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

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

[Tan Hu]

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@zte.com.cn>
Reviewed-by: Jiang Biao <jiang.biao2@zte.com.cn>
---
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

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

[Julian Anastasov]

	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@zte.com.cn>
> Reviewed-by: Jiang Biao <jiang.biao2@zte.com.cn>

	v3 looks good to me,

Acked-by: Julian Anastasov <ja@ssi.bg>

	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@ssi.bg>

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@zte.com.cn>
> > Reviewed-by: Jiang Biao <jiang.biao2@zte.com.cn>
> 
> 	v3 looks good to me,
> 
> Acked-by: Julian Anastasov <ja@ssi.bg>
> 
> 	Simon and Pablo, this can be applied to ipvs/nf tree...

Acked-by: Simon Horman <horms@verge.net.au>

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@ssi.bg>
> 

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

[Pablo Neira Ayuso]

On Tue, Jul 31, 2018 at 06:54:21PM +0200, Simon Horman wrote:
> On Wed, Jul 25, 2018 at 10:12:48PM +0300, Julian Anastasov wrote:
[...]
> > 	v3 looks good to me,
> > 
> > Acked-by: Julian Anastasov <ja@ssi.bg>
> > 
> > 	Simon and Pablo, this can be applied to ipvs/nf tree...
> 
> Acked-by: Simon Horman <horms@verge.net.au>
> 
> Pablo, please consider this for the nf tree.

Applied, thanks!