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From: Greg KH <greg@kroah.com>
To: Hugh Dickins <hughd@google.com>
Cc: Peter Xu <peterx@redhat.com>, stable <stable@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Axel Rasmussen <axelrasmussen@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Hillf Danton <hdanton@sina.com>, Igor Raits <igor@gooddata.com>
Subject: Re: [PATCH stable 5.13.y/5.12.y 0/2] mm/thp: Fix uffd-wp with fork(); crash on pmd migration entry on fork
Date: Thu, 22 Jul 2021 16:02:18 +0200	[thread overview]
Message-ID: <YPl6aimUo8XiBAcF@kroah.com> (raw)
In-Reply-To: <CANsGZ6aEW8pEncdoh_mGxKF-Se0_-O=E124EywULWvJ3qC0aVA@mail.gmail.com>

On Tue, Jul 20, 2021 at 01:32:19PM -0700, Hugh Dickins wrote:
> On Tue, Jul 20, 2021 at 8:52 AM Peter Xu <peterx@redhat.com> wrote:
> >
> > In summary: this series should be needed for 5.10/5.12/5.13. This is the
> > 5.13.y/5.12.y backport of the series, and it should be able to be applied on
> > both of the branches.  Patch 1 is a dependency of patch 2, while patch 2 should
> > be the real fix.
> >
> > This series should be able to fix a rare race that mentioned in thread:
> >
> > https://lore.kernel.org/linux-mm/796cbb7-5a1c-1ba0-dde5-479aba8224f2@google.com/
> >
> > This fact wasn't discovered when the fix got proposed and merged, because the
> > fix was originally about uffd-wp and its fork event.  However it turns out that
> > the problematic commit b569a1760782f3d is also causing crashing on fork() of
> > pmd migration entries which is even more severe than the original uffd-wp
> > problem.
> >
> > Stable kernels at least on 5.12.y has the crash reproduced, and it's possible
> > 5.13.y and 5.10.y could hit it due to having the problematic commit
> > b569a1760782f3d but lacking of the uffd-wp fix patch (8f34f1eac382, which is
> > also patch 2 of this series).
> >
> > The pmd entry crash problem was reported by Igor Raits <igor@gooddata.com> and
> > debugged by Hugh Dickins <hughd@google.com>.
> >
> > Please review, thanks.
> 
> These two 5.13.y patches look just right to me, thank you Peter (and
> 5.12.19 announced EOL overnight, so nothing more wanted for that).
> 
> But these do just amount to asking stable@vger.kernel.org to
> cherry-pick the two commits
> 5fc7a5f6fd04bc18f309d9f979b32ef7d1d0a997
> 8f34f1eac3820fc2722e5159acceb22545b30b0d

Thanks for the review, both now queued up to 5.13.y.

greg k-h


  reply	other threads:[~2021-07-22 14:02 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-10  7:33 kernel BUG at include/linux/swapops.h:204! Igor Raits
2021-07-10 12:46 ` Hillf Danton
2021-07-11  4:17 ` Hugh Dickins
2021-07-11  6:06   ` Igor Raits
2021-07-15 17:47     ` Igor Raits
2021-07-16 19:45       ` Hugh Dickins
2021-07-19 19:11         ` Hugh Dickins
2021-07-19 22:12           ` Peter Xu
2021-07-19 22:42             ` Hugh Dickins
2021-07-20  0:34               ` Peter Xu
2021-07-20  3:31                 ` Hugh Dickins
2021-07-20  7:47             ` Igor Raits
2021-07-20 16:01               ` Peter Xu
2021-07-20 16:05                 ` Igor Raits
2021-07-20 15:51           ` [PATCH stable 5.13.y/5.12.y 0/2] mm/thp: Fix uffd-wp with fork(); crash on pmd migration entry on fork Peter Xu
2021-07-20 15:51             ` [PATCH stable 5.13.y/5.12.y 1/2] mm/thp: simplify copying of huge zero page pmd when fork Peter Xu
2021-07-20 15:51             ` [PATCH stable 5.13.y/5.12.y 2/2] mm/userfaultfd: fix uffd-wp special cases for fork() Peter Xu
2021-07-20 20:32             ` [PATCH stable 5.13.y/5.12.y 0/2] mm/thp: Fix uffd-wp with fork(); crash on pmd migration entry on fork Hugh Dickins
2021-07-22 14:02               ` Greg KH [this message]
2021-07-20 15:56           ` [PATCH stable 5.10.y " Peter Xu
2021-07-20 15:56             ` [PATCH stable 5.10.y 1/2] mm/thp: simplify copying of huge zero page pmd when fork Peter Xu
2021-07-20 15:56             ` [PATCH stable 5.10.y 2/2] mm/userfaultfd: fix uffd-wp special cases for fork() Peter Xu
2021-07-20 20:38             ` [PATCH stable 5.10.y 0/2] mm/thp: Fix uffd-wp with fork(); crash on pmd migration entry on fork Hugh Dickins
2021-07-22 14:05               ` Greg KH

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