netdev - Re: [PATCH v2 net-next 10/23] rtnetlink: Update rtnl_bridge

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Date:   Mon, 8 Oct 2018 12:15:59 +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 10/23] rtnetlink: Update rtnl_bridge_getlink
 for strict data checking

On Sun, Oct 07, 2018 at 08:16:31PM -0700, David Ahern wrote:
> From: David Ahern <dsahern@...il.com>
> 
> Update rtnl_bridge_getlink for strict data checking. If the flag is set,
> the dump request is expected to have an ifinfomsg 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 IFLA_EXT_MASK
> attribute is supported.
> 
> Signed-off-by: David Ahern <dsahern@...il.com>

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

> ---
>  net/core/rtnetlink.c | 70 ++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 57 insertions(+), 13 deletions(-)
> 
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 12fd52105005..e38e1f178611 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -4021,28 +4021,72 @@ int ndo_dflt_bridge_getlink(struct sk_buff *skb, u32 pid, u32 seq,
>  }
>  EXPORT_SYMBOL_GPL(ndo_dflt_bridge_getlink);
>  
> +static int valid_bridge_getlink_req(const struct nlmsghdr *nlh,
> +				    bool strict_check, u32 *filter_mask,
> +				    struct netlink_ext_ack *extack)
> +{
> +	struct nlattr *tb[IFLA_MAX+1];
> +	int err, i;
> +
> +	if (strict_check) {
> +		struct ifinfomsg *ifm;
> +
> +		if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ifm))) {
> +			NL_SET_ERR_MSG(extack, "Invalid header for bridge 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 bridge link dump request");
> +			return -EINVAL;
> +		}
> +
> +		err = nlmsg_parse_strict(nlh, sizeof(struct ifinfomsg), tb,
> +					 IFLA_MAX, ifla_policy, extack);
> +	} else {
> +		err = nlmsg_parse(nlh, sizeof(struct ifinfomsg), tb,
> +				  IFLA_MAX, ifla_policy, extack);
> +	}
> +	if (err < 0)
> +		return err;
> +
> +	/* new attributes should only be added with strict checking */
> +	for (i = 0; i <= IFLA_MAX; ++i) {
> +		if (!tb[i])
> +			continue;
> +
> +		switch (i) {
> +		case IFLA_EXT_MASK:
> +			*filter_mask = nla_get_u32(tb[i]);
> +			break;
> +		default:
> +			if (strict_check) {
> +				NL_SET_ERR_MSG(extack, "Unsupported attribute in bridge link dump request");
> +				return -EINVAL;
> +			}
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static int rtnl_bridge_getlink(struct sk_buff *skb, struct netlink_callback *cb)
>  {
> +	const struct nlmsghdr *nlh = cb->nlh;
>  	struct net *net = sock_net(skb->sk);
>  	struct net_device *dev;
>  	int idx = 0;
>  	u32 portid = NETLINK_CB(cb->skb).portid;
> -	u32 seq = cb->nlh->nlmsg_seq;
> +	u32 seq = nlh->nlmsg_seq;
>  	u32 filter_mask = 0;
>  	int err;
>  
> -	if (nlmsg_len(cb->nlh) > sizeof(struct ifinfomsg)) {
> -		struct nlattr *extfilt;
> -
> -		extfilt = nlmsg_find_attr(cb->nlh, sizeof(struct ifinfomsg),
> -					  IFLA_EXT_MASK);
> -		if (extfilt) {
> -			if (nla_len(extfilt) < sizeof(filter_mask))
> -				return -EINVAL;
> -
> -			filter_mask = nla_get_u32(extfilt);
> -		}
> -	}
> +	err = valid_bridge_getlink_req(nlh, cb->strict_check, &filter_mask,
> +				       cb->extack);
> +	if (err < 0 && cb->strict_check)
> +		return err;
>  
>  	rcu_read_lock();
>  	for_each_netdev_rcu(net, dev) {
> -- 
> 2.11.0
>