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authorEric W. Biederman <ebiederm@xmission.com>2016-07-15 06:35:51 -0500
committerTejun Heo <tj@kernel.org>2016-07-15 07:56:38 -0400
commiteedd0f4cbf5f3b81e82649832091e1d9d53f0709 (patch)
treeb806976542cf2731a4382414a28326706cb01f7c /kernel/cgroup.c
parent7bd8830875bfa380c68f390efbad893293749324 (diff)
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cgroupns: Close race between cgroup_post_fork and copy_cgroup_ns
In most code paths involving cgroup migration cgroup_threadgroup_rwsem is taken. There are two exceptions: - remove_tasks_in_empty_cpuset calls cgroup_transfer_tasks - vhost_attach_cgroups_work calls cgroup_attach_task_all With cgroup_threadgroup_rwsem held it is guaranteed that cgroup_post_fork and copy_cgroup_ns will reference the same css_set from the process calling fork. Without such an interlock there process after fork could reference one css_set from it's new cgroup namespace and another css_set from task->cgroups, which semantically is nonsensical. Cc: stable@vger.kernel.org Fixes: a79a908fd2b0 ("cgroup: introduce cgroup namespaces") Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5f01e00cffc4..e75efa819911 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2962,6 +2962,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
int retval = 0;
mutex_lock(&cgroup_mutex);
+ percpu_down_write(&cgroup_threadgroup_rwsem);
for_each_root(root) {
struct cgroup *from_cgrp;
@@ -2976,6 +2977,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
if (retval)
break;
}
+ percpu_up_write(&cgroup_threadgroup_rwsem);
mutex_unlock(&cgroup_mutex);
return retval;
@@ -4343,6 +4345,8 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
mutex_lock(&cgroup_mutex);
+ percpu_down_write(&cgroup_threadgroup_rwsem);
+
/* all tasks in @from are being moved, all csets are source */
spin_lock_irq(&css_set_lock);
list_for_each_entry(link, &from->cset_links, cset_link)
@@ -4371,6 +4375,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
} while (task && !ret);
out_err:
cgroup_migrate_finish(&preloaded_csets);
+ percpu_up_write(&cgroup_threadgroup_rwsem);
mutex_unlock(&cgroup_mutex);
return ret;
}