On Thu, Oct 04, 2018 at 02:33:50PM -0700, David Ahern wrote:
> From: David Ahern <dsah...@gmail.com>
>
> Update neightbl_dump_info for strict data checking. If the flag is set,
> the dump request is expected to have an ndtmsg 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 <dsah...@gmail.com>
> ---
> net/core/neighbour.c | 38 +++++++++++++++++++++++++++++++++++---
> 1 file changed, 35 insertions(+), 3 deletions(-)
>
> diff --git a/net/core/neighbour.c b/net/core/neighbour.c
> index 3130d010b7ad..8e07b92403ab 100644
> --- a/net/core/neighbour.c
> +++ b/net/core/neighbour.c
> @@ -2164,15 +2164,47 @@ static int neightbl_set(struct sk_buff *skb, struct
> nlmsghdr *nlh,
> return err;
> }
>
> +static int neightbl_valid_dump_info(const struct nlmsghdr *nlh,
> + struct netlink_ext_ack *extack)
> +{
> + struct ndtmsg *ndtm;
> +
> + if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*ndtm))) {
> + NL_SET_ERR_MSG(extack, "Invalid header");
> + return -EINVAL;
> + }
> +
> + ndtm = nlmsg_data(nlh);
> + if (ndtm->ndtm_pad1 || ndtm->ndtm_pad2) {
> + NL_SET_ERR_MSG(extack, "Invalid values in header for dump
> request");
> + return -EINVAL;
> + }
> +
> + if (nlh->nlmsg_len != nlmsg_msg_size(sizeof(*ndtm))) {
> + NL_SET_ERR_MSG(extack, "Invalid data after header");
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> static int neightbl_dump_info(struct sk_buff *skb, struct netlink_callback
> *cb)
> {
> + const struct nlmsghdr *nlh = cb->nlh;
> struct net *net = sock_net(skb->sk);
> int family, tidx, nidx = 0;
> int tbl_skip = cb->args[0];
> int neigh_skip = cb->args[1];
> struct neigh_table *tbl;
>
> - family = ((struct rtgenmsg *) nlmsg_data(cb->nlh))->rtgen_family;
> + if (cb->strict_check) {
> + int err = neightbl_valid_dump_info(nlh, cb->extack);
> +
> + if (err)
> + return err;
> + }
> +
> + family = ((struct rtgenmsg *)nlmsg_data(nlh))->rtgen_family;
So this already was a problem prior to your patch: what happens when you
pass in the wrong struct? Then this case is not safe to do and might
contain all kinds of crap.
>
> for (tidx = 0; tidx < NEIGH_NR_TABLES; tidx++) {
> struct neigh_parms *p;
> @@ -2185,7 +2217,7 @@ static int neightbl_dump_info(struct sk_buff *skb,
> struct netlink_callback *cb)
> continue;
>
> if (neightbl_fill_info(skb, tbl, NETLINK_CB(cb->skb).portid,
> - cb->nlh->nlmsg_seq, RTM_NEWNEIGHTBL,
> + nlh->nlmsg_seq, RTM_NEWNEIGHTBL,
> NLM_F_MULTI) < 0)
> break;
>
> @@ -2200,7 +2232,7 @@ static int neightbl_dump_info(struct sk_buff *skb,
> struct netlink_callback *cb)
>
> if (neightbl_fill_param_info(skb, tbl, p,
> NETLINK_CB(cb->skb).portid,
> - cb->nlh->nlmsg_seq,
> + nlh->nlmsg_seq,
> RTM_NEWNEIGHTBL,
> NLM_F_MULTI) < 0)
> goto out;
> --
> 2.11.0
>
