Re: [PATCH net-next] x86: bpf_jit_comp: secure bpf jit againstspraying attacks

From: Florian Westphal
Date: Mon May 20 2013 - 10:20:01 EST

Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote:
> From: Eric Dumazet <edumazet@xxxxxxxxxx>
> hpa bringed into my attention some security related issues
> with BPF JIT on x86.
> This patch makes sure the bpf generated code is marked read only,
> as other kernel text sections.
> It also splits the unused space (we vmalloc() and only use a fraction of
> the page) in two parts, so that the generated bpf code not starts at a
> known offset in the page, but a pseudo random one.
> Refs:

What about emitting additional instructions at random locations in the
generated code itself?

Eg., after every instruction, have random chance to insert
'xor $0xcc,%al; xor $0xcc,%al', etc?
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