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From: "Mickaël Salaün" <mic@digikod.net>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: linux-kernel@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Daniel Mack <daniel@zonque.org>,
	"David S . Miller" <davem@davemloft.net>,
	Kees Cook <keescook@chromium.org>,
	Sargun Dhillon <sargun@sargun.me>,
	kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org,
	linux-security-module@vger.kernel.org, netdev@vger.kernel.org,
	Tejun Heo <tj@kernel.org>
Subject: Re: [RFC v2 09/10] landlock: Handle cgroups (program types)
Date: Sat, 27 Aug 2016 16:34:55 +0200
Message-ID: <57C1A50F.60605@digikod.net> (raw)
In-Reply-To: <20160826230539.GA26683@ast-mbp.thefacebook.com>

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On 27/08/2016 01:05, Alexei Starovoitov wrote:
> On Fri, Aug 26, 2016 at 05:10:40PM +0200, Mickaël Salaün wrote:
>
>>> As far as safety and type checking that bpf programs has to do,
>>> I like the approach of patch 06/10:
>>> +LANDLOCK_HOOK2(file_open, FILE_OPEN,
>>> +       PTR_TO_STRUCT_FILE, struct file *, file,
>>> +       PTR_TO_STRUCT_CRED, const struct cred *, cred
>>> +)
>>> teaching verifier to recognize struct file, cred, sockaddr
>>> will let bpf program access them naturally without any overhead.
>>> Though:
>>> @@ -102,6 +102,9 @@ enum bpf_prog_type {
>>>         BPF_PROG_TYPE_SCHED_CLS,
>>>         BPF_PROG_TYPE_SCHED_ACT,
>>>         BPF_PROG_TYPE_TRACEPOINT,
>>> +       BPF_PROG_TYPE_LANDLOCK_FILE_OPEN,
>>> +       BPF_PROG_TYPE_LANDLOCK_FILE_PERMISSION,
>>> +       BPF_PROG_TYPE_LANDLOCK_MMAP_FILE,
>>>  };
>>> is a bit of overkill.
>>> I think it would be cleaner to have single
>>> BPF_PROG_TYPE_LSM and at program load time pass
>>> lsm_hook_id as well, so that verifier can do safety checks
>>> based on type info provided in LANDLOCK_HOOKs
>>
>> I first started with a unique BPF_PROG_TYPE but, the thing is, the BPF
>> verifier check programs according to their types. If we need to check
>> specific context value types (e.g. PTR_TO_STRUCT_FILE), we need a
>> dedicated program types. I don't see any other way to do it with the
>> current verifier code. Moreover it's the purpose of program types, right?
> 
> Adding new bpf program type for every lsm hook is not acceptable.
> Either do one new program type + pass lsm_hook_id as suggested
> or please come up with an alternative approach.

OK, so we have to modify the verifier to not only rely on the program
type but on another value to check the context accesses. Do you have a
hint from where this value could come from? Do we need to add a new bpf
command to associate a program to a subtype?


