libext2fs: add checksums to the end of directory leaf nodes

Introduce small structures for recording directory tree checksums, and
some API changes to support writing out directory blocks with
checksums.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

10 files changed, 306 insertions, 65 deletions

diff --git a/lib/ext2fs/csum.c b/lib/ext2fs/csum.c
index 262eb759..e92bac53 100644
--- a/lib/ext2fs/csum.c
+++ b/lib/ext2fs/csum.c
@@ -93,6 +93,122 @@ errcode_t ext2fs_get_dx_countlimit(ext2_filsys fs,
 	return __get_dx_countlimit(fs, dirent, cc, offset, 0);
 }
 
+void ext2fs_initialize_dirent_tail(ext2_filsys fs,
+				   struct ext2_dir_entry_tail *t)
+{
+	memset(t, 0, sizeof(struct ext2_dir_entry_tail));
+	ext2fs_set_rec_len(fs, sizeof(struct ext2_dir_entry_tail),
+			   (struct ext2_dir_entry *)t);
+	t->det_reserved_name_len = EXT2_DIR_NAME_LEN_CSUM;
+}
+
+static errcode_t __get_dirent_tail(ext2_filsys fs,
+				   struct ext2_dir_entry *dirent,
+				   struct ext2_dir_entry_tail **tt,
+				   int need_swab)
+{
+	struct ext2_dir_entry *d;
+	void *top;
+	struct ext2_dir_entry_tail *t;
+	unsigned int rec_len;
+	errcode_t retval = 0;
+	__u16 (*translate)(__u16) = (need_swab ? disk_to_host16 : do_nothing16);
+
+	d = dirent;
+	top = EXT2_DIRENT_TAIL(dirent, fs->blocksize);
+
+	rec_len = translate(d->rec_len);
+	while (rec_len && !(rec_len & 0x3)) {
+		d = (struct ext2_dir_entry *)(((void *)d) + rec_len);
+		if ((void *)d >= top)
+			break;
+		rec_len = translate(d->rec_len);
+	}
+
+	if (d != top)
+		return EXT2_ET_DIR_NO_SPACE_FOR_CSUM;
+
+	t = (struct ext2_dir_entry_tail *)d;
+	if (t->det_reserved_zero1 ||
+	    translate(t->det_rec_len) != sizeof(struct ext2_dir_entry_tail) ||
+	    translate(t->det_reserved_name_len) != EXT2_DIR_NAME_LEN_CSUM)
+		return EXT2_ET_DIR_NO_SPACE_FOR_CSUM;
+
+	if (tt)
+		*tt = t;
+	return retval;
+}
+
+int ext2fs_dirent_has_tail(ext2_filsys fs, struct ext2_dir_entry *dirent)
+{
+	return __get_dirent_tail(fs, dirent, NULL, 0) == 0;
+}
+
+static errcode_t ext2fs_dirent_csum(ext2_filsys fs, ext2_ino_t inum,
+				    struct ext2_dir_entry *dirent, __u32 *crc,
+				    int size)
+{
+	errcode_t retval;
+	char *buf = (char *)dirent;
+	__u32 gen;
+	struct ext2_inode inode;
+
+	retval = ext2fs_read_inode(fs, inum, &inode);
+	if (retval)
+		return retval;
+
+	inum = ext2fs_cpu_to_le32(inum);
+	gen = ext2fs_cpu_to_le32(inode.i_generation);
+	*crc = ext2fs_crc32c_le(fs->csum_seed, (unsigned char *)&inum,
+				sizeof(inum));
+	*crc = ext2fs_crc32c_le(*crc, (unsigned char *)&gen, sizeof(gen));
+	*crc = ext2fs_crc32c_le(*crc, (unsigned char *)buf, size);
+
+	return 0;
+}
+
+int ext2fs_dirent_csum_verify(ext2_filsys fs, ext2_ino_t inum,
+			      struct ext2_dir_entry *dirent)
+{
+	errcode_t retval;
+	__u32 calculated;
+	struct ext2_dir_entry_tail *t;
+
+	retval = __get_dirent_tail(fs, dirent, &t, 1);
+	if (retval)
+		return 1;
+
+	/*
+	 * The checksum field is overlaid with the dirent->name field
+	 * so the swapfs.c functions won't change the endianness.
+	 */
+	retval = ext2fs_dirent_csum(fs, inum, dirent, &calculated,
+				    (void *)t - (void *)dirent);
+	if (retval)
+		return 0;
+	return ext2fs_le32_to_cpu(t->det_checksum) == calculated;
+}
+
+static errcode_t ext2fs_dirent_csum_set(ext2_filsys fs, ext2_ino_t inum,
+					struct ext2_dir_entry *dirent)
+{
+	errcode_t retval;
+	__u32 crc;
+	struct ext2_dir_entry_tail *t;
+
+	retval = __get_dirent_tail(fs, dirent, &t, 1);
+	if (retval)
+		return retval;
+
+	/* swapfs.c functions don't change the checksum endianness */
+	retval = ext2fs_dirent_csum(fs, inum, dirent, &crc,
+				    (void *)t - (void *)dirent);
+	if (retval)
+		return retval;
+	t->det_checksum = ext2fs_cpu_to_le32(crc);
+	return 0;
+}
+
 static errcode_t ext2fs_dx_csum(ext2_filsys fs, ext2_ino_t inum,
 				struct ext2_dir_entry *dirent,
 				__u32 *crc, int count_offset, int count,
@@ -179,6 +295,38 @@ static errcode_t ext2fs_dx_csum_set(ext2_filsys fs, ext2_ino_t inum,
 	return retval;
 }
 
