netdev - Re: Fwd: Simple kernel attack using socketpair. easy, 100% reproductiblle, works under guest. no way to protect :(

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Message-ID: <1290759748.2855.4.camel@edumazet-laptop>
Date:	Fri, 26 Nov 2010 09:22:28 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Shan Wei <shanwei@...fujitsu.com>
Cc:	Марк Коренберг 
	<socketpair@...il.com>, David Miller <davem@...emloft.net>,
	netdev@...r.kernel.org
Subject: Re: Fwd: Simple kernel attack using socketpair. easy, 100%
 reproductiblle, works under guest. no way to protect :(

Le vendredi 26 novembre 2010 à 15:41 +0800, Shan Wei a écrit :
> Eric Dumazet wrote, at 11/25/2010 10:11 PM:
> > @@ -1845,6 +1871,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock,
> >  		unix_state_lock(sk);
> >  		skb = skb_dequeue(&sk->sk_receive_queue);
> >  		if (skb == NULL) {
> > +			unix_sk(sk)->recursion_level = 0;
> 
> For SOCK_SEQPACKET type, no need to clear recursion_level counter?
>  
> 

There is no need actually to clear it at all.

If an application has a complex setup with a dependence tree of unix
sockets, it will break if messages are not read fast enough.

So, maybe I should remove this line so that underlying problem comes
into surface immediately, rather than while in stress load.



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