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SubjectRe: [PATCH v9 2/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions
On 08/18/17 at 04:10pm, Ard Biesheuvel wrote:
> On 17 August 2017 at 14:04, Baoquan He <bhe@redhat.com> wrote:

> > Thanks a lot for helping improving the patch log, Ingo! Will pay more
> > attention to the description in words and paragraph partition of log.
> >
> >>
> >> So if EFI is detected, iterate EFI memory map and pick the mirror region
> >> to process for adding candidate of randomization slot. If EFI is disabled
> >> or no mirror region found, still process e820 memory map.
> >>
> >> Signed-off-by: Baoquan He <bhe@redhat.com>
>
>
> Could the x86 people on cc either take these directly, or indicate
> whether they are ok with this going in via the EFI tree?

Thanks for looking into this, Ard. I saw Ingo has put these into
tip/x86/boot.

>
> >> ---
> >> arch/x86/boot/compressed/kaslr.c | 68 ++++++++++++++++++++++++++++++++++++++--
> >> 1 file changed, 66 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> >> index 99c7194f7ea6..7de23bb279ce 100644
> >> --- a/arch/x86/boot/compressed/kaslr.c
> >> +++ b/arch/x86/boot/compressed/kaslr.c
> >> @@ -37,7 +37,9 @@
> >> #include <linux/uts.h>
> >> #include <linux/utsname.h>
> >> #include <linux/ctype.h>
> >> +#include <linux/efi.h>
> >> #include <generated/utsrelease.h>
> >> +#include <asm/efi.h>
> >>
> >> /* Macros used by the included decompressor code below. */
> >> #define STATIC
> >> @@ -558,6 +560,65 @@ static void process_mem_region(struct mem_vector *entry,
> >> }
> >> }
> >>
> >> +#ifdef CONFIG_EFI
> >> +/*
> >> + * Returns true if mirror region found (and must have been processed
> >> + * for slots adding)
> >> + */
> >> +static bool
> >> +process_efi_entries(unsigned long minimum, unsigned long image_size)
> >> +{
> >> + struct efi_info *e = &boot_params->efi_info;
> >> + bool efi_mirror_found = false;
> >> + struct mem_vector region;
> >> + efi_memory_desc_t *md;
> >> + unsigned long pmap;
> >> + char *signature;
> >> + u32 nr_desc;
> >> + int i;
> >> +
> >> + signature = (char *)&e->efi_loader_signature;
> >> + if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) &&
> >> + strncmp(signature, EFI64_LOADER_SIGNATURE, 4))
> >> + return false;
> >> +
> >> +#ifdef CONFIG_X86_32
> >> + /* Can't handle data above 4GB at this time */
> >> + if (e->efi_memmap_hi) {
> >> + warn("EFI memmap is above 4GB, can't be handled now on x86_32. EFI should be disabled.\n");
> >> + return false;
> >> + }
> >> + pmap = e->efi_memmap;
> >> +#else
> >> + pmap = (e->efi_memmap | ((__u64)e->efi_memmap_hi << 32));
> >> +#endif
> >> +
> >> + nr_desc = e->efi_memmap_size / e->efi_memdesc_size;
> >> + for (i = 0; i < nr_desc; i++) {
> >> + md = efi_early_memdesc_ptr(pmap, e->efi_memdesc_size, i);
> >> + if (md->attribute & EFI_MEMORY_MORE_RELIABLE) {
> >> + region.start = md->phys_addr;
> >> + region.size = md->num_pages << EFI_PAGE_SHIFT;
> >> + process_mem_region(&region, minimum, image_size);
> >> + efi_mirror_found = true;
> >> +
> >> + if (slot_area_index == MAX_SLOT_AREA) {
> >> + debug_putstr("Aborted EFI scan (slot_areas full)!\n");
> >> + break;
> >> + }
> >> + }
> >> + }
> >> +
> >> + return efi_mirror_found;
> >> +}
> >> +#else
> >> +static inline bool
> >> +process_efi_entries(unsigned long minimum, unsigned long image_size)
> >> +{
> >> + return false;
> >> +}
> >> +#endif
> >> +
> >> static void process_e820_entries(unsigned long minimum,
> >> unsigned long image_size)
> >> {
> >> @@ -586,13 +647,16 @@ static unsigned long find_random_phys_addr(unsigned long minimum,
> >> {
> >> /* Check if we had too many memmaps. */
> >> if (memmap_too_large) {
> >> - debug_putstr("Aborted e820 scan (more than 4 memmap= args)!\n");
> >> + debug_putstr("Aborted memory entries scan (more than 4 memmap= args)!\n");
> >> return 0;
> >> }
> >>
> >> /* Make sure minimum is aligned. */
> >> minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
> >>
> >> + if (process_efi_entries(minimum, image_size))
> >> + return slots_fetch_random();
> >> +
> >> process_e820_entries(minimum, image_size);
> >> return slots_fetch_random();
> >> }
> >> @@ -652,7 +716,7 @@ void choose_random_location(unsigned long input,
> >> */
> >> min_addr = min(*output, 512UL << 20);
> >>
> >> - /* Walk e820 and find a random address. */
> >> + /* Walk available memory entries to find a random address. */
> >> random_addr = find_random_phys_addr(min_addr, output_size);
> >> if (!random_addr) {
> >> warn("Physical KASLR disabled: no suitable memory region!");
> >> --
> >> 2.5.5
> >>

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