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From:   Marco Elver <elver@google.com>
Date:   Tue, 17 Oct 2023 17:26:36 +0200
Message-ID: <CANpmjNPnP2_4oHSnhEO89ZhpqNfUg51XzL0awWVkYGNhxUayhw@mail.gmail.com>
Subject: Re: [tip: x86/bugs] x86/retpoline: Ensure default return thunk isn't
 used at runtime
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Josh Poimboeuf <jpoimboe@kernel.org>,
        "Kaplan, David" <David.Kaplan@amd.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-tip-commits@vger.kernel.org" 
        <linux-tip-commits@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        "x86@kernel.org" <x86@kernel.org>,
        "llvm@lists.linux.dev" <llvm@lists.linux.dev>,
        Dmitry Vyukov <dvyukov@google.com>,
        kasan-dev <kasan-dev@googlegroups.com>
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On Tue, 17 Oct 2023 at 17:24, Nick Desaulniers <ndesaulniers@google.com> wr=
ote:
>
> + Marco, Dmitry
>
> On Mon, Oct 16, 2023 at 10:28=E2=80=AFPM Josh Poimboeuf <jpoimboe@kernel.=
org> wrote:
> >
> > On Tue, Oct 17, 2023 at 04:31:09AM +0000, Kaplan, David wrote:
> > > Perhaps another option would be to not compile these two files with K=
CSAN, as they are already excluded from KASAN and GCOV it looks like.
> >
> > I think the latter would be the easy fix, does this make it go away?
>
> Yeah, usually when I see the other sanitizers being disabled on a per
> object basis, I think "where there's smoke, there's fire."
>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Closes: https://lore.kernel.org/lkml/20231016214810.GA3942238@dev-arch.th=
elio-3990X/

Acked-by: Marco Elver <elver@google.com>

Instrumenting these files really doesn't make sense. Thanks for
catching this and the fix!

> >
> > diff --git a/init/Makefile b/init/Makefile
> > index ec557ada3c12..cbac576c57d6 100644
> > --- a/init/Makefile
> > +++ b/init/Makefile
> > @@ -60,4 +60,5 @@ include/generated/utsversion.h: FORCE
> >  $(obj)/version-timestamp.o: include/generated/utsversion.h
> >  CFLAGS_version-timestamp.o :=3D -include include/generated/utsversion.=
h
> >  KASAN_SANITIZE_version-timestamp.o :=3D n
> > +KCSAN_SANITIZE_version-timestamp.o :=3D n
> >  GCOV_PROFILE_version-timestamp.o :=3D n
> > diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
> > index 3cd6ca15f390..c9f3e03124d7 100644
> > --- a/scripts/Makefile.vmlinux
> > +++ b/scripts/Makefile.vmlinux
> > @@ -19,6 +19,7 @@ quiet_cmd_cc_o_c =3D CC      $@
> >
> >  ifdef CONFIG_MODULES
> >  KASAN_SANITIZE_.vmlinux.export.o :=3D n
> > +KCSAN_SANITIZE_.vmlinux.export.o :=3D n
> >  GCOV_PROFILE_.vmlinux.export.o :=3D n
> >  targets +=3D .vmlinux.export.o
> >  vmlinux: .vmlinux.export.o
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers