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From fabaaaa96d54077b4a9f2c811e55dc09ff2874db Mon Sep 17 00:00:00 2001
From: Sabrina Dubroca <sd@queasysnail.net>
Date: Wed, 14 Dec 2016 13:24:55 +0100
Subject: [PATCH] net: add recursion limit to GRO
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
[ 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
Upstream-Status: Backport
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>
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
---
drivers/net/vxlan.c | 2 +-
include/linux/netdevice.h | 24 +++++++++++++++++++++++-
net/core/dev.c | 1 +
net/ethernet/eth.c | 2 +-
net/ipv4/af_inet.c | 2 +-
net/ipv4/fou.c | 4 ++--
net/ipv4/gre_offload.c | 2 +-
net/ipv4/udp_offload.c | 9 +++++++--
net/ipv6/ip6_offload.c | 2 +-
9 files changed, 38 insertions(+), 10 deletions(-)
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 940f78e..d9e873c 100644
--- 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 6c86c7e..ddd47c3a 100644
--- 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 185a339..56d820f 100644
--- 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 f3bad41..76f8389 100644
--- 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 0cc98b1..2095cd6 100644
--- 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 4b67937..b22a75c0 100644
--- 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 5a8ee32..53300b8 100644
--- 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 f938616..2af7b7e 100644
--- 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 08b6204..db0b842 100644
--- 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();
--
2.7.4
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