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Date:   Mon, 29 Jul 2019 10:52:16 -0700 (PDT)
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To:     jiri@resnulli.us
Cc:     netdev@vger.kernel.org, jakub.kicinski@netronome.com,
        sthemmin@microsoft.com, dsahern@gmail.com, mlxsw@mellanox.com
Subject: Re: [patch net-next 1/3] net: devlink: allow to change namespaces
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20190727094459.26345-2-jiri@resnulli.us>
References: <20190727094459.26345-1-jiri@resnulli.us>
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From: Jiri Pirko <jiri@resnulli.us>
Date: Sat, 27 Jul 2019 11:44:57 +0200

> +	if ((netns_pid_attr && (netns_fd_attr || netns_id_attr)) ||
> +	    (netns_fd_attr && (netns_pid_attr || netns_id_attr)) ||
> +	    (netns_id_attr && (netns_pid_attr || netns_fd_attr))) {
> +		NL_SET_ERR_MSG(info->extack, "multiple netns identifying attributes specified");
> +		return ERR_PTR(-EINVAL);
> +	}

How about:

	if (!!a + !!b + !!c > 1) {
	...

> +
> +	if (netns_pid_attr) {
> +		net = get_net_ns_by_pid(nla_get_u32(netns_pid_attr));
> +	} else if (netns_fd_attr) {
> +		net = get_net_ns_by_fd(nla_get_u32(netns_fd_attr));
> +	} else if (netns_id_attr) {
> +		net = get_net_ns_by_id(sock_net(skb->sk),
> +				       nla_get_u32(netns_id_attr));
> +		if (!net)
> +			net = ERR_PTR(-EINVAL);
> +	}
> +	if (IS_ERR(net)) {

I think this is going to be one of those cases where a compiler won't be able
to prove that 'net' is guaranteed to be initialized at this spot.  Please
rearrange this code somehow so that is unlikely to happen.

Thanks.