dir.c

  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_feature_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 if (unlikely(next_offset == size && de->name_len == 1 &&
108			  de->name[0] == '.'))
109		error_msg = "'.' directory cannot be the last in data block";
110	else
111		return 0;
112
113	if (filp)
114		ext4_error_file(filp, function, line, bh->b_blocknr,
115				"bad entry in directory: %s - offset=%u, "
116				"inode=%u, rec_len=%d, size=%d fake=%d",
117				error_msg, offset, le32_to_cpu(de->inode),
118				rlen, size, fake);
119	else
120		ext4_error_inode(dir, function, line, bh->b_blocknr,
121				"bad entry in directory: %s - offset=%u, "
122				"inode=%u, rec_len=%d, size=%d fake=%d",
123				 error_msg, offset, le32_to_cpu(de->inode),
124				 rlen, size, fake);
125
126	return 1;
127}
128
129static int ext4_readdir(struct file *file, struct dir_context *ctx)
130{
131	unsigned int offset;
132	int i;
133	struct ext4_dir_entry_2 *de;
134	int err;
135	struct inode *inode = file_inode(file);
136	struct super_block *sb = inode->i_sb;
137	struct buffer_head *bh = NULL;
138	struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
139	struct dir_private_info *info = file->private_data;
140
141	err = fscrypt_prepare_readdir(inode);
142	if (err)
143		return err;
144
145	if (is_dx_dir(inode)) {
146		err = ext4_dx_readdir(file, ctx);
147		if (err != ERR_BAD_DX_DIR)
148			return err;
149
150		/* Can we just clear INDEX flag to ignore htree information? */
151		if (!ext4_has_feature_metadata_csum(sb)) {
152			/*
153			 * We don't set the inode dirty flag since it's not
154			 * critical that it gets flushed back to the disk.
155			 */
156			ext4_clear_inode_flag(inode, EXT4_INODE_INDEX);
157		}
158	}
159
160	if (ext4_has_inline_data(inode)) {
161		int has_inline_data = 1;
162		err = ext4_read_inline_dir(file, ctx,
163					   &has_inline_data);
164		if (has_inline_data)
165			return err;
166	}
167
168	if (IS_ENCRYPTED(inode)) {
169		err = fscrypt_fname_alloc_buffer(EXT4_NAME_LEN, &fstr);
170		if (err < 0)
171			return err;
172	}
173
174	while (ctx->pos < inode->i_size) {
175		struct ext4_map_blocks map;
176
177		if (fatal_signal_pending(current)) {
178			err = -ERESTARTSYS;
179			goto errout;
180		}
181		cond_resched();
182		offset = ctx->pos & (sb->s_blocksize - 1);
183		map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
184		map.m_len = 1;
185		err = ext4_map_blocks(NULL, inode, &map, 0);
186		if (err == 0) {
187			/* m_len should never be zero but let's avoid
188			 * an infinite loop if it somehow is */
189			if (map.m_len == 0)
190				map.m_len = 1;
191			ctx->pos += map.m_len * sb->s_blocksize;
192			continue;
193		}
194		if (err > 0) {
195			pgoff_t index = map.m_pblk << inode->i_blkbits >>
196					PAGE_SHIFT;
197			if (!ra_has_index(&file->f_ra, index))
198				page_cache_sync_readahead(
199					sb->s_bdev->bd_mapping,
200					&file->f_ra, file, index,
201					1 << EXT4_SB(sb)->s_min_folio_order);
202			file->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
203			bh = ext4_bread(NULL, inode, map.m_lblk, 0);
204			if (IS_ERR(bh)) {
205				err = PTR_ERR(bh);
206				bh = NULL;
207				goto errout;
208			}
209		}
210
211		if (!bh) {
212			/* corrupt size?  Maybe no more blocks to read */
213			if (ctx->pos > inode->i_blocks << 9)
214				break;
215			ctx->pos += sb->s_blocksize - offset;
216			continue;
217		}
218
219		/* Check the checksum */
220		if (!buffer_verified(bh) &&
221		    !ext4_dirblock_csum_verify(inode, bh)) {
222			EXT4_ERROR_FILE(file, 0, "directory fails checksum "
223					"at offset %llu",
224					(unsigned long long)ctx->pos);
225			ctx->pos += sb->s_blocksize - offset;
226			brelse(bh);
227			bh = NULL;
228			continue;
229		}
230		set_buffer_verified(bh);
231
232		/* If the dir block has changed since the last call to
233		 * readdir(2), then we might be pointing to an invalid
234		 * dirent right now.  Scan from the start of the block
235		 * to make sure. */
236		if (!inode_eq_iversion(inode, info->cookie)) {
237			for (i = 0; i < sb->s_blocksize && i < offset; ) {
238				de = (struct ext4_dir_entry_2 *)
239					(bh->b_data + i);
240				/* It's too expensive to do a full
241				 * dirent test each time round this
242				 * loop, but we do have to test at
243				 * least that it is non-zero.  A
