On Mon, Jun 08, 2020 at 03:54:24PM +0300, Kirill A. Shutemov wrote:
> A 5-level paging capable machine can have memory above 46-bit in the
> physical address space. This memory is only addressable in the 5-level
> paging mode: we don't have enough virtual address space to create direct
> mapping for such memory in the 4-level paging mode
>
> Teach KASLR to avoid memory regions above MAXMEM or truncate the region
> if the end is above MAXMEM.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # v4.14
Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> ---
> arch/x86/boot/compressed/kaslr.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index d7408af55738..99db18eeb40e 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -695,7 +695,18 @@ static bool process_mem_region(struct mem_vector *region,
> unsigned long long minimum,
> unsigned long long image_size)
> {
> + unsigned long long end;
> int i;
> +
> + /* Cannot access memory region above MAXMEM: skip it. */
> + if (region->start >= MAXMEM)
> + return 0;
> +
> + /* Truncate the region if the end is above MAXMEM */
> + end = region->start + region->size;
> + end = min_t(unsigned long long, end, MAXMEM - 1);
> + region->size = end - region->start;
> +
> /*
> * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
> * use @region directly.
> --
> 2.26.2
>
>
--
Sincerely yours,
Mike.
