lkml.org 
[lkml]   [2017]   [Jul]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] x86/boot/KASLR: exclude EFI_BOOT_SERVICES_{CODE|DATA} from KASLR's choice
Date
On Fri, Jul 07, 2017 at 11:07:59AM +0800, Baoquan He wrote:
> On 07/06/17 at 03:57pm, Matt Fleming wrote:
> > On Thu, 06 Jul, at 08:31:07AM, Naoya Horiguchi wrote:
> > > + for (i = 0; i < nr_desc; i++) {
> > > + md = (efi_memory_desc_t *)(pmap + (i * e->efi_memdesc_size));
> > > +
> > > + /*
> > > + * EFI_BOOT_SERVICES_{CODE|DATA} are avoided because boot
> > > + * services regions could be accessed after ExitBootServices()
> > > + * due to the workaround for buggy firmware.
> > > + */
> > > + if (!(md->type == EFI_LOADER_CODE ||
> > > + md->type == EFI_LOADER_DATA ||
> > > + md->type == EFI_CONVENTIONAL_MEMORY))
> > > + continue;
> >
> > Wouldn't it make more sense to *only* use EFI_CONVENTIONAL_MEMORY?
> >
> > You can't re-use EFI_LOADER_* regions because the kaslr code is run so
> > early in boot that you've no idea if data the kernel will need is in
> > those EFI_LOADER_* regions.
> >
> > For example, we pass struct setup_data objects inside of
> > EFI_LOADER_DATA regions.
>
> It doesn't matter because we have tried to avoid those memory setup_data
> resides in in mem_avoid_overlap(). Here discarding EFI_LOADER_* could
> discard the whole regions while setup_data could occupy small part of
> them.

Hi Matt, Baoquan,

I added these three checks to accept any regions corresponding to
E820_TYPE_RAM except EFI_BOOT_SERVICES_*, just thinking of that it's minimum
surprising. Baoquan gave a good justification on that, so I'll leave it
as-is in next version.

Thanks,
Naoya Horiguchi

\
 
 \ /
  Last update: 2017-07-07 08:14    [W:0.121 / U:9.364 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site