netdev - Re: [net-next v2 07/13] tcp: move around a few calls in tcp_v6_conn

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Date:	Wed, 25 Jun 2014 10:29:43 -0400
From:	Paul Moore <paul@...l-moore.com>
To:	Octavian Purdila <octavian.purdila@...el.com>,
	netdev@...r.kernel.org
Cc:	linux-security-module@...r.kernel.org
Subject: Re: [net-next v2 07/13] tcp: move around a few calls in tcp_v6_conn_request

On Wednesday, June 25, 2014 05:09:56 PM Octavian Purdila wrote:
> Make the tcp_v6_conn_request calls flow similar with that of
> tcp_v4_conn_request.
> 
> Note that want_cookie can be true only if isn is zero and that is why
> we can move the if (want_cookie) block out of the if (!isn) block.
> 
> Moving security_inet_conn_request() has a couple of side effects:
> missing inet_rsk(req)->ecn_ok update and the req->cookie_ts
> update. However, neither SELinux nor Smack security hooks seems to
> check them. This change should also avoid future different behaviour
> for IPv4 and IPv6 in the security hooks.
> 
> Signed-off-by: Octavian Purdila <octavian.purdila@...el.com>
> ---
>  net/ipv6/tcp_ipv6.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)

Please send changes to the LSM hooks to the LSM mailing list (CC'd) for 
review/comment.

Mailing list issues aside, this looks fine to me; the loss of the ecn_ok and 
cookie_ts field updates should not matter to the current LSMs, or any 
reasonable future LSM, as the LSMs are more concerned about updating the LSM 
context assigned to the request_sock in this particular hook.

Acked-by: Paul Moore <paul@...l-moore.com>

> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index d780d88..91b8a2e 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -1070,16 +1070,16 @@ static int tcp_v6_conn_request(struct sock *sk,
> struct sk_buff *skb) ireq = inet_rsk(req);
>  	af_ops->init_req(req, sk, skb);
> 
> +	if (security_inet_conn_request(sk, skb, req))
> +		goto drop_and_release;
> +
>  	if (!want_cookie || tmp_opt.tstamp_ok)
>  		TCP_ECN_create_request(req, skb, sock_net(sk));
> 
> -	if (!isn) {
> -		if (want_cookie) {
> -			isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
> -			req->cookie_ts = tmp_opt.tstamp_ok;
> -			goto have_isn;
> -		}
> -
> +	if (want_cookie) {
> +		isn = cookie_init_sequence(af_ops, sk, skb, &req->mss);
> +		req->cookie_ts = tmp_opt.tstamp_ok;
> +	} else if (!isn) {
>  		/* VJ's idea. We save last timestamp seen
>  		 * from the destination in peer table, when entering
>  		 * state TIME-WAIT, and check against it before
> @@ -1116,10 +1116,6 @@ static int tcp_v6_conn_request(struct sock *sk,
> struct sk_buff *skb)
> 
>  		isn = tcp_v6_init_sequence(skb);
>  	}
> -have_isn:
> -
> -	if (security_inet_conn_request(sk, skb, req))
> -		goto drop_and_release;
> 
>  	if (!dst) {
>  		dst = af_ops->route_req(sk, (struct flowi *)&fl6, req, NULL);

-- 
paul moore
www.paul-moore.com

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