[PATCH net] Don't allow overwrite of config src addr

[PATCH net] Don't allow overwrite of config src addr

[Brian Russell]

When using IPv6 transport and a default dst, a pointer to the configured
source address is passed into the route lookup. If no source address is
configured, then the value is overwritten.

IPv6 route lookup ignores egress ifindex match if the source adress is set,
so if egress ifindex match is desired, the source address must be passed
as any. The overwrite breaks this for subsequent lookups.

Avoid this by copying the configured address to an existing stack variable
and pass a pointer to that instead.

Signed-off-by: Brian Russell <brussell@brocade.com>
---
 drivers/net/vxlan.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 30b04cf..3cca908 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -2019,7 +2019,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 
 		dst_port = rdst->remote_port ? rdst->remote_port : vxlan->cfg.dst_port;
 		vni = rdst->remote_vni;
-		src = &vxlan->cfg.saddr;
+		local_ip = vxlan->cfg.saddr;
 		dst_cache = &rdst->dst_cache;
 		md->gbp = skb->mark;
 		ttl = vxlan->cfg.ttl;
@@ -2052,7 +2052,6 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 		dst = &remote_ip;
 		dst_port = info->key.tp_dst ? : vxlan->cfg.dst_port;
 		vni = tunnel_id_to_key32(info->key.tun_id);
-		src = &local_ip;
 		dst_cache = &info->dst_cache;
 		if (info->options_len)
 			md = ip_tunnel_info_opts(info);
@@ -2061,6 +2060,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 		label = info->key.label;
 		udp_sum = !!(info->key.tun_flags & TUNNEL_CSUM);
 	}
+	src = &local_ip;
 	src_port = udp_flow_src_port(dev_net(dev), skb, vxlan->cfg.port_min,
 				     vxlan->cfg.port_max, true);
 
-- 
2.1.4

Re: [PATCH net] Don't allow overwrite of config src addr

[Sergei Shtylyov]

Hello!

On 02/20/2017 08:03 PM, Brian Russell wrote:

> When using IPv6 transport and a default dst, a pointer to the configured
> source address is passed into the route lookup. If no source address is
> configured, then the value is overwritten.
>
> IPv6 route lookup ignores egress ifindex match if the source adress is set,

    Address. Perhaps can be fixed while applying?

> so if egress ifindex match is desired, the source address must be passed
> as any. The overwrite breaks this for subsequent lookups.
>
> Avoid this by copying the configured address to an existing stack variable
> and pass a pointer to that instead.
>
> Signed-off-by: Brian Russell <brussell@brocade.com>
[...]

MBR, Sergei

Re: [PATCH net] Don't allow overwrite of config src addr

[David Miller]

From: Brian Russell <brussell@brocade.com>
Date: Mon, 20 Feb 2017 17:03:54 +0000

> When using IPv6 transport and a default dst, a pointer to the configured
> source address is passed into the route lookup. If no source address is
> configured, then the value is overwritten.
> 
> IPv6 route lookup ignores egress ifindex match if the source adress is set,
> so if egress ifindex match is desired, the source address must be passed
> as any. The overwrite breaks this for subsequent lookups.
> 
> Avoid this by copying the configured address to an existing stack variable
> and pass a pointer to that instead.
> 
> Signed-off-by: Brian Russell <brussell@brocade.com>

I really would like you to try and find a way to avoid this address copy.
It means even with a cached route, we are going to copy a 128-bit address
onto the stack _every single_ packet vxlan transmits.