mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-15 13:06:41 +07:00
f6e07d3807
According to commit 676db4af04 ("cgroupfs: create /sys/fs/cgroup to
mount cgroupfs on") the canonical mountpoint for the cgroup filesystem
is /sys/fs/cgroup. Hence, this should be used in the documentation.
Signed-off-by: Jörg Sommer <joerg@alea.gnuu.de>
Acked-by: Paul Menage <menage@google.com>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
53 lines
1.9 KiB
Plaintext
53 lines
1.9 KiB
Plaintext
Device Whitelist Controller
|
|
|
|
1. Description:
|
|
|
|
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 device
|
|
cgroup gets a copy of the parent. Administrators can then remove
|
|
devices from the whitelist or add new entries. A child cgroup can
|
|
never receive a device access which is denied by its parent. However
|
|
when a device access is removed from a parent it will not also be
|
|
removed from the child(ren).
|
|
|
|
2. User Interface
|
|
|
|
An entry is added using devices.allow, and removed using
|
|
devices.deny. For instance
|
|
|
|
echo 'c 1:3 mr' > /sys/fs/cgroup/1/devices.allow
|
|
|
|
allows cgroup 1 to read and mknod the device usually known as
|
|
/dev/null. Doing
|
|
|
|
echo a > /sys/fs/cgroup/1/devices.deny
|
|
|
|
will remove the default 'a *:* rwm' entry. Doing
|
|
|
|
echo a > /sys/fs/cgroup/1/devices.allow
|
|
|
|
will add the 'a *:* rwm' entry to the whitelist.
|
|
|
|
3. Security
|
|
|
|
Any task can move itself between cgroups. This clearly won't
|
|
suffice, but we can decide the best way to adequately restrict
|
|
movement as people get some experience with this. We may just want
|
|
to require CAP_SYS_ADMIN, which at least is a separate bit from
|
|
CAP_MKNOD. We may want to just refuse moving to a cgroup which
|
|
isn't a descendant of the current one. Or we may want to use
|
|
CAP_MAC_ADMIN, since we really are trying to lock down root.
|
|
|
|
CAP_SYS_ADMIN is needed to modify the whitelist or move another
|
|
task to a new cgroup. (Again we'll probably want to change that).
|
|
|
|
A cgroup may not be granted more permissions than the cgroup's
|
|
parent has.
|