+int ext2fs_dir_block_csum_verify(ext2_filsys fs, ext2_ino_t inum,
+				 struct ext2_dir_entry *dirent)
+{
+	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 1;
+
+	if (__get_dirent_tail(fs, dirent, NULL, 1) == 0)
+		return ext2fs_dirent_csum_verify(fs, inum, dirent);
+	if (__get_dx_countlimit(fs, dirent, NULL, NULL, 1) == 0)
+		return ext2fs_dx_csum_verify(fs, inum, dirent);
+
+	return 0;
+}
+
+errcode_t ext2fs_dir_block_csum_set(ext2_filsys fs, ext2_ino_t inum,
+				    struct ext2_dir_entry *dirent)
+{
+	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 0;
+
+	if (__get_dirent_tail(fs, dirent, NULL, 1) == 0)
+		return ext2fs_dirent_csum_set(fs, inum, dirent);
+	if (__get_dx_countlimit(fs, dirent, NULL, NULL, 1) == 0)
+		return ext2fs_dx_csum_set(fs, inum, dirent);
+
+	if (fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS)
+		return 0;
+	return EXT2_ET_DIR_NO_SPACE_FOR_CSUM;
+}
+
 #define EXT3_EXTENT_TAIL_OFFSET(hdr)	(sizeof(struct ext3_extent_header) + \
 	(sizeof(struct ext3_extent) * ext2fs_le16_to_cpu((hdr)->eh_max)))
 
diff --git a/lib/ext2fs/dir_iterate.c b/lib/ext2fs/dir_iterate.c
index 5125d199..c24015cc 100644
--- a/lib/ext2fs/dir_iterate.c
+++ b/lib/ext2fs/dir_iterate.c
@@ -192,17 +192,23 @@ int ext2fs_process_dir_block(ext2_filsys fs,
 	unsigned int	rec_len, size;
 	int		entry;
 	struct ext2_dir_entry *dirent;
+	int		csum_size = 0;
 
 	if (blockcnt < 0)
 		return 0;
 
 	entry = blockcnt ? DIRENT_OTHER_FILE : DIRENT_DOT_FILE;
 
