On 07/09/17 at 07:11am, Kees Cook wrote: > On Sun, Jul 9, 2017 at 5:37 AM, Baoquan He <b...@redhat.com> wrote: > > Kernel text may be located in non-mirror regions (movable zone) when both > > address range mirroring feature and KASLR are enabled. > > > > The address range mirroring feature arranges such mirror region into > > normal zone and other region into movable zone in order to locate > > kernel code and data in mirror region. The physical memory region > > whose descriptors in EFI memory map has EFI_MEMORY_MORE_RELIABLE > > attribute (bit: 16) are mirrored. > > > > 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 <b...@redhat.com> > > --- > > arch/x86/boot/compressed/kaslr.c | 60 > > ++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 58 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/boot/compressed/kaslr.c > > b/arch/x86/boot/compressed/kaslr.c > > index 99c7194f7ea6..7376b3473758 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 +560,54 @@ static void process_mem_region(struct mem_vector > > *entry, > > } > > } > > > > +/* Marks if efi mirror regions have been found and handled. */ > > +static bool efi_mirror_found; > > I think this is only ever checked once? How about having > process_efi_entries return bool to indicate if mirror was found? Also, > that function should be behind #ifdef. Let's do something like this:
Yes. Yours looks much better, let me change as you suggested and repost. Thanks a lot for reviewing and great suggestions! > > > > + > > +static void process_efi_entries(unsigned long minimum, > > + unsigned long image_size) > > #ifdef CONFIG_EFI > /* Returns true if mirror region found (and further scanning should stop) */ > static bool process_efi_entries(...) > { > ... > } > #else > static inline bool process_efi_entries(...) > { > return false; > } > #endif > > Then: > > > +#ifdef CONFIG_EFI > > + process_efi_entries(minimum, image_size); > > + if (efi_mirror_found) > > + return slots_fetch_random(); > > +#endif > > Can become: > > if (process_efi_entries(minimum, image_size)) > return slots_fetch_random() > > and no #ifndef needed here. > > > + > > process_e820_entries(minimum, image_size); > > return slots_fetch_random(); > > } > > @@ -652,7 +708,7 @@ 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 > > > > Otherwise, if the EFI logic is good, this looks sensible. > > Thanks for splitting up the patches! > > -Kees > > -- > Kees Cook > Pixel Security