netdev - Re: [PATCH net-next v3 03/10] udp/ipv6: prioritise the ip6 path over ip4 checks

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Date:   Mon, 16 May 2022 21:10:59 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 03/10] udp/ipv6: prioritise the ip6 path over
 ip4 checks

On 5/16/22 14:14, Paolo Abeni wrote:
> On Fri, 2022-05-13 at 16:26 +0100, Pavel Begunkov wrote:
>> For AF_INET6 sockets we care the most about ipv6 but not ip4 mappings as
>> it's requires some extra hops anyway. Take AF_INET6 case from the address
>> parsing switch and add an explicit path for it. It removes some extra
>> ifs from the path and removes the switch overhead.
>>
>> Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
>> ---
>>   net/ipv6/udp.c | 37 +++++++++++++++++--------------------
>>   1 file changed, 17 insertions(+), 20 deletions(-)
>>
>> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
>> index 85bff1252f5c..e0b1bea998ce 100644
>> --- a/net/ipv6/udp.c
>> +++ b/net/ipv6/udp.c
>> @@ -1360,30 +1360,27 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
>>   
>>   	/* destination address check */
>>   	if (sin6) {
>> -		if (addr_len < offsetof(struct sockaddr, sa_data))
>> -			return -EINVAL;
>> +		if (addr_len < SIN6_LEN_RFC2133 || sin6->sin6_family != AF_INET6) {
>> +			if (addr_len < offsetof(struct sockaddr, sa_data))
>> +				return -EINVAL;
> 
> I think you can't access 'sin6->sin6_family' before validating the
> socket address len, that is before doing:

Paolo, thanks for reviewing it!


sin6_family is protected by

if (addr_len < SIN6_LEN_RFC2133 ...)

on the previous line. I can add a BUILD_BUG_ON() if that
would be more reassuring.


> 
> if (addr_len < offsetof(struct sockaddr, sa_data))

-- 
Pavel Begunkov