linux-kernel - Re: [PATCH RFT v5 4/7] fork: Add shadow stack support to clone3()

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Date: Sat, 10 Feb 2024 00:56:35 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH RFT v5 4/7] fork: Add shadow stack support to clone3()

On Sat, 2024-02-03 at 00:05 +0000, Mark Brown wrote:
> +       if (args->shadow_stack) {
> +               addr = args->shadow_stack;
> +               size = args->shadow_stack_size;
>  
> -       size = adjust_shstk_size(stack_size);
> -       addr = alloc_shstk(0, size, 0, false);
> -       if (IS_ERR_VALUE(addr))
> -               return addr;
> +               /* There should be a valid token at the top of the
> stack. */
> +               if (!shstk_consume_token(tsk, addr + size -
> sizeof(u64)))
> +                       return (unsigned long)ERR_PTR(-EINVAL);

I think for this case, it needs:
	shstk->base = 0;
	shstk->size = 0;

To prevent trying to free the parents shadow stack when the child
exits.