lkml.org 
[lkml]   [2019]   [Apr]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 RESEND 2/2] x86/mm/KASLR: Fix the size of vmemmap section
On 04/15/19 at 09:47pm, Borislav Petkov wrote:
> On Sun, Apr 14, 2019 at 03:28:04PM +0800, Baoquan He wrote:
> > kernel_randomize_memory() hardcodes the size of vmemmap section as 1 TB,
> > to support the maximum amount of system RAM in 4-level paging mode, 64 TB.
> >
> > However, 1 TB is not enough for vmemmap in 5-level paging mode. Assuming
> > the size of struct page is 64 Bytes, to support 4 PB system RAM in 5-level,
> > 64 TB of vmemmap area is needed. The wrong hardcoding may cause vmemmap
> > stamping into the following cpu_entry_area section, if KASLR puts vmemmap
> > very close to cpu_entry_area, and the actual area of vmemmap is much bigger
> > than 1 TB.
> >
> > So here calculate the actual size of vmemmap region, then align up to 1 TB
> > boundary. In 4-level it's always 1 TB. In 5-level it's adjusted on demand.
> > The current code reserves 0.5 PB for vmemmap in 5-level. In this new methor,
> ^^^^^^^
>
> Please introduce a spellchecker into your patch creation workflow.

Sorry, forgot running checkpatch this time. Will update.

>
> > the left space can be saved to join randomization to increase the entropy.
> >
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> > arch/x86/mm/kaslr.c | 11 ++++++++++-
> > 1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
> > index 387d4ed25d7c..4679a0075048 100644
> > --- a/arch/x86/mm/kaslr.c
> > +++ b/arch/x86/mm/kaslr.c
> > @@ -52,7 +52,7 @@ static __initdata struct kaslr_memory_region {
> > } kaslr_regions[] = {
> > { &page_offset_base, 0 },
> > { &vmalloc_base, 0 },
> > - { &vmemmap_base, 1 },
> > + { &vmemmap_base, 0 },
> > };
> >
> > /* Get size in bytes used by the memory region */
> > @@ -78,6 +78,7 @@ void __init kernel_randomize_memory(void)
> > unsigned long rand, memory_tb;
> > struct rnd_state rand_state;
> > unsigned long remain_entropy;
> > + unsigned long vmemmap_size;
> >
> > vaddr_start = pgtable_l5_enabled() ? __PAGE_OFFSET_BASE_L5 : __PAGE_OFFSET_BASE_L4;
> > vaddr = vaddr_start;
> > @@ -109,6 +110,14 @@ void __init kernel_randomize_memory(void)
> > if (memory_tb < kaslr_regions[0].size_tb)
> > kaslr_regions[0].size_tb = memory_tb;
> >
> > + /**
> > + * Calculate how many TB vmemmap region needs, and aligned to
> > + * 1TB boundary.
> > + */
> > + vmemmap_size = (kaslr_regions[0].size_tb << (TB_SHIFT - PAGE_SHIFT)) *
> > + sizeof(struct page);
> > + kaslr_regions[2].size_tb = DIV_ROUND_UP(vmemmap_size, 1UL << TB_SHIFT);
> > +
> > /* Calculate entropy available between regions */
> > remain_entropy = vaddr_end - vaddr_start;
> > for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++)
> > --
>
> Kirill, ack?
>
> --
> Regards/Gruss,
> Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.

\
 
 \ /
  Last update: 2019-04-17 10:40    [W:0.150 / U:5.428 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site