netdev - Re: [PATCHv3 net] bonding: fix ICMPv6 header handling when receiving IPv6 messages

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Message-ID: <CANn89i+eZwb3+JO6oKavj5yTi74vaUY-=Pu4CaUbcq==ue9NCw@mail.gmail.com>
Date:   Wed, 9 Nov 2022 12:45:15 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Jay Vosburgh <jay.vosburgh@...onical.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Hangbin Liu <liuhangbin@...il.com>, netdev@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Toppins <jtoppins@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>,
        David Ahern <dsahern@...il.com>, Liang Li <liali@...hat.com>,
        David Ahern <dsahern@...nel.org>
Subject: Re: [PATCHv3 net] bonding: fix ICMPv6 header handling when receiving
 IPv6 messages

On Wed, Nov 9, 2022 at 12:39 PM Jay Vosburgh <jay.vosburgh@...onical.com> wrote:
>
> Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> >
> >
> >On 11/8/22 17:40, Hangbin Liu wrote:
> >> Currently, we get icmp6hdr via function icmp6_hdr(), which needs the skb
> >> transport header to be set first. But there is no rule to ask driver set
> >> transport header before netif_receive_skb() and bond_handle_frame(). So
> >> we will not able to get correct icmp6hdr on some drivers.
> >>
> >> Fix this by checking the skb length manually and getting icmp6 header based
> >> on the IPv6 header offset.
> >>
> >> Reported-by: Liang Li <liali@...hat.com>
> >> Fixes: 4e24be018eb9 ("bonding: add new parameter ns_targets")
> >> Acked-by: Jonathan Toppins <jtoppins@...hat.com>
> >> Reviewed-by: David Ahern <dsahern@...nel.org>
> >> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> >> ---
> >> v3: fix _hdr parameter warning reported by kernel test robot
> >> v2: use skb_header_pointer() to get icmp6hdr as Jay suggested.
> >> ---
> >>   drivers/net/bonding/bond_main.c | 9 +++++++--
> >>   1 file changed, 7 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> >> index e84c49bf4d0c..2c6356232668 100644
> >> --- a/drivers/net/bonding/bond_main.c
> >> +++ b/drivers/net/bonding/bond_main.c
> >> @@ -3231,12 +3231,17 @@ static int bond_na_rcv(const struct sk_buff *skb, struct bonding *bond,
> >>                     struct slave *slave)
> >>   {
> >>      struct slave *curr_active_slave, *curr_arp_slave;
> >> -    struct icmp6hdr *hdr = icmp6_hdr(skb);
> >>      struct in6_addr *saddr, *daddr;
> >> +    const struct icmp6hdr *hdr;
> >> +    struct icmp6hdr _hdr;
> >>      if (skb->pkt_type == PACKET_OTHERHOST ||
> >>          skb->pkt_type == PACKET_LOOPBACK ||
> >> -        hdr->icmp6_type != NDISC_NEIGHBOUR_ADVERTISEMENT)
> >> +        ipv6_hdr(skb)->nexthdr != NEXTHDR_ICMP)
> >
> >
> >What makes sure IPv6 header is in skb->head (linear part of the skb) ?
>
>         Ah, missed that; skb_header_pointer() will take care of that
> (copying if necessary, not that it pulls the header), but it has to be
> called first.
>
>         This isn't a problem new to this patch, the original code
> doesn't pull or copy the header, either.

Quite frankly I would simply use

if (pskb_may_pull(skb, sizeof(struct ipv6hdr) + sizeof(struct icmp6hdr))
 instead of  skb_header_pointer()
because chances are high we will need the whole thing in skb->head later.

>
>         The equivalent function for ARP, bond_arp_rcv(), more or less
> inlines skb_header_pointer(), so it doesn't have this issue.
>
>         -J
>
> >
> >> +            goto out;
> >> +
> >> +    hdr = skb_header_pointer(skb, sizeof(struct ipv6hdr), sizeof(_hdr), &_hdr);
> >> +    if (!hdr || hdr->icmp6_type != NDISC_NEIGHBOUR_ADVERTISEMENT)
> >>              goto out;
> >>      saddr = &ipv6_hdr(skb)->saddr;
>
> ---
>         -Jay Vosburgh, jay.vosburgh@...onical.com