Re: [PATCH] lib/Kconfig.debug: disable FRAME_WARN for kasan and kcsan

From: Hamza Mahfooz <hamza.mahfooz@amd.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: linux-kernel@vger.kernel.org,
	"Rodrigo Siqueira" <rodrigo.siqueira@amd.com>,
	"Harry Wentland" <harry.wentland@amd.com>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	stable@vger.kernel.org, "Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Wedson Almeida Filho" <wedsonaf@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Nick Terrell" <terrelln@fb.com>,
	"Nathan Chancellor" <nathan@kernel.org>,
	"Nick Desaulniers" <ndesaulniers@google.com>,
	"Tom Rix" <trix@redhat.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
	"Randy Dunlap" <rdunlap@infradead.org>,
	"Kees Cook" <keescook@chromium.org>,
	"Zhaoyang Huang" <zhaoyang.huang@unisoc.com>,
	"Li Hua" <hucool.lihua@huawei.com>,
	"Alexander Potapenko" <glider@google.com>,
	"Geert Uytterhoeven" <geert+renesas@glider.be>,
	"Rae Moar" <rmoar@google.com>,
	rust-for-linux@vger.kernel.org, bpf@vger.kernel.org,
	llvm@lists.linux.dev
Subject: Re: [PATCH] lib/Kconfig.debug: disable FRAME_WARN for kasan and kcsan
Date: Wed, 18 Oct 2023 14:39:48 -0400	[thread overview]
Message-ID: <d764242f-cde0-47c0-ae2c-f94b199c93df@amd.com> (raw)
In-Reply-To: <CAMuHMdXSzMJe1zyJu1HkxWggTKJj_sxkPOejjbdRjg3FeFTVHQ@mail.gmail.com>

On 10/18/23 14:29, Geert Uytterhoeven wrote:
> Hi Hamza,
> 
> On Wed, Oct 18, 2023 at 8:24 PM Hamza Mahfooz <hamza.mahfooz@amd.com> wrote:
>> With every release of LLVM, both of these sanitizers eat up more and
>> more of the stack. So, set FRAME_WARN to 0 if either of them is enabled
>> for a given build.
>>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
> 
> Thanks for your patch!
> 
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -429,11 +429,10 @@ endif # DEBUG_INFO
>>   config FRAME_WARN
>>          int "Warn for stack frames larger than"
>>          range 0 8192
>> -       default 0 if KMSAN
>> +       default 0 if KASAN || KCSAN || KMSAN
> 
> Are kernels with KASAN || KCSAN || KMSAN enabled supposed to be bootable?

They are all intended to be used for runtime debugging, so I'd imagine so.

> Stack overflows do cause crashes.

It is worth noting that FRAME_WARN has been disabled for KMSAN for quite
a while and as far as I can tell no one has complained.

> 
>>          default 2048 if GCC_PLUGIN_LATENT_ENTROPY
>>          default 2048 if PARISC
>>          default 1536 if (!64BIT && XTENSA)
>> -       default 1280 if KASAN && !64BIT
>>          default 1024 if !64BIT
>>          default 2048 if 64BIT
>>          help
> 
> Gr{oetje,eeting}s,
> 
>                          Geert
> 
-- 
Hamza