-	ctx->errcode = ext2fs_read_dir_block3(fs, *blocknr, ctx->buf, 0);
+	ctx->errcode = ext2fs_read_dir_block4(fs, *blocknr, ctx->buf, 0,
+					      ctx->dir);
 	if (ctx->errcode)
 		return BLOCK_ABORT;
 
-	while (offset < fs->blocksize) {
+	if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		csum_size = sizeof(struct ext2_dir_entry_tail);
+
+	while (offset < (fs->blocksize - csum_size)) {
 		dirent = (struct ext2_dir_entry *) (ctx->buf + offset);
 		if (ext2fs_get_rec_len(fs, dirent, &rec_len))
 			return BLOCK_ABORT;
@@ -259,8 +265,8 @@ next:
 	}
 
 	if (changed) {
-		ctx->errcode = ext2fs_write_dir_block3(fs, *blocknr, ctx->buf,
-						       0);
+		ctx->errcode = ext2fs_write_dir_block4(fs, *blocknr, ctx->buf,
+						       0, ctx->dir);
 		if (ctx->errcode)
 			return BLOCK_ABORT;
 	}
diff --git a/lib/ext2fs/dirblock.c b/lib/ext2fs/dirblock.c
index cb3a104c..54b27772 100644
--- a/lib/ext2fs/dirblock.c
+++ b/lib/ext2fs/dirblock.c
@@ -20,45 +20,36 @@
 #include "ext2_fs.h"
 #include "ext2fs.h"
 
-errcode_t ext2fs_read_dir_block3(ext2_filsys fs, blk64_t block,
-				 void *buf, int flags EXT2FS_ATTR((unused)))
+errcode_t ext2fs_read_dir_block4(ext2_filsys fs, blk64_t block,
+				 void *buf, int flags EXT2FS_ATTR((unused)),
+				 ext2_ino_t ino)
 {
 	errcode_t	retval;
-	char		*p, *end;
-	struct ext2_dir_entry *dirent;
-	unsigned int	name_len, rec_len;
-
+	int		corrupt = 0;
 
 	retval = io_channel_read_blk64(fs->io, block, 1, buf);
 	if (retval)
 		return retval;
 
-	p = (char *) buf;
-	end = (char *) buf + fs->blocksize;
-	while (p < end-8) {
-		dirent = (struct ext2_dir_entry *) p;
-#ifdef WORDS_BIGENDIAN
-		dirent->inode = ext2fs_swab32(dirent->inode);
-		dirent->rec_len = ext2fs_swab16(dirent->rec_len);
-		dirent->name_len = ext2fs_swab16(dirent->name_len);
-#endif
-		name_len = dirent->name_len;
+	if (!(fs->flags & EXT2_FLAG_IGNORE_CSUM_ERRORS) &&
+	    !ext2fs_dir_block_csum_verify(fs, ino,
+					  (struct ext2_dir_entry *)buf))
+		corrupt = 1;
+
 #ifdef WORDS_BIGENDIAN
-		if (flags & EXT2_DIRBLOCK_V2_STRUCT)
-			dirent->name_len = ext2fs_swab16(dirent->name_len);
+	retval = ext2fs_dirent_swab_in(fs, buf, flags);
 #endif
-		if ((retval = ext2fs_get_rec_len(fs, dirent, &rec_len)) != 0)
-			return retval;
-		if ((rec_len < 8) || (rec_len % 4)) {
-			rec_len = 8;
-			retval = EXT2_ET_DIR_CORRUPTED;
-		} else if (((name_len & 0xFF) + 8) > rec_len)
-			retval = EXT2_ET_DIR_CORRUPTED;
-		p += rec_len;
-	}
+	if (!retval && corrupt)
+		retval = EXT2_ET_DIR_CSUM_INVALID;
 	return retval;
 }
 
