netdev - Re: [PATCH v3 bpf-next 02/21] bpf: Sysctl hook

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Date:   Tue, 9 Apr 2019 09:54:20 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrey Ignatov <rdna@...com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Roman Gushchin <guro@...com>, kernel-team <kernel-team@...com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Jann Horn <jannh@...gle.com>,
        Mickaël Salaün <mic@...ikod.net>
Subject: Re: [PATCH v3 bpf-next 02/21] bpf: Sysctl hook

On Fri, Apr 5, 2019 at 12:36 PM Andrey Ignatov <rdna@...com> wrote:
> Containerized applications may run as root and it may create problems
> for whole host. Specifically such applications may change a sysctl and
> affect applications in other containers.
>
> Furthermore in existing infrastructure it may not be possible to just
> completely disable writing to sysctl, instead such a process should be
> gradual with ability to log what sysctl are being changed by a
> container, investigate, limit the set of writable sysctl to currently
> used ones (so that new ones can not be changed) and eventually reduce
> this set to zero.

Actual-root-in-a-container is pretty powerful. What about module
loading, or /dev files? Instead of sysctl-specific hooks, what about
VFS hooks, which would be able to cover all file-based APIs. This is
what, for example, Landlock was working on doing (also with eBPF).

-- 
Kees Cook