linux-kernel - Re: Re: [PATCH v2] ipvs: fix race between ip_vs_conn_new() andip_vs_del

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Message-ID: <201807251515493276583@zte.com.cn>
Date:   Wed, 25 Jul 2018 15:15:49 +0800 (CST)
From:   <tan.hu@....com.cn>
To:     <ja@....bg>
Cc:     <wensong@...ux-vs.org>, <horms@...ge.net.au>,
        <pablo@...filter.org>, <kadlec@...ckhole.kfki.hu>, <fw@...len.de>,
        <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <lvs-devel@...r.kernel.org>, <netfilter-devel@...r.kernel.org>,
        <coreteam@...filter.org>, <linux-kernel@...r.kernel.org>,
        <zhong.weidong@....com.cn>, <jiang.biao2@....com.cn>
Subject: Re: Re: [PATCH v2] ipvs: fix race between ip_vs_conn_new() andip_vs_del_dest()

Thanks, patch-v3 has been sent. please check it again.

> Hello,
> 
> On Wed, 25 Jul 2018, Tan Hu wrote:
> 
> > We came across infinite loop in ipvs when using ipvs in docker
> > env.
> >
> > When ipvs receives new packets and cannot find an ipvs connection,
> > it will create a new connection, then if the dest is unavailable
> > (i.e. IP_VS_DEST_F_AVAILABLE), the packet will be dropped sliently.
> >
> > But if the dropped packet is the first packet of this connection,
> > the connection control timer never has a chance to start and the
> > ipvs connection cannot be released. This will lead to memory leak, or
> > infinite loop in cleanup_net() when net namespace is released like
> > this:
> >
> > ip_vs_conn_net_cleanup at ffffffffa0a9f31a [ip_vs]
> > __ip_vs_cleanup at ffffffffa0a9f60a [ip_vs]
> > ops_exit_list at ffffffff81567a49
> > cleanup_net at ffffffff81568b40
> > process_one_work at ffffffff810a851b
> > worker_thread at ffffffff810a9356
> > kthread at ffffffff810b0b6f
> > ret_from_fork at ffffffff81697a18
> >
> > race condition:
> > CPU1 CPU2
> > ip_vs_in()
> > ip_vs_conn_new()
> > ip_vs_del_dest()
> > __ip_vs_unlink_dest()
> > ~IP_VS_DEST_F_AVAILABLE
> > cp->dest && !IP_VS_DEST_F_AVAILABLE
> > __ip_vs_conn_put
> > ...
> > cleanup_net ---> infinite looping
> >
> > Fix this by checking whether the timer already started.
> >
> > Signed-off-by: Tan Hu <tan.hu@....com.cn>
> > Reviewed-by: Jiang Biao <jiang.biao2@....com.cn>
> > ---
> > v2: fix use-after-free in CONN_ONE_PACKET case suggested by Julian Anastasov
> >
> > net/netfilter/ipvs/ip_vs_core.c | 15 +++++++++++----
> > 1 file changed, 11 insertions(+), 4 deletions(-)
> >
> > diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
> > index 0679dd1..a17104f 100644
> > --- a/net/netfilter/ipvs/ip_vs_core.c
> > +++ b/net/netfilter/ipvs/ip_vs_core.c
> > @@ -1972,13 +1972,20 @@ static int ip_vs_in_icmp_v6(struct netns_ipvs *ipvs, struct sk_buff *skb,
> > if (cp->dest && !(cp->dest->flags & IP_VS_DEST_F_AVAILABLE)) {
> > /* the destination server is not available */
> >
> > - if (sysctl_expire_nodest_conn(ipvs)) {
> > + __u32 flags = cp->flags;
> 
> Ops, now scripts/checkpatch.pl --strict /tmp/file.patch
> is complaining about extra trailing space in above line.
> You can also remove the empty line above the new code...
> 
> Regards