linux-kernel - Re: [PATCH 0/2] Revert "fs/exec: allow to unshare a time namespace on vfork+exec"

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Message-ID: <CANaxB-y3E3DgFHKM6qpgc5z-b4imdDBBKy_wnS9_Mjq6tgSAMQ@mail.gmail.com>
Date:   Tue, 13 Sep 2022 09:35:13 -0700
From:   Andrei Vagin <avagin@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrei Vagin <avagin@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Revert "fs/exec: allow to unshare a time namespace on vfork+exec"

On Tue, Sep 13, 2022 at 5:18 AM Kees Cook <keescook@...omium.org> wrote:
>
> On Tue, Sep 13, 2022 at 03:25:49AM -0700, Andrei Vagin wrote:
> > This reverts commits:
> > 133e2d3e81de ("fs/exec: allow to unshare a time namespace on vfork+exec")
> > 6342140db660 ("selftests/timens: add a test for vfork+exit")
> >
> > Alexey pointed out a few undesirable side effects of the reverted change.
> > First, it doesn't take into account that CLONE_VFORK can be used with
> > CLONE_THREAD. Second, a child process doesn't enter a target time name-space,
> > if its parent dies before the child calls exec. It happens because the parent
> > clears vfork_done.
> >
> > Eric W. Biederman suggests installing a time namespace as a task gets a new mm.
> > It includes all new processes cloned without CLONE_VM and all tasks that call
> > exec(). This is an user API change, but we think there aren't users that depend
> > on the old behavior.
>
> Can we include that patch here as well?

It is attached. I need to test it and then I will send it properly.

>
> > It is too late to make such changes in this release, so let's roll back
> > this patch and introduce the right one in the next release.
>
> Do you mean you'd like this revert to land for v6.0, and we should wait
> for the new API for later?

Yes, I mean this. I think we should merge the new patch in v6.1-rc1 so
it sits there for a while.

Thanks,
Andrei

View attachment "0001-fs-exec-switch-timens-when-a-task-gets-a-new-mm.patch" of type "text/x-patch" (5306 bytes)