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Date: Sat, 9 May 2020 18:57:36 -0400 From: Tejun Heo <tj@...nel.org> To: Zefan Li <lizefan@...wei.com> Cc: David Miller <davem@...emloft.net>, yangyingliang <yangyingliang@...wei.com>, Kefeng Wang <wangkefeng.wang@...wei.com>, huawei.libin@...wei.com, guofan5@...wei.com, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, Linux Kernel Network Developers <netdev@...r.kernel.org> Subject: Re: [PATCH v2] netprio_cgroup: Fix unlimited memory leak of v2 cgroups On Sat, May 09, 2020 at 11:32:10AM +0800, Zefan Li wrote: > 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: bd1060a1d671("sock, cgroup: add sock->sk_cgroup") > Reported-by: Yang Yingliang <yangyingliang@...wei.com> > Tested-by: Yang Yingliang <yangyingliang@...wei.com> > Signed-off-by: Zefan Li <lizefan@...wei.com> Acked-by: Tejun Heo <tj@...nel.org> Thanks. -- tejun
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