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

From: Jay Vosburgh <[email-masked]>
Date: Wed, 09 Nov 2022 12:39:28 -0800

Eric Dumazet <[email-masked]> 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 <[email-masked]>
>> Fixes: 4e24be018eb9 ("bonding: add new parameter ns_targets")
>> Acked-by: Jonathan Toppins <[email-masked]>
>> Reviewed-by: David Ahern <[email-masked]>
>> Signed-off-by: Hangbin Liu <[email-masked]>
>> ---
>> 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.

	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, [email-masked]