linux-kernel - Re: [PATCH v4 05/17] add support for Clang's Shadow Call Stack (SCS)

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Message-ID: <CANiq72=Z285XTHguDoL5Eq_7XRcounmBfscquFPRWk3BH5kLvA@mail.gmail.com>
Date:   Fri, 1 Nov 2019 23:36:05 +0100
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Dave Martin <Dave.Martin@....com>,
        Kees Cook <keescook@...omium.org>,
        Laura Abbott <labbott@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <maz@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 05/17] add support for Clang's Shadow Call Stack (SCS)

On Fri, Nov 1, 2019 at 11:12 PM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> This change adds generic support for Clang's Shadow Call Stack,
> which uses a shadow stack to protect return addresses from being
> overwritten by an attacker. Details are available here:
>
>   https://clang.llvm.org/docs/ShadowCallStack.html
>
> Note that security guarantees in the kernel differ from the
> ones documented for user space. The kernel must store addresses
> of shadow stacks used by other tasks and interrupt handlers in
> memory, which means an attacker capable reading and writing
> arbitrary memory may be able to locate them and hijack control
> flow by modifying shadow stacks that are not currently in use.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> Reviewed-by: Kees Cook <keescook@...omium.org>

Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>

Cheers,
Miguel