void nfs_fattr_free_names(struct nfs_fattr *fattr)
{
	if (fattr->valid & NFS_ATTR_FATTR_OWNER_NAME)
		nfs_fattr_free_owner_name(fattr);
	if (fattr->valid & NFS_ATTR_FATTR_GROUP_NAME)
		nfs_fattr_free_group_name(fattr);
}

The product dereferences a pointer that it expects to be valid but is NULL.