netdev - Re: [RFC 0/9] snet: Security for NETwork syscalls

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Date:	Tue, 05 Jan 2010 17:20:55 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	sam@...ack.fr
Cc:	linux-security-module@...r.kernel.org, kaber@...sh.net,
	zbr@...emap.net, nhorman@...driver.com, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org, hadi@...erus.ca
Subject: Re: [RFC 0/9] snet: Security for NETwork syscalls

Samir Bellabes wrote:
> I'm currently testing security_sock_rcv_skb() hook - which is inside
> sk_filter() - to get skbuffs when then are arriving, and so trying to
> push the buffer to userspace. In case this is not userfull, userspace
> is able to use the NFQUEUE of netfilter to get skbuff, and deal
> with incoming datas.

Pushing buffer to userspace and wait for userspace's decision will sleep.
sk_filter() which calls security_sock_rcv_skb() hook is called from
(e.g.) tcp_v6_do_rcv() and comment of tcp_v6_do_rcv() says that
"The socket must have it's spinlock held when we get here." 
Also, comment of rxrpc_queue_rcv_skb() says that
"the caller must hold a lock on call->lock".
I think it is not permitted to do sleeping operation inside
security_sock_rcv_skb().
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