cgroup: Add generic cgroup subsystem permission checks.
Rather than using explicit euid == 0 checks when trying to move
tasks into a cgroup via CFS, move permission checks into each
specific cgroup subsystem. If a subsystem does not specify a
'can_attach' handler, then we fall back to doing our checks the old way.
This way non-root processes can add arbitrary processes to
a cgroup if all the registered subsystems on that cgroup agree.
Also change explicit euid == 0 check to CAP_SYS_ADMIN
Signed-off-by: San Mehat <san@google.com>
diff --git a/kernel/sched.c b/kernel/sched.c
index ea7a385..13f13af 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8803,6 +8803,15 @@
static int
cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
{
+ if ((current != tsk) && (!capable(CAP_SYS_NICE))) {
+ const struct cred *cred = current_cred(), *tcred;
+
+ tcred = __task_cred(tsk);
+
+ if (cred->euid != tcred->uid && cred->euid != tcred->suid)
+ return -EPERM;
+ }
+
#ifdef CONFIG_RT_GROUP_SCHED
if (!sched_rt_can_attach(cgroup_tg(cgrp), tsk))
return -EINVAL;