rmdir() will fail with it. From this behavior, pre_destroy() can be
called multiple times against a cgroup.
+int allow_attach(struct cgroup *cgrp, struct task_struct *task)
+(cgroup_mutex held by caller)
+
+Called prior to moving a task into a cgroup; if the subsystem
+returns an error, this will abort the attach operation. Used
+to extend the permission checks - if all subsystems in a cgroup
+return 0, the attach will be allowed to proceed, even if the
+default permission check (root or same user) fails.
+
int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *task)
(cgroup_mutex held by caller)
struct cgroup *cgrp);
int (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
+ int (*allow_attach)(struct cgroup *cgrp, struct task_struct *tsk);
int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *tsk);
int (*can_attach_task)(struct cgroup *cgrp, struct task_struct *tsk);
return retval;
}
+static int cgroup_allow_attach(struct cgroup *cgrp, struct task_struct *tsk)
+{
+ struct cgroup_subsys *ss;
+ int ret;
+
+ for_each_subsys(cgrp->root, ss) {
+ if (ss->allow_attach) {
+ ret = ss->allow_attach(cgrp, tsk);
+ if (ret)
+ return ret;
+ } else {
+ return -EACCES;
+ }
+ }
+
+ return 0;
+}
+
/*
* Find the task_struct of the task to attach by vpid and pass it along to the
* function to attach either it or all tasks in its threadgroup. Will take
if (cred->euid &&
cred->euid != tcred->uid &&
cred->euid != tcred->suid) {
- rcu_read_unlock();
- cgroup_unlock();
- return -EACCES;
+ /*
+ * if the default permission check fails, give each
+ * cgroup a chance to extend the permission check
+ */
+ ret = cgroup_allow_attach(cgrp, tsk);
+ if (ret) {
+ rcu_read_unlock();
+ cgroup_unlock();
+ return ret;
+ }
}
get_task_struct(tsk);
rcu_read_unlock();
sched_destroy_group(tg);
}
+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)
{
.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,