Messages in this thread | | | Date | Tue, 5 Feb 2019 15:44:41 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH 2/2] x86/boot: increase maximum number of avoided KASLR regions |
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On Wed, Jan 30, 2019 at 05:40:03PM +0100, Julian Stecklina wrote: > From: Julian Stecklina <jsteckli@amazon.de> > > The boot code has a limit of 4 "non-standard" regions to avoid for > KASLR. This limit is easy to reach when supplying memmap= parameters to > the kernel. In this case, KASLR would be disabled. > > Increase the limit to avoid turning off KASLR even when the user is > heavily manipulating the memory map. > > Signed-off-by: Julian Stecklina <jsteckli@amazon.de> > --- > arch/x86/boot/compressed/kaslr.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c > index 5657e34..f078d60 100644 > --- a/arch/x86/boot/compressed/kaslr.c > +++ b/arch/x86/boot/compressed/kaslr.c > @@ -92,8 +92,8 @@ struct mem_vector { > unsigned long long size; > }; > > -/* Only supporting at most 4 unusable memmap regions with kaslr */ > -#define MAX_MEMMAP_REGIONS 4 > +/* Only supporting at most this many unusable memmap regions with kaslr */ > +#define MAX_MEMMAP_REGIONS 16 > > static bool memmap_too_large; > > @@ -213,7 +213,7 @@ static void mem_avoid_memmap(char *str) > i++; > } > > - /* More than 4 memmaps, fail kaslr */ > + /* Can't store all regions, fail kaslr */ > if ((i >= MAX_MEMMAP_REGIONS) && str) > memmap_too_large = true; > } > --
Lemme add some of the folks from f28442497b5caf7bf573ade22a7f8d3559e3ef56 to Cc.
It all looks arbitrary to me: first 4 unusable memmap regions, this patch raises it to 16. Why are we even imposing such a limit?
Hmm.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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