linux-kernel - Re: [PATCH] net: filter: fix upper BPF instruction limit

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Message-ID: <53A40948.5020201@redhat.com>
Date:	Fri, 20 Jun 2014 12:13:28 +0200
From:	Daniel Borkmann <dborkman@...hat.com>
To:	Kees Cook <keescook@...omium.org>
CC:	Alexei Starovoitov <ast@...mgrid.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Chema Gonzalez <chema@...gle.com>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: filter: fix upper BPF instruction limit

Hi Kees,

On 06/19/2014 01:28 AM, Kees Cook wrote:
> On Wed, Jun 18, 2014 at 4:19 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
>> On Wed, Jun 18, 2014 at 3:55 PM, Kees Cook <keescook@...omium.org> wrote:
>>> On Wed, Jun 18, 2014 at 3:48 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
>>>> On Wed, Jun 18, 2014 at 3:34 PM, Kees Cook <keescook@...omium.org> wrote:
...
>>>> I wonder how did you catch this? :)
>>>> Just code inspection or seccomp actually generating such programs?
>>>
>>> In the process of merging my seccomp thread-sync series back with
>>> mainline, I got uncomfortable that I was moving filter size validation
>>> around without actually testing it. When I added it, I was happy that
>>> my series was correctly checking size limits, but then discovered my
>>> newly added check actually failed on an earlier kernel (3.2). Tracking
>>> it down found the corner case under 3.15.
>>>
>>> Here's the test I added to the seccomp regression tests, if you're interested:
>>> https://github.com/kees/seccomp/commit/794d54a340cde70a3bdf7fe0ade1f95d160b2883
>>
>> Nice. I'm assuming https://github.com/redpig/seccomp is still the main tree
>> for seccomp testsuite…
>
> Yes. Will hasn't pulled this most recent set of changes.

We were actually thinking about extending lib/test_bpf module with seccomp
tests, which is possible to a limited extend, but seccomp is also a bit
more than just running a BPF program and making sure results fit.

Are there any plans to put and extend test cases from [1] via user space
side into the kernel self-test directory, i.e. into something like
tools/testing/selftests/seccomp/ so that in future new tests can be added
or run from there? Might be worth to consider.

Thanks,

Daniel

  [1] https://github.com/redpig/seccomp
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