netdev - Re: [RFC v3 19/22] landlock: Add interrupted origin

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Date:   Wed, 14 Sep 2016 18:19:14 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Daniel Mack <daniel@...que.org>,
        David Drysdale <drysdale@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Elena Reshetova <elena.reshetova@...el.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        James Morris <james.l.morris@...cle.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Moore <pmoore@...hat.com>,
        Sargun Dhillon <sargun@...gun.me>,
        "Serge E . Hallyn" <serge@...lyn.com>, Tejun Heo <tj@...nel.org>,
        Will Drewry <wad@...omium.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        Linux API <linux-api@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        "open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>
Subject: Re: [RFC v3 19/22] landlock: Add interrupted origin

On Wed, Sep 14, 2016 at 3:14 PM, Mickaël Salaün <mic@...ikod.net> wrote:
>
> On 14/09/2016 20:29, Andy Lutomirski wrote:
>> On Wed, Sep 14, 2016 at 12:24 AM, Mickaël Salaün <mic@...ikod.net> wrote:
>>> This third origin of hook call should cover all possible trigger paths
>>> (e.g. page fault). Landlock eBPF programs can then take decisions
>>> accordingly.
>>>
>>> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
>>> Cc: Alexei Starovoitov <ast@...nel.org>
>>> Cc: Andy Lutomirski <luto@...capital.net>
>>> Cc: Daniel Borkmann <daniel@...earbox.net>
>>> Cc: Kees Cook <keescook@...omium.org>
>>> ---
>>
>>
>>>
>>> +       if (unlikely(in_interrupt())) {
>>
>> IMO security hooks have no business being called from interrupts.
>> Aren't they all synchronous things done by tasks?  Interrupts are
>> driver things.
>>
>> Are you trying to check for page faults and such?
>
> Yes, that was the idea you did put in my mind. Not sure how to deal with
> this.
>

It's not so easy, unfortunately.  The easiest reliable way might be to
set a TS_ flag on all syscall entries when TIF_SECCOMP or similar is
set.

--Andy