1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *  linux/fs/ext2/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 *  ext2 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 * All code that works with directory layout had been switched to pagecache
 22 * and moved here. AV
 23 */
 24
 25#include "ext2.h"
 26#include <linux/buffer_head.h>
 27#include <linux/pagemap.h>
 28#include <linux/swap.h>
 29#include <linux/iversion.h>
 30
 31typedef struct ext2_dir_entry_2 ext2_dirent;
 32
 33/*
 34 * Tests against MAX_REC_LEN etc were put in place for 64k block
 35 * sizes; if that is not possible on this arch, we can skip
 36 * those tests and speed things up.
 37 */
 38static inline unsigned ext2_rec_len_from_disk(__le16 dlen)
 39{
 40	unsigned len = le16_to_cpu(dlen);
 41
 42#if (PAGE_SIZE >= 65536)
 43	if (len == EXT2_MAX_REC_LEN)
 44		return 1 << 16;
 45#endif
 46	return len;
 47}
 48
 49static inline __le16 ext2_rec_len_to_disk(unsigned len)
 50{
 51#if (PAGE_SIZE >= 65536)
 52	if (len == (1 << 16))
 53		return cpu_to_le16(EXT2_MAX_REC_LEN);
 54	else
 55		BUG_ON(len > (1 << 16));
 56#endif
 57	return cpu_to_le16(len);
 58}
 59
 60/*
 61 * ext2 uses block-sized chunks. Arguably, sector-sized ones would be
 62 * more robust, but we have what we have
 63 */
 64static inline unsigned ext2_chunk_size(struct inode *inode)
 65{
 66	return inode->i_sb->s_blocksize;
 67}
 68
 69static inline void ext2_put_page(struct page *page)
 70{
 71	kunmap(page);
 72	put_page(page);
 73}
 74
 75/*
 76 * Return the offset into page `page_nr' of the last valid
 77 * byte in that page, plus one.
 78 */
 79static unsigned
 80ext2_last_byte(struct inode *inode, unsigned long page_nr)
 81{
 82	unsigned last_byte = inode->i_size;
 83
 84	last_byte -= page_nr << PAGE_SHIFT;
 85	if (last_byte > PAGE_SIZE)
 86		last_byte = PAGE_SIZE;
 87	return last_byte;
 88}
 89
 90static int ext2_commit_chunk(struct page *page, loff_t pos, unsigned len)
 91{
 92	struct address_space *mapping = page->mapping;
 93	struct inode *dir = mapping->host;
 94	int err = 0;
 95
 96	inode_inc_iversion(dir);
 97	block_write_end(NULL, mapping, pos, len, len, page, NULL);
 98
 99	if (pos+len > dir->i_size) {
100		i_size_write(dir, pos+len);
101		mark_inode_dirty(dir);
102	}
103
104	if (IS_DIRSYNC(dir)) {
105		err = write_one_page(page);
106		if (!err)
107			err = sync_inode_metadata(dir, 1);
108	} else {
109		unlock_page(page);
110	}
111
112	return err;
113}
114
115static bool ext2_check_page(struct page *page, int quiet)
116{
117	struct inode *dir = page->mapping->host;
118	struct super_block *sb = dir->i_sb;
119	unsigned chunk_size = ext2_chunk_size(dir);
120	char *kaddr = page_address(page);
121	u32 max_inumber = le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count);
