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References: <20210309123544.14040-1-msuchanek@suse.de>
In-Reply-To: <20210309123544.14040-1-msuchanek@suse.de>
From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Tue, 9 Mar 2021 22:22:36 +0900
Message-ID: <CAK7LNAT+8mGunqXSPLHxhF1FTXQEzbAoKPY=48pBgtLbhcB0jg@mail.gmail.com>
Subject: Re: [PATCH] arm64: make STACKPROTECTOR_PER_TASK configurable.
To:     Michal Suchanek <msuchanek@suse.de>
Cc:     linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, Mar 9, 2021 at 9:35 PM Michal Suchanek <msuchanek@suse.de> wrote:
>
> When using dummy-tools STACKPROTECTOR_PER_TASK is unconditionally
> selected. This defeats the purpose of the all-enabled tool.
>
> Description copied from arm
>
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Michal Suchanek <msuchanek@suse.de>


Could you explain what problem
this patch is trying to solve?


> ---
>  arch/arm64/Kconfig | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index a8ff7cd5f096..f59d391e31a4 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1549,9 +1549,20 @@ config RANDOMIZE_MODULE_REGION_FULL
>  config CC_HAVE_STACKPROTECTOR_SYSREG
>         def_bool $(cc-option,-mstack-protector-guard=sysreg -mstack-protector-guard-reg=sp_el0 -mstack-protector-guard-offset=0)
>
> +
>  config STACKPROTECTOR_PER_TASK
> -       def_bool y
> +       bool "Use a unique stack canary value for each task"
>         depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_SYSREG
> +       default y
> +       help
> +         Due to the fact that GCC uses an ordinary symbol reference from
> +         which to load the value of the stack canary, this value can only
> +         change at reboot time on SMP systems, and all tasks running in the
> +         kernel's address space are forced to use the same canary value for
> +         the entire duration that the system is up.
> +
> +         Enable this option to switch to a different method that uses a
> +         different canary value for each task.
>
>  endmenu
>
> --
> 2.26.2
>


-- 
Best Regards
Masahiro Yamada