linux-kernel - Re: [PATCH 0/5] 4.14 backports of fixes for "CoW after fork() issue"

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Message-ID: <CAJuCfpFgHMMWZgch5gfjHj936gmpDztb8ZT-vJn6G0-r5BvceA@mail.gmail.com>
Date:   Wed, 7 Apr 2021 09:33:34 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>, Peter Xu <peterx@...hat.com>,
        stable <stable@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jann Horn <jannh@...gle.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>, Shaohua Li <shli@...com>,
        Nadav Amit <namit@...are.com>, Linux-MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH 0/5] 4.14 backports of fixes for "CoW after fork() issue"

On Wed, Apr 7, 2021 at 9:07 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Wed, Apr 7, 2021 at 6:22 AM Vlastimil Babka <vbabka@...e.cz> wrote:
> >
> > 1) Ignore the issue (outside of Android at least). The security model of zygote
> > is unusual. Where else a parent of fork() doesn't trust the child, which is the
> > same binary?
>
> Agreed. I think this is basically an android-only issue (with
> _possibly_ some impact on crazy "pin-and-fork" loads), and doesn't
> necessarily merit a backport at all.
>
> If Android people insist on using very old kernels, knowing that they
> do things that are questionable with those old kernels, at some point
> it's just _their_ problem.

We don't really insist on using old kernels but rather we are stuck
with them for some time.
Trying my hand at backporting the patchsets Peter mentioned proved
this to be far from easy with many dependencies. Let me look into
Vlastimil's suggestion to backport only 17839856fd58 and it sounds
like 5.4 already followed that path. Thanks for all the information!
Suren.

>
>                  Linus
>
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