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Date:   Wed, 5 Jul 2023 10:27:45 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Linux regressions mailing list <regressions@lists.linux.dev>
Cc:     Suren Baghdasaryan <surenb@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Jacob Young <jacobly.alt@gmail.com>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Memory Management <linux-mm@kvack.org>,
        Linux PowerPC <linuxppc-dev@lists.ozlabs.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: Fwd: Memory corruption in multithreaded user space program while
 calling fork
Message-ID: <2023070544-porous-prenatal-406a@gregkh>
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On Wed, Jul 05, 2023 at 10:51:57AM +0200, Linux regression tracking (Thorsten Leemhuis) wrote:
> On 05.07.23 09:08, Greg KH wrote:
> > On Tue, Jul 04, 2023 at 01:22:54PM -0700, Suren Baghdasaryan wrote:
> >> On Tue, Jul 4, 2023 at 9:18 AM Andrew Morton <akpm@linux-foundation.org> wrote:
> >>> On Tue, 4 Jul 2023 09:00:19 +0100 Greg KH <gregkh@linuxfoundation.org> wrote:
> >>>>>>>> Thanks! I'll investigate this later today. After discussing with
> >>>>>>>> Andrew, we would like to disable CONFIG_PER_VMA_LOCK by default until
> >>>>>>>> the issue is fixed. I'll post a patch shortly.
> >>>>>>>
> >>>>>>> Posted at: https://lore.kernel.org/all/20230703182150.2193578-1-surenb@google.com/
> >>>>>>
> >>>>>> As that change fixes something in 6.4, why not cc: stable on it as well?
> >>>>>
> >>>>> Sorry, I thought since per-VMA locks were introduced in 6.4 and this
> >>>>> patch is fixing 6.4 I didn't need to send it to stable for older
> >>>>> versions. Did I miss something?
> >>>>
> >>>> 6.4.y is a stable kernel tree right now, so yes, it needs to be included
> >>>> there :)
> >>>
> >>> I'm in wait-a-few-days-mode on this.  To see if we have a backportable
> >>> fix rather than disabling the feature in -stable.
> 
> Andrew, how long will you remain in "wait-a-few-days-mode"? Given what
> Greg said below and that we already had three reports I know of I'd
> prefer if we could fix this rather sooner than later in mainline --
> especially as Arch Linux and openSUSE Tumbleweed likely have switched to
> 6.4.y already or will do so soon.

Ick, yeah, and Fedora should be switching soon too, and I want to drop
support for 6.3.y "any day now".  Is there just a revert we can do now
first to resolve the regression and then work on fixing this up "better"
for 6.6-rc1?

thanks,

greg k-h