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Date:   Wed, 18 Oct 2023 14:39:48 -0400
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Subject: Re: [PATCH] lib/Kconfig.debug: disable FRAME_WARN for kasan and kcsan
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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>,
        =?UTF-8?Q?Bj=C3=B6rn_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
References: <20231018182412.80291-1-hamza.mahfooz@amd.com>
 <CAMuHMdXSzMJe1zyJu1HkxWggTKJj_sxkPOejjbdRjg3FeFTVHQ@mail.gmail.com>
From:   Hamza Mahfooz <hamza.mahfooz@amd.com>
In-Reply-To: <CAMuHMdXSzMJe1zyJu1HkxWggTKJj_sxkPOejjbdRjg3FeFTVHQ@mail.gmail.com>
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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