linux-kernel - Re: linux 5.14.3: free_user_ns causes NULL pointer dereference

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Date:   Thu, 30 Sep 2021 15:06:40 +0200
From:   Alexey Gladkov <legion@...nel.org>
To:     Jordan Glover <Golden_Miller83@...tonmail.ch>
Cc:     ebiederm@...ssion.com, LKML <linux-kernel@...r.kernel.org>,
        linux-mm@...ck.org, containers@...ts.linux-foundation.org,
        Yu Zhao <yuzhao@...gle.com>
Subject: Re: linux 5.14.3: free_user_ns causes NULL pointer dereference

On Wed, Sep 29, 2021 at 09:39:06PM +0000, Jordan Glover wrote:
> > I'm still investigating, but I would like to rule out one option.
> >
> > Could you check out the patch?
> 
> 
> Thx, I added it to my kernel and will report in few days.
> Does this patch try to fix the issue or make it easier to track?

I suspect the error is caused by a race between allow_ucounts() and
put_ucounts(). I think this patch could solve the problem.

-- 
Rgrds, legion