From: Andy Lutomirski <luto@amacapital.net>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: "LSM List" <linux-security-module@vger.kernel.org>,
"Network Development" <netdev@vger.kernel.org>,
"Alexei Starovoitov" <ast@kernel.org>,
"Linux API" <linux-api@vger.kernel.org>,
"Sargun Dhillon" <sargun@sargun.me>, "Tejun Heo" <tj@kernel.org>,
"Kees Cook" <keescook@chromium.org>,
"David S . Miller" <davem@davemloft.net>,
"open list:CONTROL GROUP (CGROUP)" <cgroups@vger.kernel.org>,
"Mickaël Salaün" <mic@digikod.net>,
"Daniel Mack" <daniel@zonque.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
"Daniel Borkmann" <daniel@iogearbox.net>
Subject: Re: [RFC v2 09/10] landlock: Handle cgroups (performance)
Date: Tue, 30 Aug 2016 20:29:17 -0700 [thread overview]
Message-ID: <CALCETrUeRH6bpY_7WQh_SKiURPEExtw67+Mj26u4aveV9EgWxA@mail.gmail.com> (raw)
In-Reply-To: <20160831013605.GB75654@ast-mbp.thefacebook.com>
On Tue, Aug 30, 2016 at 6:36 PM, Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
> On Tue, Aug 30, 2016 at 02:45:14PM -0700, Andy Lutomirski wrote:
>>
>> One might argue that landlock shouldn't be tied to seccomp (in theory,
>> attached progs could be given access to syscall_get_xyz()), but I
>
> proposed lsm is way more powerful than syscall_get_xyz.
> no need to dumb it down.
I think you're misunderstanding me.
Mickaël's code allows one to make the LSM hook filters depend on the
syscall using SECCOMP_RET_LANDLOCK. I'm suggesting that a similar
effect could be achieved by allowing the eBPF LSM hook to call
syscall_get_xyz() if it wants to.
>
>> think that the seccomp attachment mechanism is the right way to
>> install unprivileged filters. It handles the no_new_privs stuff, it
>> allows TSYNC, it's totally independent of systemwide policy, etc.
>>
>> Trying to use cgroups or similar for this is going to be much nastier.
>> Some tighter sandboxes (Sandstorm, etc) aren't even going to dream of
>> putting cgroupfs in their containers, so requiring cgroups or similar
>> would be a mess for that type of application.
>
> I don't see why it is a 'mess'. cgroups are already used by majority
> of the systems, so I don't see why requiring a cgroup is such a big deal.
Requiring cgroup to be configured in isn't a big deal. Requiring
> But let's say we don't do them. How implementation is going to look like
> for task based hierarchy? Note that we need an array of bpf_prog pointers.
> One for each lsm hook. Where this array is going to be stored?
> We cannot put in task_struct, since it's too large. Cannot put it
> into 'struct seccomp' directly either, unless it will become a pointer.
> Is that the proposal?
It would go in struct seccomp_filter or in something pointed to from there.
> So now we will be wasting extra 1kbyte of memory per task. Not great.
> We'd want to optimize it by sharing this such struct seccomp with prog array
> across threads of the same task? Or dynimically allocating it when
> landlock is in use? May sound nice, but how to account for that kernel
> memory? I guess also solvable by charging memlock.
> With cgroup based approach we don't need to worry about all that.
>
The considerations are essentially identical either way.
With cgroups, if you want to share the memory between multiple
separate sandboxes (Firejail instances, Sandstorm grains, Chromium
instances, xdg-apps, etc), you'd need to get them to all coordinate to
share a cgroup. With a seccomp-like interface, you'd need to get them
to coordinate to share an installed layer (using my FD idea or
similar).
There would *not* be any duplication of this memory just because a
sandboxed process called fork().
--Andy
--
Andy Lutomirski
AMA Capital Management, LLC
next prev parent reply other threads:[~2016-08-31 3:29 UTC|newest]
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 [this message]
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 ` [RFC v2 09/10] landlock: Handle cgroups (program types) Mickaël Salaün
2016-08-27 18:19 ` 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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