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  parent reply index

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-25 10:32 [RFC v2 00/10] Landlock LSM: Unprivileged sandboxing Mickaël Salaün
2016-08-25 10:32 ` [RFC v2 01/10] landlock: Add Kconfig Mickaël Salaün
2016-08-25 10:32 ` [RFC v2 02/10] bpf: Move u64_to_ptr() to BPF headers and inline it Mickaël Salaün
2016-08-25 10:32 ` [RFC v2 03/10] bpf,landlock: Add a new arraymap type to deal with (Landlock) handles Mickaël Salaün
2016-08-25 10:32 ` [RFC v2 04/10] seccomp: Split put_seccomp_filter() with put_seccomp() Mickaël Salaün
2016-08-25 10:32 ` [RFC v2 05/10] seccomp: Handle Landlock Mickaël Salaün
2016-08-25 10:32 ` [RFC v2 06/10] landlock: Add LSM hooks Mickaël Salaün
2016-08-30 18:56   ` Andy Lutomirski
2016-08-30 20:10     ` Mickaël Salaün
2016-08-30 20:18       ` Andy Lutomirski
2016-08-30 20:27         ` Mickaël Salaün
2016-08-25 10:32 ` [RFC v2 07/10] landlock: Add errno check Mickaël Salaün
2016-08-25 11:13   ` Andy Lutomirski
2016-08-25 10:32 ` [RFC v2 08/10] landlock: Handle file system comparisons Mickaël Salaün
2016-08-25 11:12   ` Andy Lutomirski
2016-08-25 14:10     ` Mickaël Salaün
2016-08-26 14:57       ` Andy Lutomirski
2016-08-27 13:45         ` Mickaël Salaün
2016-08-25 10:32 ` [RFC v2 09/10] landlock: Handle cgroups Mickaël Salaün
2016-08-25 11:09   ` Andy Lutomirski
2016-08-25 14:44     ` Mickaël Salaün
2016-08-26 12:55       ` Tejun Heo
2016-08-26 14:20       ` Andy Lutomirski
2016-08-26 15:50         ` Tejun Heo
2016-08-26  2:14   ` Alexei Starovoitov
2016-08-26 15:10     ` Mickaël Salaün
2016-08-26 23:05       ` Alexei Starovoitov
2016-08-27  7:30         ` Andy Lutomirski
2016-08-27 18:11           ` Alexei Starovoitov
2016-08-28  8:14             ` Andy Lutomirski
2016-08-27 14:06         ` [RFC v2 09/10] landlock: Handle cgroups (performance) Mickaël Salaün
2016-08-27 18:06           ` Alexei Starovoitov
2016-08-27 19:35             ` Mickaël Salaün
2016-08-27 20:43               ` Alexei Starovoitov
2016-08-27 21:14                 ` Mickaël Salaün
2016-08-28  8:13                   ` Andy Lutomirski
2016-08-28  9:42                     ` Mickaël Salaün
2016-08-30 18:55                       ` Andy Lutomirski
2016-08-30 20:20                         ` Mickaël Salaün
2016-08-30 20:23                           ` Andy Lutomirski
2016-08-30 20:33                             ` Mickaël Salaün
2016-08-30 20:55                               ` Alexei Starovoitov
2016-08-30 21:45                                 ` Andy Lutomirski
2016-08-31  1:36                                   ` Alexei Starovoitov
2016-08-31  3:29                                     ` Andy Lutomirski
2016-08-27 14:19         ` [RFC v2 09/10] landlock: Handle cgroups (netfilter match) Mickaël Salaün
2016-08-27 18:32           ` Alexei Starovoitov
2016-08-27 14:34         ` Mickaël Salaün [this message]
2016-08-27 18:19           ` [RFC v2 09/10] landlock: Handle cgroups (program types) Alexei Starovoitov
2016-08-27 19:55             ` Mickaël Salaün
2016-08-27 20:56               ` Alexei Starovoitov
2016-08-27 21:18                 ` Mickaël Salaün
2016-08-25 10:32 ` [RFC v2 10/10] samples/landlock: Add sandbox example Mickaël Salaün
2016-08-25 11:05 ` [RFC v2 00/10] Landlock LSM: Unprivileged sandboxing Andy Lutomirski
2016-08-25 13:57   ` Mickaël Salaün
2016-08-27  7:40 ` Andy Lutomirski
2016-08-27 15:10   ` Mickaël Salaün
2016-08-27 15:21     ` [RFC v2 00/10] Landlock LSM: Unprivileged sandboxing (cgroup delegation) Mickaël Salaün
2016-08-30 16:06 ` [RFC v2 00/10] Landlock LSM: Unprivileged sandboxing Andy Lutomirski
2016-08-30 19:51   ` Mickaël Salaün
2016-08-30 19:55     ` Andy Lutomirski
2016-09-15  9:19 ` Pavel Machek
2016-09-20 17:08   ` Mickaël Salaün
2016-09-24  7:45     ` Pavel Machek
2016-10-03 22:56     ` Kees Cook
2016-10-05 20:30       ` Mickaël Salaün

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