netdev - RE: [PATCH net-next] x86: bpf_jit_comp: secure bpf jit against spraying attacks

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Message-ID: <1369056893.3301.160.camel@edumazet-glaptop>
Date:	Mon, 20 May 2013 06:34:53 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: RE: [PATCH net-next] x86: bpf_jit_comp: secure bpf jit against
 spraying attacks

On Mon, 2013-05-20 at 09:51 +0100, David Laight wrote:

> Hmmm.... anyone looking to overwrite kernel code will then start
> looking for blocks of 0xcc bytes and know that what follows
> is the beginning of a function.
> That isn't any harder than random writes.
> 
> Copying a random part of .rodata might be better - especially
> if you can find part of .rodata.str*.

That's not the point. We want to catch jumps to before/after the code.

An attacker having full access to kernel code in read and write mode has
full power anyway to do whatever he wants.


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