Re: [PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary

From	Kees Cook <keescook@google.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary
Date	2017-05-24 18:20 +0200
Message-ID	<tKHaV-4zP-1@gated-at.bofh.it> (permalink)
References	<tKGRz-4dh-7@gated-at.bofh.it> <tKGRA-4dh-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, May 24, 2017 at 8:57 AM,  <riel@redhat.com> wrote:
> From: Rik van Riel <riel@redhat.com>
>
> Use the ascii-armor canary to prevent unterminated C string overflows
> from being able to successfully overwrite the canary, even if they
> somehow obtain the canary value.
>
> Inspired by execshield ascii-armor and Daniel Micay's linux-hardened tree.
>
> Signed-off-by: Rik van Riel <riel@redhat.com>

Acked-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
>  arch/arm64/include/asm/stackprotector.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/include/asm/stackprotector.h b/arch/arm64/include/asm/stackprotector.h
> index fe5e287dc56b..b86a0865ddf1 100644
> --- a/arch/arm64/include/asm/stackprotector.h
> +++ b/arch/arm64/include/asm/stackprotector.h
> @@ -30,6 +30,7 @@ static __always_inline void boot_init_stack_canary(void)
>         /* Try to get a semi random initial value. */
>         get_random_bytes(&canary, sizeof(canary));
>         canary ^= LINUX_VERSION_CODE;
> +       canary &= CANARY_MASK;
>
>         current->stack_canary = canary;
>         __stack_chk_guard = current->stack_canary;
> --
> 2.9.3
>



-- 
Kees Cook
Pixel Security

Thread

[PATCH v2 0/5] stackprotector: ascii armor the stack canary riel@redhat.com - 2017-05-24 18:00 +0200
  [PATCH 1/5] random,stackprotect: introduce get_random_canary function riel@redhat.com - 2017-05-24 18:00 +0200
    Re: [PATCH 1/5] random,stackprotect: introduce get_random_canary function Kees Cook <keescook@google.com> - 2017-05-24 18:20 +0200
  [PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary riel@redhat.com - 2017-05-24 18:00 +0200
    Re: [PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary Kees Cook <keescook@google.com> - 2017-05-24 18:20 +0200
  [PATCH 3/5] x86: ascii armor the x86_64 boot init stack canary riel@redhat.com - 2017-05-24 18:00 +0200
    Re: [PATCH 3/5] x86: ascii armor the x86_64 boot init stack canary Kees Cook <keescook@google.com> - 2017-05-24 18:20 +0200
  [PATCH 2/5] fork,random: use get_random_canary to set tsk->stack_canary riel@redhat.com - 2017-05-24 18:00 +0200
    Re: [PATCH 2/5] fork,random: use get_random_canary to set tsk->stack_canary Kees Cook <keescook@google.com> - 2017-05-24 18:20 +0200
  [PATCH 5/5] sh64: ascii armor the sh64 boot init stack canary Rik van Riel <riel@redhat.com> - 2017-05-24 18:40 +0200
    Re: [PATCH 5/5] sh64: ascii armor the sh64 boot init stack canary Kees Cook <keescook@google.com> - 2017-05-24 18:40 +0200
  [PATCH 5/5] sh64: ascii armor the sh64 boot init stack canary riel@redhat.com - 2017-05-24 18:50 +0200

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