Messages in this thread | | | Date | Tue, 3 Oct 2023 21:06:51 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86_64: test that userspace stack is in fact NX |
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* Dave Hansen <dave.hansen@intel.com> wrote:
> On 10/3/23 06:00, Alexey Dobriyan wrote: > > On Mon, Oct 02, 2023 at 07:23:10AM -0700, Dave Hansen wrote: > >> Basically, could you spend a moment in the changelog to talk about: > >> > >> 1. 32-bit kernels on NX hardware > >> and > >> 2. 64-bit kernels on non-NX hardware > > > > Sure. My logic whas that i386 is dead arch, but this test is easy to > > port to i386, only 2 simple functions. > > I honestly don't feel strongly about it one way or the other. But > whatever we do, let's explain it, please. > > > I don't want to parse /proc/cpuinfo. If someone knows they're shipping > > NX-incapable hardware, just let them disable the test. > > Other than clearcpuid=nx, I don't _think_ we have any way to clear the > X86_FEATURE_NX bit right now. That should mean that you can use regular > old CPUID to see if the booted kernel supports NX. [...]
I think that's probably overkill - the test should report a failure if NX is not available for whatever reason.
Because not having NX in 2023 on any system that is threatened is a big security vulnerability in itself, and whether the vendor or owner intentionally did that or not doesn't really matter, and a failing kernel testcase will be the least of their problems.
In fact I'd argue that we should fail this testcase in that situation as a matter of principle: NX clearly doesn't work and there's very few situations where that's acceptable.
Anyone who doesn't want or have NX can skip paying attention to this failing testcase just fine.
Thanks,
Ingo
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