+errcode_t ext2fs_read_dir_block3(ext2_filsys fs, blk64_t block,
+				 void *buf, int flags EXT2FS_ATTR((unused)))
+{
+	return ext2fs_read_dir_block4(fs, block, buf, flags, 0);
+}
+
 errcode_t ext2fs_read_dir_block2(ext2_filsys fs, blk_t block,
 				 void *buf, int flags EXT2FS_ATTR((unused)))
 {
@@ -72,45 +63,40 @@ errcode_t ext2fs_read_dir_block(ext2_filsys fs, blk_t block,
 }
 
 
-errcode_t ext2fs_write_dir_block3(ext2_filsys fs, blk64_t block,
-				  void *inbuf, int flags EXT2FS_ATTR((unused)))
+errcode_t ext2fs_write_dir_block4(ext2_filsys fs, blk64_t block,
+				  void *inbuf, int flags EXT2FS_ATTR((unused)),
+				  ext2_ino_t ino)
 {
-#ifdef WORDS_BIGENDIAN
 	errcode_t	retval;
-	char		*p, *end;
-	char		*buf = 0;
-	unsigned int	rec_len;
-	struct ext2_dir_entry *dirent;
+	char		*buf = inbuf;
 
+#ifdef WORDS_BIGENDIAN
 	retval = ext2fs_get_mem(fs->blocksize, &buf);
 	if (retval)
 		return retval;
 	memcpy(buf, inbuf, fs->blocksize);
-	p = buf;
-	end = buf + fs->blocksize;
-	while (p < end) {
-		dirent = (struct ext2_dir_entry *) p;
-		if ((retval = ext2fs_get_rec_len(fs, dirent, &rec_len)) != 0)
-			return retval;
-		if ((rec_len < 8) ||
-		    (rec_len % 4)) {
-			ext2fs_free_mem(&buf);
-			return (EXT2_ET_DIR_CORRUPTED);
-		}
-		p += rec_len;
-		dirent->inode = ext2fs_swab32(dirent->inode);
-		dirent->rec_len = ext2fs_swab16(dirent->rec_len);
-		dirent->name_len = ext2fs_swab16(dirent->name_len);
-
-		if (flags & EXT2_DIRBLOCK_V2_STRUCT)
-			dirent->name_len = ext2fs_swab16(dirent->name_len);
-	}
+	retval = ext2fs_dirent_swab_out(fs, buf, flags);
+	if (retval)
+		return retval;
+#endif
+	retval = ext2fs_dir_block_csum_set(fs, ino,
+					   (struct ext2_dir_entry *)buf);
+	if (retval)
+		goto out;
+
 	retval = io_channel_write_blk64(fs->io, block, 1, buf);
+
+out:
+#ifdef WORDS_BIGENDIAN
 	ext2fs_free_mem(&buf);
-	return retval;
-#else
-	return io_channel_write_blk64(fs->io, block, 1, (char *) inbuf);
 #endif
+	return retval;
+}
+
+errcode_t ext2fs_write_dir_block3(ext2_filsys fs, blk64_t block,
+				  void *inbuf, int flags EXT2FS_ATTR((unused)))
+{
+	return ext2fs_write_dir_block4(fs, block, inbuf, flags, 0);
 }
 
 errcode_t ext2fs_write_dir_block2(ext2_filsys fs, blk_t block,
diff --git a/lib/ext2fs/expanddir.c b/lib/ext2fs/expanddir.c
index 41c40882..22558d66 100644
--- a/lib/ext2fs/expanddir.c
+++ b/lib/ext2fs/expanddir.c
@@ -24,6 +24,7 @@ struct expand_dir_struct {
 	int		newblocks;
 	blk64_t		goal;
 	errcode_t	err;
+	ext2_ino_t	dir;
 };
 
