[PATCH v2] ipvs: fix race between ip_vs_conn_new() and ip_vs_del_dest()

To: wensong@xxxxxxxxxxxx, horms@xxxxxxxxxxxx, ja@xxxxxx, pablo@xxxxxxxxxxxxx, kadlec@xxxxxxxxxxxxxxxxx, fw@xxxxxxxxx, davem@xxxxxxxxxxxxx
Subject: [PATCH v2] ipvs: fix race between ip_vs_conn_new() and ip_vs_del_dest()
Cc: netdev@xxxxxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxx, coreteam@xxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, zhong.weidong@xxxxxxxxxx, jiang.biao2@xxxxxxxxxx
From: Tan Hu <>
Date: Wed, 25 Jul 2018 10:49:40 +0800
We came across infinite loop in ipvs when using ipvs in docker

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

    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
      cp->dest && !IP_VS_DEST_F_AVAILABLE
    cleanup_net  ---> infinite looping

Fix this by checking whether the timer already started.

Signed-off-by: Tan Hu <>
Reviewed-by: Jiang Biao <jiang.biao2@xxxxxxxxxx>
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; 
+               /* when timer already started, silently drop the packet.*/
+               if (timer_pending(&cp->timer))
+                       __ip_vs_conn_put(cp);
+               else
+                       ip_vs_conn_put(cp);
+               if (sysctl_expire_nodest_conn(ipvs) &&
+                   !(flags & IP_VS_CONN_F_ONE_PACKET)) {
                        /* try to expire the connection immediately */
-               /* don't restart its timer, and silently
-                  drop the packet. */
-               __ip_vs_conn_put(cp);
                return NF_DROP;

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