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@xxxxxxxxxx>
> Reviewed-by: Jiang Biao <jiang.biao2@xxxxxxxxxx>
v3 looks good to me,
Acked-by: Julian Anastasov <ja@xxxxxx>
Simon and Pablo, this can be applied to ipvs/nf tree...
> ---
> v2: fix use-after-free in CONN_ONE_PACKET case suggested by Julian Anastasov
> v3: remove trailing whitespace for patch checking
>
> 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 */
> ip_vs_conn_expire_now(cp);
> }
> - /* don't restart its timer, and silently
> - drop the packet. */
> - __ip_vs_conn_put(cp);
> +
> return NF_DROP;
> }
>
> --
> 1.8.3.1
Regards
--
Julian Anastasov <ja@xxxxxx>
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