Messages in this thread | | | Date | Fri, 11 Aug 2023 12:13:30 -0700 | Subject | Re: [PATCH RESEND] x86/pti: Fix kernel warnings for pti= and nopti cmdline options. | From | Sohil Mehta <> |
| |
On 8/11/2023 11:23 AM, Jo Van Bulck wrote:
> On 08.08.23 17:13, Sohil Mehta wrote:> Can mitigations be off through > some other mechanisms such as kernel config? > I validated this both with and without the proposed patch. >
Great, thanks for checking that. The existing print is accurate then. If it is printed "disabled on command line.", then PTI has been disabled due to a command line option.
>> Maybe split the mitigations_off check into a separate if and it's own >> unique print message? >> Also, with the separated check you can avoid the unnecessary re-setting >> of pti_mode when pti_mode == PTI_FORCE_OFF is true. > > Thanks, makes sense. I'll make sure to do this in the next patch revision. >
Based on above, even when you split the if check only a single print would be enough, right?
>> In the rare case that both pti= and nopti is set the existing code seems >> to ignore the nopti option. Would the new implementation do the same? > > Good point. In my understanding, passing such conflicting options is > undefined as per the specification [2] and I'm not sure if backwards > compatibility is a requirement? >
> That being said, I can see the argument that in this case of > security-sensitive functionality, it may be desirable to maintain > identical behavior for identical kernel parameter combinations and > sequences.
I don't believe that is a requirement either. Sometimes kernel command lines can get very long and people make mistakes. I just thought it is neat that the current code is defaulting that way and we should probably keep the same behavior since it makes sense.
> > --> I can update the patch to ensure backwards-compatible behavior in > both cases for the next patch revision. >
I agree, in both cases pti= overriding the other option (nopti or mitigations=off) sounds reasonable to me.
Sohil
| |