Re: [PATCH RFT v11 0/8] fork: Support shadow stacks in clone3()

[Yury Khrustalev <yury.khrustalev@arm.com>]

On Wed, Oct 30, 2024 at 02:08:59PM +0000, Mark Brown wrote:
> On Sat, Oct 05, 2024 at 11:31:27AM +0100, Mark Brown wrote:
> > The kernel has recently added support for shadow stacks, currently
> > x86 only using their CET feature but both arm64 and RISC-V have
> > equivalent features (GCS and Zicfiss respectively), I am actively
> > working on GCS[1].  With shadow stacks the hardware maintains an
> > additional stack containing only the return addresses for branch
> > instructions which is not generally writeable by userspace and ensures
> > that any returns are to the recorded addresses.  This provides some
> > protection against ROP attacks and making it easier to collect call
> > stacks.  These shadow stacks are allocated in the address space of the
> > userspace process.
> 
> Does anyone have any thoughts on this?  I reworked things to specify the
> address for the shadow stack pointer rather than the extent of the stack
> as Rick and Yuri suggested, otherwise the only change from the prior
> version was rebasing onto the arm64 GCS support since that's queued in
> -next.  I think the only substantial question is picking the ABI for
> specifying the shadow stack.

I will need more time to review this as both my primary and shadow stacks
are full with other work. At a glance, I cannot offer any informed opinion
for choosing ABI atm. Apologies for the delay.

Kind regards,
Yury