Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <000000000000385cbf05ea3f1862@google.com> <00000000000028a44005ea40352b@google.com>
 <Y0CbtVwW6+QIYJdQ@slm.duckdns.org> <Y0HBlJ4AoZba93Uf@cae.in-ulm.de>
 <20221009084039.cw6meqbvy4362lsa@wittgenstein> <Y0LITEA/22Z7YVSa@cae.in-ulm.de>
 <Y0Rn5qzP6MjayoCz@slm.duckdns.org> <CAJD7tka2jwPnYyCmLu0T5Oq_X-LJCx7TVqLayLPS_6fOjqf93A@mail.gmail.com>
 <Y0R31xyfivqtKb9h@slm.duckdns.org>
In-Reply-To: <Y0R31xyfivqtKb9h@slm.duckdns.org>
From:   Yosry Ahmed <yosryahmed@google.com>
Date:   Mon, 10 Oct 2022 12:57:34 -0700
Message-ID: <CAJD7tkaQeFYq6prHiTiGeEyC-ka8ujAFXV--BkROJbVDaOZ78Q@mail.gmail.com>
Subject: Re: [PATCH] cgroup: Fix crash with CLONE_INTO_CGROUP and v1 cgroups
To:     Tejun Heo <tj@kernel.org>
Cc:     "Christian A. Ehrhardt" <lk@c--e.de>,
        Christian Brauner <brauner@kernel.org>,
        syzbot <syzbot+534ee3d24c37c411f37f@syzkaller.appspotmail.com>,
        gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com,
        Martin KaFai Lau <martin.lau@linux.dev>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Oct 10, 2022 at 12:51 PM Tejun Heo <tj@kernel.org> wrote:
>
> Hello,
>
> On Mon, Oct 10, 2022 at 11:50:50AM -0700, Yosry Ahmed wrote:
> > The purpose of f3a2aebdd6 was to make cgroup_get_from_fd() support
> > cgroup1, which IIUC makes sense. It was unrelated to IDs.
>
> Ah, right you are. For some reason, I thought this was ID based.
>
> > There are currently two users of
> > cgroup_get_from_file()/cgroup_get_from_fd() AFAICT, one of which is
> > the fork code fixed by this commit, the second is BPF cgroup prog
> > attachment. I can send another patch to add explicit filtering in the
> > BPF attachment code as well.
> >
> > Alternatively, we can have separate functions that do the filtering if
> > needed. For example:
> > cgroup_get_from_fd() / cgroup_get_from_file() -> support both v1 and v2
> > cgroup_get_dfl_from_fd() / cgroup_get_dfl_from_file() -> support only v2
> >
> > We can then use the versions with filtering for all the current users
> > except cgroup_iter (that needs to support both v1 and v2). WDYT?
>
> Yes, but please leave the existing ones v2 only and add new ones which
> allows cgroup1 too.

Any suggestions for the new names though? Given that the new ones
would be the ones that will support both versions, I am not sure how
to name them differently in a meaningful way. Maybe something like
cgroup_get_all_from_[fd/file]() ?

IMO, we can rename the current versions to
cgroup_get_dfl_from_[fd/file](), and the new ones (which support both)
as cgroup_get_from_fd/file(). In this case it's obvious that one
version specifically works on "dfl", aka cgroup2.

Alternatively, we can have separate versions for v1,
cgroup1_get_from_[fd/file](), but then callers that want both v1 and
v2 will have to make 2 separate calls unnecessarily.

Thoughts?

>
> Thanks.
>
> --
> tejun