linux-kernel - Re: [PATCH v2 1/3] vmlinux.lds.h: Add .gnu.version* to DISCARDS

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Message-ID: <202006221629.5C8CF8AE2@keescook>
Date:   Mon, 22 Jun 2020 16:30:18 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Fāng-ruì Sòng <maskray@...gle.com>
Cc:     Borislav Petkov <bp@...e.de>, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        linux-arch@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] vmlinux.lds.h: Add .gnu.version* to DISCARDS

On Mon, Jun 22, 2020 at 04:04:40PM -0700, Fāng-ruì Sòng wrote:
> On Mon, Jun 22, 2020 at 3:57 PM Kees Cook <keescook@...omium.org> wrote:
> >
> > On Mon, Jun 22, 2020 at 03:52:37PM -0700, Fangrui Song wrote:
> > > > And it's not in the output:
> > > >
> > > > $ readelf -Vs arch/x86/boot/compressed/vmlinux | grep version
> > > > No version information found in this file.
> > > >
> > > > So... for the kernel we need to silence it right now.
> > >
> > > Re-link with -M (or -Map file) to check where .gnu.version{,_d,_r} input
> > > sections come from?
> >
> > It's not reporting it correctly:
> >
> > .gnu.version_d  0x00000000008966b0        0x0
> >  .gnu.version_d
> >                 0x00000000008966b0        0x0 arch/x86/boot/compressed/kernel_info.o
> >
> > .gnu.version    0x00000000008966b0        0x0
> >  .gnu.version   0x00000000008966b0        0x0 arch/x86/boot/compressed/kernel_info.o
> >
> > .gnu.version_r  0x00000000008966b0        0x0
> >  .gnu.version_r
> >                 0x00000000008966b0        0x0 arch/x86/boot/compressed/kernel_info.o
> >
> > it just reports whatever file is listed on the link command line first.
> >
> > > If it is a bug, we should probably figure out which version of binutils
> > > has fixed the bug.
> >
> > I see this with binutils 2.34...
> >
> > --
> > Kees Cook
> 
> :( It deserves a binutils bug
> (https://sourceware.org/bugzilla/enter_bug.cgi?product=binutils ) and
> a comment..

https://sourceware.org/bugzilla/show_bug.cgi?id=26153

> With the description adjusted to say that this works around a bug
> 
> Reviewed-by: Fangrui Song <maskray@...gle.com>

Adjusted, and thanks!

-- 
Kees Cook