net: add recursion limit to GRO

[ Debian: net-add-recursion-limit-to-gro.patch ]

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.

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>
Signed-off-by: Philipp Hahn <hahn@univention.de>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 940f78e419932824d9c2132a2fb8313cf995a0e4..d9e873c3a273d8d9e0944d8640b93313c5c85745 100644 (file)
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -635,7 +635,7 @@ static struct sk_buff **vxlan_gro_receive(struct sk_buff **head,
                }
        }
 
-       pp = eth_gro_receive(head, skb);
+       pp = call_gro_receive(eth_gro_receive, head, skb);
 
 out:
        skb_gro_remcsum_cleanup(skb, &grc);

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 6c86c7edafa7186b6c125996b6776b77f575ae20..ddd47c3a757d359fb5f7235e87fb857cee18b432 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1957,7 +1957,10 @@ struct napi_gro_cb {
        /* Used in foo-over-udp, set in udp[46]_gro_receive */
        u8      is_ipv6:1;
 
-       /* 7 bit hole */
+       /* Number of gro_receive callbacks this packet already went through */
+       u8 recursion_counter:4;
+
+       /* 3 bit hole */
 
        /* used to support CHECKSUM_COMPLETE for tunneling protocols */
        __wsum  csum;
@@ -1968,6 +1971,25 @@ struct napi_gro_cb {
 
 #define NAPI_GRO_CB(skb) ((struct napi_gro_cb *)(skb)->cb)
 
+#define GRO_RECURSION_LIMIT 15
+static inline int gro_recursion_inc_test(struct sk_buff *skb)
+{
+       return ++NAPI_GRO_CB(skb)->recursion_counter == GRO_RECURSION_LIMIT;
+}
+
+typedef struct sk_buff **(*gro_receive_t)(struct sk_buff **, struct sk_buff *);
+static inline struct sk_buff **call_gro_receive(gro_receive_t cb,
+                                               struct sk_buff **head,
+                                               struct sk_buff *skb)
+{
+       if (gro_recursion_inc_test(skb)) {
+               NAPI_GRO_CB(skb)->flush |= 1;
+               return NULL;
+       }
+
+       return cb(head, skb);
+}
+
 struct packet_type {
        __be16                  type;   /* This is really htons(ether_type). */
        struct net_device       *dev;   /* NULL is wildcarded here           */

diff --git a/net/core/dev.c b/net/core/dev.c
index 185a3398c651d51f9b2ce461e1d818d21a3e7d09..56d820fc270721a2140164c0fab583aad31ff30b 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4060,6 +4060,7 @@ 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)->udp_mark = 0;
+               NAPI_GRO_CB(skb)->recursion_counter = 0;
                NAPI_GRO_CB(skb)->gro_remcsum_start = 0;
 
                /* Setup for GRO checksum validation */

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index f3bad41d725f449f91d0b1b4f7119a9c9660e976..76f8389eacd27ac29624a6e2b08c4d597aaa460d 100644 (file)
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -434,7 +434,7 @@ 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 0cc98b135b8fe87a63b8ea9868091f33da856785..2095cd6c31fd6f4cefaf9b0dbd6ffbfb2ce7ba62 100644 (file)
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1377,7 +1377,7 @@ static struct sk_buff **inet_gro_receive(struct sk_buff **head,
        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 4b67937692c99b1b3dcb0a499072c539003a9581..b22a75c0a3d93c1fbb2b71ad4132d2ad85526b12 100644 (file)
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -188,7 +188,7 @@ static struct sk_buff **fou_gro_receive(struct sk_buff **head,
        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();
@@ -355,7 +355,7 @@ static struct sk_buff **gue_gro_receive(struct sk_buff **head,
        if (WARN_ON(!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();

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 5a8ee3282550880a7749b8d6a9086dc413661519..53300b88d5694f617eddade46812efbbfb1001f1 100644 (file)
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -214,7 +214,7 @@ 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);
 
 out_unlock:
        rcu_read_unlock();

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index f9386160cbee0288e294ea2cd8ba3b5be65cdbf6..2af7b7e1a0f6da91f3d39849131b7383ea57d6ea 100644 (file)
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -339,8 +339,13 @@ unflush:
        skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
        skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
        NAPI_GRO_CB(skb)->proto = uo_priv->offload->ipproto;
-       pp = uo_priv->offload->callbacks.gro_receive(head, skb,
-                                                    uo_priv->offload);
+
+       if (gro_recursion_inc_test(skb)) {
+               pp = NULL;
+       } else {
+               pp = uo_priv->offload->callbacks.gro_receive(head, skb,
+                                                            uo_priv->offload);
+       }
 
 out_unlock:
        rcu_read_unlock();

diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index 08b62047c67f311ca808533cb7a83b5caab0cfc8..db0b8428d248fb500f8c63507fe192c2df3a63dd 100644 (file)
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -247,7 +247,7 @@ 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();