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Subject: Re: [PATCH] kasan: push back KASAN_STACK detection to clang-10
To:     Arnd Bergmann <arnd@arndb.de>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Qian Cai <cai@lca.pw>, Mark Brown <broonie@kernel.org>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
References: <20190718141503.3258299-1-arnd@arndb.de>
From:   Andrey Ryabinin <aryabinin@virtuozzo.com>
Message-ID: <0ee5952b-5a76-c8a5-a30a-ee3c46a54814@virtuozzo.com>
Date:   Thu, 18 Jul 2019 19:18:28 +0300
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On 7/18/19 5:14 PM, Arnd Bergmann wrote:
> asan-stack mode still uses dangerously large kernel stacks of
> tens of kilobytes in some drivers, and it does not seem that anyone
> is working on the clang bug.
> 
> Let's push this back to clang-10 for now so users don't run into
> this by accident, and we can test-build allmodconfig kernels using
> clang-9 without drowning in warnings.
> 
> Link: https://bugs.llvm.org/show_bug.cgi?id=38809
> Fixes: 6baec880d7a5 ("kasan: turn off asan-stack for clang-8 and earlier")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  lib/Kconfig.kasan | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan
> index 4fafba1a923b..2f260bb63d77 100644
> --- a/lib/Kconfig.kasan
> +++ b/lib/Kconfig.kasan
> @@ -106,7 +106,7 @@ endchoice
>  
>  config KASAN_STACK_ENABLE
>  	bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
> -	default !(CLANG_VERSION < 90000)
> +	default !(CLANG_VERSION < 100000)

Wouldn't be better to make this thing for any clang version? And only when the bug is
finally fixed, specify the clang version which can enable this safely.


>  	depends on KASAN
>  	help
>  	  The LLVM stack address sanitizer has a know problem that
>