linux-kernel - Re: [PATCH v2 2/4] seccomp: Refactor notification handler to prepare for new semantics

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Date:   Tue, 1 Jun 2021 12:22:07 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Rodrigo Campos <rodrigo@...volk.io>
Cc:     Sargun Dhillon <sargun@...gun.me>,
        LKML <linux-kernel@...r.kernel.org>, containers@...ts.linux.dev,
        Tycho Andersen <tycho@...ho.pizza>,
        Andy Lutomirski <luto@...nel.org>,
        Mauricio Vásquez Bernal 
        <mauricio@...volk.io>, Giuseppe Scrivano <gscrivan@...hat.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v2 2/4] seccomp: Refactor notification handler to prepare
 for new semantics

On Sat, May 29, 2021 at 12:31:55AM +0200, Rodrigo Campos wrote:
> On Fri, May 28, 2021 at 7:14 PM Kees Cook <keescook@...omium.org> wrote:
> >
> > 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@...omium.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?
> 
> Oh, right! Yes. Here it goes so it's simpler to add :)
> 
> Tested-by: Rodrigo Campos <rodrigo@...volk.io>

Thanks; this is in v5.13-rc4 now:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ddc473916955f7710d1eb17c1273d91c8622a9fe

-- 
Kees Cook