On 03/24/17 at 10:29am, Dave Young wrote: > Hi, Baoquan > > On 03/23/17 at 11:27am, Baoquan He wrote: > > Currently KASLR is enabled on three regions: the direct mapping of physical > > memory, vamlloc and vmemmap. However EFI region is also mistakenly included > > for VA space randomization because of misusing EFI_VA_START macro and > > assuming EFI_VA_START < EFI_VA_END. > > > > The EFI region is reserved for EFI runtime services virtual mapping which > > should not be included in kaslr ranges. It will be re-used by kexec/kdump > > kernel, the mistake may cause failure when jump to kexec/kdump kernel if > > vmemmap allocation stomps on the allocated efi mapping region. > > No need to mention kexec/kdump in changelog although it is true that > kexec kernel will use the persistent efi runtime mapping. The main point > is it is wrong to use the reserved vm space for efi.
I only say the consequence from kdump point of view and point out that. Anyway I am fine w/o kexec/kdump text. Will repost this patch only without kexec-ed kernel saying. > > Also I think this patch can be sent as a standalone patch, no need to be > a patch series. For the second patch I think it depends on efi > maintainer's opinion, personally I think only this simple fix for kaslr only > will be better. > > > > > In Documentation/x86/x86_64/mm.txt, we can see: > > ffffffef00000000 - fffffffeffffffff (=64 GB) EFI region mapping space > > EFI use the space from -4G to -64G thus EFI_VA_START > EFI_VA_END > > Here EFI_VA_START = -4G, and EFI_VA_END = -64G > > > > Changing EFI_VA_START to EFI_VA_END in mm/kaslr.c fixes this problem. > > > > Cc: <sta...@vger.kernel.org> #4.8+ > > Signed-off-by: Baoquan He <b...@redhat.com> > > Acked-by: Dave Young <dyo...@redhat.com> > > Reviewed-by: Bhupesh Sharma <bhsha...@redhat.com> > > Acked-by: Thomas Garnier <thgar...@google.com> > > Cc: Thomas Gleixner <t...@linutronix.de> > > Cc: Ingo Molnar <mi...@redhat.com> > > Cc: "H. Peter Anvin" <h...@zytor.com> > > Cc: x...@kernel.org > > Cc: Thomas Garnier <thgar...@google.com> > > Cc: Kees Cook <keesc...@chromium.org> > > Cc: Borislav Petkov <b...@alien8.de> > > Cc: Andrew Morton <a...@linux-foundation.org> > > Cc: Masahiro Yamada <yamada.masah...@socionext.com> > > --- > > arch/x86/mm/kaslr.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > > index 887e571..aed2064 100644 > > --- a/arch/x86/mm/kaslr.c > > +++ b/arch/x86/mm/kaslr.c > > @@ -48,7 +48,7 @@ static const unsigned long vaddr_start = > > __PAGE_OFFSET_BASE; > > #if defined(CONFIG_X86_ESPFIX64) > > static const unsigned long vaddr_end = ESPFIX_BASE_ADDR; > > #elif defined(CONFIG_EFI) > > -static const unsigned long vaddr_end = EFI_VA_START; > > +static const unsigned long vaddr_end = EFI_VA_END; > > #else > > static const unsigned long vaddr_end = __START_KERNEL_map; > > #endif > > @@ -105,7 +105,7 @@ void __init kernel_randomize_memory(void) > > */ > > BUILD_BUG_ON(vaddr_start >= vaddr_end); > > BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) && > > - vaddr_end >= EFI_VA_START); > > + vaddr_end >= EFI_VA_END); > > BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) || > > IS_ENABLED(CONFIG_EFI)) && > > vaddr_end >= __START_KERNEL_map); > > -- > > 2.5.5 > > > > Thanks > Dave
