Re: [PATCH v2 net-next 13/23] rtnetlink: Update ipmr_rtm_dumplink for strict data checking

[Christian Brauner <christian@brauner.io>]

On Sun, Oct 07, 2018 at 08:16:34PM -0700, David Ahern wrote:
> From: David Ahern <dsahern@gmail.com>
> 
> Update ipmr_rtm_dumplink 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/ipv4/ipmr.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
> index 5660adcf7a04..e7322e407bb4 100644
> --- a/net/ipv4/ipmr.c
> +++ b/net/ipv4/ipmr.c
> @@ -2710,6 +2710,31 @@ static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb)
>  	return true;
>  }
>  
> +static int ipmr_valid_dumplink(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(extack, "ipv4: Invalid header for ipmr link dump");
> +		return -EINVAL;
> +	}
> +
> +	if (nlmsg_attrlen(nlh, sizeof(*ifm))) {
> +		NL_SET_ERR_MSG(extack, "Invalid data after header in ipmr link dump");
> +		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(extack, "Invalid values in header for ipmr link dump request");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
>  static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb)
>  {
>  	struct net *net = sock_net(skb->sk);
> @@ -2718,6 +2743,13 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb)
>  	unsigned int e = 0, s_e;
>  	struct mr_table *mrt;
>  
> +	if (cb->strict_check) {
> +		int err = ipmr_valid_dumplink(cb->nlh, cb->extack);
> +
> +		if (err < 0)
> +			return err;
> +	}
> +
>  	s_t = cb->args[0];
>  	s_e = cb->args[1];
>  
> -- 
> 2.11.0
>