xref: /openbmc/linux/fs/ext4/dir.c (revision 7587eb18)
1 /*
2  *  linux/fs/ext4/dir.c
3  *
4  * Copyright (C) 1992, 1993, 1994, 1995
5  * Remy Card (card@masi.ibp.fr)
6  * Laboratoire MASI - Institut Blaise Pascal
7  * Universite Pierre et Marie Curie (Paris VI)
8  *
9  *  from
10  *
11  *  linux/fs/minix/dir.c
12  *
13  *  Copyright (C) 1991, 1992  Linus Torvalds
14  *
15  *  ext4 directory handling functions
16  *
17  *  Big-endian to little-endian byte-swapping/bitmaps by
18  *        David S. Miller (davem@caip.rutgers.edu), 1995
19  *
20  * Hash Tree Directory indexing (c) 2001  Daniel Phillips
21  *
22  */
23 
24 #include <linux/fs.h>
25 #include <linux/buffer_head.h>
26 #include <linux/slab.h>
27 #include "ext4.h"
28 #include "xattr.h"
29 
30 static int ext4_dx_readdir(struct file *, struct dir_context *);
31 
32 /**
33  * Check if the given dir-inode refers to an htree-indexed directory
34  * (or a directory which could potentially get converted to use htree
35  * indexing).
36  *
37  * Return 1 if it is a dx dir, 0 if not
38  */
39 static int is_dx_dir(struct inode *inode)
40 {
41 	struct super_block *sb = inode->i_sb;
42 
43 	if (ext4_has_feature_dir_index(inode->i_sb) &&
44 	    ((ext4_test_inode_flag(inode, EXT4_INODE_INDEX)) ||
45 	     ((inode->i_size >> sb->s_blocksize_bits) == 1) ||
46 	     ext4_has_inline_data(inode)))
47 		return 1;
48 
49 	return 0;
50 }
51 
52 /*
53  * Return 0 if the directory entry is OK, and 1 if there is a problem
54  *
55  * Note: this is the opposite of what ext2 and ext3 historically returned...
56  *
57  * bh passed here can be an inode block or a dir data block, depending
58  * on the inode inline data flag.
59  */
60 int __ext4_check_dir_entry(const char *function, unsigned int line,
61 			   struct inode *dir, struct file *filp,
62 			   struct ext4_dir_entry_2 *de,
63 			   struct buffer_head *bh, char *buf, int size,
64 			   unsigned int offset)
65 {
66 	const char *error_msg = NULL;
67 	const int rlen = ext4_rec_len_from_disk(de->rec_len,
68 						dir->i_sb->s_blocksize);
69 
70 	if (unlikely(rlen < EXT4_DIR_REC_LEN(1)))
71 		error_msg = "rec_len is smaller than minimal";
72 	else if (unlikely(rlen % 4 != 0))
73 		error_msg = "rec_len % 4 != 0";
74 	else if (unlikely(rlen < EXT4_DIR_REC_LEN(de->name_len)))
75 		error_msg = "rec_len is too small for name_len";
76 	else if (unlikely(((char *) de - buf) + rlen > size))
77 		error_msg = "directory entry across range";
78 	else if (unlikely(le32_to_cpu(de->inode) >
79 			le32_to_cpu(EXT4_SB(dir->i_sb)->s_es->s_inodes_count)))
80 		error_msg = "inode out of bounds";
81 	else
82 		return 0;
83 
84 	if (filp)
85 		ext4_error_file(filp, function, line, bh->b_blocknr,
86 				"bad entry in directory: %s - offset=%u(%u), "
87 				"inode=%u, rec_len=%d, name_len=%d",
88 				error_msg, (unsigned) (offset % size),
89 				offset, le32_to_cpu(de->inode),
90 				rlen, de->name_len);
91 	else
92 		ext4_error_inode(dir, function, line, bh->b_blocknr,
93 				"bad entry in directory: %s - offset=%u(%u), "
94 				"inode=%u, rec_len=%d, name_len=%d",
95 				error_msg, (unsigned) (offset % size),
96 				offset, le32_to_cpu(de->inode),
97 				rlen, de->name_len);
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 ext4_str fname_crypto_str = {.name = NULL, .len = 0};
113 
114 	if (ext4_encrypted_inode(inode)) {
115 		err = ext4_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 = ext4_fname_crypto_alloc_buffer(inode, EXT4_NAME_LEN,
143 						     &fname_crypto_str);
144 		if (err < 0)
145 			return err;
146 	}
147 
148 	offset = ctx->pos & (sb->s_blocksize - 1);
149 
