udf: Avoid run away loop when partition table length is corrupted

Check provided length of partition table so that (possibly maliciously)
corrupted partition table cannot cause accessing data beyond current buffer.

Signed-off-by: Jan Kara <jack@suse.cz>
static struct inode *udf_alloc_inode(struct super_block *sb)
{
	struct udf_inode_info *ei;
	ei = kmem_cache_alloc(udf_inode_cachep, GFP_KERNEL);
	if (!ei)
		return NULL;

	ei->i_unique = 0;
	ei->i_lenExtents = 0;
	ei->i_next_alloc_block = 0;
	ei->i_next_alloc_goal = 0;
	ei->i_strat4096 = 0;
	init_rwsem(&ei->i_data_sem);

	return &ei->vfs_inode;
}

static struct inode *udf_alloc_inode(struct super_block *sb)
{
	struct udf_inode_info *ei;
	ei = kmem_cache_alloc(udf_inode_cachep, GFP_KERNEL);
	if (!ei)
		return NULL;

	ei->i_unique = 0;
	ei->i_lenExtents = 0;
	ei->i_next_alloc_block = 0;
	ei->i_next_alloc_goal = 0;
	ei->i_strat4096 = 0;
	init_rwsem(&ei->i_data_sem);

	return &ei->vfs_inode;
}