244				 * failure will be detected in the
245				 * dirent test below. */
246				if (ext4_rec_len_from_disk(de->rec_len,
247					sb->s_blocksize) < ext4_dir_rec_len(1,
248									inode))
249					break;
250				i += ext4_rec_len_from_disk(de->rec_len,
251							    sb->s_blocksize);
252			}
253			offset = i;
254			ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
255				| offset;
256			info->cookie = inode_query_iversion(inode);
257		}
258
259		while (ctx->pos < inode->i_size
260		       && offset < sb->s_blocksize) {
261			de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
262			if (ext4_check_dir_entry(inode, file, de, bh,
263						 bh->b_data, bh->b_size,
264						 offset)) {
265				/*
266				 * On error, skip to the next block
267				 */
268				ctx->pos = (ctx->pos |
269						(sb->s_blocksize - 1)) + 1;
270				break;
271			}
272			offset += ext4_rec_len_from_disk(de->rec_len,
273					sb->s_blocksize);
274			if (le32_to_cpu(de->inode)) {
275				if (!IS_ENCRYPTED(inode)) {
276					if (!dir_emit(ctx, de->name,
277					    de->name_len,
278					    le32_to_cpu(de->inode),
279					    get_dtype(sb, de->file_type)))
280						goto done;
281				} else {
282					int save_len = fstr.len;
283					struct fscrypt_str de_name =
284							FSTR_INIT(de->name,
285								de->name_len);
286					u32 hash;
287					u32 minor_hash;
288
289					if (IS_CASEFOLDED(inode)) {
290						hash = EXT4_DIRENT_HASH(de);
291						minor_hash = EXT4_DIRENT_MINOR_HASH(de);
292					} else {
293						hash = 0;
294						minor_hash = 0;
295					}
296
297					/* Directory is encrypted */
298					err = fscrypt_fname_disk_to_usr(inode,
299						hash, minor_hash, &de_name, &fstr);
300					de_name = fstr;
301					fstr.len = save_len;
302					if (err)
303						goto errout;
304					if (!dir_emit(ctx,
305					    de_name.name, de_name.len,
306					    le32_to_cpu(de->inode),
307					    get_dtype(sb, de->file_type)))
308						goto done;
309				}
310			}
311			ctx->pos += ext4_rec_len_from_disk(de->rec_len,
312						sb->s_blocksize);
313		}
314		if ((ctx->pos < inode->i_size) && !dir_relax_shared(inode))
315			goto done;
316		brelse(bh);
317		bh = NULL;
318	}
319done:
320	err = 0;
321errout:
322	fscrypt_fname_free_buffer(&fstr);
323	brelse(bh);
324	return err;
325}
326
327static inline int is_32bit_api(void)
328{
329#ifdef CONFIG_COMPAT
330	return in_compat_syscall();
331#else
332	return (BITS_PER_LONG == 32);
333#endif
334}
335
336/*
337 * These functions convert from the major/minor hash to an f_pos
338 * value for dx directories
339 *
340 * Upper layer (for example NFS) should specify FMODE_32BITHASH or
341 * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
342 * directly on both 32-bit and 64-bit nodes, under such case, neither
343 * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
344 */
345static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
346{
347	if ((filp->f_mode & FMODE_32BITHASH) ||
348	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
349		return major >> 1;
350	else
351		return ((__u64)(major >> 1) << 32) | (__u64)minor;
352}
353
354static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
355{
356	if ((filp->f_mode & FMODE_32BITHASH) ||
357	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
358		return (pos << 1) & 0xffffffff;
359	else
360		return ((pos >> 32) << 1) & 0xffffffff;
361}
362
363static inline __u32 pos2min_hash(struct file *filp, loff_t pos)
364{
365	if ((filp->f_mode & FMODE_32BITHASH) ||
366	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
367		return 0;
368	else
369		return pos & 0xffffffff;
370}
371
372/*
373 * Return 32- or 64-bit end-of-file for dx directories
374 */
375static inline loff_t ext4_get_htree_eof(struct file *filp)
376{
377	if ((filp->f_mode & FMODE_32BITHASH) ||
378	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
379		return EXT4_HTREE_EOF_32BIT;
380	else
381		return EXT4_HTREE_EOF_64BIT;
382}
383
384
385/*
386 * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
387 * directories, where the "offset" is in terms of the filename hash
388 * value instead of the byte offset.
389 *
390 * Because we may return a 64-bit hash that is well beyond offset limits,
391 * we need to pass the max hash as the maximum allowable offset in
392 * the htree directory case.