150 	while (ctx->pos < inode->i_size) {
151 		struct ext4_map_blocks map;
152 
153 		if (fatal_signal_pending(current)) {
154 			err = -ERESTARTSYS;
155 			goto errout;
156 		}
157 		cond_resched();
158 		map.m_lblk = ctx->pos >> EXT4_BLOCK_SIZE_BITS(sb);
159 		map.m_len = 1;
160 		err = ext4_map_blocks(NULL, inode, &map, 0);
161 		if (err > 0) {
162 			pgoff_t index = map.m_pblk >>
163 					(PAGE_SHIFT - inode->i_blkbits);
164 			if (!ra_has_index(&file->f_ra, index))
165 				page_cache_sync_readahead(
166 					sb->s_bdev->bd_inode->i_mapping,
167 					&file->f_ra, file,
168 					index, 1);
169 			file->f_ra.prev_pos = (loff_t)index << PAGE_SHIFT;
170 			bh = ext4_bread(NULL, inode, map.m_lblk, 0);
171 			if (IS_ERR(bh)) {
172 				err = PTR_ERR(bh);
173 				bh = NULL;
174 				goto errout;
175 			}
176 		}
177 
178 		if (!bh) {
179 			if (!dir_has_error) {
180 				EXT4_ERROR_FILE(file, 0,
181 						"directory contains a "
182 						"hole at offset %llu",
183 					   (unsigned long long) ctx->pos);
184 				dir_has_error = 1;
185 			}
186 			/* corrupt size?  Maybe no more blocks to read */
187 			if (ctx->pos > inode->i_blocks << 9)
188 				break;
189 			ctx->pos += sb->s_blocksize - offset;
190 			continue;
191 		}
192 
193 		/* Check the checksum */
194 		if (!buffer_verified(bh) &&
195 		    !ext4_dirent_csum_verify(inode,
196 				(struct ext4_dir_entry *)bh->b_data)) {
197 			EXT4_ERROR_FILE(file, 0, "directory fails checksum "
198 					"at offset %llu",
199 					(unsigned long long)ctx->pos);
200 			ctx->pos += sb->s_blocksize - offset;
201 			brelse(bh);
202 			bh = NULL;
203 			continue;
204 		}
205 		set_buffer_verified(bh);
206 
207 		/* If the dir block has changed since the last call to
208 		 * readdir(2), then we might be pointing to an invalid
209 		 * dirent right now.  Scan from the start of the block
210 		 * to make sure. */
211 		if (file->f_version != inode->i_version) {
212 			for (i = 0; i < sb->s_blocksize && i < offset; ) {
213 				de = (struct ext4_dir_entry_2 *)
214 					(bh->b_data + i);
215 				/* It's too expensive to do a full
216 				 * dirent test each time round this
217 				 * loop, but we do have to test at
218 				 * least that it is non-zero.  A
219 				 * failure will be detected in the
220 				 * dirent test below. */
221 				if (ext4_rec_len_from_disk(de->rec_len,
222 					sb->s_blocksize) < EXT4_DIR_REC_LEN(1))
223 					break;
224 				i += ext4_rec_len_from_disk(de->rec_len,
225 							    sb->s_blocksize);
226 			}
227 			offset = i;
228 			ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1))
229 				| offset;
230 			file->f_version = inode->i_version;
231 		}
232 
233 		while (ctx->pos < inode->i_size
234 		       && offset < sb->s_blocksize) {
235 			de = (struct ext4_dir_entry_2 *) (bh->b_data + offset);
236 			if (ext4_check_dir_entry(inode, file, de, bh,
237 						 bh->b_data, bh->b_size,
238 						 offset)) {
239 				/*
240 				 * On error, skip to the next block
241 				 */
242 				ctx->pos = (ctx->pos |
243 						(sb->s_blocksize - 1)) + 1;
244 				break;
245 			}
246 			offset += ext4_rec_len_from_disk(de->rec_len,
247 					sb->s_blocksize);
248 			if (le32_to_cpu(de->inode)) {
249 				if (!ext4_encrypted_inode(inode)) {
250 					if (!dir_emit(ctx, de->name,
251 					    de->name_len,
252 					    le32_to_cpu(de->inode),
253 					    get_dtype(sb, de->file_type)))
254 						goto done;
255 				} else {
256 					int save_len = fname_crypto_str.len;
257 
258 					/* Directory is encrypted */
259 					err = ext4_fname_disk_to_usr(inode,
260 						NULL, de, &fname_crypto_str);
261 					fname_crypto_str.len = save_len;
