linux-kernel - Re: [PATCH RFC RFT 2/5] fork: Add shadow stack support to clone3()

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Date:   Thu, 26 Oct 2023 23:32:51 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH RFC RFT 2/5] fork: Add shadow stack support to clone3()

On Thu, 2023-10-26 at 13:40 -0700, Deepak Gupta wrote:
> 
> FWIW, from arch specific perspective, RISC-V shadow stack extension
> has
> `ssamoswap` to perform this token exchange. But I understand x86 has
> this
> limitation (not sure about arm GCS).
> 
>  From security perspective:--
> Someone having ability to execute clone3 with control on input,
> probably
> already achieved some level of control flow bending because they need
> to
> corrupt memory and then carefully control registers input to clone3.
> Although if it is purely a data oriented gadget, I think it is
> possible.

struct clone_args should be data somewhere, at least temporarily.

> 
> Since this RFC is mostly concerned about `size` of shadow stack. I
> think
> we should limit it to size only.

Seems reasonable to me. It still leaves open the option of adding an
shadow stack address field later AFAICT.