netdev - Re: [PATCH net-next] net/sched: act_mirred: Ensure mac_len is pulled prior redirect to a non mac_header

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Date:   Tue, 24 Dec 2019 12:43:32 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     shmulik@...anetworks.com
Cc:     Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>,
        "David S . Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Shmulik Ladkani <shmulik.ladkani@...il.com>,
        Shmulik Ladkani <sladkani@...ofpoint.com>
Subject: Re: [PATCH net-next] net/sched: act_mirred: Ensure mac_len is pulled
 prior redirect to a non mac_header_xmit target device

On Mon, Dec 23, 2019 at 4:33 AM <shmulik@...anetworks.com> wrote:
>
> From: Shmulik Ladkani <sladkani@...ofpoint.com>
>
> There's no skb_pull performed when a mirred action is set at egress of a
> mac device, with a target device/action that expects skb->data to point
> at the network header.
>
> As a result, either the target device is errornously given an skb with
> data pointing to the mac (egress case), or the net stack receives the
> skb with data pointing to the mac (ingress case).
>
> E.g:
>  # tc qdisc add dev eth9 root handle 1: prio
>  # tc filter add dev eth9 parent 1: prio 9 protocol ip handle 9 basic \
>    action mirred egress redirect dev tun0
>
>  (tun0 is a tun device. result: tun0 errornously gets the eth header
>   instead of the iph)
>
> Revise the push/pull logic of tcf_mirred_act() to not rely on the
> skb_at_tc_ingress() vs tcf_mirred_act_wants_ingress() comparison, as it
> does not cover all "pull" cases.
>
> Instead, calculate whether the required action on the target device
> requires the data to point at the network header, and compare this to
> whether skb->data points to network header - and make the push/pull
> adjustments as necessary.

This is a bug fix, please target it for -net and add a proper Fixes tag.

BTW, please make the subject shorter.

Thanks.