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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Thu, 4 Mar 2021 10:54:34 -0800
Message-ID: <CABBYNZ+FQRJm-OUv-J6byNMzK8W0znU18FB3fwDVvFPGa=d2XQ@mail.gmail.com>
Subject: Re: [PATCH 1/3] build: Add warnings for non-literal strings
To:     Bastien Nocera <hadess@hadess.net>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
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Hi Bastien,

On Thu, Mar 4, 2021 at 10:46 AM Bastien Nocera <hadess@hadess.net> wrote:
>
> On Thu, 2021-03-04 at 10:35 -0800, Luiz Augusto von Dentz wrote:
> > Hi Bastien,
> >
> > On Thu, Mar 4, 2021 at 9:21 AM Bastien Nocera <hadess@hadess.net>
> > wrote:
> > >
> > > ---
> > >  acinclude.m4 | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/acinclude.m4 b/acinclude.m4
> > > index 529848357..6ae34b8ae 100644
> > > --- a/acinclude.m4
> > > +++ b/acinclude.m4
> > > @@ -21,7 +21,7 @@ AC_DEFUN([COMPILER_FLAGS], [
> > >                 with_cflags="$with_cflags -Wredundant-decls"
> > >                 with_cflags="$with_cflags -Wcast-align"
> > >                 with_cflags="$with_cflags -Wswitch-enum"
> > > -               with_cflags="$with_cflags -Wformat -Wformat-security"
> > > +               with_cflags="$with_cflags -Wformat -Wformat-security
> > > -Wformat-nonliteral"
> >
> > Does it actually have any benefit of having the format as always
> > string literal? I'm not really a big fan of using pragmas.
>
> It's a security feature[1], so it's pretty important that we avoid
> using non-literals when some of the arguments are user controlled,
> especially in a networked daemon. We already enabled
> "-Wformat-security", so not that much of a difference.
>
> This warning is also enabled by default on Fedora's GCC, so I get to
> see it whether I want to or not.
>
> I'd be happy actually fixing those warnings if you don't want pragmas
> at all, it would just be more code movement. If we can get those
> patches in, I can do a follow-up.
>
> [1]: Quick search gave me this explanation:
> https://owasp.org/www-community/attacks/Format_string_attack

You should probably add the above link in the patch description,
regarding the use of pragma. I'd say we need to convert to use
literals directly then since otherwise we are not actually fixing
anything just returning it back to ignore the error where we don't use
literals.

> > >                 with_cflags="$with_cflags -DG_DISABLE_DEPRECATED"
> > >                 with_cflags="$with_cflags -
> > > DGLIB_VERSION_MIN_REQUIRED=GLIB_VERSION_2_28"
> > >                 with_cflags="$with_cflags -
> > > DGLIB_VERSION_MAX_ALLOWED=GLIB_VERSION_2_32"
> > > --
> > > 2.29.2
> > >
> >
> >
>
>


-- 
Luiz Augusto von Dentz