dir_iterate.c revision 543547a52a20cb7e69d74921b2f691078fd55d83 
1/*
2 * dir_iterate.c --- ext2fs directory iteration operations
3 *
4 * Copyright (C) 1993, 1994, 1994, 1995, 1996, 1997 Theodore Ts'o.
5 *
6 * %Begin-Header%
7 * This file may be redistributed under the terms of the GNU Library
8 * General Public License, version 2.
9 * %End-Header%
10 */
11
12#include <stdio.h>
13#include <string.h>
14#if HAVE_UNISTD_H
15#include <unistd.h>
16#endif
17#if HAVE_ERRNO_H
18#include <errno.h>
19#endif
20
21#include "ext2_fs.h"
22#include "ext2fsP.h"
23
24#define EXT4_MAX_REC_LEN		((1<<16)-1)
25
26errcode_t ext2fs_get_rec_len(ext2_filsys fs,
27			     struct ext2_dir_entry *dirent,
28			     unsigned int *rec_len)
29{
30	unsigned int len = dirent->rec_len;
31
32	if (len == EXT4_MAX_REC_LEN || len == 0)
33		*rec_len = fs->blocksize;
34	else
35		*rec_len = (len & 65532) | ((len & 3) << 16);
36	return 0;
37}
38
39errcode_t ext2fs_set_rec_len(ext2_filsys fs,
40			     unsigned int len,
41			     struct ext2_dir_entry *dirent)
42{
43	if ((len > fs->blocksize) || (fs->blocksize > (1 << 18)) || (len & 3))
44		return EINVAL;
45	if (len < 65536) {
46		dirent->rec_len = len;
47		return 0;
48	}
49	if (len == fs->blocksize) {
50		if (fs->blocksize == 65536)
51			dirent->rec_len = EXT4_MAX_REC_LEN;
52		else
53			dirent->rec_len = 0;
54	} else
55		dirent->rec_len = (len & 65532) | ((len >> 16) & 3);
56	return 0;
57}
58
59/*
60 * This function checks to see whether or not a potential deleted
61 * directory entry looks valid.  What we do is check the deleted entry
62 * and each successive entry to make sure that they all look valid and
63 * that the last deleted entry ends at the beginning of the next
64 * undeleted entry.  Returns 1 if the deleted entry looks valid, zero
65 * if not valid.
66 */
67static int ext2fs_validate_entry(ext2_filsys fs, char *buf,
68				 unsigned int offset,
69				 unsigned int final_offset)
70{
71	struct ext2_dir_entry *dirent;
72	unsigned int rec_len;
73#define DIRENT_MIN_LENGTH 12
74
75	while ((offset < final_offset) &&
76	       (offset <= fs->blocksize - DIRENT_MIN_LENGTH)) {
77		dirent = (struct ext2_dir_entry *)(buf + offset);
78		if (ext2fs_get_rec_len(fs, dirent, &rec_len))
79			return 0;
80		offset += rec_len;
81		if ((rec_len < 8) ||
82		    ((rec_len % 4) != 0) ||
83		    ((((unsigned) dirent->name_len & 0xFF)+8) > rec_len))
84			return 0;
85	}
86	return (offset == final_offset);
87}
88
89errcode_t ext2fs_dir_iterate2(ext2_filsys fs,
90			      ext2_ino_t dir,
91			      int flags,
92			      char *block_buf,
93			      int (*func)(ext2_ino_t	dir,
94					  int		entry,
95					  struct ext2_dir_entry *dirent,
96					  int	offset,
97					  int	blocksize,
98					  char	*buf,
99					  void	*priv_data),
100			      void *priv_data)
101{
102	struct		dir_context	ctx;
103	errcode_t	retval;
104
105	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
106
107	retval = ext2fs_check_directory(fs, dir);
108	if (retval)
109		return retval;
110
111	ctx.dir = dir;
112	ctx.flags = flags;
113	if (block_buf)
114		ctx.buf = block_buf;
115	else {
116		retval = ext2fs_get_mem(fs->blocksize, &ctx.buf);
117		if (retval)
118			return retval;
119	}
120	ctx.func = func;
121	ctx.priv_data = priv_data;
122	ctx.errcode = 0;
123	retval = ext2fs_block_iterate2(fs, dir, BLOCK_FLAG_READ_ONLY, 0,
124				       ext2fs_process_dir_block, &ctx);
125	if (!block_buf)
126		ext2fs_free_mem(&ctx.buf);
127	if (retval)
128		return retval;
129	return ctx.errcode;
130}
131
132struct xlate {
133	int (*func)(struct ext2_dir_entry *dirent,
134		    int		offset,
