udp: restrict offloads to one namespace

udp tunnel offloads tend to aggregate datagrams based on inner
headers. gro engine gets notified by tunnel implementations about
possible offloads. The match is solely based on the port number.

Imagine a tunnel bound to port 53, the offloading will look into all
DNS packets and tries to aggregate them based on the inner data found
within. This could lead to data corruption and malformed DNS packets.

While this patch minimizes the problem and helps an administrator to find
the issue by querying ip tunnel/fou, a better way would be to match on
the specific destination ip address so if a user space socket is bound
to the same address it will conflict.

Cc: Tom Herbert <tom@herbertland.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 8 insertions, 4 deletions

diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index bd903fe0f750..976f0dcf6991 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -498,7 +498,7 @@ static int fou_create(struct net *net, struct fou_cfg *cfg,
         sk->sk_allocation = GFP_ATOMIC;
 
         if (cfg->udp_config.family == AF_INET) {
-                err = udp_add_offload(&fou->udp_offloads);
+                err = udp_add_offload(net, &fou->udp_offloads);
                 if (err)
                         goto error;
         }
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index f9386160cbee..5d396b96ae8b 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -21,6 +21,7 @@ static struct udp_offload_priv __rcu *udp_offload_base __read_mostly;
 
 struct udp_offload_priv {
         struct udp_offload      *offload;
+        possible_net_t  net;
         struct rcu_head         rcu;
         struct udp_offload_priv __rcu *next;
 };
@@ -241,13 +242,14 @@ out:
         return segs;
 }
 
-int udp_add_offload(struct udp_offload *uo)
+int udp_add_offload(struct net *net, struct udp_offload *uo)
 {
         struct udp_offload_priv *new_offload = kzalloc(sizeof(*new_offload), GFP_ATOMIC);
 
         if (!new_offload)
                 return -ENOMEM;
 
+        write_pnet(&new_offload->net, net);
         new_offload->offload = uo;
 
         spin_lock(&udp_offload_lock);
@@ -311,7 +313,8 @@ struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
         rcu_read_lock();
         uo_priv = rcu_dereference(udp_offload_base);
         for (; uo_priv != NULL; uo_priv = rcu_dereference(uo_priv->next)) {
-                if (uo_priv->offload->port == uh->dest &&
+                if (net_eq(read_pnet(&uo_priv->net), dev_net(skb->dev)) &&
+                    uo_priv->offload->port == uh->dest &&
                     uo_priv->offload->callbacks.gro_receive)
                         goto unflush;
         }
@@ -389,7 +392,8 @@ int udp_gro_complete(struct sk_buff *skb, int nhoff)
 
         uo_priv = rcu_dereference(udp_offload_base);
         for (; uo_priv != NULL; uo_priv = rcu_dereference(uo_priv->next)) {
-                if (uo_priv->offload->port == uh->dest &&
+                if (net_eq(read_pnet(&uo_priv->net), dev_net(skb->dev)) &&
+                    uo_priv->offload->port == uh->dest &&
                     uo_priv->offload->callbacks.gro_complete)
                         break;
         }