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Date:   Tue, 28 Sep 2021 13:40:48 +0000
To:     ebiederm@xmission.com
From:   Jordan Glover <Golden_Miller83@protonmail.ch>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        "linux-mm\\@kvack.org" <linux-mm@kvack.org>,
        "legion\\@kernel.org" <legion@kernel.org>,
        "containers\\@lists.linux-foundation.org" 
        <containers@lists.linux-foundation.org>,
        Yu Zhao <yuzhao@google.com>
Reply-To: Jordan Glover <Golden_Miller83@protonmail.ch>
Subject: Re: linux 5.14.3: free_user_ns causes NULL pointer dereference
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On Thursday, September 16th, 2021 at 5:30 PM, <ebiederm@xmission.com> wrote=
:

> Jordan Glover Golden_Miller83@protonmail.ch writes:
>
> > On Wednesday, September 15th, 2021 at 10:42 PM, Jordan Glover Golden_Mi=
ller83@protonmail.ch wrote:
> >
> > > I had about 2 containerized (flatpak/bubblewrap) apps (browser + musi=
c player) running . I quickly closed them with intent to shutdown the syste=
m but instead get the freeze and had to use magic sysrq to reboot. System l=
ogs end with what I posted and before there is nothing suspicious.
> > >
> > > Maybe it's some random fluke. I'll reply if I hit it again.
> >
> > Heh, it jut happened again. This time closing firefox alone had such
> > effect:
>
> Ok. It looks like he have a couple of folks seeing issues here.
> I thought we had all of the issues sorted out for the release of v5.14,
> but it looks like there is still some little bug left.
>
> If Alex doesn't beat me to it I will see if I can come up with a
> debugging patch to make it easy to help track down where the reference
> count is going wrong. It will be a little bit as my brain is mush at
> the moment.
>
> Eric

As the issue persist in 5.14.7 I would be very interested in such patch.

For now the thing is mostly reproducible when I close several tabs in ff th=
en
close the browser in short period of time. When I close tabs then wait out
a bit then close the browser it doesn't happen so I guess some interrupted
cleanup triggers it.

Jordan