393 *
394 * For non-htree, ext4_llseek already chooses the proper max offset.
395 */
396static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
397{
398	struct inode *inode = file->f_mapping->host;
399	struct dir_private_info *info = file->private_data;
400	int dx_dir = is_dx_dir(inode);
401	loff_t ret, htree_max = ext4_get_htree_eof(file);
402
403	if (likely(dx_dir))
404		ret = generic_file_llseek_size(file, offset, whence,
405						    htree_max, htree_max);
406	else
407		ret = ext4_llseek(file, offset, whence);
408	info->cookie = inode_peek_iversion(inode) - 1;
409	return ret;
410}
411
412/*
413 * This structure holds the nodes of the red-black tree used to store
414 * the directory entry in hash order.
415 */
416struct fname {
417	__u32		hash;
418	__u32		minor_hash;
419	struct rb_node	rb_hash;
420	struct fname	*next;
421	__u32		inode;
422	__u8		name_len;
423	__u8		file_type;
424	char		name[] __counted_by(name_len);
425};
426
427/*
428 * This function implements a non-recursive way of freeing all of the
429 * nodes in the red-black tree.
430 */
431static void free_rb_tree_fname(struct rb_root *root)
432{
433	struct fname *fname, *next;
434
435	rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
436		while (fname) {
437			struct fname *old = fname;
438			fname = fname->next;
439			kfree(old);
440		}
441
442	*root = RB_ROOT;
443}
444
445static void ext4_htree_init_dir_info(struct file *filp, loff_t pos)
446{
447	struct dir_private_info *p = filp->private_data;
448
449	if (is_dx_dir(file_inode(filp)) && !p->initialized) {
450		p->curr_hash = pos2maj_hash(filp, pos);
451		p->curr_minor_hash = pos2min_hash(filp, pos);
452		p->initialized = true;
453	}
454}
455
456void ext4_htree_free_dir_info(struct dir_private_info *p)
457{
458	free_rb_tree_fname(&p->root);
459	kfree(p);
460}
461
462/*
463 * Given a directory entry, enter it into the fname rb tree.
464 *
465 * When filename encryption is enabled, the dirent will hold the
466 * encrypted filename, while the htree will hold decrypted filename.
467 * The decrypted filename is passed in via ent_name.  parameter.
468 */
469int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
470			     __u32 minor_hash,
471			    struct ext4_dir_entry_2 *dirent,
472			    struct fscrypt_str *ent_name)
473{
474	struct rb_node **p, *parent = NULL;
475	struct fname *fname, *new_fn;
476	struct dir_private_info *info;
477
478	info = dir_file->private_data;
479	p = &info->root.rb_node;
480
481	/* Create and allocate the fname structure */
482	new_fn = kzalloc(struct_size(new_fn, name, ent_name->len + 1),
483			 GFP_KERNEL);
484	if (!new_fn)
485		return -ENOMEM;
486	new_fn->hash = hash;
487	new_fn->minor_hash = minor_hash;
488	new_fn->inode = le32_to_cpu(dirent->inode);
489	new_fn->name_len = ent_name->len;
490	new_fn->file_type = dirent->file_type;
491	memcpy(new_fn->name, ent_name->name, ent_name->len);
492
493	while (*p) {
494		parent = *p;
495		fname = rb_entry(parent, struct fname, rb_hash);
496
497		/*
498		 * If the hash and minor hash match up, then we put
499		 * them on a linked list.  This rarely happens...
500		 */
501		if ((new_fn->hash == fname->hash) &&
502		    (new_fn->minor_hash == fname->minor_hash)) {
503			new_fn->next = fname->next;
504			fname->next = new_fn;
505			return 0;
506		}
507
508		if (new_fn->hash < fname->hash)
509			p = &(*p)->rb_left;
510		else if (new_fn->hash > fname->hash)
511			p = &(*p)->rb_right;
512		else if (new_fn->minor_hash < fname->minor_hash)
513			p = &(*p)->rb_left;
514		else /* if (new_fn->minor_hash > fname->minor_hash) */
515			p = &(*p)->rb_right;
516	}
517
518	rb_link_node(&new_fn->rb_hash, parent, p);
519	rb_insert_color(&new_fn->rb_hash, &info->root);
520	return 0;
521}
522
523
524
525/*
526 * This is a helper function for ext4_dx_readdir.  It calls filldir
527 * for all entries on the fname linked list.  (Normally there is only
528 * one entry on the linked list, unless there are 62 bit hash collisions.)