262 					if (err < 0)
263 						goto errout;
264 					if (!dir_emit(ctx,
265 					    fname_crypto_str.name, err,
266 					    le32_to_cpu(de->inode),
267 					    get_dtype(sb, de->file_type)))
268 						goto done;
269 				}
270 			}
271 			ctx->pos += ext4_rec_len_from_disk(de->rec_len,
272 						sb->s_blocksize);
273 		}
274 		if ((ctx->pos < inode->i_size) && !dir_relax_shared(inode))
275 			goto done;
276 		brelse(bh);
277 		bh = NULL;
278 		offset = 0;
279 	}
280 done:
281 	err = 0;
282 errout:
283 #ifdef CONFIG_EXT4_FS_ENCRYPTION
284 	ext4_fname_crypto_free_buffer(&fname_crypto_str);
285 #endif
286 	brelse(bh);
287 	return err;
288 }
289 
290 static inline int is_32bit_api(void)
291 {
292 #ifdef CONFIG_COMPAT
293 	return in_compat_syscall();
294 #else
295 	return (BITS_PER_LONG == 32);
296 #endif
297 }
298 
299 /*
300  * These functions convert from the major/minor hash to an f_pos
301  * value for dx directories
302  *
303  * Upper layer (for example NFS) should specify FMODE_32BITHASH or
304  * FMODE_64BITHASH explicitly. On the other hand, we allow ext4 to be mounted
305  * directly on both 32-bit and 64-bit nodes, under such case, neither
306  * FMODE_32BITHASH nor FMODE_64BITHASH is specified.
307  */
308 static inline loff_t hash2pos(struct file *filp, __u32 major, __u32 minor)
309 {
310 	if ((filp->f_mode & FMODE_32BITHASH) ||
311 	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
312 		return major >> 1;
313 	else
314 		return ((__u64)(major >> 1) << 32) | (__u64)minor;
315 }
316 
317 static inline __u32 pos2maj_hash(struct file *filp, loff_t pos)
318 {
319 	if ((filp->f_mode & FMODE_32BITHASH) ||
320 	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
321 		return (pos << 1) & 0xffffffff;
322 	else
323 		return ((pos >> 32) << 1) & 0xffffffff;
324 }
325 
326 static inline __u32 pos2min_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 0;
331 	else
332 		return pos & 0xffffffff;
333 }
334 
335 /*
336  * Return 32- or 64-bit end-of-file for dx directories
337  */
338 static inline loff_t ext4_get_htree_eof(struct file *filp)
339 {
340 	if ((filp->f_mode & FMODE_32BITHASH) ||
341 	    (!(filp->f_mode & FMODE_64BITHASH) && is_32bit_api()))
342 		return EXT4_HTREE_EOF_32BIT;
343 	else
344 		return EXT4_HTREE_EOF_64BIT;
345 }
346 
347 
348 /*
349  * ext4_dir_llseek() calls generic_file_llseek_size to handle htree
350  * directories, where the "offset" is in terms of the filename hash
351  * value instead of the byte offset.
352  *
353  * Because we may return a 64-bit hash that is well beyond offset limits,
354  * we need to pass the max hash as the maximum allowable offset in
355  * the htree directory case.
356  *
357  * For non-htree, ext4_llseek already chooses the proper max offset.
358  */
359 static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence)
360 {
361 	struct inode *inode = file->f_mapping->host;
362 	int dx_dir = is_dx_dir(inode);
363 	loff_t htree_max = ext4_get_htree_eof(file);
364 
365 	if (likely(dx_dir))
366 		return generic_file_llseek_size(file, offset, whence,
367 						    htree_max, htree_max);
368 	else
369 		return ext4_llseek(file, offset, whence);
370 }
371 
372 /*
373  * This structure holds the nodes of the red-black tree used to store
374  * the directory entry in hash order.
375  */
376 struct fname {
377 	__u32		hash;
378 	__u32		minor_hash;
379 	struct rb_node	rb_hash;
380 	struct fname	*next;
381 	__u32		inode;
382 	__u8		name_len;
383 	__u8		file_type;
384 	char		name[0];
385 };
386 
387 /*
388  * This functoin implements a non-recursive way of freeing all of the
389  * nodes in the red-black tree.
