ext4: check inline directory before converting

Before converting an inline directory to a regular directory, check
the directory entries to make sure they're not obviously broken.
This helps us to avoid a BUG_ON if one of the dirents is trashed.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>

fs/ext4/dir.c

@@ -571,6 +571,31 @@ static int ext4_release_dir(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+int ext4_check_all_de(struct inode *dir, struct buffer_head *bh, void *buf,
+		      int buf_size)
+{
+	struct ext4_dir_entry_2 *de;
+	int nlen, rlen;
+	unsigned int offset = 0;
+	char *top;
+
+	de = (struct ext4_dir_entry_2 *)buf;
+	top = buf + buf_size;
+	while ((char *) de < top) {
+		if (ext4_check_dir_entry(dir, NULL, de, bh,
+					 buf, buf_size, offset))
+			return -EIO;
+		nlen = EXT4_DIR_REC_LEN(de->name_len);
+		rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
+		de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
+		offset += rlen;
+	}
+	if ((char *) de > top)
+		return -EIO;
+
+	return 0;
+}
+
 const struct file_operations ext4_dir_operations = {
 	.llseek		= ext4_dir_llseek,
 	.read		= generic_read_dir,

fs/ext4/ext4.h

@@ -2028,6 +2028,8 @@ static inline  unsigned char get_dtype(struct super_block *sb, int filetype)
 
 	return ext4_filetype_table[filetype];
 }
+extern int ext4_check_all_de(struct inode *dir, struct buffer_head *bh,
+			     void *buf, int buf_size);
 
 /* fsync.c */
 extern int ext4_sync_file(struct file *, loff_t, loff_t, int);

fs/ext4/inline.c

@@ -1172,6 +1172,18 @@ static int ext4_convert_inline_data_nolock(handle_t *handle,
 	if (error < 0)
 		goto out;
 
+	/*
+	 * Make sure the inline directory entries pass checks before we try to
+	 * convert them, so that we avoid touching stuff that needs fsck.
+	 */
+	if (S_ISDIR(inode->i_mode)) {
+		error = ext4_check_all_de(inode, iloc->bh,
+					buf + EXT4_INLINE_DOTDOT_SIZE,
+					inline_size - EXT4_INLINE_DOTDOT_SIZE);
+		if (error)
+			goto out;
+	}
+
 	error = ext4_destroy_inline_data_nolock(handle, inode);
 	if (error)
 		goto out;