122	unsigned offs, rec_len;
123	unsigned limit = PAGE_SIZE;
124	ext2_dirent *p;
125	char *error;
126
127	if ((dir->i_size >> PAGE_SHIFT) == page->index) {
128		limit = dir->i_size & ~PAGE_MASK;
129		if (limit & (chunk_size - 1))
130			goto Ebadsize;
131		if (!limit)
132			goto out;
133	}
134	for (offs = 0; offs <= limit - EXT2_DIR_REC_LEN(1); offs += rec_len) {
135		p = (ext2_dirent *)(kaddr + offs);
136		rec_len = ext2_rec_len_from_disk(p->rec_len);
137
138		if (unlikely(rec_len < EXT2_DIR_REC_LEN(1)))
139			goto Eshort;
140		if (unlikely(rec_len & 3))
141			goto Ealign;
142		if (unlikely(rec_len < EXT2_DIR_REC_LEN(p->name_len)))
143			goto Enamelen;
144		if (unlikely(((offs + rec_len - 1) ^ offs) & ~(chunk_size-1)))
145			goto Espan;
146		if (unlikely(le32_to_cpu(p->inode) > max_inumber))
147			goto Einumber;
148	}
149	if (offs != limit)
150		goto Eend;
151out:
152	SetPageChecked(page);
153	return true;
154
155	/* Too bad, we had an error */
156
157Ebadsize:
158	if (!quiet)
159		ext2_error(sb, __func__,
160			"size of directory #%lu is not a multiple "
161			"of chunk size", dir->i_ino);
162	goto fail;
163Eshort:
164	error = "rec_len is smaller than minimal";
165	goto bad_entry;
166Ealign:
167	error = "unaligned directory entry";
168	goto bad_entry;
169Enamelen:
170	error = "rec_len is too small for name_len";
171	goto bad_entry;
172Espan:
173	error = "directory entry across blocks";
174	goto bad_entry;
175Einumber:
176	error = "inode out of bounds";
177bad_entry:
178	if (!quiet)
179		ext2_error(sb, __func__, "bad entry in directory #%lu: : %s - "
180			"offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
181			dir->i_ino, error, (page->index<<PAGE_SHIFT)+offs,
182			(unsigned long) le32_to_cpu(p->inode),
183			rec_len, p->name_len);
184	goto fail;
185Eend:
186	if (!quiet) {
187		p = (ext2_dirent *)(kaddr + offs);
188		ext2_error(sb, "ext2_check_page",
189			"entry in directory #%lu spans the page boundary"
190			"offset=%lu, inode=%lu",
191			dir->i_ino, (page->index<<PAGE_SHIFT)+offs,
192			(unsigned long) le32_to_cpu(p->inode));
193	}
194fail:
195	SetPageError(page);
196	return false;
197}
198
199static struct page * ext2_get_page(struct inode *dir, unsigned long n,
200				   int quiet)
201{
202	struct address_space *mapping = dir->i_mapping;
203	struct page *page = read_mapping_page(mapping, n, NULL);
204	if (!IS_ERR(page)) {
205		kmap(page);
206		if (unlikely(!PageChecked(page))) {
207			if (PageError(page) || !ext2_check_page(page, quiet))
208				goto fail;
209		}
210	}
211	return page;
212
213fail:
214	ext2_put_page(page);
215	return ERR_PTR(-EIO);
216}
217
218/*
219 * NOTE! unlike strncmp, ext2_match returns 1 for success, 0 for failure.
220 *
221 * len <= EXT2_NAME_LEN and de != NULL are guaranteed by caller.
