kernel: memcg: fix possible use-after-free in memcg_write_event_control()

In the Linux kernel, the following vulnerability has been resolved: memcg: fix possible use-after-free in memcgwriteeventcontrol memcgwriteeventcontrol accesses the dentry-dname of the specified control fd to route the write call. As a cgroup interface file can't be renamed, it's safe to access...