cgroups: fix API thinko
Add cgroup_attach_task_all()
The existing cgroup_attach_task_current_cg() API is called by a thread to
attach another thread to all of its cgroups; this is unsuitable for cases
where a privileged task wants to attach itself to the cgroups of a less
privileged one, since the call must be made from the context of the target
task.
This patch adds a more generic cgroup_attach_task_all() API that allows
both the source task and to-be-moved task to be specified.
cgroup_attach_task_current_cg() becomes a specialization of the more
generic new function.
[menage@google.com: rewrote changelog]
[akpm@linux-foundation.org: address reviewer comments]
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Ben Blum <bblum@google.com>
Cc: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ed3e92e..0c99102 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -578,7 +578,12 @@
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
int cgroup_scan_tasks(struct cgroup_scanner *scan);
int cgroup_attach_task(struct cgroup *, struct task_struct *);
-int cgroup_attach_task_current_cg(struct task_struct *);
+int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
+
+static inline int cgroup_attach_task_current_cg(struct task_struct *tsk)
+{
+ return cgroup_attach_task_all(current, tsk);
+}
/*
* CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
@@ -636,6 +641,11 @@
}
/* No cgroups - nothing to do */
+static inline int cgroup_attach_task_all(struct task_struct *from,
+ struct task_struct *t)
+{
+ return 0;
+}
static inline int cgroup_attach_task_current_cg(struct task_struct *t)
{
return 0;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 192f88c..c9483d8 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1791,19 +1791,20 @@
}
/**
- * cgroup_attach_task_current_cg - attach task 'tsk' to current task's cgroup
+ * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
+ * @from: attach to all cgroups of a given task
* @tsk: the task to be attached
*/
-int cgroup_attach_task_current_cg(struct task_struct *tsk)
+int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
{
struct cgroupfs_root *root;
- struct cgroup *cur_cg;
int retval = 0;
cgroup_lock();
for_each_active_root(root) {
- cur_cg = task_cgroup_from_root(current, root);
- retval = cgroup_attach_task(cur_cg, tsk);
+ struct cgroup *from_cg = task_cgroup_from_root(from, root);
+
+ retval = cgroup_attach_task(from_cg, tsk);
if (retval)
break;
}
@@ -1811,7 +1812,7 @@
return retval;
}
-EXPORT_SYMBOL_GPL(cgroup_attach_task_current_cg);
+EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
/*
* Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex