this
238				 * loop, but we do have to test at
239				 * least that it is non-zero.  A
240				 * failure will be detected in the
241				 * dirent test below. */
242				if (ext4_rec_len_from_disk(de->rec_len,
243					sb->s_blocksize) < ext4_dir_rec_len(1,
244									inode))
245					break;
246				i += ext4_rec_len_from_disk(de->rec_len,
247							    sb->s_blocksize);
248			}
249			offset = i;
250			ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
251				| offset;
252			file->f_version = inode_query_iversion(inode);
253		}
254
255		while (ctx->pos < inode->i_size
256		       && offset < sb->s_blocksize) {
257			de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
258			if (ext4_check_dir_entry(inode, file, de, bh,
259						 bh->b_data, bh->b_size,
260						 offset)) {
261				/*
262				 * On error, skip to the next block
263				 */
264				ctx->pos = (ctx->pos |
265						(sb->s_blocksize - 1)) + 1;
266				break;
267			}
268			offset += ext4_rec_len_from_disk(de->rec_len,
269					sb->s_blocksize);
270			if (le32_to_cpu(de->inode)) {
271				if (!IS_ENCRYPTED(inode)) {
272					if (!dir_emit(ctx, de->name,
273					    de->name_len,
274					    le32_to_cpu(de->inode),
275					    get_dtype(sb, de->file_type)))
276						goto done;
277				} else {
278					int save_len = fstr.len;
279					struct fscrypt_str de_name =
280							FSTR_INIT(de->name,
281								de->name_len);
282
283					/* Directory is encrypted */
284					err = fscrypt_fname_disk_to_usr(inode,
285						EXT4_DIRENT_HASH(de),
286						EXT4_DIRENT_MINOR_HASH(de),
287						&de_name, &fstr);
288					de_name = fstr;
289					fstr.len = save_len;
290					if (err)
291						goto errout;
292					if (!dir_emit(ctx,
293					    de_name.name, de_name.len,
294					    le32_to_cpu(de->inode),
295					    get_dtype(sb, de->file_type)))
296						goto done;
297				}
298			}
299			ctx->pos += ext4_rec_len_from_disk(de->rec_len,
300						sb->s_blocksize);
301		}
302		if ((ctx->pos < inode->i_size) && !dir_relax_shared(inode))
303			goto done;
304		brelse(bh);
305		bh = NULL;
306	}
307done:
308	err = 0;
309errout:
310	fscrypt_fname_free_buffer(&fstr);
311	brelse(bh);
312	return err;
313}
314
315static inline int is_32bit_api(void)
316{
317#ifdef CONFIG_COMPAT
318	return in_compat_syscall();
319#else
320	return (BITS_PER_LONG == 32);
321#endif
322}
323
324/*
325 * These functions convert from the major/minor hash to an f_pos
326 * value for dx directories
327 *
328 * Upper layer (for example NFS) should specify FMODE_32BITHASH or
329 * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
330 * directly on both 32-bit and 64-bit nodes, under such case, neither
331 * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
332 */
333static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
334{
335	if ((filp->f_mode & FMODE_32BITHASH) ||
336	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
337		return major >> 1;
338	else
339		return ((__u64)(major >> 1) << 32) | (__u64)minor;
340}
341
342static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
343{
344	if ((filp->f_mode & FMODE_32BITHASH) ||
345	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
346		return (pos << 1) & 0xffffffff;
347	else
348		return ((pos >> 32) << 1) & 0xffffffff;
349}
350
351static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
352{
353	if ((filp->f_mode & FMODE_32BITHASH) ||
354	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
355		return 0;
356	else
357		return pos & 0xffffffff;
358}
359
360/*
361 * Return 32- or 64-bit end-of-file for dx directories
362 */
363static inline loff_t ext4_get_htree_eof(struct file *filp)
364{
365	if ((filp->f_mode & FMODE_32BITHASH) ||
366	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
367		return EXT4_HTREE_EOF_32BIT;
368	else
369		return EXT4_HTREE_EOF_64BIT;
370}
371
372
373/*
374 * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
375 * directories, where the "offset" is in terms of the filename hash
376 * value instead of the byte offset.
377 *
378 * Because we may return a 64-bit hash that is well beyond offset limits,
379 * we need to pass the max hash as the maximum allowable offset in
380 * the htree directory case.
381 *
382 * For non-htree, ext4_llseek already chooses the proper max offset.