390  */
391 static void free_rb_tree_fname(struct rb_root *root)
392 {
393 	struct fname *fname, *next;
394 
395 	rbtree_postorder_for_each_entry_safe(fname, next, root, rb_hash)
396 		while (fname) {
397 			struct fname *old = fname;
398 			fname = fname->next;
399 			kfree(old);
400 		}
401 
402 	*root = RB_ROOT;
403 }
404 
405 
406 static struct dir_private_info *ext4_htree_create_dir_info(struct file *filp,
407 							   loff_t pos)
408 {
409 	struct dir_private_info *p;
410 
411 	p = kzalloc(sizeof(struct dir_private_info), GFP_KERNEL);
412 	if (!p)
413 		return NULL;
414 	p->curr_hash = pos2maj_hash(filp, pos);
415 	p->curr_minor_hash = pos2min_hash(filp, pos);
416 	return p;
417 }
418 
419 void ext4_htree_free_dir_info(struct dir_private_info *p)
420 {
421 	free_rb_tree_fname(&p->root);
422 	kfree(p);
423 }
424 
425 /*
426  * Given a directory entry, enter it into the fname rb tree.
427  *
428  * When filename encryption is enabled, the dirent will hold the
429  * encrypted filename, while the htree will hold decrypted filename.
430  * The decrypted filename is passed in via ent_name.  parameter.
431  */
432 int ext4_htree_store_dirent(struct file *dir_file, __u32 hash,
433 			     __u32 minor_hash,
434 			    struct ext4_dir_entry_2 *dirent,
435 			    struct ext4_str *ent_name)
436 {
437 	struct rb_node **p, *parent = NULL;
438 	struct fname *fname, *new_fn;
439 	struct dir_private_info *info;
440 	int len;
441 
442 	info = dir_file->private_data;
443 	p = &info->root.rb_node;
444 
445 	/* Create and allocate the fname structure */
446 	len = sizeof(struct fname) + ent_name->len + 1;
447 	new_fn = kzalloc(len, GFP_KERNEL);
448 	if (!new_fn)
449 		return -ENOMEM;
450 	new_fn->hash = hash;
451 	new_fn->minor_hash = minor_hash;
452 	new_fn->inode = le32_to_cpu(dirent->inode);
453 	new_fn->name_len = ent_name->len;
454 	new_fn->file_type = dirent->file_type;
455 	memcpy(new_fn->name, ent_name->name, ent_name->len);
456 	new_fn->name[ent_name->len] = 0;
457 
458 	while (*p) {
459 		parent = *p;
460 		fname = rb_entry(parent, struct fname, rb_hash);
461 
462 		/*
463 		 * If the hash and minor hash match up, then we put
464 		 * them on a linked list.  This rarely happens...
465 		 */
466 		if ((new_fn->hash == fname->hash) &&
467 		    (new_fn->minor_hash == fname->minor_hash)) {
468 			new_fn->next = fname->next;
469 			fname->next = new_fn;
470 			return 0;
471 		}
472 
473 		if (new_fn->hash < fname->hash)
474 			p = &(*p)->rb_left;
475 		else if (new_fn->hash > fname->hash)
476 			p = &(*p)->rb_right;
477 		else if (new_fn->minor_hash < fname->minor_hash)
478 			p = &(*p)->rb_left;
479 		else /* if (new_fn->minor_hash > fname->minor_hash) */
480 			p = &(*p)->rb_right;
481 	}
482 
483 	rb_link_node(&new_fn->rb_hash, parent, p);
484 	rb_insert_color(&new_fn->rb_hash, &info->root);
485 	return 0;
486 }
487 
488 
489 
490 /*
491  * This is a helper function for ext4_dx_readdir.  It calls filldir
492  * for all entres on the fname linked list.  (Normally there is only
493  * one entry on the linked list, unless there are 62 bit hash collisions.)
494  */
495 static int call_filldir(struct file *file, struct dir_context *ctx,
496 			struct fname *fname)
497 {
498 	struct dir_private_info *info = file->private_data;
499 	struct inode *inode = file_inode(file);
500 	struct super_block *sb = inode->i_sb;
501 
502 	if (!fname) {
503 		ext4_msg(sb, KERN_ERR, "%s:%d: inode #%lu: comm %s: "
504 			 "called with null fname?!?", __func__, __LINE__,
505 			 inode->i_ino, current->comm);
506 		return 0;
507 	}
508 	ctx->pos = hash2pos(file, fname->hash, fname->minor_hash);
509 	while (fname) {
510 		if (!dir_emit(ctx, fname->name,
511 				fname->name_len,
512 				fname->inode,
513 				get_dtype(sb, fname->file_type))) {
514 			info->extra_fname = fname;
515 			return 1;
516 		}
517 		fname = fname->next;
518 	}
519 	return 0;
520 }
521 
522 static int ext4_dx_readdir(struct file *file, struct dir_context *ctx)
523 {
524 	struct dir_private_info *info = file->private_data;
525 	struct inode *inode = file_inode(file);
526 	struct fname *fname;
527 	int	ret;
528 
529 	if (!info) {
530 		info = ext4_htree_create_dir_info(file, ctx->pos);
531 		if (!info)
532 			return -ENOMEM;
533 		file->private_data = info;
534 	}
535 
536 	if (ctx->pos == ext4_get_htree_eof(file))
537 		return 0;	/* EOF */
538 
539 	/* Some one has messed with f_pos; reset the world */
540 	if (info->last_pos != ctx->pos) {
541 		free_rb_tree_fname(&info->root);
542 		info->curr_node = NULL;
543 		info->extra_fname = NULL;
544 		info->curr_hash = pos2maj_hash(file, ctx->pos);
545 		info->curr_minor_hash = pos2min_hash(file, ctx->pos);
546 	}
547 
548 	/*
549 	 * If there are any leftover names on the hash collision
550 	 * chain, return them first.
