Re: [PATCH 0/2 v2] userns: show current values of user namespace counters
From: Andrei Vagin
Date: Mon Oct 10 2016 - 14:55:33 EST
On Thu, Oct 06, 2016 at 02:33:53PM -0500, Eric W. Biederman wrote:
> Andrei Vagin <avagin@xxxxxxxxxxxxx> writes:
> > Hello Eric,
> > What do you think about this series? It should be useful to know current
> > usage for user counters.
> I am in favor of knowing the values. Unless there is a good reason not
> to we should export the values with a read-only sysctl. I believe that
> is what other similar limits do.
I want to have a place where I will be able to get limits for all
users. I can't imagine how to do this with a sysctl. It will looks like
multiline sysct-s, what doesn't look good. I will think. If you will
have any ideas let me know. Thanks.
> As for having per process knowledge I think that is probably something
> we want to solve for these sysctls as well.
> I don't think I saw anyone looking at this code from the perspective of
> information leaks. I think we need to ask that question, as similar
> interfaces have been problematic from an information leak point of view.
It's a good question.
> In short I what you are trying to do here is valuable, I just want
> to make certain we have a maintainable pattern when we export these.
> > Thanks,
> > Andrei
> > On Mon, Aug 15, 2016 at 01:10:20PM -0700, Andrei Vagin wrote:
> >> Recently Eric added user namespace counters. User namespace counters is
> >> a feature that allows to limit the number of various kernel objects a
> >> user can create. These limits are set via /proc/sys/user/ sysctls on a
> >> per user namespace basis and are applicable to all users in that
> >> namespace.
> >> User namespace counters are not in the upstream tree yet,
> >> you can find them in Eric's tree:
> >> https://git.kernel.org/cgit/linux/kernel/git/ebiederm/user-namespace.git/log/?h=for-testing
> >> This patch adds /proc/<pid>/userns_counts files to provide current usage
> >> of user namespace counters.
> >> > cat /proc/813/userns_counts
> >> user_namespaces 101000 1
> >> pid_namespaces 101000 1
> >> ipc_namespaces 101000 4
> >> net_namespaces 101000 2
> >> mnt_namespaces 101000 5
> >> mnt_namespaces 100000 1
> >> The meanings of the columns are as follows, from left to right:
> >> Name Object name
> >> UID User ID
> >> Usage Current usage
> >> The full documentation is in the second patch.
> >> v2: - describe this file in Documentation/filesystems/proc.txt
> >> - move and rename into /proc/<pid>/userns_counts
> >> Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
> >> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> >> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> >> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
> >> Andrei Vagin (1):
> >> kernel: show current values of user namespace counters
> >> Kirill Kolyshkin (1):
> >> Documentation: describe /proc/<pid>/userns_counts
> >> Documentation/filesystems/proc.txt | 30 +++++++++++
> >> fs/proc/array.c | 55 ++++++++++++++++++++
> >> fs/proc/base.c | 1 +
> >> fs/proc/internal.h | 1 +
> >> include/linux/user_namespace.h | 8 +++
> >> kernel/ucount.c | 102 +++++++++++++++++++++++++++++++++++++
> >> 6 files changed, 197 insertions(+)
> >> --
> >> 2.5.5