Netdev List

* Re: [PATCH net-next 06/20] net/ipv4: Update inet_dump_ifaddr for strict data checking
From: Christian Brauner @ 2018-10-05 18:02 UTC (permalink / raw)
  To: David Ahern; +Cc: netdev, davem, jbenc, stephen, David Ahern
In-Reply-To: <20181004213355.14899-7-dsahern@kernel.org>

On Thu, Oct 04, 2018 at 02:33:41PM -0700, David Ahern wrote:
> From: David Ahern <dsahern@gmail.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@gmail.com>
> ---
>  net/ipv4/devinet.c | 53 +++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 43 insertions(+), 10 deletions(-)
> 
> diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
> index ab2b11df5ea4..af968d4fe4fc 100644
> --- a/net/ipv4/devinet.c
> +++ b/net/ipv4/devinet.c
> @@ -1662,15 +1662,16 @@ static int inet_fill_ifaddr(struct sk_buff *skb, struct in_ifaddr *ifa,
>  
>  static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
>  {
> +	struct netlink_ext_ack *extack = cb->extack;
> +	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;
> @@ -1684,15 +1685,47 @@ 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) {
> +		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;
> +		}
> +
> +		ifm = nlmsg_data(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;
> +		}
> +
> +		err = nlmsg_parse(nlh, sizeof(struct ifaddrmsg), tb, IFA_MAX,
> +				  ifa_ipv4_policy, extack);
> +		if (err < 0)
> +			return err;
>  
> -			tgt_net = rtnl_get_net_ns_capable(skb->sk,
> -							  fillargs.netnsid);
> -			if (IS_ERR(tgt_net))
> -				return PTR_ERR(tgt_net);
> +		for (i = 0; i <= IFA_MAX; ++i) {
> +			if (!tb[i])
> +				continue;
> +			if (i == IFA_TARGET_NETNSID) {

Nit: For the sake of readability there could be an additional newline between the 
"continue" and the next if () condition.

> +				fillargs.netnsid = nla_get_s32(tb[i]);
> +
> +				tgt_net = rtnl_get_net_ns_capable(skb->sk,
> +								  fillargs.netnsid);
> +				if (IS_ERR(tgt_net)) {
> +					NL_SET_ERR_MSG(extack, "Invalid target namespace id");

Nit: Hm, maybe "Invalid target network namespace id" would be better.
You never know what namespace comes along some time later. :)

> +					return PTR_ERR(tgt_net);
> +				}
> +			} else {
> +				NL_SET_ERR_MSG(extack, "Unsupported attribute in dump request");
> +				return -EINVAL;
> +			}
>  		}
>  	}
>  
> -- 
> 2.11.0
> 

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