net: add recursion limit to GRO

Currently, GRO can do unlimited recursion through the gro_receive
handlers.  This was fixed for tunneling protocols by limiting tunnel GRO
to one level with encap_mark, but both VLAN and TEB still have this
problem.  Thus, the kernel is vulnerable to a stack overflow, if we
receive a packet composed entirely of VLAN headers.

This patch adds a recursion counter to the GRO layer to prevent stack
overflow.  When a gro_receive function hits the recursion limit, GRO is
aborted for this skb and it is processed normally.  This recursion
counter is put in the GRO CB, but could be turned into a percpu counter
if we run out of space in the CB.

Thanks to Vladimír Beneš <vbenes@redhat.com> for the initial bug report.

Fixes: CVE-2016-7039
Fixes: 9b174d88c257 ("net: Add Transparent Ethernet Bridging GRO support.")
Fixes: 66e5133f19e9 ("vlan: Add GRO support for non hardware accelerated vlan")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Jiri Benc <jbenc@redhat.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

8 files changed, 9 insertions, 8 deletions

diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 8de138d3306bd..f2531ad66b68b 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -664,7 +664,7 @@ static struct sk_buff **vlan_gro_receive(struct sk_buff **head,
 
 	skb_gro_pull(skb, sizeof(*vhdr));
 	skb_gro_postpull_rcsum(skb, vhdr, sizeof(*vhdr));
-	pp = ptype->callbacks.gro_receive(head, skb);
+	pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
 
 out_unlock:
 	rcu_read_unlock();
diff --git a/net/core/dev.c b/net/core/dev.c
index b09ac57f43483..dbc8713069107 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4511,6 +4511,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
 		NAPI_GRO_CB(skb)->flush = 0;
 		NAPI_GRO_CB(skb)->free = 0;
 		NAPI_GRO_CB(skb)->encap_mark = 0;
+		NAPI_GRO_CB(skb)->recursion_counter = 0;
 		NAPI_GRO_CB(skb)->is_fou = 0;
 		NAPI_GRO_CB(skb)->is_atomic = 1;
 		NAPI_GRO_CB(skb)->gro_remcsum_start = 0;
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 66dff5e3d7728..02acfff36028b 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -439,7 +439,7 @@ struct sk_buff **eth_gro_receive(struct sk_buff **head,
 
 	skb_gro_pull(skb, sizeof(*eh));
 	skb_gro_postpull_rcsum(skb, eh, sizeof(*eh));
-	pp = ptype->callbacks.gro_receive(head, skb);
+	pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
 
 out_unlock:
 	rcu_read_unlock();
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 1effc986739e5..9648c97e541f0 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1391,7 +1391,7 @@ struct sk_buff **inet_gro_receive(struct sk_buff **head, struct sk_buff *skb)
 	skb_gro_pull(skb, sizeof(*iph));
 	skb_set_transport_header(skb, skb_gro_offset(skb));
 
-	pp = ops->callbacks.gro_receive(head, skb);
+	pp = call_gro_receive(ops->callbacks.gro_receive, head, skb);
 
 out_unlock:
 	rcu_read_unlock();
diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index cf50f7e2b0124..030d1531e897a 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -249,7 +249,7 @@ static struct sk_buff **fou_gro_receive(struct sock *sk,
 	if (!ops || !ops->callbacks.gro_receive)
 		goto out_unlock;
 
-	pp = ops->callbacks.gro_receive(head, skb);
+	pp = call_gro_receive(ops->callbacks.gro_receive, head, skb);
 
 out_unlock:
 	rcu_read_unlock();
@@ -441,7 +441,7 @@ next_proto:
 	if (WARN_ON_ONCE(!ops || !ops->callbacks.gro_receive))
 		goto out_unlock;
 
-	pp = ops->callbacks.gro_receive(head, skb);
+	pp = call_gro_receive(ops->callbacks.gro_receive, head, skb);
 	flush = 0;
 
 out_unlock:
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 96e0efecefa6a..d5cac99170b19 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -229,7 +229,7 @@ static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 	/* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 	skb_gro_postpull_rcsum(skb, greh, grehlen);
 
-	pp = ptype->callbacks.gro_receive(head, skb);
+	pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
 	flush = 0;
 
 out_unlock:
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index f9333c9636076..b2be1d9757efb 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -295,7 +295,7 @@ unflush:
 
 	skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
 	skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
-	pp = udp_sk(sk)->gro_receive(sk, head, skb);
+	pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);
 
 out_unlock:
 	rcu_read_unlock();
diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index e7bfd55899a34..1fcf61f1cbc33 100644
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -246,7 +246,7 @@ static struct sk_buff **ipv6_gro_receive(struct sk_buff **head,
 
 	skb_gro_postpull_rcsum(skb, iph, nlen);
 
-	pp = ops->callbacks.gro_receive(head, skb);
+	pp = call_gro_receive(ops->callbacks.gro_receive, head, skb);
 
 out_unlock:
 	rcu_read_unlock();