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  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:   Tue, 20 Jul 2021 13:32:19 -0700
From:   Hugh Dickins <>
To:     Peter Xu <>
Cc:     stable <>, linux-mm <>,
        linux-kernel <>,
        Axel Rasmussen <>,
        Andrew Morton <>,
        Hillf Danton <>, Igor Raits <>
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

On Tue, Jul 20, 2021 at 8:52 AM Peter Xu <> 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:
> 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 <> and
> debugged by Hugh Dickins <>.
> 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 to
cherry-pick the two commits


(I'd usually reply with alpine rather than gmail, but I see extra
blank lines on these 0/2s that way; but the patches themselves are

> Peter Xu (2):
>   mm/thp: simplify copying of huge zero page pmd when fork
>   mm/userfaultfd: fix uffd-wp special cases for fork()
>  include/linux/huge_mm.h |  2 +-
>  include/linux/swapops.h |  2 ++
>  mm/huge_memory.c        | 36 +++++++++++++++++-------------------
>  mm/memory.c             | 25 +++++++++++++------------
>  4 files changed, 33 insertions(+), 32 deletions(-)
> --
> 2.31.1

Powered by blists - more mailing lists