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

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Message-ID: <CANn89iKW60QdMRbpyaYry4Vdfxm41ifh4qFt1azU5FCYkUJBiA@mail.gmail.com>
Date:   Wed, 9 Nov 2022 13:48:11 -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 1:23 PM Jay Vosburgh <jay.vosburgh@...onical.com> wrote:
>
> Eric Dumazet <edumazet@...gle.com> wrote:
>
> >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.
>
>         Well, it was set up this way with skb_header_pointer() instead
> of pskb_may_pull() by you in de063b7040dc ("bonding: remove packet
> cloning in recv_probe()") so the bonding rx_handler wouldn't change or
> clone the skb.  Now, I'm not sure if we should follow your advice to go
> against your advice.

Ah... I forgot about this, thanks for reminding me it ;)


>
>         Also, we'd have to un-const the skb parameter through the call
> chain from bond_handle_frame().
>
>         -J
>
> >>
> >>         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