Re: [PATCH 5/6] x86/shstk: don't create the shadow stack for PF_USER_WORKERs

[Deepak Gupta]

On Fri, Aug 15, 2025 at 12:44:14PM +0100, Mark Brown wrote:
> On Thu, Aug 14, 2025 at 10:43:45PM +0000, Edgecombe, Rick P wrote:
> > On Thu, 2025-08-14 at 19:33 +0100, Mark Brown wrote:
>
> > > Perhaps we should factor the logic for deciding if we need to allocate a
> > > userspace shadow stack out into the arch independent code and do
> > > something like set a flag in kernel_clone_args that the arches can
> > > check?  I think the logic is the same for all arches at the minute and
> > > don't see a reason why it'd diverge.
>
> > Sounds good. Like a little start to this:
> > https://lore.kernel.org/lkml/20241010-shstk_converge-v1-0-631beca676e7@xxxxxxxxxxxx/
>
> Yes, exactly.
>
> > >   That'd collide a bit with my
> > > clone3() series, there's some overlap there with that creating another
> > > reason why the decision would change.  Reducing the duplication would be
> > > nice.
>
> > Argh, I need to test the latest of that still.
>
> Yury pointed me at some newer x86 systems I was able to get access to so
> I was finally able to test that one myself before sending it out,
> confirmation would be good but hopefully it's fine.  I've been holding
> back on sending a rebased version out since Deepak was going to help me
> get set up to test it on RISC-V.  Though I see now that the RISC-V code
> has vanished from -next (I guess due to fallout from the issues with the
> merge to Linus, it looks like there's almost nothing in the branch
> currently), not sure what the plan is there?
>
> Perhaps I should just send it out, but given the difficulty getting
> anyone to pay attention I was trying to avoid issues with missing
> updates for newly added RISC-V shadow stacks.

Yes I was trying to get that sorted as well. Because now I'll have to
rebase my changes to 6.17. So I wanted to make sure that it applies
cleanly. I suggest that you send it out because risc-v was left out
anyways. I'll apply your patch series on my risc-v shadow stack changes
(on top of 6.17) and will report back. It might be easier that way.

How does that sound?