linux-kernel - Re: [PATCH] randstruct: disable Clang 15 support

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Date:   Wed, 8 Feb 2023 10:04:13 -0800
From:   Bill Wendling <morbo@...gle.com>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Eric Biggers <ebiggers@...nel.org>,
        linux-hardening@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] randstruct: disable Clang 15 support

On Wed, Feb 8, 2023 at 6:32 AM Nathan Chancellor <nathan@...nel.org> wrote:
>
> On Tue, Feb 07, 2023 at 10:51:33PM -0800, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@...gle.com>
> >
> > The randstruct support released in Clang 15 is unsafe to use due to a
> > bug that can cause miscompilations: "-frandomize-layout-seed
> > inconsistently randomizes all-function-pointers structs"
> > (https://github.com/llvm/llvm-project/issues/60349).  It has been fixed
> > on the Clang 16 release branch, so add a Clang version check.
> >
> > Fixes: 035f7f87b729 ("randstruct: Enable Clang support")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Eric Biggers <ebiggers@...gle.com>
>
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>
>
Reviewed-by: Bill Wendling <morbo@...gle.com>

> > ---
> >  security/Kconfig.hardening | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
> > index 53baa95cb644f..0f295961e7736 100644
> > --- a/security/Kconfig.hardening
> > +++ b/security/Kconfig.hardening
> > @@ -281,6 +281,9 @@ endmenu
> >
> >  config CC_HAS_RANDSTRUCT
> >       def_bool $(cc-option,-frandomize-layout-seed-file=/dev/null)
> > +     # Randstruct was first added in Clang 15, but it isn't safe to use until
> > +     # Clang 16 due to https://github.com/llvm/llvm-project/issues/60349
> > +     depends on !CC_IS_CLANG || CLANG_VERSION >= 160000
> >
> >  choice
> >       prompt "Randomize layout of sensitive kernel structures"
> >
> > base-commit: 4ec5183ec48656cec489c49f989c508b68b518e3
> > --
> > 2.39.1
> >
> >