 static int expand_dir_proc(ext2_filsys	fs,
@@ -62,7 +63,8 @@ static int expand_dir_proc(ext2_filsys	fs,
 			return BLOCK_ABORT;
 		}
 		es->done = 1;
-		retval = ext2fs_write_dir_block(fs, new_blk, block);
+		retval = ext2fs_write_dir_block4(fs, new_blk, block, 0,
+						 es->dir);
 	} else {
 		retval = ext2fs_get_mem(fs->blocksize, &block);
 		if (retval) {
@@ -110,6 +112,7 @@ errcode_t ext2fs_expand_dir(ext2_filsys fs, ext2_ino_t dir)
 	es.err = 0;
 	es.goal = 0;
 	es.newblocks = 0;
+	es.dir = dir;
 
 	retval = ext2fs_block_iterate3(fs, dir, BLOCK_FLAG_APPEND,
 				       0, expand_dir_proc, &es);
diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in
index 7289ae1c..430d5670 100644
--- a/lib/ext2fs/ext2_err.et.in
+++ b/lib/ext2fs/ext2_err.et.in
@@ -458,4 +458,7 @@ ec	EXT2_ET_EXTENT_CSUM_INVALID,
 ec	EXT2_ET_DIR_NO_SPACE_FOR_CSUM,
 	"Directory block does not have space for checksum"
 
+ec	EXT2_ET_DIR_CSUM_INVALID,
+	"Directory block checksum does not match directory block"
+
 	end
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index ba4521ad..cc473990 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -943,6 +943,18 @@ extern __u32 ext2fs_crc32c_be(__u32 crc, unsigned char const *p, size_t len);
 extern __u32 ext2fs_crc32c_le(__u32 crc, unsigned char const *p, size_t len);
 
 /* csum.c */
+#define EXT2_DIRENT_TAIL(block, blocksize) \
+	((struct ext2_dir_entry_tail *)(((void *)(block)) + \
+	(blocksize) - sizeof(struct ext2_dir_entry_tail)))
+
+extern void ext2fs_initialize_dirent_tail(ext2_filsys fs,
+					  struct ext2_dir_entry_tail *t);
+extern int ext2fs_dirent_has_tail(ext2_filsys fs,
+				  struct ext2_dir_entry *dirent);
+extern int ext2fs_dir_block_csum_verify(ext2_filsys fs, ext2_ino_t inum,
+					struct ext2_dir_entry *dirent);
+extern errcode_t ext2fs_dir_block_csum_set(ext2_filsys fs, ext2_ino_t inum,
+					   struct ext2_dir_entry *dirent);
 extern errcode_t ext2fs_get_dx_countlimit(ext2_filsys fs,
 					  struct ext2_dir_entry *dirent,
 					  struct ext2_dx_countlimit **cc,
@@ -1025,12 +1037,16 @@ extern errcode_t ext2fs_read_dir_block2(ext2_filsys fs, blk_t block,
 					void *buf, int flags);
 extern errcode_t ext2fs_read_dir_block3(ext2_filsys fs, blk64_t block,
 					void *buf, int flags);
+extern errcode_t ext2fs_read_dir_block4(ext2_filsys fs, blk64_t block,
+					void *buf, int flags, ext2_ino_t ino);
 extern errcode_t ext2fs_write_dir_block(ext2_filsys fs, blk_t block,
 					void *buf);
 extern errcode_t ext2fs_write_dir_block2(ext2_filsys fs, blk_t block,
 					 void *buf, int flags);
 extern errcode_t ext2fs_write_dir_block3(ext2_filsys fs, blk64_t block,
 					 void *buf, int flags);
+extern errcode_t ext2fs_write_dir_block4(ext2_filsys fs, blk64_t block,
+					 void *buf, int flags, ext2_ino_t ino);
 
 /* dirhash.c */
 extern errcode_t ext2fs_dirhash(int version, const char *name, int len,
@@ -1427,6 +1443,8 @@ extern errcode_t ext2fs_read_bb_FILE(ext2_filsys fs, FILE *f,
 extern errcode_t ext2fs_create_resize_inode(ext2_filsys fs);
 
 /* swapfs.c */
+extern errcode_t ext2fs_dirent_swab_in(ext2_filsys fs, char *buf, int flags);
+extern errcode_t ext2fs_dirent_swab_out(ext2_filsys fs, char *buf, int flags);
 extern void ext2fs_swap_ext_attr(char *to, char *from, int bufsize,
 				 int has_header);
 extern void ext2fs_swap_ext_attr_header(struct ext2_ext_attr_header *to_header,
diff --git a/lib/ext2fs/link.c b/lib/ext2fs/link.c
index 2d03b573..2dec5dc2 100644
--- a/lib/ext2fs/link.c
+++ b/lib/ext2fs/link.c
@@ -41,6 +41,7 @@ static int link_proc(struct ext2_dir_entry *dirent,
 	struct ext2_dir_entry *next;
 	unsigned int rec_len, min_rec_len, curr_rec_len;
 	int ret = 0;
+	int csum_size = 0;
 
 	rec_len = EXT2_DIR_REC_LEN(ls->namelen);
 
@@ -48,12 +49,15 @@ static int link_proc(struct ext2_dir_entry *dirent,
 	if (ls->err)
 		return DIRENT_ABORT;
 
+	if (EXT2_HAS_RO_COMPAT_FEATURE(ls->fs->super,
+				       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		csum_size = sizeof(struct ext2_dir_entry_tail);
 	/*
 	 * See if the following directory entry (if any) is unused;
 	 * if so, absorb it into this one.
 	 */
 	next = (struct ext2_dir_entry *) (buf + offset + curr_rec_len);
-	if ((offset + (int) curr_rec_len < blocksize - 8) &&
+	if ((offset + (int) curr_rec_len < blocksize - (8 + csum_size)) &&
 	    (next->inode == 0) &&
 	    (offset + (int) curr_rec_len + (int) next->rec_len <= blocksize)) {
 		curr_rec_len += next->rec_len;
diff --git a/lib/ext2fs/mkdir.c b/lib/ext2fs/mkdir.c
index 861ddabb..4a854391 100644
--- a/lib/ext2fs/mkdir.c
+++ b/lib/ext2fs/mkdir.c
@@ -100,7 +100,7 @@ errcode_t ext2fs_mkdir(ext2_filsys fs, ext2_ino_t parent, ext2_ino_t inum,
 	retval = ext2fs_write_new_inode(fs, ino, &inode);
 	if (retval)
 		goto cleanup;
-	retval = ext2fs_write_dir_block(fs, blk, block);
+	retval = ext2fs_write_dir_block4(fs, blk, block, 0, ino);
 	if (retval)
 		goto cleanup;
 
diff --git a/lib/ext2fs/newdir.c b/lib/ext2fs/newdir.c
index b0a1e476..2cd541d7 100644
--- a/lib/ext2fs/newdir.c
+++ b/lib/ext2fs/newdir.c
@@ -34,6 +34,8 @@ errcode_t ext2fs_new_dir_block(ext2_filsys fs, ext2_ino_t dir_ino,
 	char			*buf;
 	int			rec_len;
 	int			filetype = 0;
+	struct ext2_dir_entry_tail	*t;
+	int			csum_size = 0;
 
 	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 
@@ -43,7 +45,11 @@ errcode_t ext2fs_new_dir_block(ext2_filsys fs, ext2_ino_t dir_ino,
 	memset(buf, 0, fs->blocksize);
 	dir = (struct ext2_dir_entry *) buf;
 
-	retval = ext2fs_set_rec_len(fs, fs->blocksize, dir);
+	if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+				       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		csum_size = sizeof(struct ext2_dir_entry_tail);
+
+	retval = ext2fs_set_rec_len(fs, fs->blocksize - csum_size, dir);
 	if (retval)
 		return retval;
 
