[PATCH net] net: fix use-after-free in GRO with ESP

[PATCH net] net: fix use-after-free in GRO with ESP

[Sabrina Dubroca]

Since the addition of GRO for ESP, gro_receive can consume the skb and
return -EINPROGRESS. In that case, the lower layer GRO handler cannot
touch the skb anymore.

Commit 5f114163f2f5 ("net: Add a skb_gro_flush_final helper.") converted
some of the gro_receive handlers that can lead to ESP's gro_receive so
that they wouldn't access the skb when -EINPROGRESS is returned, but
missed other spots, mainly in tunneling protocols.

This patch finishes the conversion to using skb_gro_flush_final(), and
adds a new helper, skb_gro_flush_final_remcsum(), used in VXLAN and
GUE.

Fixes: 5f114163f2f5 ("net: Add a skb_gro_flush_final helper.")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
---
 drivers/net/geneve.c      |  2 +-
 drivers/net/vxlan.c       |  4 +---
 include/linux/netdevice.h | 20 ++++++++++++++++++++
 net/8021q/vlan.c          |  2 +-
 net/ipv4/fou.c            |  4 +---
 net/ipv4/gre_offload.c    |  2 +-
 net/ipv4/udp_offload.c    |  2 +-
 7 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index 750eaa53bf0c..ada33c2d9ac2 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -476,7 +476,7 @@ static struct sk_buff **geneve_gro_receive(struct sock *sk,
 out_unlock:
 	rcu_read_unlock();
 out:
-	NAPI_GRO_CB(skb)->flush |= flush;
+	skb_gro_flush_final(skb, pp, flush);
 
 	return pp;
 }
diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index aee0e60471f1..f6bb1d54d4bd 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -623,9 +623,7 @@ static struct sk_buff **vxlan_gro_receive(struct sock *sk,
 	flush = 0;
 
 out:
-	skb_gro_remcsum_cleanup(skb, &grc);
-	skb->remcsum_offload = 0;
-	NAPI_GRO_CB(skb)->flush |= flush;
+	skb_gro_flush_final_remcsum(skb, pp, flush, &grc);
 
 	return pp;
 }
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3ec9850c7936..3d0cc0b5cec2 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2789,11 +2789,31 @@ static inline void skb_gro_flush_final(struct sk_buff *skb, struct sk_buff **pp,
 	if (PTR_ERR(pp) != -EINPROGRESS)
 		NAPI_GRO_CB(skb)->flush |= flush;
 }
+static inline void skb_gro_flush_final_remcsum(struct sk_buff *skb,
+					       struct sk_buff **pp,
+					       int flush,
+					       struct gro_remcsum *grc)
+{
+	if (PTR_ERR(pp) != -EINPROGRESS) {
+		NAPI_GRO_CB(skb)->flush |= flush;
+		skb_gro_remcsum_cleanup(skb, grc);
+		skb->remcsum_offload = 0;
+	}
+}
 #else
 static inline void skb_gro_flush_final(struct sk_buff *skb, struct sk_buff **pp, int flush)
 {
 	NAPI_GRO_CB(skb)->flush |= flush;
 }
+static inline void skb_gro_flush_final_remcsum(struct sk_buff *skb,
+					       struct sk_buff **pp,
+					       int flush,
+					       struct gro_remcsum *grc)
+{
+	NAPI_GRO_CB(skb)->flush |= flush;
+	skb_gro_remcsum_cleanup(skb, grc);
+	skb->remcsum_offload = 0;
+}
 #endif
 
 static inline int dev_hard_header(struct sk_buff *skb, struct net_device *dev,
diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 73a65789271b..8ccee3d01822 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -693,7 +693,7 @@ static struct sk_buff **vlan_gro_receive(struct sk_buff **head,
 out_unlock:
 	rcu_read_unlock();
 out:
-	NAPI_GRO_CB(skb)->flush |= flush;
+	skb_gro_flush_final(skb, pp, flush);
 
 	return pp;
 }
diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 1540db65241a..c9ec1603666b 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -448,9 +448,7 @@ static struct sk_buff **gue_gro_receive(struct sock *sk,
 out_unlock:
 	rcu_read_unlock();
 out:
-	NAPI_GRO_CB(skb)->flush |= flush;
-	skb_gro_remcsum_cleanup(skb, &grc);
-	skb->remcsum_offload = 0;
+	skb_gro_flush_final_remcsum(skb, pp, flush, &grc);
 
 	return pp;
 }
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index 1859c473b21a..6a7d980105f6 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -223,7 +223,7 @@ static struct sk_buff **gre_gro_receive(struct sk_buff **head,
 out_unlock:
 	rcu_read_unlock();
 out:
-	NAPI_GRO_CB(skb)->flush |= flush;
+	skb_gro_flush_final(skb, pp, flush);
 
 	return pp;
 }
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 92dc9e5a7ff3..69c54540d5b4 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -394,7 +394,7 @@ struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
 out_unlock:
 	rcu_read_unlock();
 out:
-	NAPI_GRO_CB(skb)->flush |= flush;
+	skb_gro_flush_final(skb, pp, flush);
 	return pp;
 }
 EXPORT_SYMBOL(udp_gro_receive);
-- 
2.18.0

Re: [PATCH net] net: fix use-after-free in GRO with ESP

[David Miller]

From: Sabrina Dubroca <sd@queasysnail.net>
Date: Sat, 30 Jun 2018 17:38:55 +0200

> Since the addition of GRO for ESP, gro_receive can consume the skb and
> return -EINPROGRESS. In that case, the lower layer GRO handler cannot
> touch the skb anymore.
> 
> Commit 5f114163f2f5 ("net: Add a skb_gro_flush_final helper.") converted
> some of the gro_receive handlers that can lead to ESP's gro_receive so
> that they wouldn't access the skb when -EINPROGRESS is returned, but
> missed other spots, mainly in tunneling protocols.
> 
> This patch finishes the conversion to using skb_gro_flush_final(), and
> adds a new helper, skb_gro_flush_final_remcsum(), used in VXLAN and
> GUE.
> 
> Fixes: 5f114163f2f5 ("net: Add a skb_gro_flush_final helper.")
> Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
> Reviewed-by: Stefano Brivio <sbrivio@redhat.com>

Applied and queued up for -stable, thank you.