linux-kernel - Re: [PATCH] ipv4: tcp: security_sk_alloc() needed for unicast

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Message-ID: <5799181.tjlnF0gIh2@sifl>
Date:	Thu, 09 Aug 2012 11:07:15 -0400
From:	Paul Moore <paul@...l-moore.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Eric Paris <eparis@...isplace.org>,
	John Stultz <johnstul@...ibm.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	lkml <linux-kernel@...r.kernel.org>,
	James Morris <james.l.morris@...cle.com>,
	selinux@...ho.nsa.gov, john.johansen@...onical.com,
	LSM <linux-security-module@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] ipv4: tcp: security_sk_alloc() needed for unicast_sock

On Thursday, August 09, 2012 04:50:33 PM Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> commit be9f4a44e7d41cee (ipv4: tcp: remove per net tcp_sock) added a
> selinux regression, reported and bisected by John Stultz
> 
> selinux_ip_postroute_compat() expect to find a valid sk->sk_security
> pointer, but this field is NULL for unicast_sock
> 
> Fix this by adding a new 'kernel' parameter to security_sk_alloc(),
> set to true if socket might already have a valid sk->sk_security
> pointer. ip_send_unicast_reply() uses a percpu fake socket, so the first
> call to security_sk_alloc() will populate sk->sk_security pointer,
> subsequent ones will reuse existing context.
> 
> Reported-by: John Stultz <johnstul@...ibm.com>
> Bisected-by: John Stultz <johnstul@...ibm.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Paul Moore <paul@...l-moore.com>
> Cc: Eric Paris <eparis@...isplace.org>
> Cc: "Serge E. Hallyn" <serge@...lyn.com>

...

> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> index 76dde25..b233d6e 100644
> --- a/net/ipv4/ip_output.c
> +++ b/net/ipv4/ip_output.c
> @@ -1524,6 +1524,8 @@ void ip_send_unicast_reply(struct net *net, struct
> sk_buff *skb, __be32 daddr, sk->sk_priority = skb->priority;
>  	sk->sk_protocol = ip_hdr(skb)->protocol;
>  	sk->sk_bound_dev_if = arg->bound_dev_if;
> +	if (security_sk_alloc(sk, PF_INET, GFP_ATOMIC, true))
> +		goto out;
>  	sock_net_set(sk, net);
>  	__skb_queue_head_init(&sk->sk_write_queue);
>  	sk->sk_sndbuf = sysctl_wmem_default;

Is is possible to do the call to security_sk_alloc() in the ip_init() function 
or does the per-cpu nature of the socket make this a pain?

-- 
paul moore
www.paul-moore.com

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