222 */
223static inline int ext2_match (int len, const char * const name,
224					struct ext2_dir_entry_2 * de)
225{
226	if (len != de->name_len)
227		return 0;
228	if (!de->inode)
229		return 0;
230	return !memcmp(name, de->name, len);
231}
232
233/*
234 * p is at least 6 bytes before the end of page
235 */
236static inline ext2_dirent *ext2_next_entry(ext2_dirent *p)
237{
238	return (ext2_dirent *)((char *)p +
239			ext2_rec_len_from_disk(p->rec_len));
240}
241
242static inline unsigned 
243ext2_validate_entry(char *base, unsigned offset, unsigned mask)
244{
245	ext2_dirent *de = (ext2_dirent*)(base + offset);
246	ext2_dirent *p = (ext2_dirent*)(base + (offset&mask));
247	while ((char*)p < (char*)de) {
248		if (p->rec_len == 0)
249			break;
250		p = ext2_next_entry(p);
251	}
252	return (char *)p - base;
253}
254
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
255static inline void ext2_set_de_type(ext2_dirent *de, struct inode *inode)
256{
 
257	if (EXT2_HAS_INCOMPAT_FEATURE(inode->i_sb, EXT2_FEATURE_INCOMPAT_FILETYPE))
258		de->file_type = fs_umode_to_ftype(inode->i_mode);
259	else
260		de->file_type = 0;
261}
262
263static int
264ext2_readdir(struct file *file, struct dir_context *ctx)
265{
266	loff_t pos = ctx->pos;
267	struct inode *inode = file_inode(file);
268	struct super_block *sb = inode->i_sb;
269	unsigned int offset = pos & ~PAGE_MASK;
270	unsigned long n = pos >> PAGE_SHIFT;
271	unsigned long npages = dir_pages(inode);
272	unsigned chunk_mask = ~(ext2_chunk_size(inode)-1);
 
273	bool need_revalidate = !inode_eq_iversion(inode, file->f_version);
274	bool has_filetype;
275
276	if (pos > inode->i_size - EXT2_DIR_REC_LEN(1))
277		return 0;
278
279	has_filetype =
280		EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE);
281
282	for ( ; n < npages; n++, offset = 0) {
283		char *kaddr, *limit;
284		ext2_dirent *de;
285		struct page *page = ext2_get_page(inode, n, 0);
286
287		if (IS_ERR(page)) {
288			ext2_error(sb, __func__,
289				   "bad page in #%lu",
290				   inode->i_ino);
291			ctx->pos += PAGE_SIZE - offset;
292			return PTR_ERR(page);
293		}
294		kaddr = page_address(page);
295		if (unlikely(need_revalidate)) {
296			if (offset) {
297				offset = ext2_validate_entry(kaddr, offset, chunk_mask);
298				ctx->pos = (n<<PAGE_SHIFT) + offset;
299			}
300			file->f_version = inode_query_iversion(inode);
301			need_revalidate = false;
302		}
303		de = (ext2_dirent *)(kaddr+offset);
304		limit = kaddr + ext2_last_byte(inode, n) - EXT2_DIR_REC_LEN(1);
305		for ( ;(char*)de <= limit; de = ext2_next_entry(de)) {
306			if (de->rec_len == 0) {
307				ext2_error(sb, __func__,
308					"zero-length directory entry");
309				ext2_put_page(page);
310				return -EIO;
311			}
312			if (de->inode) {
313				unsigned char d_type = DT_UNKNOWN;
314
315				if (has_filetype)
316					d_type = fs_ftype_to_dtype(de->file_type);
317
318				if (!dir_emit(ctx, de->name, de->name_len,
319						le32_to_cpu(de->inode),
320						d_type)) {
321					ext2_put_page(page);
322					return 0;
323				}
324			}
325			ctx->pos += ext2_rec_len_from_disk(de->rec_len);
326		}
327		ext2_put_page(page);
328	}
329	return 0;
330}
331
332/*
333 *	ext2_find_entry()
334 *
335 * finds an entry in the specified directory with the wanted name. It
336 * returns the page in which the entry was found (as a parameter - res_page),
337 * and the entry itself. Page is returned mapped and unlocked.
338 * Entry is guaranteed to be valid.
