linux-kernel - Re: [RFC][PATCH] Makefile: globally enable VLA warning

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Message-ID: <CAGXu5j+8uqu7vQeupbPF26UTnAvTrwYObqrVAueM9ztFKaH-qw@mail.gmail.com>
Date:   Tue, 26 Jun 2018 15:02:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Joe Perches <joe@...ches.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        David Airlie <airlied@...ux.ie>,
        linux-kbuild <linux-kbuild@...r.kernel.org>,
        intel-gfx@...ts.freedesktop.org,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC][PATCH] Makefile: globally enable VLA warning

On Tue, Jun 26, 2018 at 1:21 PM, Joe Perches <joe@...ches.com> wrote:
> On Tue, 2018-06-26 at 10:40 -0700, Kees Cook wrote:
>> This is the patch I've got prepared now that fixes for all VLAs have been
>> sent to maintainers (some are still under review/adjustment, but there
>> aren't any unexplored cases left). My intention would be to have this land
>> at the end of the next merge window after all the pending VLA patches
>> have landed. I just wanted to get any feedback here, since it touches
>> a couple areas in the process and I didn't want anyone to be surprised. :)
> []
>> diff --git a/Makefile b/Makefile
> []
>> @@ -778,6 +778,9 @@ NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
>>  # warn about C99 declaration after statement
>>  KBUILD_CFLAGS += $(call cc-option,-Wdeclaration-after-statement,)
>>
>> +# VLAs should not be used anywhere in the kernel
>> +KBUILD_CFLAGS += $(call cc-option,-Wvla)
>
> I'd probably spell out what a VLA is here.
> # VLAs (Variable Length Arrays) should not be used anywhere in the kernel
>
> Beyond that, seems sensible, thanks.

Ah yes, good idea. I've made that change locally now. Thanks!

-Kees

-- 
Kees Cook
Pixel Security