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

From: Jiri Kosina
Date: Wed Apr 29 2015 - 10:57:07 EST

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@xxxxxxx>
> Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

Applied to for-4.2/kaslr.


Jiri Kosina
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