Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Tue, 2 May 2017 09:33:46 -0700
From: Andy Lutomirski <>
To: Djalal Harouni <>, "Eric W. Biederman" <>
Cc: Andy Lutomirski <>, 
	Linux Kernel Mailing List <>, Kees Cook <>, 
	Andrew Morton <>, Linux FS Devel <>, 
	"" <>, 
	LSM List <>, 
	Linux API <>, Dongsu Park <>, 
	Casey Schaufler <>, James Morris <>, 
	"Serge E. Hallyn" <>, Jeff Layton <>, 
	"J. Bruce Fields" <>, Alexander Viro <>, 
	Alexey Dobriyan <>, Ingo Molnar <>, Oleg Nesterov <>, 
	Michal Hocko <>, Jonathan Corbet <>
Subject: Re: [PATCH RFC v2 4/6] proc: support mounting private procfs
 instances inside same pid namespace

On Tue, May 2, 2017 at 7:29 AM, Djalal Harouni <> wrote:
> On Thu, Apr 27, 2017 at 12:13 AM, Andy Lutomirski <> wrote:
>> On Tue, Apr 25, 2017 at 5:23 AM, Djalal Harouni <> wrote:
> [...]
>>> We have to align procfs and modernize it to have a per mount context
>>> where at least the mount option do not propagate to all other mounts,
>>> then maybe we can continue to implement new features. One example is to
>>> require CAP_SYS_ADMIN in the init user namespace on some /proc/* which are
>>> not pids and which are are not virtualized by design, or CAP_NET_ADMIN
>>> inside userns on the net bits that are virtualized, etc.
>>> These mount options won't propagate to previous mounts, and the system
>>> will continue to be usable.
>>> Ths patch introduces the new 'limit_pids' mount option as it was also
>>> suggesed by Andy Lutomirski [1]. When this option is passed we
>>> automatically create a private procfs instance. This is not the default
>>> behaviour since we do not want to break userspace and we do not want to
>>> provide different devices IDs by default, please see [1] for why.
>> I think that calling the option to make a separate instance
>> "limit_pids" is extremely counterintuitive.
> Ok.
>> My strong preference would be to make proc *always* make a separate
>> instance (unless it's a bind mount) and to make it work.  If that
>> means fudging stat() output, so be it.
> I also agree, but as said if we change stat(), userspace won't be able
> to notice if these two proc instances are really separated, the device
> ID is the only indication here.

I re-read all the threads and I'm still not convinced I see why we
need new_instance to be non-default.  It's true that the device
numbers of /proc/ns/* matter, but if you look (with stat -L, for
example), they're *already* not tied to the procfs instance.

I'm okay with adding new_instance to be on the safe side, but I'd like
it to be done in a way that we could make it become the default some
day without breaking anything.  This means that we need to be rather
careful about how new_instance and hidepid interact.

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.