Commit 090e28b2 authored by Zefan Li's avatar Zefan Li Committed by Jakub Kicinski

netprio_cgroup: Fix unlimited memory leak of v2 cgroups

If systemd is configured to use hybrid mode which enables the use of
both cgroup v1 and v2, systemd will create new cgroup on both the default
root (v2) and netprio_cgroup hierarchy (v1) for a new session and attach
task to the two cgroups. If the task does some network thing then the v2
cgroup can never be freed after the session exited.

One of our machines ran into OOM due to this memory leak.

In the scenario described above when sk_alloc() is called
cgroup_sk_alloc() thought it's in v2 mode, so it stores
the cgroup pointer in sk->sk_cgrp_data and increments
the cgroup refcnt, but then sock_update_netprioidx()
thought it's in v1 mode, so it stores netprioidx value
in sk->sk_cgrp_data, so the cgroup refcnt will never be freed.

Currently we do the mode switch when someone writes to the ifpriomap
cgroup control file. The easiest fix is to also do the switch when
a task is attached to a new cgroup.

Fixes: bd1060a1 ("sock, cgroup: add sock->sk_cgroup")
Reported-by: default avatarYang Yingliang <yangyingliang@huawei.com>
Tested-by: default avatarYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: default avatarZefan Li <lizefan@huawei.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 99352c79
......@@ -236,6 +236,8 @@ static void net_prio_attach(struct cgroup_taskset *tset)
struct task_struct *p;
struct cgroup_subsys_state *css;
cgroup_sk_alloc_disable();
cgroup_taskset_for_each(p, css, tset) {
void *v = (void *)(unsigned long)css->id;
......
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