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      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 
     26 errcode_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 (fs->blocksize < 65536)
     33 		*rec_len = len;
     34 	else if (len == EXT4_MAX_REC_LEN || len == 0)
     35 		*rec_len = fs->blocksize;
     36 	else
     37 		*rec_len = (len & 65532) | ((len & 3) << 16);
     38 	return 0;
     39 }
     40 
     41 errcode_t ext2fs_set_rec_len(ext2_filsys fs,
     42 			     unsigned int len,
     43 			     struct ext2_dir_entry *dirent)
     44 {
     45 	if ((len > fs->blocksize) || (fs->blocksize > (1 << 18)) || (len & 3))
     46 		return EINVAL;
     47 	if (len < 65536) {
     48 		dirent->rec_len = len;
     49 		return 0;
     50 	}
     51 	if (len == fs->blocksize) {
     52 		if (fs->blocksize == 65536)
     53 			dirent->rec_len = EXT4_MAX_REC_LEN;
     54 		else
     55 			dirent->rec_len = 0;
     56 	} else
     57 		dirent->rec_len = (len & 65532) | ((len >> 16) & 3);
     58 	return 0;
     59 }
     60 
     61 /*
     62  * This function checks to see whether or not a potential deleted
     63  * directory entry looks valid.  What we do is check the deleted entry
     64  * and each successive entry to make sure that they all look valid and
     65  * that the last deleted entry ends at the beginning of the next
     66  * undeleted entry.  Returns 1 if the deleted entry looks valid, zero
     67  * if not valid.
     68  */
     69 static int ext2fs_validate_entry(ext2_filsys fs, char *buf,
     70 				 unsigned int offset,
     71 				 unsigned int final_offset)
     72 {
     73 	struct ext2_dir_entry *dirent;
     74 	unsigned int rec_len;
     75 #define DIRENT_MIN_LENGTH 12
     76 
     77 	while ((offset < final_offset) &&
     78 	       (offset <= fs->blocksize - DIRENT_MIN_LENGTH)) {
     79 		dirent = (struct ext2_dir_entry *)(buf + offset);
     80 		if (ext2fs_get_rec_len(fs, dirent, &rec_len))
     81 			return 0;
     82 		offset += rec_len;
     83 		if ((rec_len < 8) ||
     84 		    ((rec_len % 4) != 0) ||
     85 		    ((((unsigned) dirent->name_len & 0xFF)+8) > rec_len))
     86 			return 0;
     87 	}
     88 	return (offset == final_offset);
     89 }
     90 
     91 errcode_t ext2fs_dir_iterate2(ext2_filsys fs,
     92 			      ext2_ino_t dir,
     93 			      int flags,
     94 			      char *block_buf,
     95 			      int (*func)(ext2_ino_t	dir,
     96 					  int		entry,
     97 					  struct ext2_dir_entry *dirent,
     98 					  int	offset,
     99 					  int	blocksize,
    100 					  char	*buf,
    101 					  void	*priv_data),
    102 			      void *priv_data)
    103 {
    104 	struct		dir_context	ctx;
    105 	errcode_t	retval;
    106 
    107 	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
    108 
    109 	retval = ext2fs_check_directory(fs, dir);
    110 	if (retval)
    111 		return retval;
    112 
    113 	ctx.dir = dir;
    114 	ctx.flags = flags;
    115 	if (block_buf)
    116 		ctx.buf = block_buf;
    117 	else {
    118 		retval = ext2fs_get_mem(fs->blocksize, &ctx.buf);
    119 		if (retval)
    120 			return retval;
    121 	}
    122 	ctx.func = func;
    123 	ctx.priv_data = priv_data;
    124 	ctx.errcode = 0;
    125 	retval = ext2fs_block_iterate2(fs, dir, BLOCK_FLAG_READ_ONLY, 0,
    126 				       ext2fs_process_dir_block, &ctx);
    127 	if (!block_buf)
    128 		ext2fs_free_mem(&ctx.buf);
    129 	if (retval)
    130 		return retval;
    131 	return ctx.errcode;
    132 }
    133 
    134 struct xlate {
    135 	int (*func)(struct ext2_dir_entry *dirent,
    136 		    int		offset,
    137 		    int		blocksize,
    138 		    char	*buf,
    139 		    void	*priv_data);
    140 	void *real_private;
    141 };
    142 
    143 static int xlate_func(ext2_ino_t dir EXT2FS_ATTR((unused)),
    144 		      int entry EXT2FS_ATTR((unused)),
    145 		      struct ext2_dir_entry *dirent, int offset,
