netdev - Re: [PATCH v2 net-next 15/23] net/neighbor: Update neigh_dump

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Date:   Mon, 8 Oct 2018 12:47:05 +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 15/23] net/neighbor: Update neigh_dump_info
 for strict data checking

On Sun, Oct 07, 2018 at 08:16:36PM -0700, David Ahern wrote:
> From: David Ahern <dsahern@...il.com>
> 
> Update neigh_dump_info for strict data checking. If the flag is set,
> the dump request is expected to have an ndmsg 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 NDA_IFINDEX and
> NDA_MASTER attributes are supported.
> 
> Existing code does not fail the dump if nlmsg_parse fails. That behavior
> is kept for non-strict checking.
> 
> Signed-off-by: David Ahern <dsahern@...il.com>

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

> ---
>  net/core/neighbour.c | 82 ++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 67 insertions(+), 15 deletions(-)
> 
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index b06f794bf91e..7c8a3a0ee059 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -2426,11 +2426,73 @@ static int pneigh_dump_table(struct neigh_table *tbl, struct sk_buff *skb,
>  
>  }
>  
> +static int neigh_valid_dump_req(const struct nlmsghdr *nlh,
> +				bool strict_check,
> +				struct neigh_dump_filter *filter,
> +				struct netlink_ext_ack *extack)
> +{
> +	struct nlattr *tb[NDA_MAX + 1];
> +	int err, i;
> +
> +	if (strict_check) {
> +		struct ndmsg *ndm;
> +
> +		if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ndm))) {
> +			NL_SET_ERR_MSG(extack, "Invalid header for neighbor dump request");
> +			return -EINVAL;
> +		}
> +
> +		ndm = nlmsg_data(nlh);
> +		if (ndm->ndm_pad1  || ndm->ndm_pad2  || ndm->ndm_ifindex ||
> +		    ndm->ndm_state || ndm->ndm_flags || ndm->ndm_type) {
> +			NL_SET_ERR_MSG(extack, "Invalid values in header for neighbor dump request");
> +			return -EINVAL;
> +		}
> +
> +		err = nlmsg_parse_strict(nlh, sizeof(struct ndmsg), tb, NDA_MAX,
> +					 NULL, extack);
> +	} else {
> +		err = nlmsg_parse(nlh, sizeof(struct ndmsg), tb, NDA_MAX,
> +				  NULL, extack);
> +	}
> +	if (err < 0)
> +		return err;
> +
> +	for (i = 0; i <= NDA_MAX; ++i) {
> +		if (!tb[i])
> +			continue;
> +
> +		/* all new attributes should require strict_check */
> +		switch (i) {
> +		case NDA_IFINDEX:
> +			if (nla_len(tb[i]) != sizeof(u32)) {
> +				NL_SET_ERR_MSG(extack, "Invalid IFINDEX attribute in neighbor dump request");
> +				return -EINVAL;
> +			}
> +			filter->dev_idx = nla_get_u32(tb[i]);
> +			break;
> +		case NDA_MASTER:
> +			if (nla_len(tb[i]) != sizeof(u32)) {
> +				NL_SET_ERR_MSG(extack, "Invalid MASTER attribute in neighbor dump request");
> +				return -EINVAL;
> +			}
> +			filter->master_idx = nla_get_u32(tb[i]);
> +			break;
> +		default:
> +			if (strict_check) {
> +				NL_SET_ERR_MSG(extack, "Unsupported attribute in neighbor dump request");
> +				return -EINVAL;
> +			}
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static int neigh_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
>  {
>  	const struct nlmsghdr *nlh = cb->nlh;
>  	struct neigh_dump_filter filter = {};
> -	struct nlattr *tb[NDA_MAX + 1];
>  	struct neigh_table *tbl;
>  	int t, family, s_t;
>  	int proxy = 0;
> @@ -2445,20 +2507,10 @@ static int neigh_dump_info(struct sk_buff *skb, struct netlink_callback *cb)
>  	    ((struct ndmsg *)nlmsg_data(nlh))->ndm_flags == NTF_PROXY)
>  		proxy = 1;
>  
> -	err = nlmsg_parse(nlh, sizeof(struct ndmsg), tb, NDA_MAX, NULL,
> -			  cb->extack);
> -	if (!err) {
> -		if (tb[NDA_IFINDEX]) {
> -			if (nla_len(tb[NDA_IFINDEX]) != sizeof(u32))
> -				return -EINVAL;
> -			filter.dev_idx = nla_get_u32(tb[NDA_IFINDEX]);
> -		}
> -		if (tb[NDA_MASTER]) {
> -			if (nla_len(tb[NDA_MASTER]) != sizeof(u32))
> -				return -EINVAL;
> -			filter.master_idx = nla_get_u32(tb[NDA_MASTER]);
> -		}
> -	}
> +	err = neigh_valid_dump_req(nlh, cb->strict_check, &filter, cb->extack);
> +	if (err < 0 && cb->strict_check)
> +		return err;
> +
>  	s_t = cb->args[0];
>  
>  	for (t = 0; t < NEIGH_NR_TABLES; t++) {
> -- 
> 2.11.0
>