MIME-Version: 1.0
References: <20230203194201.92015-1-ebiggers@kernel.org> <63deacb1.170a0220.f078.6779@mx.google.com>
In-Reply-To: <63deacb1.170a0220.f078.6779@mx.google.com>
From:   Fangrui Song <maskray@google.com>
Date:   Mon, 6 Feb 2023 15:41:05 -0800
Message-ID: <CAFP8O3Kwa2V7GvJPEbr87o6hMi8i2JquWniFOaiFR3nv9pGc_g@mail.gmail.com>
Subject: Re: [PATCH] randstruct: temporarily disable clang support
To:     Kees Cook <keescook@chromium.org>
Cc:     Eric Biggers <ebiggers@kernel.org>,
        linux-hardening@vger.kernel.org, llvm@lists.linux.dev,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Sat, Feb 4, 2023 at 11:06 AM Kees Cook <keescook@chromium.org> wrote:
>
> On Fri, Feb 03, 2023 at 11:42:01AM -0800, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> >
> > Randstruct with clang is currently unsafe to use in any clang release
> > that supports it, due to a clang bug that is causing miscompilations:
> > "-frandomize-layout-seed inconsistently randomizes all-function-pointer=
s
> > structs" (https://github.com/llvm/llvm-project/issues/60349).  Disable
> > it temporarily until the bug is fixed and the fix is released in a clan=
g
> > version that can be checked for.
> >
> > Fixes: 035f7f87b729 ("randstruct: Enable Clang support")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > ---
> >  security/Kconfig.hardening | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
> > index 53baa95cb644..aad16187148c 100644
> > --- a/security/Kconfig.hardening
> > +++ b/security/Kconfig.hardening
> > @@ -280,7 +280,8 @@ config ZERO_CALL_USED_REGS
> >  endmenu
> >
> >  config CC_HAS_RANDSTRUCT
> > -     def_bool $(cc-option,-frandomize-layout-seed-file=3D/dev/null)
> > +     # Temporarily disabled due to https://github.com/llvm/llvm-projec=
t/issues/60349
> > +     def_bool n
> >
> >  choice
> >       prompt "Randomize layout of sensitive kernel structures"
> >
> > base-commit: 7b753a909f426f2789d9db6f357c3d59180a9354
> > --
> > 2.39.1
>
> This should be fixed with greater precision -- i.e. this is nearly fixed
> in Clang now, and is likely to be backported. So I think we'll need
> versioned checks here.
>
> --
> Kees Cook
>

Bill has requested cherry-pick the llvm-project fix into the
release/16.x branch [1].
https://github.com/llvm/llvm-project-release-prs/pull/276
It may take one day to land.

[1]: https://github.com/llvm/llvm-project/tree/release/16.x

--=20
=E5=AE=8B=E6=96=B9=E7=9D=BF