linux-kernel - Re: [PATCH net-next 1/2] bpf: enable non-root eBPF programs

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Date:	Tue, 6 Oct 2015 09:13:47 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Alexei Starovoitov <ast@...mgrid.com>
Cc:	Daniel Borkmann <daniel@...earbox.net>,
	"David S. Miller" <davem@...emloft.net>,
	Andy Lutomirski <luto@...capital.net>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Kees Cook <keescook@...omium.org>, linux-api@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] bpf: enable non-root eBPF programs


* Alexei Starovoitov <ast@...mgrid.com> wrote:

> On 10/5/15 3:14 PM, Daniel Borkmann wrote:
> >One scenario that comes to mind ... what happens when there are kernel
> >pointers stored in skb->cb[] (either from the current layer or an old
> >one from a different layer that the skb went through previously, but
> >which did not get overwritten)?
> >
> >Socket filters could read a portion of skb->cb[] also when unprived and
> >leak that out through maps. I think the verifier doesn't catch that,
> >right?
> 
> grrr. indeed. previous layer before sk_filter() can leave junk in there.

Could this be solved by activating zeroing/sanitizing of this data if there's an 
active BPF function around that can access that socket?

Thanks,

	Ingo
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