On Fri, Sep 23, 2022 at 09:53:02PM +0200, Ard Biesheuvel wrote: > On Fri, 23 Sept 2022 at 20:31, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > > > On Fri, Sep 23, 2022 at 04:26:58PM +0200, Ard Biesheuvel wrote: > > > I was basically making the point that we still support i386 without > > > PAE (which is a prerequisite for supporting non-executable mappings), > > > and if we are going to be pedantic about security on this > > > architecture, we should probably make PAE mandatory as well. > > > > My expectation would be that if someone is running modern kernels on i386, > > they're not using PAE. If they care about PAE, I'd expect them to have > > long since moved to x86_64. > > > > Not sure I follow. If they care about PAE, they turn it on. Or do you > mean 'if they care about being able to address lots of physical > memory'? Because the *other* reason you might care about PAE is > because it gives you NX support. Right, I meant if they care about NX (and the topic of this thread) they want PAE, and if they want PAE, they likely moved to x86_64 long long ago for new kernels. > But currently, PAE is not even enabled in the i386_defconfig, and > defaults to off. This means people that are unaware of this won't > enable it, and will be running without NX support. And they all make me cry. ;) > > > If we are ok with the current state, enabling this permission check on > > > i386 makes no sense. > > > > I'd agree. If it's a choice between "spend a lot of time making sure > > this works correctly on i386" and "don't do this at all on i386", I > > would pick the latter. If someone steps up to do the former, then by > > all means take the patches. > > > > OK, so it seems we're all in violent agreement here. And if there is > ever a push for enabling security features on 32-bit, we can add this > to the laundry list of things that need to be looked at. Yup. -- Kees Cook
