linux-kernel - Re: [PATCH stable 5.10 0/3] ARM FDT relocation backports

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Date:   Mon, 10 May 2021 11:37:01 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ard Biesheuvel <ardb@...nel.org>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        "# 3.4.x" <stable@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        Russell King <linux@...linux.org.uk>,
        Nicolas Pitre <nico@...xnic.net>,
        Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Desaulniers <ndesaulniers@...ogle.com>,
        Joe Perches <joe@...ches.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Tian Tao <tiantao6@...ilicon.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH stable 5.10 0/3] ARM FDT relocation backports

On Mon, May 10, 2021 at 9:43 AM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Sun, May 09, 2021 at 06:22:05PM -0700, Florian Fainelli wrote:

> > This does not qualify as a regression in that it has never worked for
> > the specific platform that I have shown above until your 3 commits came
> > in and fixed that particular FDT placement. To me this qualifies as a
> > bug fix, and given that the 3 (now 4) commits applied without hunks, it
> > seems reasonable to me to back port those to stable.
>
> As this isn't a regression, why not just use 5.12 on these platforms?
> Why is 5.4 and 5.10 needed?

Actually I think it *is* a regression, but not a common one. The bug that
Ard is fixing can appear when the kernel grows over a certain size.

If a user compile in a new set of functionality and the kernel size
reach a tripping point so that the DTB ends up just outside the 1:1
lowmem map, disaster strikes.

This has been a long standing mysterious bug for people using
attached device trees.

Yours,
Linus Walleij