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Message-ID: <CAGXu5j+b2UfdPs1yoweAy=jAFj9UQMGYYy1EjQUCi3JNjZD90A@mail.gmail.com>
Date: Wed, 24 May 2017 09:16:51 -0700
From: Kees Cook <keescook@...gle.com>
To: Rik van Riel <riel@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Daniel Micay <danielmicay@...il.com>,
"Ted Ts'o" <tytso@....edu>, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...capital.net>,
Ingo Molnar <mingo@...nel.org>, "x86@...nel.org" <x86@...nel.org>,
"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
Catalin Marinas <catalin.marinas@....com>, linux-sh <linux-sh@...r.kernel.org>,
Yoshinori Sato <ysato@...rs.sourceforge.jp>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 4/5] arm64: ascii armor the arm64 boot init stack canary
On Wed, May 24, 2017 at 8:57 AM, <riel@...hat.com> wrote:
> From: Rik van Riel <riel@...hat.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@...hat.com>
Acked-by: Kees Cook <keescook@...omium.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
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