linux-kernel - Re: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 15 Nov 2019 13:02:08 +0100
From:   Marco Elver <elver@...gle.com>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     LKMM Maintainers -- Akira Yokosawa <akiyks@...il.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Alexander Potapenko <glider@...gle.com>,
        Andrea Parri <parri.andrea@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Boqun Feng <boqun.feng@...il.com>,
        Borislav Petkov <bp@...en8.de>, Daniel Axtens <dja@...ens.net>,
        Daniel Lustig <dlustig@...dia.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Howells <dhowells@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jade Alglave <j.alglave@....ac.uk>,
        Joel Fernandes <joel@...lfernandes.org>,
        Jonathan Corbet <corbet@....net>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Luc Maranget <luc.maranget@...ia.fr>,
        Mark Rutland <mark.rutland@....com>,
        Nicholas Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        linux-efi@...r.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH v4 00/10] Add Kernel Concurrency Sanitizer (KCSAN)

On Thu, 14 Nov 2019 at 23:16, Paul E. McKenney <paulmck@...nel.org> wrote:
>
> On Thu, Nov 14, 2019 at 10:33:03PM +0100, Marco Elver wrote:
> > On Thu, 14 Nov 2019, Paul E. McKenney wrote:
> >
> > > On Thu, Nov 14, 2019 at 07:02:53PM +0100, Marco Elver wrote:
> > > > This is the patch-series for the Kernel Concurrency Sanitizer (KCSAN).
> > > > KCSAN is a sampling watchpoint-based *data race detector*. More details
> > > > are included in **Documentation/dev-tools/kcsan.rst**. This patch-series
> > > > only enables KCSAN for x86, but we expect adding support for other
> > > > architectures is relatively straightforward (we are aware of
> > > > experimental ARM64 and POWER support).
> > > >
> > > > To gather early feedback, we announced KCSAN back in September, and have
> > > > integrated the feedback where possible:
> > > > http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@mail.gmail.com
> > > >
> > > > The current list of known upstream fixes for data races found by KCSAN
> > > > can be found here:
> > > > https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan
> > > >
> > > > We want to point out and acknowledge the work surrounding the LKMM,
> > > > including several articles that motivate why data races are dangerous
> > > > [1, 2], justifying a data race detector such as KCSAN.
> > > >
> > > > [1] https://lwn.net/Articles/793253/
> > > > [2] https://lwn.net/Articles/799218/
> > >
> > > I queued this and ran a quick rcutorture on it, which completed
> > > successfully with quite a few reports.
> >
> > Great. Many thanks for queuing this in -rcu. And regarding merge window
> > you mentioned, we're fine with your assumption to targeting the next
> > (v5.6) merge window.
> >
> > I've just had a look at linux-next to check what a future rebase
> > requires:
> >
> > - There is a change in lib/Kconfig.debug and moving KCSAN to the
> >   "Generic Kernel Debugging Instruments" section seems appropriate.
> > - bitops-instrumented.h was removed and split into 3 files, and needs
> >   re-inserting the instrumentation into the right places.
> >
> > Otherwise there are no issues. Let me know what you recommend.
>
> Sounds good!
>
> I will be rebasing onto v5.5-rc1 shortly after it comes out.  My usual
> approach is to fix any conflicts during that rebasing operation.
> Does that make sense, or would you prefer to send me a rebased stack at
> that point?  Either way is fine for me.

That's fine with me, thanks!  To avoid too much additional churn on
your end, I just replied to the bitops patch with a version that will
apply with the change to bitops-instrumented infrastructure.

Also considering the merge window, we had a discussion and there are
some arguments for targeting the v5.5 merge window:
- we'd unblock ARM and POWER ports;
- we'd unblock people wanting to use the data_race macro;
- we'd unblock syzbot just tracking upstream;
Unless there are strong reasons to not target v5.5, I leave it to you
if you think it's appropriate.

Thanks,
-- Marco