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Message-ID: <20181005175922.4oiwihofhsvcu4ok@brauner.io>
Date: Fri, 5 Oct 2018 19:59:23 +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 net-next 08/20] rtnetlink: Update rtnl_dump_ifinfo for
strict data checking
On Thu, Oct 04, 2018 at 02:33:43PM -0700, David Ahern wrote:
> From: David Ahern <dsahern@...il.com>
>
> Update rtnl_dump_ifinfo 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 IFA_TARGET_NETNSID,
> IFLA_EXT_MASK, IFLA_MASTER, and IFLA_LINKINFO 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>
> ---
> net/core/rtnetlink.c | 97 +++++++++++++++++++++++++++++++++++++---------------
> 1 file changed, 69 insertions(+), 28 deletions(-)
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index c3b434d724ea..4fd27b5db787 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -1880,6 +1880,8 @@ EXPORT_SYMBOL_GPL(rtnl_get_net_ns_capable);
>
> static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
> {
> + struct netlink_ext_ack *extack = cb->extack;
> + const struct nlmsghdr *nlh = cb->nlh;
> struct net *net = sock_net(skb->sk);
> struct net *tgt_net = net;
> int h, s_h;
> @@ -1892,44 +1894,84 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
> unsigned int flags = NLM_F_MULTI;
> int master_idx = 0;
> int netnsid = -1;
> - int err;
> + int err, i;
> int hdrlen;
>
> s_h = cb->args[0];
> s_idx = cb->args[1];
>
> - /* A hack to preserve kernel<->userspace interface.
> - * The correct header is ifinfomsg. It is consistent with rtnl_getlink.
> - * However, before Linux v3.9 the code here assumed rtgenmsg and that's
> - * what iproute2 < v3.9.0 used.
> - * We can detect the old iproute2. Even including the IFLA_EXT_MASK
> - * attribute, its netlink message is shorter than struct ifinfomsg.
> - */
> - hdrlen = nlmsg_len(cb->nlh) < sizeof(struct ifinfomsg) ?
> - sizeof(struct rtgenmsg) : sizeof(struct ifinfomsg);
> + if (cb->strict_check) {
> + struct ifinfomsg *ifm;
>
> - if (nlmsg_parse(cb->nlh, hdrlen, tb, IFLA_MAX,
> - ifla_policy, cb->extack) >= 0) {
> - if (tb[IFLA_TARGET_NETNSID]) {
> - netnsid = nla_get_s32(tb[IFLA_TARGET_NETNSID]);
> - tgt_net = rtnl_get_net_ns_capable(skb->sk, netnsid);
> - if (IS_ERR(tgt_net))
> - return PTR_ERR(tgt_net);
> + hdrlen = sizeof(*ifm);
> + if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen)) {
> + NL_SET_ERR_MSG(extack, "Invalid header");
> + return -EINVAL;
> }
>
> - if (tb[IFLA_EXT_MASK])
> - ext_filter_mask = nla_get_u32(tb[IFLA_EXT_MASK]);
> -
> - if (tb[IFLA_MASTER])
> - master_idx = nla_get_u32(tb[IFLA_MASTER]);
> + ifm = nlmsg_data(nlh);
> + if (ifm->__ifi_pad || ifm->ifi_type || ifm->ifi_flags ||
> + ifm->ifi_change) {
> + NL_SET_ERR_MSG(extack, "Invalid values in header for dump request");
> + return -EINVAL;
> + }
> + if (ifm->ifi_index) {
> + NL_SET_ERR_MSG(extack, "Filter by device index not supported");
> + return -EINVAL;
> + }
> + } else {
> + /* A hack to preserve kernel<->userspace interface.
> + * The correct header is ifinfomsg. It is consistent with
> + * rtnl_getlink. However, before Linux v3.9 the code here
> + * assumed rtgenmsg and that's what iproute2 < v3.9.0 used.
> + * We can detect the old iproute2. Even including the
> + * IFLA_EXT_MASK attribute, its netlink message is shorter
> + * than struct ifinfomsg.
> + */
> + hdrlen = nlmsg_len(nlh) < sizeof(struct ifinfomsg) ?
> + sizeof(struct rtgenmsg) : sizeof(struct ifinfomsg);
> + }
>
> - if (tb[IFLA_LINKINFO])
> - kind_ops = linkinfo_to_kind_ops(tb[IFLA_LINKINFO]);
> + err = nlmsg_parse(nlh, hdrlen, tb, IFLA_MAX, ifla_policy, extack);
> + if (err < 0) {
> + if (cb->strict_check)
> + return -EINVAL;
> + goto walk_entries;
> + }
>
> - if (master_idx || kind_ops)
> - flags |= NLM_F_DUMP_FILTERED;
> + for (i = 0; i <= IFLA_MAX; ++i) {
> + if (!tb[i])
> + continue;
> + switch (i) {
> + case IFLA_TARGET_NETNSID:
> + netnsid = nla_get_s32(tb[i]);
> + tgt_net = rtnl_get_net_ns_capable(skb->sk, netnsid);
> + if (IS_ERR(tgt_net)) {
> + NL_SET_ERR_MSG(extack, "Invalid target namespace id");
> + return PTR_ERR(tgt_net);
> + }
> + break;
> + case IFLA_EXT_MASK:
> + ext_filter_mask = nla_get_u32(tb[i]);
> + break;
> + case IFLA_MASTER:
> + master_idx = nla_get_u32(tb[i]);
> + break;
> + case IFLA_LINKINFO:
> + kind_ops = linkinfo_to_kind_ops(tb[i]);
> + break;
> + default:
> + if (cb->strict_check) {
> + NL_SET_ERR_MSG(extack, "Unsupported attribute in dump request");
> + return -EINVAL;
> + }
> + }
This might make sense to be split into two helpers for parsing:
<blablabla>_strict() and <blablabla>_lenient(). :)
> }
>
> + if (master_idx || kind_ops)
> + flags |= NLM_F_DUMP_FILTERED;
> +
> +walk_entries:
> for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
> idx = 0;
> head = &tgt_net->dev_index_head[h];
> @@ -1941,8 +1983,7 @@ static int rtnl_dump_ifinfo(struct sk_buff *skb, struct netlink_callback *cb)
> err = rtnl_fill_ifinfo(skb, dev, net,
> RTM_NEWLINK,
> NETLINK_CB(cb->skb).portid,
> - cb->nlh->nlmsg_seq, 0,
> - flags,
> + nlh->nlmsg_seq, 0, flags,
> ext_filter_mask, 0, NULL, 0,
> netnsid);
>
> --
> 2.11.0
>
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