@@ -57,7 +63,7 @@ errcode_t ext2fs_new_dir_block(ext2_filsys fs, ext2_ino_t dir_ino,
 		dir->inode = dir_ino;
 		dir->name_len = 1 | filetype;
 		dir->name[0] = '.';
-		rec_len = fs->blocksize - EXT2_DIR_REC_LEN(1);
+		rec_len = (fs->blocksize - csum_size) - EXT2_DIR_REC_LEN(1);
 		dir->rec_len = EXT2_DIR_REC_LEN(1);
 
 		/*
@@ -73,6 +79,11 @@ errcode_t ext2fs_new_dir_block(ext2_filsys fs, ext2_ino_t dir_ino,
 		dir->name[1] = '.';
 
 	}
+
+	if (csum_size) {
+		t = EXT2_DIRENT_TAIL(buf, fs->blocksize);
+		ext2fs_initialize_dirent_tail(fs, t);
+	}
 	*block = buf;
 	return 0;
 }
diff --git a/lib/ext2fs/swapfs.c b/lib/ext2fs/swapfs.c
index 7c99373c..69916e59 100644
--- a/lib/ext2fs/swapfs.c
+++ b/lib/ext2fs/swapfs.c
@@ -350,4 +350,66 @@ void ext2fs_swap_mmp(struct mmp_struct *mmp)
 	mmp->mmp_check_interval = ext2fs_swab16(mmp->mmp_check_interval);
 }
 
+errcode_t ext2fs_dirent_swab_in(ext2_filsys fs, char *buf, int flags)
+{
+	errcode_t	retval;
+	char		*p, *end;
+	struct ext2_dir_entry *dirent;
+	unsigned int	name_len, rec_len;
+
+	p = (char *) buf;
+	end = (char *) buf + fs->blocksize;
+	while (p < end-8) {
+		dirent = (struct ext2_dir_entry *) p;
+		dirent->inode = ext2fs_swab32(dirent->inode);
+		dirent->rec_len = ext2fs_swab16(dirent->rec_len);
+		dirent->name_len = ext2fs_swab16(dirent->name_len);
+		name_len = dirent->name_len;
+		if (flags & EXT2_DIRBLOCK_V2_STRUCT)
+			dirent->name_len = ext2fs_swab16(dirent->name_len);
+		retval = ext2fs_get_rec_len(fs, dirent, &rec_len);
+		if (retval)
+			return retval;
+		if ((rec_len < 8) || (rec_len % 4)) {
+			rec_len = 8;
+			retval = EXT2_ET_DIR_CORRUPTED;
+		} else if (((name_len & 0xFF) + 8) > rec_len)
+			retval = EXT2_ET_DIR_CORRUPTED;
+		p += rec_len;
+	}
+
+	return 0;
+}
+
+errcode_t ext2fs_dirent_swab_out(ext2_filsys fs, char *buf, int flags)
+{
+	errcode_t	retval;
+	char		*p, *end;
+	unsigned int	rec_len;
+	struct ext2_dir_entry *dirent;
+
+	p = buf;
+	end = buf + fs->blocksize;
+	while (p < end) {
+		dirent = (struct ext2_dir_entry *) p;
+		retval = ext2fs_get_rec_len(fs, dirent, &rec_len);
+		if (retval)
+			return retval;
+		if ((rec_len < 8) ||
+		    (rec_len % 4)) {
+			ext2fs_free_mem(&buf);
+			return EXT2_ET_DIR_CORRUPTED;
+		}
+		p += rec_len;
+		dirent->inode = ext2fs_swab32(dirent->inode);
+		dirent->rec_len = ext2fs_swab16(dirent->rec_len);
+		dirent->name_len = ext2fs_swab16(dirent->name_len);
+
+		if (flags & EXT2_DIRBLOCK_V2_STRUCT)
+			dirent->name_len = ext2fs_swab16(dirent->name_len);
+	}
+
+	return 0;
+}
+
 #endif