linux-hardening - Re: [PATCH -next v3 2/2] powerpc: add support for syscall stack randomization

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Message-ID: <202207271331.B227002C@keescook>
Date:   Wed, 27 Jul 2022 13:32:09 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Xiu Jianfeng <xiujianfeng@...wei.com>
Cc:     mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        npiggin@...il.com, christophe.leroy@...roup.eu, tglx@...utronix.de,
        mark.rutland@....com, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH -next v3 2/2] powerpc: add support for syscall stack
 randomization

On Fri, Jul 01, 2022 at 04:24:35PM +0800, Xiu Jianfeng wrote:
> Add support for adding a random offset to the stack while handling
> syscalls. This patch uses mftb() instead of get_random_int() for better
> performance.
> 
> In order to avoid unconditional stack canaries on syscall entry (due to
> the use of alloca()), also disable stack protector to avoid triggering
> needless checks and slowing down the entry path. As there is no general
> way to control stack protector coverage with a function attribute, this
> must be disabled at the compilation unit level.
> 
> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

-- 
Kees Cook