netdev - Re: [PATCH net-next 03/13] ipv4: Create init helper for fib

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Date:   Wed, 27 Mar 2019 08:12:11 +0000
From:   Ido Schimmel <idosch@...lanox.com>
To:     David Ahern <dsahern@...nel.org>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Jiri Pirko <jiri@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        David Ahern <dsahern@...il.com>
Subject: Re: [PATCH net-next 03/13] ipv4: Create init helper for fib_nh

On Tue, Mar 26, 2019 at 08:29:32PM -0700, David Ahern wrote:
> +int fib_nh_init(struct net *net, struct fib_nh *nh,
> +		struct fib_config *cfg, int nh_weight,
> +		struct netlink_ext_ack *extack)
> +{
> +	int err = -ENOMEM;
> +
> +	nh->nh_pcpu_rth_output = alloc_percpu(struct rtable __rcu *);
> +	if (!nh->nh_pcpu_rth_output)
> +		goto failure;
> +
> +	if (cfg->fc_encap) {
> +		struct lwtunnel_state *lwtstate;
> +
> +		err = -EINVAL;
> +		if (cfg->fc_encap_type == LWTUNNEL_ENCAP_NONE) {
> +			NL_SET_ERR_MSG(extack, "LWT encap type not specified");
> +			goto failure;

This is very confusing and probably error-prone. You call
alloc_percpu(), but don't free it in the error path and instead rely on
the call to free_fib_info() in the error path of fib_create_info().
Better to free it here and NULL-ify the pointer. Then the call to
rt_fibinfo_free_cpus() in free_fib_info_rcu() is basically a NOP.

> +		}
> +		err = lwtunnel_build_state(cfg->fc_encap_type,
> +					   cfg->fc_encap, AF_INET, cfg,
> +					   &lwtstate, extack);
> +		if (err)
> +			goto failure;
> +
> +		nh->nh_lwtstate = lwtstate_get(lwtstate);
> +	}
> +
> +	nh->nh_oif   = cfg->fc_oif;
> +	nh->nh_gw    = cfg->fc_gw;
> +	nh->nh_flags = cfg->fc_flags;
> +
> +#ifdef CONFIG_IP_ROUTE_CLASSID
> +	nh->nh_tclassid = cfg->fc_flow;
> +	if (nh->nh_tclassid)
> +		net->ipv4.fib_num_tclassid_users++;
> +#endif
> +#ifdef CONFIG_IP_ROUTE_MULTIPATH
> +	nh->nh_weight = nh_weight;
> +#endif
> +	err = 0;
> +
> +failure:
> +	return err;
> +}