linux-kernel - Re: [PATCH 0/7] ARM: support THREAD_INFO_IN

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Message-ID: <CAMj1kXF8X0j7Be_+3Z4uHcq0ZHKxsB5hW-7PEVb4dB54HFJgOg@mail.gmail.com>
Date:   Wed, 8 Sep 2021 09:47:36 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Cc:     Keith Packard <keithpac@...zon.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Abbott Liu <liuwenliang@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Christoph Lameter <cl@...ux.com>,
        Dennis Zhou <dennis@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Jens Axboe <axboe@...nel.dk>, Joe Perches <joe@...ches.com>,
        Kees Cook <keescook@...omium.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Mike Rapoport <rppt@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nick Desaulniers <ndesaulniers@...ogle.com>,
        Nicolas Pitre <nico@...xnic.net>,
        Russell King <linux@...linux.org.uk>,
        Tejun Heo <tj@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Valentin Schneider <valentin.schneider@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Wolfram Sang (Renesas)" <wsa+renesas@...g-engineering.com>,
        YiFei Zhu <yifeifz2@...inois.edu>
Subject: Re: [PATCH 0/7] ARM: support THREAD_INFO_IN_TASK (v3)

On Wed, 8 Sept 2021 at 09:01, Krzysztof Kozlowski
<krzysztof.kozlowski@...onical.com> wrote:
>
> On 08/09/2021 00:00, Keith Packard wrote:
> > Placing thread_info in the kernel stack leaves it vulnerable to stack
> > overflow attacks. This short series addresses that by using the
> > existing THREAD_INFO_IN_TASK infrastructure.
> >
> > This is the third version of this series, in this version the changes
> > are restricted to hardware which provides the TPIDRPRW register. This
> > register is repurposed from holding the per_cpu_offset value to
> > holding the 'current' value as that allows fetching this value
> > atomically so that it can be used in a preemptable context.
> >
> > The series is broken into seven pieces:
> >
> >  1) Change the secondary_start_kernel API to receive the cpu
> >     number. This avoids needing to be able to find this value independently in
> >     future patches.
> >
> >  2) Change the secondary_start_kernel API to also receive the 'task'
> >     value. Passing the value to this function also avoids needing to
> >     be able to discover it independently.
> >
> >  3) A cleanup which avoids assuming that THREAD_INFO_IN_TASK is not set.
> >
> >  4) A hack, borrowed from the powerpc arch, which allows locating the 'cpu'
> >     field in either thread_info or task_struct, without requiring linux/sched.h
> >     to be included in asm/smp.h
> >
> >  5) Disable the optimization storing per_cpu_offset in TPIDRPRW. This leaves
> >     the register free to hold 'current' instead.
> >
> >  6) Use TPIDRPRW for 'current'. This is enabled for either CPU_V6K or CPU_V7,
> >     but not if CPU_V6 is also enabled.
> >
> >  7) Enable THREAD_INFO_IN_TASK whenever TPIDRPRW is used to hold 'current'.
>
> Hi,
>
> Thanks for your patches. This seems to be a v3 but the patches are not
> marked with it. Use "-v3" in format-patch to get it right.
>
> The email here also lacks diffstat which is useful, for example to check
> whether any maintainer's relevant files are touched here. You can get it
> with "--cover-letter".
>
> In total the command should look like:
>     git format-patch --cover-letter -v3 -7 HEAD
>
> Of course you can use any other tools to achieve the same result but as
> of now - result is not the same.
>

Also, this ended up in my GMail spam folder, likely due to some
antispam ID header being set incorrectly?