529 */
530static int call_filldir(struct file *file, struct dir_context *ctx,
531			struct fname *fname)
532{
533	struct dir_private_info *info = file->private_data;
534	struct inode *inode = file_inode(file);
535	struct super_block *sb = inode->i_sb;
536
537	if (!fname) {
538		ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
539			 "called with null fname?!?", __func__, __LINE__,
540			 inode->i_ino, current->comm);
541		return 0;
542	}
543	ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
544	while (fname) {
545		if (!dir_emit(ctx, fname->name,
546				fname->name_len,
547				fname->inode,
548				get_dtype(sb, fname->file_type))) {
549			info->extra_fname = fname;
550			return 1;
551		}
552		fname = fname->next;
553	}
554	return 0;
555}
556
557static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
558{
559	struct dir_private_info *info = file->private_data;
560	struct inode *inode = file_inode(file);
561	struct fname *fname;
562	int ret = 0;
563
564	ext4_htree_init_dir_info(file, ctx->pos);
565
566	if (ctx->pos == ext4_get_htree_eof(file))
567		return 0;	/* EOF */
568
569	/* Some one has messed with f_pos; reset the world */
570	if (info->last_pos != ctx->pos) {
571		free_rb_tree_fname(&info->root);
572		info->curr_node = NULL;
573		info->extra_fname = NULL;
574		info->curr_hash = pos2maj_hash(file, ctx->pos);
575		info->curr_minor_hash = pos2min_hash(file, ctx->pos);
576	}
577
578	/*
579	 * If there are any leftover names on the hash collision
580	 * chain, return them first.
581	 */
582	if (info->extra_fname) {
583		if (call_filldir(file, ctx, info->extra_fname))
584			goto finished;
585		info->extra_fname = NULL;
586		goto next_node;
587	} else if (!info->curr_node)
588		info->curr_node = rb_first(&info->root);
589
590	while (1) {
591		/*
592		 * Fill the rbtree if we have no more entries,
593		 * or the inode has changed since we last read in the
594		 * cached entries.
595		 */
596		if ((!info->curr_node) ||
597		    !inode_eq_iversion(inode, info->cookie)) {
598			info->curr_node = NULL;
599			free_rb_tree_fname(&info->root);
600			info->cookie = inode_query_iversion(inode);
601			ret = ext4_htree_fill_tree(file, info->curr_hash,
602						   info->curr_minor_hash,
603						   &info->next_hash);
604			if (ret < 0)
605				goto finished;
606			if (ret == 0) {
607				ctx->pos = ext4_get_htree_eof(file);
608				break;
609			}
610			info->curr_node = rb_first(&info->root);
611		}
612
613		fname = rb_entry(info->curr_node, struct fname, rb_hash);
614		info->curr_hash = fname->hash;
615		info->curr_minor_hash = fname->minor_hash;
616		if (call_filldir(file, ctx, fname))
617			break;
618	next_node:
619		info->curr_node = rb_next(info->curr_node);
620		if (info->curr_node) {
621			fname = rb_entry(info->curr_node, struct fname,
622					 rb_hash);
623			info->curr_hash = fname->hash;
624			info->curr_minor_hash = fname->minor_hash;
625		} else {
626			if (info->next_hash == ~0) {
627				ctx->pos = ext4_get_htree_eof(file);
628				break;
629			}
630			info->curr_hash = info->next_hash;
631			info->curr_minor_hash = 0;
632		}
633	}
634finished:
635	info->last_pos = ctx->pos;
636	return ret < 0 ? ret : 0;
637}
638
639static int ext4_release_dir(struct inode *inode, struct file *filp)
640{
641	if (filp->private_data)
642		ext4_htree_free_dir_info(filp->private_data);
643
644	return 0;
645}
646
647int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
648		      int buf_size)
649{
650	struct ext4_dir_entry_2 *de;
651	int rlen;
652	unsigned int offset = 0;
653	char *top;
654
655	de = buf;
656	top = buf + buf_size;
657	while ((char *) de < top) {
658		if (ext4_check_dir_entry(dir, NULL, de, bh,
659					 buf, buf_size, offset))
660			return -EFSCORRUPTED;
661		rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
662		de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
663		offset += rlen;
664	}
665	if ((char *) de > top)
666		return -EFSCORRUPTED;
667
668	return 0;
669}
670
671static int ext4_dir_open(struct inode *inode, struct file *file)
672{
673	struct dir_private_info *info;
674
675	info = kzalloc(sizeof(*info), GFP_KERNEL);
676	if (!info)
677		return -ENOMEM;
678	file->private_data = info;
679	return 0;
680}
681
682const struct file_operations ext4_dir_operations = {
683	.open		= ext4_dir_open,
684	.llseek		= ext4_dir_llseek,
685	.read		= generic_read_dir,
686	.iterate_shared	= ext4_readdir,
687	.unlocked_ioctl = ext4_ioctl,
688#ifdef CONFIG_COMPAT
689	.compat_ioctl	= ext4_compat_ioctl,
690#endif
691	.fsync		= ext4_sync_file,
692	.release	= ext4_release_dir,
693};