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

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  Re: [RFC v3 19/22] landlock: Add interrupted origin Kees Cook <keescook@chromium.org> - 2016-10-04 01:50 +0200
    Re: [RFC v3 19/22] landlock: Add interrupted origin Mickaël Salaün <mic@digikod.net> - 2016-10-05 23:10 +0200

#1495107 — Re: [RFC v3 19/22] landlock: Add interrupted origin

On Wed, Sep 14, 2016 at 6:19 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> On Wed, Sep 14, 2016 at 3:14 PM, Mickaël Salaün <mic@digikod.net> wrote:
>>
>> On 14/09/2016 20:29, Andy Lutomirski wrote:
>>> On Wed, Sep 14, 2016 at 12:24 AM, Mickaël Salaün <mic@digikod.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@digikod.net>
>>>> Cc: Alexei Starovoitov <ast@kernel.org>
>>>> Cc: Andy Lutomirski <luto@amacapital.net>
>>>> Cc: Daniel Borkmann <daniel@iogearbox.net>
>>>> Cc: Kees Cook <keescook@chromium.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.

For making this series smaller, let's leave the idea idea of interrupt
hooks out -- the intention is for stricter syscall filtering, yes?

Once things are more well established and there's a use-case for this,
it can be added back in.

-Kees


-- 
Kees Cook
Nexus Security

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#1496051

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On 04/10/2016 01:46, Kees Cook wrote:
> On Wed, Sep 14, 2016 at 6:19 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>> On Wed, Sep 14, 2016 at 3:14 PM, Mickaël Salaün <mic@digikod.net> wrote:
>>>
>>> On 14/09/2016 20:29, Andy Lutomirski wrote:
>>>> On Wed, Sep 14, 2016 at 12:24 AM, Mickaël Salaün <mic@digikod.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@digikod.net>
>>>>> Cc: Alexei Starovoitov <ast@kernel.org>
>>>>> Cc: Andy Lutomirski <luto@amacapital.net>
>>>>> Cc: Daniel Borkmann <daniel@iogearbox.net>
>>>>> Cc: Kees Cook <keescook@chromium.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.
> 
> For making this series smaller, let's leave the idea idea of interrupt
> hooks out -- the intention is for stricter syscall filtering, yes?
> 
> Once things are more well established and there's a use-case for this,
> it can be added back in.

Right, I'm no more convinced it's worth it.

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