Re: [PATCH] ipvs: fix race between ip_vs_conn_new() and ip_vs_del_dest()
From: Julian Anastasov <ja@ssi.bg>
Date: 2018-07-24 19:56:11
Also in:
lkml, lvs-devel, netfilter-devel
Hello, On Tue, 24 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.Looks like an old bug...
quoted hunk ↗ jump to hunk
Signed-off-by: Tan Hu <redacted> Reviewed-by: Jiang Biao <redacted> --- net/netfilter/ipvs/ip_vs_core.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c index 0679dd1..ca9e7cc 100644 --- a/net/netfilter/ipvs/ip_vs_core.c +++ b/net/netfilter/ipvs/ip_vs_core.c@@ -1972,13 +1972,17 @@ 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 */
Add: 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);
When ip_vs_conn_put is called for IP_VS_CONN_F_ONE_PACKET it is possible to call ip_vs_conn_expire and to free cp with ip_vs_conn_rcu_free immediately. What we can do is to avoid the ip_vs_conn_expire_now call in such case by reading the flags early (as above) and adding the needed check (as below).
+
if (sysctl_expire_nodest_conn(ipvs)) {Add !(flags & IP_VS_CONN_F_ONE_PACKET) check in above 'if'.
/* try to expire the connection immediately */ ip_vs_conn_expire_now(cp); } - /* don't restart its timer, and silently - drop the packet. */ - __ip_vs_conn_put(cp); + return NF_DROP; }
Regards