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
'allow_attach' handler, then we fall back to doing our checks
the old way.
Use the 'allow_attach' handler for the 'cpu' cgroup to allow
non-root processes to add arbitrary processes to a 'cpu' cgroup
if it has the CAP_SYS_NICE capability set.
This version of the patch adds a 'allow_attach' handler instead
of reusing the 'can_attach' handler. If the 'can_attach' handler
is reused, a new cgroup that implements 'can_attach' but not
the permission checks could end up with no permission checks
at all.
Change-Id: Icfa950aa9321d1ceba362061d32dc7dfa2c64f0c
Original-Author: San Mehat <san@google.com>
Signed-off-by: Colin Cross <ccross@android.com>
diff --git a/kernel/sched.c b/kernel/sched.c
index db2b408..bdfcce7 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8799,6 +8799,20 @@
}
static int
+cpu_cgroup_allow_attach(struct cgroup *cgrp, struct task_struct *tsk)
+{
+ const struct cred *cred = current_cred(), *tcred;
+
+ tcred = __task_cred(tsk);
+
+ if ((current != tsk) && !capable(CAP_SYS_NICE) &&
+ cred->euid != tcred->uid && cred->euid != tcred->suid)
+ return -EACCES;
+
+ return 0;
+}
+
+static int
cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
{
#ifdef CONFIG_RT_GROUP_SCHED
@@ -8903,6 +8917,7 @@
.name = "cpu",
.create = cpu_cgroup_create,
.destroy = cpu_cgroup_destroy,
+ .allow_attach = cpu_cgroup_allow_attach,
.can_attach_task = cpu_cgroup_can_attach_task,
.attach_task = cpu_cgroup_attach_task,
.exit = cpu_cgroup_exit,