Add FS_USERNS_FLAG to cgroup fs

allowing root in a non-init user namespace to mount it.  This should
now be safe, because

1. non-init-root cannot mount a previously unbound subsystem
2. the task doing the mount must be privileged with respect to the
   user namespace owning the cgroup namespace
3. the mounted subsystem will have its current cgroup as the root dentry.
   the permissions will be unchanged, so tasks will receive no new
   privilege over the cgroups which they did not have on the original
   mounts.

Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com>
This commit is contained in:
Serge Hallyn 2016-01-29 02:54:11 -06:00 committed by Tejun Heo
parent d4021f6cd4
commit 1c53753e0d

View File

@ -2227,12 +2227,14 @@ static struct file_system_type cgroup_fs_type = {
.name = "cgroup",
.mount = cgroup_mount,
.kill_sb = cgroup_kill_sb,
.fs_flags = FS_USERNS_MOUNT,
};
static struct file_system_type cgroup2_fs_type = {
.name = "cgroup2",
.mount = cgroup_mount,
.kill_sb = cgroup_kill_sb,
.fs_flags = FS_USERNS_MOUNT,
};
static char *cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,