    146 		      int blocksize, char *buf, void *priv_data)
    147 {
    148 	struct xlate *xl = (struct xlate *) priv_data;
    149 
    150 	return (*xl->func)(dirent, offset, blocksize, buf, xl->real_private);
    151 }
    152 
    153 extern errcode_t ext2fs_dir_iterate(ext2_filsys fs,
    154 			      ext2_ino_t dir,
    155 			      int flags,
    156 			      char *block_buf,
    157 			      int (*func)(struct ext2_dir_entry *dirent,
    158 					  int	offset,
    159 					  int	blocksize,
    160 					  char	*buf,
    161 					  void	*priv_data),
    162 			      void *priv_data)
    163 {
    164 	struct xlate xl;
    165 
    166 	xl.real_private = priv_data;
    167 	xl.func = func;
    168 
    169 	return ext2fs_dir_iterate2(fs, dir, flags, block_buf,
    170 				   xlate_func, &xl);
    171 }
    172 
    173 
    174 /*
    175  * Helper function which is private to this module.  Used by
    176  * ext2fs_dir_iterate() and ext2fs_dblist_dir_iterate()
    177  */
    178 int ext2fs_process_dir_block(ext2_filsys fs,
    179 			     blk_t	*blocknr,
    180 			     e2_blkcnt_t blockcnt,
    181 			     blk_t	ref_block EXT2FS_ATTR((unused)),
    182 			     int	ref_offset EXT2FS_ATTR((unused)),
    183 			     void	*priv_data)
    184 {
    185 	struct dir_context *ctx = (struct dir_context *) priv_data;
    186 	unsigned int	offset = 0;
    187 	unsigned int	next_real_entry = 0;
    188 	int		ret = 0;
    189 	int		changed = 0;
    190 	int		do_abort = 0;
    191 	unsigned int	rec_len, size;
    192 	int		entry;
    193 	struct ext2_dir_entry *dirent;
    194 
    195 	if (blockcnt < 0)
    196 		return 0;
    197 
    198 	entry = blockcnt ? DIRENT_OTHER_FILE : DIRENT_DOT_FILE;
    199 
    200 	ctx->errcode = ext2fs_read_dir_block(fs, *blocknr, ctx->buf);
    201 	if (ctx->errcode)
    202 		return BLOCK_ABORT;
    203 
    204 	while (offset < fs->blocksize) {
    205 		dirent = (struct ext2_dir_entry *) (ctx->buf + offset);
    206 		if (ext2fs_get_rec_len(fs, dirent, &rec_len))
    207 			return BLOCK_ABORT;
    208 		if (((offset + rec_len) > fs->blocksize) ||
    209 		    (rec_len < 8) ||
    210 		    ((rec_len % 4) != 0) ||
    211 		    ((((unsigned) dirent->name_len & 0xFF)+8) > rec_len)) {
    212 			ctx->errcode = EXT2_ET_DIR_CORRUPTED;
    213 			return BLOCK_ABORT;
    214 		}
    215 		if (!dirent->inode &&
    216 		    !(ctx->flags & DIRENT_FLAG_INCLUDE_EMPTY))
    217 			goto next;
    218 
    219 		ret = (ctx->func)(ctx->dir,
    220 				  (next_real_entry > offset) ?
    221 				  DIRENT_DELETED_FILE : entry,
    222 				  dirent, offset,
    223 				  fs->blocksize, ctx->buf,
    224 				  ctx->priv_data);
    225 		if (entry < DIRENT_OTHER_FILE)
    226 			entry++;
    227 
    228 		if (ret & DIRENT_CHANGED) {
    229 			if (ext2fs_get_rec_len(fs, dirent, &rec_len))
    230 				return BLOCK_ABORT;
    231 			changed++;
    232 		}
    233 		if (ret & DIRENT_ABORT) {
    234 			do_abort++;
    235 			break;
    236 		}
    237 next:
    238  		if (next_real_entry == offset)
    239 			next_real_entry += rec_len;
    240 
    241  		if (ctx->flags & DIRENT_FLAG_INCLUDE_REMOVED) {
    242 			size = ((dirent->name_len & 0xFF) + 11) & ~3;
    243 
    244 			if (rec_len != size)  {
    245 				unsigned int final_offset;
    246 
    247 				final_offset = offset + rec_len;
    248 				offset += size;
    249 				while (offset < final_offset &&
    250 				       !ext2fs_validate_entry(fs, ctx->buf,
    251 							      offset,
    252 							      final_offset))
    253 					offset += 4;
    254 				continue;
    255 			}
    256 		}
    257 		offset += rec_len;
    258 	}
    259 
    260 	if (changed) {
    261 		ctx->errcode = ext2fs_write_dir_block(fs, *blocknr, ctx->buf);
    262 		if (ctx->errcode)
    263 			return BLOCK_ABORT;
    264 	}
    265 	if (do_abort)
    266 		return BLOCK_ABORT;
    267 	return 0;
    268 }
    269 
    270