netdev - Re: [PATCH net] sctp: do not check port in sctp_inet6_cmp

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Date:   Wed, 11 Apr 2018 10:36:07 -0400
From:   Neil Horman <nhorman@...driver.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org,
        davem@...emloft.net,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net] sctp: do not check port in sctp_inet6_cmp_addr

On Wed, Apr 11, 2018 at 08:58:05PM +0800, Xin Long wrote:
> pf->cmp_addr() is called before binding a v6 address to the sock. It
> should not check ports, like in sctp_inet_cmp_addr.
> 
> But sctp_inet6_cmp_addr checks the addr by invoking af(6)->cmp_addr,
> sctp_v6_cmp_addr where it also compares the ports.
> 
> This would cause that setsockopt(SCTP_SOCKOPT_BINDX_ADD) could bind
> multiple duplicated IPv6 addresses after Commit 40b4f0fd74e4 ("sctp:
> lack the check for ports in sctp_v6_cmp_addr").
> 
> This patch is to remove af->cmp_addr called in sctp_inet6_cmp_addr,
> but do the proper check for both v6 addrs and v4mapped addrs.
> 
> Fixes: 40b4f0fd74e4 ("sctp: lack the check for ports in sctp_v6_cmp_addr")
> Reported-by: Jianwen Ji <jiji@...hat.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>
> ---
>  net/sctp/ipv6.c | 27 ++++++++++++++++++++++++---
>  1 file changed, 24 insertions(+), 3 deletions(-)
> 
> diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
> index f1fc48e..be4b72c 100644
> --- a/net/sctp/ipv6.c
> +++ b/net/sctp/ipv6.c
> @@ -846,8 +846,8 @@ static int sctp_inet6_cmp_addr(const union sctp_addr *addr1,
>  			       const union sctp_addr *addr2,
>  			       struct sctp_sock *opt)
>  {
> -	struct sctp_af *af1, *af2;
>  	struct sock *sk = sctp_opt2sk(opt);
> +	struct sctp_af *af1, *af2;
>  
>  	af1 = sctp_get_af_specific(addr1->sa.sa_family);
>  	af2 = sctp_get_af_specific(addr2->sa.sa_family);
> @@ -863,10 +863,31 @@ static int sctp_inet6_cmp_addr(const union sctp_addr *addr1,
>  	if (sctp_is_any(sk, addr1) || sctp_is_any(sk, addr2))
>  		return 1;
>  
> -	if (addr1->sa.sa_family != addr2->sa.sa_family)
> +	if (addr1->sa.sa_family != addr2->sa.sa_family) {
> +		if (addr1->sa.sa_family == AF_INET &&
> +		    addr2->sa.sa_family == AF_INET6 &&
> +		    ipv6_addr_v4mapped(&addr2->v6.sin6_addr))
> +			if (addr2->v6.sin6_addr.s6_addr32[3] ==
> +			    addr1->v4.sin_addr.s_addr)
> +				return 1;
> +		if (addr2->sa.sa_family == AF_INET &&
> +		    addr1->sa.sa_family == AF_INET6 &&
> +		    ipv6_addr_v4mapped(&addr1->v6.sin6_addr))
> +			if (addr1->v6.sin6_addr.s6_addr32[3] ==
> +			    addr2->v4.sin_addr.s_addr)
> +				return 1;
> +		return 0;
> +	}
> +
> +	if (!ipv6_addr_equal(&addr1->v6.sin6_addr, &addr2->v6.sin6_addr))
> +		return 0;
> +
> +	if ((ipv6_addr_type(&addr1->v6.sin6_addr) & IPV6_ADDR_LINKLOCAL) &&
> +	    addr1->v6.sin6_scope_id && addr2->v6.sin6_scope_id &&
> +	    addr1->v6.sin6_scope_id != addr2->v6.sin6_scope_id)
>  		return 0;
>  
> -	return af1->cmp_addr(addr1, addr2);
> +	return 1;
>  }
>  
>  /* Verify that the provided sockaddr looks bindable.   Common verification,
> -- 
> 2.1.0
> 
This looks correct to me, but is it worth duplicating the comparison code like
this from the cmp_addr function?  It might be more worthwhile to add a flag to
the cmp_addr method to direct weather it needs to check port values or not.
That way you could continue to use the cmp_addr function here.

Neil

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