netdev - Re: [PATCH v6 net-next 1/9] ipeh: Fix destopts and hopopts counters on drop

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Date:   Sun, 22 Dec 2019 11:20:57 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Tom Herbert <tom@...bertland.com>
Cc:     David Miller <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        simon.horman@...ronome.com, Tom Herbert <tom@...ntonium.net>
Subject: Re: [PATCH v6 net-next 1/9] ipeh: Fix destopts and hopopts counters
 on drop

On Fri, Dec 20, 2019 at 6:39 PM Tom Herbert <tom@...bertland.com> wrote:
>
> From: Tom Herbert <tom@...ntonium.net>
>
> For destopts, bump IPSTATS_MIB_INHDRERRORS when limit of length
> of extension header is exceeded.
>
> For hop-by-hop options, bump IPSTATS_MIB_INHDRERRORS in same
> situations as for when destopts are dropped.
>
> Signed-off-by: Tom Herbert <tom@...bertland.com>
> ---
>  net/ipv6/exthdrs.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
> index ab5add0..f605e4e 100644
> --- a/net/ipv6/exthdrs.c
> +++ b/net/ipv6/exthdrs.c
> @@ -288,9 +288,9 @@ static int ipv6_destopt_rcv(struct sk_buff *skb)
>         if (!pskb_may_pull(skb, skb_transport_offset(skb) + 8) ||
>             !pskb_may_pull(skb, (skb_transport_offset(skb) +
>                                  ((skb_transport_header(skb)[1] + 1) << 3)))) {
> +fail_and_free:
>                 __IP6_INC_STATS(dev_net(dst->dev), idev,
>                                 IPSTATS_MIB_INHDRERRORS);
> -fail_and_free:
>                 kfree_skb(skb);
>                 return -1;
>         }
> @@ -820,8 +820,10 @@ static const struct tlvtype_proc tlvprochopopt_lst[] = {
>
>  int ipv6_parse_hopopts(struct sk_buff *skb)
>  {
> +       struct inet6_dev *idev = __in6_dev_get(skb->dev);
>         struct inet6_skb_parm *opt = IP6CB(skb);
>         struct net *net = dev_net(skb->dev);
> +       struct dst_entry *dst = skb_dst(skb);
>         int extlen;
>
>         /*
> @@ -834,6 +836,8 @@ int ipv6_parse_hopopts(struct sk_buff *skb)
>             !pskb_may_pull(skb, (sizeof(struct ipv6hdr) +
>                                  ((skb_transport_header(skb)[1] + 1) << 3)))) {
>  fail_and_free:
> +               __IP6_INC_STATS(dev_net(dst->dev), idev,
> +                               IPSTATS_MIB_INHDRERRORS);

ip6_rcv_core, the only caller of ipv6_parse_hopopts, checks
skb_valid_dst(skb) before deref. Does this need the same?