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Date:   Fri, 28 May 2021 10:14:31 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Rodrigo Campos <rodrigo@kinvolk.io>
Cc:     Sargun Dhillon <sargun@sargun.me>,
        LKML <linux-kernel@vger.kernel.org>, containers@lists.linux.dev,
        Tycho Andersen <tycho@tycho.pizza>,
        Andy Lutomirski <luto@kernel.org>,
        Mauricio =?iso-8859-1?Q?V=E1squez?= Bernal 
        <mauricio@kinvolk.io>, Giuseppe Scrivano <gscrivan@redhat.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= <mic@linux.microsoft.com>
Subject: Re: [PATCH v2 2/4] seccomp: Refactor notification handler to prepare
 for new semantics
Message-ID: <202105281014.EECE3D3048@keescook>
References: <20210517193908.3113-1-sargun@sargun.me>
 <20210517193908.3113-3-sargun@sargun.me>
 <CACaBj2YUiowSKzvh02OjpQNqQViA8N0eyRMimkK=90NagRF40w@mail.gmail.com>
 <202105271137.C491991621@keescook>
 <CACaBj2aaDkJwDM8ugR5LxWEOho3nZuHjYLLsth3XYjf39tpaQQ@mail.gmail.com>
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On Fri, May 28, 2021 at 05:27:39PM +0200, Rodrigo Campos wrote:
> On Thu, May 27, 2021 at 8:42 PM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Thu, May 27, 2021 at 01:51:13PM +0200, Rodrigo Campos wrote:
> > >
> > > Kees, as I mentioned in the linked thread, this issue is present in
> > > 5.9+ kernels. Should we add the cc to stable for this patch? Or should
> > > we cc to stable the one linked, that just fixes the issue without
> > > semantic changes to userspace?
> >
> > It sounds like the problem is with Go, using addfd, on 5.9-5.13 kernels,
> > yes?
> 
> Yes.
> 
> > Would the semantic change be a problem there? (i.e. it sounds like
> > the semantic change was fine for the 5.14+ kernels, so I'm assuming it's
> > fine for earlier ones too.)
> 
> No, I don't think it will cause any problem.
> 
> > > Just to be clear, the other patch that fixes the problem without
> > > userspace visible changes is this:
> > > https://lore.kernel.org/lkml/20210413160151.3301-1-rodrigo@kinvolk.io/
> >
> > I'd prefer to use the now-in-next fix if we can. Is it possible to build
> > a test case that triggers the race so we can have some certainty that
> > any fix in -stable covers it appropriately?
> 
> I've verified that Sargun's patch also solves the problem in mainline.
> I have now also verified that it applies cleany and fixes the issue
> for linux-stable/5.10.y and linux-stable/5.12.y too (without the patch
> I see the problem, with the patch I don't see it).  5.11 is already
> EOL, so I didn't try it (probably will work as well).

Oh, btw, may I add a Tested-by: from you for this fix?

Thanks!

-Kees

-- 
Kees Cook