On 03/24/17 at 09:08am, Ingo Molnar wrote: > > * Baoquan He <bhe@xxxxxxxxxx> 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. 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: <stable@xxxxxxxxxxxxxxx> #4.8+ > > Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> > > Acked-by: Dave Young <dyoung@xxxxxxxxxx> > > Reviewed-by: Bhupesh Sharma <bhsharma@xxxxxxxxxx> > > Acked-by: Thomas Garnier <thgarnie@xxxxxxxxxx> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > > Cc: x86@xxxxxxxxxx > > Cc: linux-efi@xxxxxxxxxxxxxxx > > Cc: Thomas Garnier <thgarnie@xxxxxxxxxx> > > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > > Cc: Borislav Petkov <bp@xxxxxxxxx> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> > > Cc: Dave Young <dyoung@xxxxxxxxxx> > > Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx> > > So I applied this kexec fix and extended the changelog to clearly show why this > fix matters in practice. > > Also, to make sure I understood it correctly: these addresses are all dynamic on > 64-bit kernels, i.e. we are establishing and then tearing down these page tables > around EFI calls, and they are 'normally' not present at all, right? Ingo, if I understand the question right "these addresses" means EFI va addresses then it is right, EFI switch to its own page tables, so they are not present in kernel page tables. > > Thanks, > > Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
