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authorColin Cross <ccross@android.com>2011-07-12 19:53:24 -0700
committerColin Cross <ccross@android.com>2012-04-09 13:53:11 -0700
commit4a12178d3dd5b06a215076c60dc7cb124d711373 (patch)
tree1dc08159c9da00136cfb3dc6d18a1d8c138eef1b /kernel
parentc0f6fa8c409fc7fe63bfd0a57efad29dec262bcb (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.c33
-rw-r--r--kernel/sched/core.c18
2 files changed, 48 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0de816098bf..0d4bff5e7ee 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2119,6 +2119,24 @@ out_free_group_list:
return retval;
}
+static int cgroup_allow_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
+{
+ struct cgroup_subsys *ss;
+ int ret;
+
+ for_each_subsys(cgrp->root, ss) {
+ if (ss->allow_attach) {
+ ret = ss->allow_attach(cgrp, tset);
+ 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 lock
@@ -2150,9 +2168,18 @@ retry_find_task:
if (cred->euid &&
cred->euid != tcred->uid &&
cred->euid != tcred->suid) {
- rcu_read_unlock();
- ret = -EACCES;
- goto out_unlock_cgroup;
+ /*
+ * if the default permission check fails, give each
+ * cgroup a chance to extend the permission check
+ */
+ struct cgroup_taskset tset = { };
+ tset.single.task = tsk;
+ tset.single.cgrp = cgrp;
+ ret = cgroup_allow_attach(cgrp, &tset);
+ if (ret) {
+ rcu_read_unlock();
+ goto out_unlock_cgroup;
+ }
}
} else
tsk = current;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 819719b4a7f..6a084dbc5f8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7633,6 +7633,23 @@ static void cpu_cgroup_destroy(struct cgroup *cgrp)
sched_destroy_group(tg);
}
+static int
+cpu_cgroup_allow_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
+{
+ const struct cred *cred = current_cred(), *tcred;
+ struct task_struct *task;
+
+ cgroup_taskset_for_each(task, cgrp, tset) {
+ tcred = __task_cred(task);
+
+ if ((current != task) && !capable(CAP_SYS_NICE) &&
+ cred->euid != tcred->uid && cred->euid != tcred->suid)
+ return -EACCES;
+ }
+
+ return 0;
+}
+
static int cpu_cgroup_can_attach(struct cgroup *cgrp,
struct cgroup_taskset *tset)
{
@@ -7994,6 +8011,7 @@ struct cgroup_subsys cpu_cgroup_subsys = {
.destroy = cpu_cgroup_destroy,
.can_attach = cpu_cgroup_can_attach,
.attach = cpu_cgroup_attach,
+ .allow_attach = cpu_cgroup_allow_attach,
.exit = cpu_cgroup_exit,
.populate = cpu_cgroup_populate,
.subsys_id = cpu_cgroup_subsys_id,