135		    int		blocksize,
136		    char	*buf,
137		    void	*priv_data);
138	void *real_private;
139};
140
141static int xlate_func(ext2_ino_t dir EXT2FS_ATTR((unused)),
142		      int entry EXT2FS_ATTR((unused)),
143		      struct ext2_dir_entry *dirent, int offset,
144		      int blocksize, char *buf, void *priv_data)
145{
146	struct xlate *xl = (struct xlate *) priv_data;
147
148	return (*xl->func)(dirent, offset, blocksize, buf, xl->real_private);
149}
150
151extern errcode_t ext2fs_dir_iterate(ext2_filsys fs,
152			      ext2_ino_t dir,
153			      int flags,
154			      char *block_buf,
155			      int (*func)(struct ext2_dir_entry *dirent,
156					  int	offset,
157					  int	blocksize,
158					  char	*buf,
159					  void	*priv_data),
160			      void *priv_data)
161{
162	struct xlate xl;
163
164	xl.real_private = priv_data;
165	xl.func = func;
166
167	return ext2fs_dir_iterate2(fs, dir, flags, block_buf,
168				   xlate_func, &xl);
169}
170
171
172/*
173 * Helper function which is private to this module.  Used by
174 * ext2fs_dir_iterate() and ext2fs_dblist_dir_iterate()
175 */
176int ext2fs_process_dir_block(ext2_filsys fs,
177			     blk_t	*blocknr,
178			     e2_blkcnt_t blockcnt,
179			     blk_t	ref_block EXT2FS_ATTR((unused)),
180			     int	ref_offset EXT2FS_ATTR((unused)),
181			     void	*priv_data)
182{
183	struct dir_context *ctx = (struct dir_context *) priv_data;
184	unsigned int	offset = 0;
185	unsigned int	next_real_entry = 0;
186	int		ret = 0;
187	int		changed = 0;
188	int		do_abort = 0;
189	unsigned int	rec_len, size;
190	int		entry;
191	struct ext2_dir_entry *dirent;
192
193	if (blockcnt < 0)
194		return 0;
195
196	entry = blockcnt ? DIRENT_OTHER_FILE : DIRENT_DOT_FILE;
197
198	ctx->errcode = ext2fs_read_dir_block(fs, *blocknr, ctx->buf);
199	if (ctx->errcode)
200		return BLOCK_ABORT;
201
202	while (offset < fs->blocksize) {
203		dirent = (struct ext2_dir_entry *) (ctx->buf + offset);
204		if (ext2fs_get_rec_len(fs, dirent, &rec_len))
205			return BLOCK_ABORT;
206		if (((offset + rec_len) > fs->blocksize) ||
207		    (rec_len < 8) ||
208		    ((rec_len % 4) != 0) ||
209		    ((((unsigned) dirent->name_len & 0xFF)+8) > rec_len)) {
210			ctx->errcode = EXT2_ET_DIR_CORRUPTED;
211			return BLOCK_ABORT;
212		}
213		if (!dirent->inode &&
214		    !(ctx->flags & DIRENT_FLAG_INCLUDE_EMPTY))
215			goto next;
216
217		ret = (ctx->func)(ctx->dir,
218				  (next_real_entry > offset) ?
219				  DIRENT_DELETED_FILE : entry,
220				  dirent, offset,
221				  fs->blocksize, ctx->buf,
222				  ctx->priv_data);
223		if (entry < DIRENT_OTHER_FILE)
224			entry++;
225
226		if (ret & DIRENT_CHANGED) {
227			if (ext2fs_get_rec_len(fs, dirent, &rec_len))
228				return BLOCK_ABORT;
229			changed++;
230		}
231		if (ret & DIRENT_ABORT) {
232			do_abort++;
233			break;
234		}
235next:
236 		if (next_real_entry == offset)
237			next_real_entry += rec_len;
238
239 		if (ctx->flags & DIRENT_FLAG_INCLUDE_REMOVED) {
240			size = ((dirent->name_len & 0xFF) + 11) & ~3;
241
242			if (rec_len != size)  {
243				unsigned int final_offset;
244
245				final_offset = offset + rec_len;
246				offset += size;
247				while (offset < final_offset &&
248				       !ext2fs_validate_entry(fs, ctx->buf,
249							      offset,
250							      final_offset))
251					offset += 4;
252				continue;
253			}
254		}
255		offset += rec_len;
256	}
257
258	if (changed) {
259		ctx->errcode = ext2fs_write_dir_block(fs, *blocknr, ctx->buf);
260		if (ctx->errcode)
261			return BLOCK_ABORT;
262	}
263	if (do_abort)
264		return BLOCK_ABORT;
265	return 0;
266}
267
268