netdev - Re: [PATCH net 2/2] net/sched: sch_frag: fix stack OOB read while fragmenting IPv4 packets

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Date:   Mon, 19 Apr 2021 11:46:40 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Davide Caratti <dcaratti@...hat.com>
Cc:     Jamal Hadi Salim <jhs@...atatu.com>, Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, wenxu <wenxu@...oud.cn>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net 2/2] net/sched: sch_frag: fix stack OOB read while
 fragmenting IPv4 packets

On Mon, Apr 19, 2021 at 8:24 AM Davide Caratti <dcaratti@...hat.com> wrote:
> diff --git a/net/sched/sch_frag.c b/net/sched/sch_frag.c
> index e1e77d3fb6c0..8c06381391d6 100644
> --- a/net/sched/sch_frag.c
> +++ b/net/sched/sch_frag.c
> @@ -90,16 +90,16 @@ static int sch_fragment(struct net *net, struct sk_buff *skb,
>         }
>
>         if (skb_protocol(skb, true) == htons(ETH_P_IP)) {
> -               struct dst_entry sch_frag_dst;
> +               struct rtable sch_frag_rt = { 0 };

Is setting these fields 0 sufficient here? Because normally a struct table
is initialized by rt_dst_alloc() which sets several of them to non-zero,
notably, rt->rt_type and rt->rt_uncached.

Similar for the IPv6 part, which is initialized by rt6_info_init().

Thanks.