netdev - Re: [PATCH v2 net-next 07/23] net/ipv4: Update inet_dump

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Date:   Mon, 8 Oct 2018 12:06:57 +0200
From:   Christian Brauner <christian@...uner.io>
To:     David Ahern <dsahern@...nel.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, jbenc@...hat.com,
        stephen@...workplumber.org, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH v2 net-next 07/23] net/ipv4: Update inet_dump_ifaddr for
 strict data checking

On Sun, Oct 07, 2018 at 08:16:28PM -0700, David Ahern wrote:
> From: David Ahern <dsahern@...il.com>
> 
> Update inet_dump_ifaddr for strict data checking. If the flag is set,
> the dump request is expected to have an ifaddrmsg struct as the header
> potentially followed by one or more attributes. Any data passed in the
> header or as an attribute is taken as a request to influence the data
> returned. Only values supported by the dump handler are allowed to be
> non-0 or set in the request. At the moment only the IFA_TARGET_NETNSID
> attribute is supported. Follow on patches can support for other fields
> (e.g., honor ifa_index and only return data for the given device index).
> 
> Signed-off-by: David Ahern <dsahern@...il.com>

Thanks, with the *_strict() it looks way cleaner now.

Acked-by: Christian Brauner <christian@...uner.io>

> ---
>  net/ipv4/devinet.c | 72 +++++++++++++++++++++++++++++++++++++++++++++---------
>  1 file changed, 61 insertions(+), 11 deletions(-)
> 
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index ab2b11df5ea4..6f2bbd04e950 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1660,17 +1660,70 @@ static int inet_fill_ifaddr(struct sk_buff *skb, struct in_ifaddr *ifa,
>  	return -EMSGSIZE;
>  }
>  
> +static int inet_valid_dump_ifaddr_req(const struct nlmsghdr *nlh,
> +				      struct inet_fill_args *fillargs,
> +				      struct net **tgt_net, struct sock *sk,
> +				      struct netlink_ext_ack *extack)
> +{
> +	struct nlattr *tb[IFA_MAX+1];
> +	struct ifaddrmsg *ifm;
> +	int err, i;
> +
> +	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ifm))) {
> +		NL_SET_ERR_MSG(extack, "ipv4: Invalid header for address dump request");
> +		return -EINVAL;
> +	}
> +
> +	ifm = nlmsg_data(nlh);
> +	if (ifm->ifa_prefixlen || ifm->ifa_flags || ifm->ifa_scope) {
> +		NL_SET_ERR_MSG(extack, "ipv4: Invalid values in header for address dump request");
> +		return -EINVAL;
> +	}
> +	if (ifm->ifa_index) {
> +		NL_SET_ERR_MSG(extack, "ipv4: Filter by device index not supported for address dump");
> +		return -EINVAL;
> +	}
> +
> +	err = nlmsg_parse_strict(nlh, sizeof(*ifm), tb, IFA_MAX,
> +				 ifa_ipv4_policy, extack);
> +	if (err < 0)
> +		return err;
> +
> +	for (i = 0; i <= IFA_MAX; ++i) {
> +		if (!tb[i])
> +			continue;
> +
> +		if (i == IFA_TARGET_NETNSID) {
> +			struct net *net;
> +
> +			fillargs->netnsid = nla_get_s32(tb[i]);
> +
> +			net = rtnl_get_net_ns_capable(sk, fillargs->netnsid);
> +			if (IS_ERR(net)) {
> +				NL_SET_ERR_MSG(extack, "ipv4: Invalid target network namespace id");
> +				return PTR_ERR(net);
> +			}
> +			*tgt_net = net;
> +		} else {
> +			NL_SET_ERR_MSG(extack, "ipv4: Unsupported attribute in dump request");
> +			return -EINVAL;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
>  {
> +	const struct nlmsghdr *nlh = cb->nlh;
>  	struct inet_fill_args fillargs = {
>  		.portid = NETLINK_CB(cb->skb).portid,
> -		.seq = cb->nlh->nlmsg_seq,
> +		.seq = nlh->nlmsg_seq,
>  		.event = RTM_NEWADDR,
>  		.flags = NLM_F_MULTI,
>  		.netnsid = -1,
>  	};
>  	struct net *net = sock_net(skb->sk);
> -	struct nlattr *tb[IFA_MAX+1];
>  	struct net *tgt_net = net;
>  	int h, s_h;
>  	int idx, s_idx;
> @@ -1684,16 +1737,13 @@ static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
>  	s_idx = idx = cb->args[1];
>  	s_ip_idx = ip_idx = cb->args[2];
>  
> -	if (nlmsg_parse(cb->nlh, sizeof(struct ifaddrmsg), tb, IFA_MAX,
> -			ifa_ipv4_policy, cb->extack) >= 0) {
> -		if (tb[IFA_TARGET_NETNSID]) {
> -			fillargs.netnsid = nla_get_s32(tb[IFA_TARGET_NETNSID]);
> +	if (cb->strict_check) {
> +		int err;
>  
> -			tgt_net = rtnl_get_net_ns_capable(skb->sk,
> -							  fillargs.netnsid);
> -			if (IS_ERR(tgt_net))
> -				return PTR_ERR(tgt_net);
> -		}
> +		err = inet_valid_dump_ifaddr_req(nlh, &fillargs, &tgt_net,
> +						 skb->sk, cb->extack);
> +		if (err < 0)
> +			return err;
>  	}
>  
>  	for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
> -- 
> 2.11.0
>