339 */
340struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
341			const struct qstr *child, struct page **res_page)
342{
343	const char *name = child->name;
344	int namelen = child->len;
345	unsigned reclen = EXT2_DIR_REC_LEN(namelen);
346	unsigned long start, n;
347	unsigned long npages = dir_pages(dir);
348	struct page *page = NULL;
349	struct ext2_inode_info *ei = EXT2_I(dir);
350	ext2_dirent * de;
351	int dir_has_error = 0;
352
353	if (npages == 0)
354		goto out;
355
356	/* OFFSET_CACHE */
357	*res_page = NULL;
358
359	start = ei->i_dir_start_lookup;
360	if (start >= npages)
361		start = 0;
362	n = start;
363	do {
364		char *kaddr;
365		page = ext2_get_page(dir, n, dir_has_error);
366		if (!IS_ERR(page)) {
367			kaddr = page_address(page);
368			de = (ext2_dirent *) kaddr;
369			kaddr += ext2_last_byte(dir, n) - reclen;
370			while ((char *) de <= kaddr) {
371				if (de->rec_len == 0) {
372					ext2_error(dir->i_sb, __func__,
373						"zero-length directory entry");
374					ext2_put_page(page);
375					goto out;
376				}
377				if (ext2_match (namelen, name, de))
378					goto found;
379				de = ext2_next_entry(de);
380			}
381			ext2_put_page(page);
382		} else
383			dir_has_error = 1;
384
385		if (++n >= npages)
386			n = 0;
387		/* next page is past the blocks we've got */
388		if (unlikely(n > (dir->i_blocks >> (PAGE_SHIFT - 9)))) {
389			ext2_error(dir->i_sb, __func__,
390				"dir %lu size %lld exceeds block count %llu",
391				dir->i_ino, dir->i_size,
392				(unsigned long long)dir->i_blocks);
393			goto out;
394		}
395	} while (n != start);
396out:
397	return NULL;
398
399found:
400	*res_page = page;
401	ei->i_dir_start_lookup = n;
402	return de;
403}
404
405struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
406{
407	struct page *page = ext2_get_page(dir, 0, 0);
408	ext2_dirent *de = NULL;
409
410	if (!IS_ERR(page)) {
411		de = ext2_next_entry((ext2_dirent *) page_address(page));
412		*p = page;
413	}
414	return de;
415}
416
417ino_t ext2_inode_by_name(struct inode *dir, const struct qstr *child)
418{
419	ino_t res = 0;
420	struct ext2_dir_entry_2 *de;
421	struct page *page;
422	
423	de = ext2_find_entry (dir, child, &page);
424	if (de) {
425		res = le32_to_cpu(de->inode);
426		ext2_put_page(page);
427	}
428	return res;
429}
430
431static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len)
432{
433	return __block_write_begin(page, pos, len, ext2_get_block);
434}
435
436/* Releases the page */
437void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
438		   struct page *page, struct inode *inode, int update_times)
439{
440	loff_t pos = page_offset(page) +
441			(char *) de - (char *) page_address(page);
442	unsigned len = ext2_rec_len_from_disk(de->rec_len);
443	int err;
444
445	lock_page(page);
446	err = ext2_prepare_chunk(page, pos, len);
447	BUG_ON(err);
448	de->inode = cpu_to_le32(inode->i_ino);
449	ext2_set_de_type(de, inode);
450	err = ext2_commit_chunk(page, pos, len);
451	ext2_put_page(page);
452	if (update_times)
453		dir->i_mtime = dir->i_ctime = current_time(dir);
454	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
455	mark_inode_dirty(dir);
456}
457
458/*
459 *	Parent is locked.
460 */
461int ext2_add_link (struct dentry *dentry, struct inode *inode)
462{
463	struct inode *dir = d_inode(dentry->d_parent);
464	const char *name = dentry->d_name.name;
465	int namelen = dentry->d_name.len;
466	unsigned chunk_size = ext2_chunk_size(dir);
467	unsigned reclen = EXT2_DIR_REC_LEN(namelen);
468	unsigned short rec_len, name_len;
469	struct page *page = NULL;
470	ext2_dirent * de;
471	unsigned long npages = dir_pages(dir);
472	unsigned long n;
473	char *kaddr;
474	loff_t pos;
475	int err;
476
477	/*
478	 * We take care of directory expansion in the same loop.
479	 * This code plays outside i_size, so it locks the page
480	 * to protect that region.
