Re: [PATCH v3] ipvs: fix race between ip_vs_conn_new() and ip_vs_del_dest()

[Simon Horman]

On Wed, Jul 25, 2018 at 10:12:48PM +0300, Julian Anastasov wrote:
> 
> 	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...

Acked-by: Simon Horman <horms@xxxxxxxxxxxx>

Pablo, please consider this for the 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>
>