isofs: avoid info leak on export

For type 1 the parent_offset member in struct isofs_fid gets copied
uninitialized to userland. Fix this by initializing it to 0.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
isofs_export_iget(struct super_block *sb,
		  unsigned long block,
		  unsigned long offset,
		  __u32 generation)
{
	struct inode *inode;

	if (block == 0)
		return ERR_PTR(-ESTALE);
	inode = isofs_iget(sb, block, offset);
	if (IS_ERR(inode))
		return ERR_CAST(inode);
	if (generation && inode->i_generation != generation) {
		iput(inode);
		return ERR_PTR(-ESTALE);
	}
	return d_obtain_alias(inode);
}

isofs_export_iget(struct super_block *sb,
		  unsigned long block,
		  unsigned long offset,
		  __u32 generation)
{
	struct inode *inode;

	if (block == 0)
		return ERR_PTR(-ESTALE);
	inode = isofs_iget(sb, block, offset);
	if (IS_ERR(inode))
		return ERR_CAST(inode);
	if (generation && inode->i_generation != generation) {
		iput(inode);
		return ERR_PTR(-ESTALE);
	}
	return d_obtain_alias(inode);
}