481	 */
482	for (n = 0; n <= npages; n++) {
483		char *dir_end;
484
485		page = ext2_get_page(dir, n, 0);
486		err = PTR_ERR(page);
487		if (IS_ERR(page))
488			goto out;
489		lock_page(page);
490		kaddr = page_address(page);
491		dir_end = kaddr + ext2_last_byte(dir, n);
492		de = (ext2_dirent *)kaddr;
493		kaddr += PAGE_SIZE - reclen;
494		while ((char *)de <= kaddr) {
495			if ((char *)de == dir_end) {
496				/* We hit i_size */
497				name_len = 0;
498				rec_len = chunk_size;
499				de->rec_len = ext2_rec_len_to_disk(chunk_size);
500				de->inode = 0;
501				goto got_it;
502			}
503			if (de->rec_len == 0) {
504				ext2_error(dir->i_sb, __func__,
505					"zero-length directory entry");
506				err = -EIO;
507				goto out_unlock;
508			}
509			err = -EEXIST;
510			if (ext2_match (namelen, name, de))
511				goto out_unlock;
512			name_len = EXT2_DIR_REC_LEN(de->name_len);
513			rec_len = ext2_rec_len_from_disk(de->rec_len);
514			if (!de->inode && rec_len >= reclen)
515				goto got_it;
516			if (rec_len >= name_len + reclen)
517				goto got_it;
518			de = (ext2_dirent *) ((char *) de + rec_len);
519		}
520		unlock_page(page);
521		ext2_put_page(page);
522	}
523	BUG();
524	return -EINVAL;
525
526got_it:
527	pos = page_offset(page) +
528		(char*)de - (char*)page_address(page);
529	err = ext2_prepare_chunk(page, pos, rec_len);
530	if (err)
531		goto out_unlock;
532	if (de->inode) {
533		ext2_dirent *de1 = (ext2_dirent *) ((char *) de + name_len);
534		de1->rec_len = ext2_rec_len_to_disk(rec_len - name_len);
535		de->rec_len = ext2_rec_len_to_disk(name_len);
536		de = de1;
537	}
538	de->name_len = namelen;
539	memcpy(de->name, name, namelen);
540	de->inode = cpu_to_le32(inode->i_ino);
541	ext2_set_de_type (de, inode);
542	err = ext2_commit_chunk(page, pos, rec_len);
543	dir->i_mtime = dir->i_ctime = current_time(dir);
544	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
545	mark_inode_dirty(dir);
546	/* OFFSET_CACHE */
547out_put:
548	ext2_put_page(page);
549out:
550	return err;
551out_unlock:
552	unlock_page(page);
553	goto out_put;
554}
555
556/*
557 * ext2_delete_entry deletes a directory entry by merging it with the
558 * previous entry. Page is up-to-date. Releases the page.
559 */
560int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
561{
562	struct inode *inode = page->mapping->host;
563	char *kaddr = page_address(page);
564	unsigned from = ((char*)dir - kaddr) & ~(ext2_chunk_size(inode)-1);
565	unsigned to = ((char *)dir - kaddr) +
566				ext2_rec_len_from_disk(dir->rec_len);
567	loff_t pos;
568	ext2_dirent * pde = NULL;
569	ext2_dirent * de = (ext2_dirent *) (kaddr + from);
570	int err;
571
572	while ((char*)de < (char*)dir) {
573		if (de->rec_len == 0) {
574			ext2_error(inode->i_sb, __func__,
575				"zero-length directory entry");
576			err = -EIO;
577			goto out;
578		}
579		pde = de;
580		de = ext2_next_entry(de);
581	}
582	if (pde)
583		from = (char*)pde - (char*)page_address(page);
584	pos = page_offset(page) + from;
585	lock_page(page);
586	err = ext2_prepare_chunk(page, pos, to - from);
587	BUG_ON(err);
588	if (pde)
589		pde->rec_len = ext2_rec_len_to_disk(to - from);
590	dir->inode = 0;
591	err = ext2_commit_chunk(page, pos, to - from);
592	inode->i_ctime = inode->i_mtime = current_time(inode);
593	EXT2_I(inode)->i_flags &= ~EXT2_BTREE_FL;
594	mark_inode_dirty(inode);
595out:
596	ext2_put_page(page);
597	return err;
598}
599
600/*
601 * Set the first fragment of directory.
