From: Willem de Bruijn <willemb@google.com>
Date: Fri, 19 Jan 2018 09:29:18 -0500
Subject: gso: validate gso_type in GSO handlers
Patch-mainline: v4.15
Git-commit: 121d57af308d0cf943f08f4738d24d3966c38cd9
References: bsc#1076830

Validate gso_type during segmentation as SKB_GSO_DODGY sources
may pass packets where the gso_type does not match the contents.

Syzkaller was able to enter the SCTP gso handler with a packet of
gso_type SKB_GSO_TCPV4.

On entry of transport layer gso handlers, verify that the gso_type
matches the transport protocol.

Fixes: 90017accff61 ("sctp: Add GSO support")
Link: http://lkml.kernel.org/r/<001a1137452496ffc305617e5fe0@google.com>
Reported-by: syzbot+fee64147a25aecd48055@syzkaller.appspotmail.com
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>

---
 net/ipv4/esp4_offload.c  | 3 +++
 net/ipv4/tcp_offload.c   | 3 +++
 net/ipv4/udp_offload.c   | 3 +++
 net/ipv6/esp6_offload.c  | 3 +++
 net/ipv6/tcpv6_offload.c | 3 +++
 net/ipv6/udp_offload.c   | 3 +++
 net/sctp/offload.c       | 3 +++
 7 files changed, 21 insertions(+)

diff --git a/net/ipv4/esp4_offload.c b/net/ipv4/esp4_offload.c
index 50112324fa5c..227e06d33caf 100644
--- a/net/ipv4/esp4_offload.c
+++ b/net/ipv4/esp4_offload.c
@@ -121,6 +121,9 @@ static struct sk_buff *esp4_gso_segment(struct sk_buff *skb,
 	if (!xo)
 		goto out;
 
+	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_ESP))
+		goto out;
+
 	seq = xo->seq.low;
 
 	x = skb->sp->xvec[skb->sp->len - 1];
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index bc68da38ea86..366b1becff9d 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -32,6 +32,9 @@ static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
 static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
 					netdev_features_t features)
 {
+	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
+		return ERR_PTR(-EINVAL);
+
 	if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
 		return ERR_PTR(-EINVAL);
 
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 01801b77bd0d..ea6e6e7df0ee 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -203,6 +203,9 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 		goto out;
 	}
 
+	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP))
+		goto out;
+
 	if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 		goto out;
 
diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c
index 1cf437f75b0b..be470db6cee2 100644
--- a/net/ipv6/esp6_offload.c
+++ b/net/ipv6/esp6_offload.c
@@ -148,6 +148,9 @@ static struct sk_buff *esp6_gso_segment(struct sk_buff *skb,
 	if (!xo)
 		goto out;
 
+	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_ESP))
+		goto out;
+
 	seq = xo->seq.low;
 
 	x = skb->sp->xvec[skb->sp->len - 1];
diff --git a/net/ipv6/tcpv6_offload.c b/net/ipv6/tcpv6_offload.c
index d883c9204c01..278e49cd67d4 100644
--- a/net/ipv6/tcpv6_offload.c
+++ b/net/ipv6/tcpv6_offload.c
@@ -46,6 +46,9 @@ static struct sk_buff *tcp6_gso_segment(struct sk_buff *skb,
 {
 	struct tcphdr *th;
 
+	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6))
+		return ERR_PTR(-EINVAL);
+
 	if (!pskb_may_pull(skb, sizeof(*th)))
 		return ERR_PTR(-EINVAL);
 
diff --git a/net/ipv6/udp_offload.c b/net/ipv6/udp_offload.c
index a0f89ad76f9d..2a04dc9c781b 100644
--- a/net/ipv6/udp_offload.c
+++ b/net/ipv6/udp_offload.c
@@ -42,6 +42,9 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 		const struct ipv6hdr *ipv6h;
 		struct udphdr *uh;
 
+		if (!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP))
+			goto out;
+
 		if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 			goto out;
 
diff --git a/net/sctp/offload.c b/net/sctp/offload.c
index 275925b93b29..35bc7106d182 100644
--- a/net/sctp/offload.c
+++ b/net/sctp/offload.c
@@ -45,6 +45,9 @@ static struct sk_buff *sctp_gso_segment(struct sk_buff *skb,
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	struct sctphdr *sh;
 
+	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_SCTP))
+		goto out;
+
 	sh = sctp_hdr(skb);
 	if (!pskb_may_pull(skb, sizeof(*sh)))
 		goto out;
-- 
2.16.1