linux-kernel - Re: [PATCH 00/29] vmlinux.lds.h: Refactor EXCEPTION

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Date:   Thu, 10 Oct 2019 16:57:36 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-alpha@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-c6x-dev@...ux-c6x.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Michal Simek <monstr@...str.eu>, linux-parisc@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/29] vmlinux.lds.h: Refactor EXCEPTION_TABLE and NOTES

On Thu, Oct 10, 2019 at 08:03:31PM +0200, Borislav Petkov wrote:
> On Thu, Sep 26, 2019 at 10:55:33AM -0700, Kees Cook wrote:
> > This series works to move the linker sections for NOTES and
> > EXCEPTION_TABLE into the RO_DATA area, where they belong on most
> > (all?) architectures. The problem being addressed was the discovery
> > by Rick Edgecombe that the exception table was accidentally marked
> > executable while he was developing his execute-only-memory series. When
> > permissions were flipped from readable-and-executable to only-executable,
> > the exception table became unreadable, causing things to explode rather
> > badly. :)
> > 
> > Roughly speaking, the steps are:
> > 
> > - regularize the linker names for PT_NOTE and PT_LOAD program headers
> >   (to "note" and "text" respectively)
> > - regularize restoration of linker section to program header assignment
> >   (when PT_NOTE exists)
> > - move NOTES into RO_DATA
> > - finish macro naming conversions for RO_DATA and RW_DATA
> > - move EXCEPTION_TABLE into RO_DATA on architectures where this is clear
> > - clean up some x86-specific reporting of kernel memory resources
> > - switch x86 linker fill byte from x90 (NOP) to 0xcc (INT3), just because
> >   I finally realized what that trailing ": 0x9090" meant -- and we should
> >   trap, not slide, if execution lands in section padding
> 
> Yap, nice patchset overall.

Thanks!

> > Since these changes are treewide, I'd love to get architecture-maintainer
> > Acks and either have this live in x86 -tip or in my own tree, however
> > people think it should go.
> 
> Sure, I don't mind taking v2 through tip once I get ACKs from the
> respective arch maintainers.

Okay, excellent. I've only had acks from arm64, but I'll call it out
again in v2. Thanks for the review!

-- 
Kees Cook