On Thu, 18 Apr 2019, Kees Cook wrote: > On Wed, May 11, 2016 at 5:45 AM Hector Marco-Gisbert <hecmargi@xxxxxx> wrote: > *thread necromancy* > > I'd still like to see this get landed. READ_IMPLIES_EXEC is way too > powerful (it impacts, for example, mmap() regions of device driver > memory, forcing drivers to not be able to disallow VM_EXEC[1]). > > The only case it could break is on an AMD K8 (Athlon only, I assume?), > which seems unlikely to have a modern kernel run on it. If there is > still concern, then we could just test against the NX CPU feature: > > diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h > index 69c0f892e310..367cd36259a4 100644 > --- a/arch/x86/include/asm/elf.h > +++ b/arch/x86/include/asm/elf.h > @@ -280,10 +280,12 @@ extern u32 elf_hwcap2; > > /* > * An executable for which elf_read_implies_exec() returns TRUE will > - * have the READ_IMPLIES_EXEC personality flag set automatically. > + * have the READ_IMPLIES_EXEC personality flag set automatically when > + * a CPU did not support NX or is using a 32-bit memory layout. > */ > -#define elf_read_implies_exec(ex, executable_stack) \ > - (executable_stack != EXSTACK_DISABLE_X) > +#define elf_read_implies_exec(ex, executable_stack) \ > + (mmap_is_ia32() || !(__supported_pte_mask & _PAGE_NX) ? \ What's special about ia32? All what matters is whether PAGE_NX is supported or not. That has nothing to do with 32/64bit unless I'm missing something (as usual). Thanks, tglx
