Re: [PATCH 4/7] x86/entry: Increase entry_stack size to a full page

[Marco Elver]

On Thu, 18 Jun 2020 at 16:50, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> Marco crashed in bad_iret with a Clang11/KCSAN build due to
> overflowing the stack. Now that we run C code on it, expand it to a
> full page.
>
> Suggested-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Reported-by: Marco Elver <elver@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

This fixes the unpredictable crashes.

Tested-by: Marco Elver <elver@xxxxxxxxxx>

Thanks!


> ---
>  arch/x86/include/asm/processor.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -370,7 +370,7 @@ struct x86_hw_tss {
>  #define IO_BITMAP_OFFSET_INVALID       (__KERNEL_TSS_LIMIT + 1)
>
>  struct entry_stack {
> -       unsigned long           words[64];
> +       char    stack[PAGE_SIZE];
>  };
>
>  struct entry_stack_page {
>
>