383 */
384static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
385{
386	struct inode *inode = file->f_mapping->host;
387	int dx_dir = is_dx_dir(inode);
388	loff_t ret, htree_max = ext4_get_htree_eof(file);
389
390	if (likely(dx_dir))
391		ret = generic_file_llseek_size(file, offset, whence,
392						    htree_max, htree_max);
393	else
394		ret = ext4_llseek(file, offset, whence);
395	file->f_version = inode_peek_iversion(inode) - 1;
396	return ret;
397}
398
399/*
400 * This structure holds the nodes of the red-black tree used to store
401 * the directory entry in hash order.
402 */
403struct fname {
404	__u32		hash;
405	__u32		minor_hash;
406	struct rb_node	rb_hash;
407	struct fname	*next;
408	__u32		inode;
409	__u8		name_len;
410	__u8		file_type;
411	char		name[];
412};
413
414/*
415 * This function implements a non-recursive way of freeing all of the
416 * nodes in the red-black tree.
417 */
418static void free_rb_tree_fname(struct rb_root *root)
419{
420	struct fname *fname, *next;
421
422	rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
423		while (fname) {
424			struct fname *old = fname;
425			fname = fname->next;
426			kfree(old);
427		}
428
429	*root = RB_ROOT;
430}
431
432
433static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
434							   loff_t pos)
435{
436	struct dir_private_info *p;
437
438	p = kzalloc(sizeof(*p), GFP_KERNEL);
439	if (!p)
440		return NULL;
441	p->curr_hash = pos2maj_hash(filp, pos);
442	p->curr_minor_hash = pos2min_hash(filp, pos);
443	return p;
444}
445
446void ext4_htree_free_dir_info(struct dir_private_info *p)
447{
448	free_rb_tree_fname(&p->root);
449	kfree(p);
450}
451
452/*
453 * Given a directory entry, enter it into the fname rb tree.
454 *
455 * When filename encryption is enabled, the dirent will hold the
456 * encrypted filename, while the htree will hold decrypted filename.
457 * The decrypted filename is passed in via ent_name.  parameter.
458 */
459int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
460			     __u32 minor_hash,
461			    struct ext4_dir_entry_2 *dirent,
462			    struct fscrypt_str *ent_name)
463{
464	struct rb_node **p, *parent = NULL;
465	struct fname *fname, *new_fn;
466	struct dir_private_info *info;
467	int len;
468
469	info = dir_file->private_data;
470	p = &info->root.rb_node;
471
472	/* Create and allocate the fname structure */
473	len = sizeof(struct fname) + ent_name->len + 1;
474	new_fn = kzalloc(len, GFP_KERNEL);
475	if (!new_fn)
476		return -ENOMEM;
477	new_fn->hash = hash;
478	new_fn->minor_hash = minor_hash;
479	new_fn->inode = le32_to_cpu(dirent->inode);
480	new_fn->name_len = ent_name->len;
481	new_fn->file_type = dirent->file_type;
482	memcpy(new_fn->name, ent_name->name, ent_name->len);
483
484	while (*p) {
485		parent = *p;
486		fname = rb_entry(parent, struct fname, rb_hash);
487
488		/*
489		 * If the hash and minor hash match up, then we put
490		 * them on a linked list.  This rarely happens...
491		 */
492		if ((new_fn->hash == fname->hash) &&
493		    (new_fn->minor_hash == fname->minor_hash)) {
494			new_fn->next = fname->next;
495			fname->next = new_fn;
496			return 0;
497		}
498
499		if (new_fn->hash < fname->hash)
500			p = &(*p)->rb_left;
501		else if (new_fn->hash > fname->hash)
502			p = &(*p)->rb_right;
503		else if (new_fn->minor_hash < fname->minor_hash)
504			p = &(*p)->rb_left;
505		else /* if (new_fn->minor_hash > fname->minor_hash) */
506			p = &(*p)->rb_right;
507	}
508
509	rb_link_node(&new_fn->rb_hash, parent, p);
510	rb_insert_color(&new_fn->rb_hash, &info->root);
511	return 0;
512}
513
514
515
516/*
517 * This is a helper function for ext4_dx_readdir.  It calls filldir
518 * for all entries on the fname linked list.  (Normally there is only
519 * one entry on the linked list, unless there are 62 bit hash collisions.)
