linux-kernel - Re: [PATCH 0/9] Enable orphan section warning

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Message-ID: <202004021023.D3D8AA3BE@keescook>
Date:   Thu, 2 Apr 2020 10:26:38 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Sedat Dilek <sedat.dilek@...il.com>
Cc:     Borislav Petkov <bp@...e.de>, "H.J. Lu" <hjl.tools@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Peter Collingbourne <pcc@...gle.com>,
        James Morse <james.morse@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Masahiro Yamada <masahiroy@...nel.org>, x86@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        linux-kbuild@...r.kernel.org,
        Clang-Built-Linux ML <clang-built-linux@...glegroups.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/9] Enable orphan section warning

On Thu, Apr 02, 2020 at 06:20:57PM +0200, Sedat Dilek wrote:
> On Fri, Feb 28, 2020 at 1:22 AM Kees Cook <keescook@...omium.org> wrote:
> >
> > Hi!
> >
> > A recent bug was solved for builds linked with ld.lld, and tracking
> > it down took way longer than it needed to (a year). Ultimately, it
> > boiled down to differences between ld.bfd and ld.lld's handling of
> > orphan sections. Similarly, the recent FGKASLR series brough up orphan
> > section handling too[2]. In both cases, it would have been nice if the
> > linker was running with --orphan-handling=warn so that surprise sections
> > wouldn't silently get mapped into the kernel image at locations up to
> > the whim of the linker's orphan handling logic. Instead, all desired
> > sections should be explicitly identified in the linker script (to be
> > either kept or discarded) with any orphans throwing a warning. The
> > powerpc architecture actually already does this, so this series seeks
> > to extend this coverage to x86, arm64, and arm.
> >
> > This series depends on tip/x86/boot (where recent .eh_frame fixes[3]
> > landed), and has a minor conflict[4] with the ARM tree (related to
> > the earlier mentioned bug). As it uses refactorings in the asm-generic
> > linker script, and makes changes to kbuild, I think the cleanest place
> > for this series to land would also be through -tip. Once again (like
> > my READ_IMPLIES_EXEC series), I'm looking to get maintainer Acks so
> > this can go all together with the least disruption. Splitting it up by
> > architecture seems needlessly difficult.
> >
> > Thanks!
> >
> 
> Hi Kees,
> 
> what is the status of this patchset?
> Looks like it is not in tip or linux-next Git.

Based on the feedback, I have 3 TODO items:

- track down and eliminate (or explain) the source of the .got.plt on arm64
- enable orphan warnings for _all_ architectures
- refactor final link logic to perform the orphan warning in a clean way

I'm working through these (and other work) still. I'm hoping to have
another version up some time next week.

-- 
Kees Cook