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authorColin Cross <ccross@android.com>2011-07-12 19:53:24 -0700
committerDan Willemsen <dwillemsen@nvidia.com>2011-11-30 21:38:49 -0800
commita237ee7830a0445a27af7fd24bdc3414b9553d35 (patch)
treec0c9be8c1f24e09a673643426db50c193791e838 /kernel
parentf971f6c015d74c9653a15fa1357144ead2ff7e7e (diff)
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup.c31
-rw-r--r--kernel/sched.c15
2 files changed, 43 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 84dd3818633f..bab5a7911b84 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2202,6 +2202,24 @@ out_free_group_list:
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
@@ -2247,9 +2265,16 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
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();
diff --git a/kernel/sched.c b/kernel/sched.c
index 7de220e79dff..e7ec90424ded 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8966,6 +8966,20 @@ cpu_cgroup_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
}
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
@@ -9070,6 +9084,7 @@ struct cgroup_subsys cpu_cgroup_subsys = {
.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,