linux-kernel - Re: [PATCH 2/2] livepatch: x86: make kASLR logic more accurate

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Date:	Wed, 29 Apr 2015 16:56:54 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
cc:	x86@...nel.org, Borislav Petkov <bp@...en8.de>,
	Kees Cook <keescook@...omium.org>,
	Seth Jennings <sjenning@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>, linux-kernel@...r.kernel.org,
	live-patching@...r.kernel.org
Subject: Re: [PATCH 2/2] livepatch: x86: make kASLR logic more accurate

On Tue, 28 Apr 2015, Josh Poimboeuf wrote:

> On Mon, Apr 27, 2015 at 04:28:58PM +0200, Jiri Kosina wrote:
> > We give up old_addr hint from the coming patch module in cases when kernel 
> > load base has been randomized (as in such case, the coming module has no 
> > idea about the exact randomization offset).
> > 
> > We are currently too pessimistic, and give up immediately as soon as 
> > CONFIG_RANDOMIZE_BASE is set; this doesn't however directly imply that the 
> > load base has actually been randomized. There are config options that 
> > disable kASLR (such as hibernation), user could have disabled kaslr on 
> > kernel command-line, etc.
> > 
> > The loader propagates the information whether kernel has been randomized 
> > through bootparams. This allows us to have the condition more accurate.
> > 
> > On top of that, it seems unnecessary to give up old_addr hints even if 
> > randomization is active. The relocation offset can be computed using 
> > kaslr_ofsset(), and therefore old_addr can be adjusted accordingly.
> > 
> > Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> 
> Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>

Applied to for-4.2/kaslr.

Thanks,

-- 
Jiri Kosina
SUSE Labs
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