551 	 */
552 	if (info->extra_fname) {
553 		if (call_filldir(file, ctx, info->extra_fname))
554 			goto finished;
555 		info->extra_fname = NULL;
556 		goto next_node;
557 	} else if (!info->curr_node)
558 		info->curr_node = rb_first(&info->root);
559 
560 	while (1) {
561 		/*
562 		 * Fill the rbtree if we have no more entries,
563 		 * or the inode has changed since we last read in the
564 		 * cached entries.
565 		 */
566 		if ((!info->curr_node) ||
567 		    (file->f_version != inode->i_version)) {
568 			info->curr_node = NULL;
569 			free_rb_tree_fname(&info->root);
570 			file->f_version = inode->i_version;
571 			ret = ext4_htree_fill_tree(file, info->curr_hash,
572 						   info->curr_minor_hash,
573 						   &info->next_hash);
574 			if (ret < 0)
575 				return ret;
576 			if (ret == 0) {
577 				ctx->pos = ext4_get_htree_eof(file);
578 				break;
579 			}
580 			info->curr_node = rb_first(&info->root);
581 		}
582 
583 		fname = rb_entry(info->curr_node, struct fname, rb_hash);
584 		info->curr_hash = fname->hash;
585 		info->curr_minor_hash = fname->minor_hash;
586 		if (call_filldir(file, ctx, fname))
587 			break;
588 	next_node:
589 		info->curr_node = rb_next(info->curr_node);
590 		if (info->curr_node) {
591 			fname = rb_entry(info->curr_node, struct fname,
592 					 rb_hash);
593 			info->curr_hash = fname->hash;
594 			info->curr_minor_hash = fname->minor_hash;
595 		} else {
596 			if (info->next_hash == ~0) {
597 				ctx->pos = ext4_get_htree_eof(file);
598 				break;
599 			}
600 			info->curr_hash = info->next_hash;
601 			info->curr_minor_hash = 0;
602 		}
603 	}
604 finished:
605 	info->last_pos = ctx->pos;
606 	return 0;
607 }
608 
609 static int ext4_dir_open(struct inode * inode, struct file * filp)
610 {
611 	if (ext4_encrypted_inode(inode))
612 		return ext4_get_encryption_info(inode) ? -EACCES : 0;
613 	return 0;
614 }
615 
616 static int ext4_release_dir(struct inode *inode, struct file *filp)
617 {
618 	if (filp->private_data)
619 		ext4_htree_free_dir_info(filp->private_data);
620 
621 	return 0;
622 }
623 
624 int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
625 		      int buf_size)
626 {
627 	struct ext4_dir_entry_2 *de;
628 	int nlen, rlen;
629 	unsigned int offset = 0;
630 	char *top;
631 
632 	de = (struct ext4_dir_entry_2 *)buf;
633 	top = buf + buf_size;
634 	while ((char *) de < top) {
635 		if (ext4_check_dir_entry(dir, NULL, de, bh,
636 					 buf, buf_size, offset))
637 			return -EFSCORRUPTED;
638 		nlen = EXT4_DIR_REC_LEN(de->name_len);
639 		rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
640 		de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
641 		offset += rlen;
642 	}
643 	if ((char *) de > top)
644 		return -EFSCORRUPTED;
645 
646 	return 0;
647 }
648 
649 const struct file_operations ext4_dir_operations = {
650 	.llseek		= ext4_dir_llseek,
651 	.read		= generic_read_dir,
652 	.iterate_shared	= ext4_readdir,
653 	.unlocked_ioctl = ext4_ioctl,
654 #ifdef CONFIG_COMPAT
655 	.compat_ioctl	= ext4_compat_ioctl,
656 #endif
657 	.fsync		= ext4_sync_file,
658 	.open		= ext4_dir_open,
659 	.release	= ext4_release_dir,
660 };
661