Messages in this thread | | | Date | Mon, 31 Mar 2008 09:00:53 -0500 | From | "Serge E. Hallyn" <> | Subject | Re: [PATCH 1/1] cgroups: implement device whitelist (v6) |
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Quoting Pavel Machek (pavel@ucw.cz): > On Wed 2008-03-26 13:05:43, Serge E. Hallyn wrote: > > (This is identical to the version I sent on Mar 19 in response to > > the comments by Daniel Hokka Zakrisson, which are the last > > comments I've gotten.) > > > > Implement a cgroup to track and enforce open and mknod restrictions on device > > files. A device cgroup associates a device access whitelist with each > > cgroup. A whitelist entry has 4 fields. 'type' is a (all), c (char), or > > b (block). 'all' means it applies to all types and all major and minor > > numbers. Major and minor are either an integer or * for all. > > Access is a composition of r (read), w (write), and m (mknod). > > > > The root device cgroup starts with rwm to 'all'. A child devcg gets > > a copy of the parent. Admins can then remove devices from the > > whitelist or add new entries. A child cgroup can never receive a > > device access which is denied its parent. However when a device > > access is removed from a parent it will not also be removed from the > > child(ren). > > > > An entry is added using devices.allow, and removed using > > devices.deny. For instance > > > > echo 'c 1:3 mr' > /cgroups/1/devices.allow > > > > allows cgroup 1 to read and mknod the device usually known as > > /dev/null. Doing > > > > echo a > /cgroups/1/devices.deny > > Can't you use selinux or something?
No. At the moment SELinux can't authorize based on type/major:minor. I would like to add that support later on, but even when I do, folks such as the openvz folks do not want to rely on any security modules.
> Or just fix the userland as this is for old-udev compatibility, only?
Until the part of Miklos' user mounts patches go in which enforces MNT_NODEV on mounts made by someone who is !capable(CAP_MKNOD), using capability bounding sets is completely inadequate.
> The interface is ugly...
What's ugly about it? How could we clean it up?
> > diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h > > index 1ddebfc..e287745 100644 > > --- a/include/linux/cgroup_subsys.h > > +++ b/include/linux/cgroup_subsys.h > > @@ -42,3 +42,9 @@ SUBSYS(mem_cgroup) > > #endif > > > > /* */ > > + > > +#ifdef CONFIG_CGROUP_DEVICE > > +SUBSYS(devices) > > +#endif > > + > > +/* */ > > I don't know what this is, but it does not look like C...
Huh?
-serge
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