Re: [PATCH v2 net-next 12/23] rtnetlink: Update inet6_dump_ifinfo for strict data checking

[Christian Brauner <christian@brauner.io>]

On Sun, Oct 07, 2018 at 08:16:33PM -0700, David Ahern wrote:
> From: David Ahern <dsahern@gmail.com>
> 
> Update inet6_dump_ifinfo for strict data checking. If the flag is
> set, the dump request is expected to have an ifinfomsg struct as
> the header. All elements of the struct are expected to be 0 and no
> attributes can be appended.
> 
> Signed-off-by: David Ahern <dsahern@gmail.com>

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

> ---
>  net/ipv6/addrconf.c | 35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
> 
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index 095d3f56f0a9..ce071d85ad00 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -5644,6 +5644,31 @@ static int inet6_fill_ifinfo(struct sk_buff *skb, struct inet6_dev *idev,
>  	return -EMSGSIZE;
>  }
>  
> +static int inet6_valid_dump_ifinfo(const struct nlmsghdr *nlh,
> +				   struct netlink_ext_ack *extack)
> +{
> +	struct ifinfomsg *ifm;
> +
> +	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ifm))) {
> +		NL_SET_ERR_MSG_MOD(extack, "Invalid header for link dump request");
> +		return -EINVAL;
> +	}
> +
> +	if (nlmsg_attrlen(nlh, sizeof(*ifm))) {
> +		NL_SET_ERR_MSG_MOD(extack, "Invalid data after header");
> +		return -EINVAL;
> +	}
> +
> +	ifm = nlmsg_data(nlh);
> +	if (ifm->__ifi_pad || ifm->ifi_type || ifm->ifi_flags ||
> +	    ifm->ifi_change || ifm->ifi_index) {
> +		NL_SET_ERR_MSG_MOD(extack, "Invalid values in header for dump request");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
>  static int inet6_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
>  {
>  	struct net *net = sock_net(skb->sk);
> @@ -5653,6 +5678,16 @@ static int inet6_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
>  	struct inet6_dev *idev;
>  	struct hlist_head *head;
>  
> +	/* only requests using strict checking can pass data to
> +	 * influence the dump
> +	 */
> +	if (cb->strict_check) {
> +		int err = inet6_valid_dump_ifinfo(cb->nlh, cb->extack);
> +
> +		if (err < 0)
> +			return err;
> +	}
> +
>  	s_h = cb->args[0];
>  	s_idx = cb->args[1];
>  
> -- 
> 2.11.0
>