520 */
521static int call_filldir(struct file *file, struct dir_context *ctx,
522			struct fname *fname)
523{
524	struct dir_private_info *info = file->private_data;
525	struct inode *inode = file_inode(file);
526	struct super_block *sb = inode->i_sb;
527
528	if (!fname) {
529		ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
530			 "called with null fname?!?", __func__, __LINE__,
531			 inode->i_ino, current->comm);
532		return 0;
533	}
534	ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
535	while (fname) {
536		if (!dir_emit(ctx, fname->name,
537				fname->name_len,
538				fname->inode,
539				get_dtype(sb, fname->file_type))) {
540			info->extra_fname = fname;
541			return 1;
542		}
543		fname = fname->next;
544	}
545	return 0;
546}
547
548static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
549{
550	struct dir_private_info *info = file->private_data;
551	struct inode *inode = file_inode(file);
552	struct fname *fname;
553	int ret = 0;
554
555	if (!info) {
556		info = ext4_htree_create_dir_info(file, ctx->pos);
557		if (!info)
558			return -ENOMEM;
559		file->private_data = info;
560	}
561
562	if (ctx->pos == ext4_get_htree_eof(file))
563		return 0;	/* EOF */
564
565	/* Some one has messed with f_pos; reset the world */
566	if (info->last_pos != ctx->pos) {
567		free_rb_tree_fname(&info->root);
568		info->curr_node = NULL;
569		info->extra_fname = NULL;
570		info->curr_hash = pos2maj_hash(file, ctx->pos);
571		info->curr_minor_hash = pos2min_hash(file, ctx->pos);
572	}
573
574	/*
575	 * If there are any leftover names on the hash collision
576	 * chain, return them first.
577	 */
578	if (info->extra_fname) {
579		if (call_filldir(file, ctx, info->extra_fname))
580			goto finished;
581		info->extra_fname = NULL;
582		goto next_node;
583	} else if (!info->curr_node)
584		info->curr_node = rb_first(&info->root);
585
586	while (1) {
587		/*
588		 * Fill the rbtree if we have no more entries,
589		 * or the inode has changed since we last read in the
590		 * cached entries.
591		 */
592		if ((!info->curr_node) ||
593		    !inode_eq_iversion(inode, file->f_version)) {
594			info->curr_node = NULL;
595			free_rb_tree_fname(&info->root);
596			file->f_version = inode_query_iversion(inode);
597			ret = ext4_htree_fill_tree(file, info->curr_hash,
598						   info->curr_minor_hash,
599						   &info->next_hash);
600			if (ret < 0)
601				goto finished;
602			if (ret == 0) {
603				ctx->pos = ext4_get_htree_eof(file);
604				break;
605			}
606			info->curr_node = rb_first(&info->root);
607		}
608
609		fname = rb_entry(info->curr_node, struct fname, rb_hash);
610		info->curr_hash = fname->hash;
611		info->curr_minor_hash = fname->minor_hash;
612		if (call_filldir(file, ctx, fname))
613			break;
614	next_node:
615		info->curr_node = rb_next(info->curr_node);
616		if (info->curr_node) {
617			fname = rb_entry(info->curr_node, struct fname,
618					 rb_hash);
619			info->curr_hash = fname->hash;
620			info->curr_minor_hash = fname->minor_hash;
621		} else {
622			if (info->next_hash == ~0) {
623				ctx->pos = ext4_get_htree_eof(file);
624				break;
625			}
626			info->curr_hash = info->next_hash;
627			info->curr_minor_hash = 0;
628		}
629	}
630finished:
631	info->last_pos = ctx->pos;
632	return ret < 0 ? ret : 0;
633}
634
635static int ext4_release_dir(struct inode *inode, struct file *filp)
636{
637	if (filp->private_data)
638		ext4_htree_free_dir_info(filp->private_data);
639
640	return 0;
641}
642
643int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
644		      int buf_size)
645{
646	struct ext4_dir_entry_2 *de;
647	int rlen;
648	unsigned int offset = 0;
649	char *top;
650
651	de = buf;
652	top = buf + buf_size;
653	while ((char *) de < top) {
654		if (ext4_check_dir_entry(dir, NULL, de, bh,
655					 buf, buf_size, offset))
656			return -EFSCORRUPTED;
657		rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
658		de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
659		offset += rlen;
660	}
661	if ((char *) de > top)
662		return -EFSCORRUPTED;
663
664	return 0;
665}
666
667const struct file_operations ext4_dir_operations = {
668	.llseek		= ext4_dir_llseek,
669	.read		= generic_read_dir,
670	.iterate_shared	= ext4_readdir,
671	.unlocked_ioctl = ext4_ioctl,
672#ifdef CONFIG_COMPAT
673	.compat_ioctl	= ext4_compat_ioctl,
674#endif
675	.fsync		= ext4_sync_file,
676	.release	= ext4_release_dir,
677};
678