static bool nfs_fattr_map_group_name(struct nfs_server *server, struct nfs_fattr *fattr)
{
	struct nfs4_string *group = fattr->group_name;
	kgid_t gid;

	if (!(fattr->valid & NFS_ATTR_FATTR_GROUP_NAME))
		return false;
	if (nfs_map_group_to_gid(server, group->data, group->len, &gid) == 0) {
		fattr->gid = gid;
		fattr->valid |= NFS_ATTR_FATTR_GROUP;
	}
	return true;
}

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