602 */
603int ext2_make_empty(struct inode *inode, struct inode *parent)
604{
605	struct page *page = grab_cache_page(inode->i_mapping, 0);
606	unsigned chunk_size = ext2_chunk_size(inode);
607	struct ext2_dir_entry_2 * de;
608	int err;
609	void *kaddr;
610
611	if (!page)
612		return -ENOMEM;
613
614	err = ext2_prepare_chunk(page, 0, chunk_size);
615	if (err) {
616		unlock_page(page);
617		goto fail;
618	}
619	kaddr = kmap_atomic(page);
620	memset(kaddr, 0, chunk_size);
621	de = (struct ext2_dir_entry_2 *)kaddr;
622	de->name_len = 1;
623	de->rec_len = ext2_rec_len_to_disk(EXT2_DIR_REC_LEN(1));
624	memcpy (de->name, ".\0\0", 4);
625	de->inode = cpu_to_le32(inode->i_ino);
626	ext2_set_de_type (de, inode);
627
628	de = (struct ext2_dir_entry_2 *)(kaddr + EXT2_DIR_REC_LEN(1));
629	de->name_len = 2;
630	de->rec_len = ext2_rec_len_to_disk(chunk_size - EXT2_DIR_REC_LEN(1));
631	de->inode = cpu_to_le32(parent->i_ino);
632	memcpy (de->name, "..\0", 4);
633	ext2_set_de_type (de, inode);
634	kunmap_atomic(kaddr);
635	err = ext2_commit_chunk(page, 0, chunk_size);
636fail:
637	put_page(page);
638	return err;
639}
640
641/*
642 * routine to check that the specified directory is empty (for rmdir)
643 */
644int ext2_empty_dir (struct inode * inode)
645{
646	struct page *page = NULL;
647	unsigned long i, npages = dir_pages(inode);
648	int dir_has_error = 0;
649
650	for (i = 0; i < npages; i++) {
651		char *kaddr;
652		ext2_dirent * de;
653		page = ext2_get_page(inode, i, dir_has_error);
654
655		if (IS_ERR(page)) {
656			dir_has_error = 1;
657			continue;
658		}
659
660		kaddr = page_address(page);
661		de = (ext2_dirent *)kaddr;
662		kaddr += ext2_last_byte(inode, i) - EXT2_DIR_REC_LEN(1);
663
664		while ((char *)de <= kaddr) {
665			if (de->rec_len == 0) {
666				ext2_error(inode->i_sb, __func__,
667					"zero-length directory entry");
668				printk("kaddr=%p, de=%p\n", kaddr, de);
669				goto not_empty;
670			}
671			if (de->inode != 0) {
672				/* check for . and .. */
673				if (de->name[0] != '.')
674					goto not_empty;
675				if (de->name_len > 2)
676					goto not_empty;
677				if (de->name_len < 2) {
678					if (de->inode !=
679					    cpu_to_le32(inode->i_ino))
680						goto not_empty;
681				} else if (de->name[1] != '.')
682					goto not_empty;
683			}
684			de = ext2_next_entry(de);
685		}
686		ext2_put_page(page);
687	}
688	return 1;
689
690not_empty:
691	ext2_put_page(page);
692	return 0;
693}
694
695const struct file_operations ext2_dir_operations = {
696	.llseek		= generic_file_llseek,
697	.read		= generic_read_dir,
698	.iterate_shared	= ext2_readdir,
699	.unlocked_ioctl = ext2_ioctl,
700#ifdef CONFIG_COMPAT
701	.compat_ioctl	= ext2_compat_ioctl,
702#endif
703	.fsync		= ext2_fsync,
704};