linux-kernel - Re: [RFC v3 02/10] Revert "lsm: Remove the socket_post

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Message-Id: <201105041128.BAB13061.LMHVtOSOQOFFJF@I-love.SAKURA.ne.jp>
Date:	Wed, 4 May 2011 11:28:24 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	paul.moore@...com, sam@...ack.fr
Cc:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org, hadi@...erus.ca, kaber@...sh.net,
	zbr@...emap.net, root@...aldomain.pl
Subject: Re: [RFC v3 02/10] Revert "lsm: Remove the socket_post_accept() hook"

Paul Moore wrote:
> On Tuesday, May 03, 2011 10:24:15 AM Samir Bellabes wrote:
> > snet needs to reintroduce this hook, as it was designed to be: a hook for
> > updating security informations on objects.
> 
> Looking at this and 5/10 again, it seems that you should be able to do what 
> you need with the sock_graft() hook.  Am I missing something?
> 
> My apologies if we've already discussed this approach previously ...

static void snet_socket_post_accept(struct socket *sock, struct socket *newsock)
{
	static void snet_do_send_event(struct snet_info *info)
	{
		int snet_nl_send_event(struct snet_info *info)
		{
			skb_rsp = genlmsg_new(size, GFP_KERNEL);
			genlmsg_unicast()
		}
	}
}

First problem with using snet_do_send_event() from security_sock_graft() is
that we have to use GFP_ATOMIC rather than GFP_KERNEL because we are inside
write_lock_bh()/write_unlock_bh().

static inline int genlmsg_unicast(struct net *net, struct sk_buff *skb, u32 pid)
{
	static inline int nlmsg_unicast(struct sock *sk, struct sk_buff *skb, u32 pid)
	{
		int netlink_unicast(struct sock *ssk, struct sk_buff *skb,
			u32 pid, MSG_DONTWAIT)
		{
			int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
				      long *timeo, struct sock *ssk)
			{
				if (!*timeo) {
					return -EAGAIN;
			}
		}
	}
}

Second problem is that genlmsg_unicast() might return -EAGAIN because we can't
sleep inside write_lock_bh()/write_unlock_bh().

Third problem (though independent with security_sock_graft()) is that
snet_do_send_event() ignores snet_nl_send_event() failure.
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