netdev - Re: [PATCH RFC net-next 5/5] net/ipv6: Update inet6_dump_addr to support NLM_F_DUMP_PROPER

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Date:   Fri, 28 Sep 2018 20:42:26 +0200
From:   Christian Brauner <christian@...uner.io>
To:     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 RFC net-next 5/5] net/ipv6: Update inet6_dump_addr to
 support NLM_F_DUMP_PROPER_HDR

On Fri, Sep 28, 2018 at 08:45:02AM -0700, dsahern@...nel.org wrote:
> From: David Ahern <dsahern@...il.com>
> 
> Update inet6_dump_addr to check for NLM_F_DUMP_PROPER_HDR in the netlink
> message header. 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 suppored 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
> will 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>
> ---
>  net/ipv6/addrconf.c | 50 ++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 40 insertions(+), 10 deletions(-)
> 
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 375ea9d9869b..888e5a4b8dd2 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -5001,6 +5001,8 @@ static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb,
>  static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
>  			   enum addr_type_t type)
>  {
> +	struct netlink_ext_ack *extack = cb->extack;
> +	const struct nlmsghdr *nlh = cb->nlh;
>  	struct inet6_fill_args fillargs = {
>  		.portid = NETLINK_CB(cb->skb).portid,
>  		.seq = cb->nlh->nlmsg_seq,
> @@ -5009,7 +5011,6 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
>  		.type = type,
>  	};
>  	struct net *net = sock_net(skb->sk);
> -	struct nlattr *tb[IFA_MAX+1];
>  	struct net *tgt_net = net;
>  	int h, s_h;
>  	int idx, ip_idx;
> @@ -5022,17 +5023,46 @@ static int inet6_dump_addr(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_ipv6_policy, NULL) >= 0) {
> -		if (tb[IFA_TARGET_NETNSID]) {
> -			fillargs.netnsid = nla_get_s32(tb[IFA_TARGET_NETNSID]);
> +	if (nlh->nlmsg_flags & NLM_F_DUMP_PROPER_HDR) {
> +		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, "Invalid header");
> +			return -EINVAL;
> +		}
>  
> -			tgt_net = rtnl_get_net_ns_capable(skb->sk,
> -							  fillargs.netnsid);
> -			if (IS_ERR(tgt_net))
> -				return PTR_ERR(tgt_net);
> +		ifm = (struct ifaddrmsg *)nlmsg_data(cb->nlh);
> +		if (ifm->ifa_prefixlen || ifm->ifa_flags || ifm->ifa_scope) {
> +			NL_SET_ERR_MSG(extack, "Invalid values in header for dump request");
> +			return -EINVAL;
> +		}
> +		if (ifm->ifa_index) {
> +			NL_SET_ERR_MSG(extack, "Filter by device index not supported");
> +			return -EINVAL;
> +		}
>  
> -			fillargs.flags |= NLM_F_DUMP_FILTERED;
> +		err = nlmsg_parse(cb->nlh, sizeof(struct ifaddrmsg), tb, IFA_MAX,
> +				  ifa_ipv6_policy, NULL);
> +		if (err < 0)
> +			return err;
> +
> +		for (i = 0; i < IFA_MAX; ++i) {
> +			if (i == IFA_TARGET_NETNSID) {
> +				fillargs.netnsid = nla_get_s32(tb[i]);
> +
> +				tgt_net = rtnl_get_net_ns_capable(skb->sk,
> +								  fillargs.netnsid);
> +				if (IS_ERR(tgt_net))
> +					return PTR_ERR(tgt_net);
> +
> +				fillargs.flags |= NLM_F_DUMP_FILTERED;
> +			}
> +			if (tb[i]) {
> +				NL_SET_ERR_MSG(extack, "Unsupported attribute in dump request");
> +				return -EINVAL;
> +			}

Same comment/question as for ipv4. Shouldn't it be:


   	for (i = 0; i < IFA_MAX; ++i) {
   		if (i == IFA_TARGET_NETNSID && tb[i]) {
   			fillargs.netnsid = nla_get_s32(tb[i]);

   			tgt_net = rtnl_get_net_ns_capable(skb->sk,
   							  fillargs.netnsid);
   			if (IS_ERR(tgt_net))
   				return PTR_ERR(tgt_net);

   			fillargs.flags |= NLM_F_DUMP_FILTERED;
			continue;
   		}
   		if (tb[i]) {
   			NL_SET_ERR_MSG(extack, "Unsupported attribute in dump request");
   			return -EINVAL;
   		}
>  		}
>  	}
>  
> -- 
> 2.11.0
>