diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 0f0f9ce..b181dfb 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -543,6 +543,7 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
 		skb->data_len += len;
 		skb->len += len;
 		skb->truesize += truesize;
+		skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG;
 		atomic_add(truesize, &skb->sk->sk_wmem_alloc);
 		while (len) {
 			int off = base & ~PAGE_MASK;
@@ -598,7 +599,7 @@ static int macvtap_skb_from_vnet_hdr(struct sk_buff *skb,
 
 	if (vnet_hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
 		skb_shinfo(skb)->gso_size = vnet_hdr->gso_size;
-		skb_shinfo(skb)->gso_type = gso_type;
+		skb_shinfo(skb)->gso_type |= gso_type;
 
 		/* Header must be checked, and gso_segs computed. */
 		skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index c81680d..293ce8d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1005,6 +1005,7 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
 		skb->data_len += len;
 		skb->len += len;
 		skb->truesize += truesize;
+		skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG;
 		atomic_add(truesize, &skb->sk->sk_wmem_alloc);
 		while (len) {
 			int off = base & ~PAGE_MASK;
@@ -1150,16 +1151,18 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 	}
 
 	if (gso.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
+		unsigned short gso_type = 0;
+
 		pr_debug("GSO!\n");
 		switch (gso.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
 		case VIRTIO_NET_HDR_GSO_TCPV4:
-			skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
+			gso_type = SKB_GSO_TCPV4;
 			break;
 		case VIRTIO_NET_HDR_GSO_TCPV6:
-			skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
+			gso_type = SKB_GSO_TCPV6;
 			break;
 		case VIRTIO_NET_HDR_GSO_UDP:
-			skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
+			gso_type = SKB_GSO_UDP;
 			break;
 		default:
 			tun->dev->stats.rx_frame_errors++;
@@ -1168,9 +1171,10 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		}
 
 		if (gso.gso_type & VIRTIO_NET_HDR_GSO_ECN)
-			skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
+			gso_type |= SKB_GSO_TCP_ECN;
 
 		skb_shinfo(skb)->gso_size = gso.gso_size;
+		skb_shinfo(skb)->gso_type |= gso_type;
 		if (skb_shinfo(skb)->gso_size == 0) {
 			tun->dev->stats.rx_frame_errors++;
 			kfree_skb(skb);
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 701408a..58914c8 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -220,6 +220,7 @@ static void set_skb_frag(struct sk_buff *skb, struct page *page,
 	skb->len += size;
 	skb->truesize += PAGE_SIZE;
 	skb_shinfo(skb)->nr_frags++;
+	skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG;
 	*len -= size;
 }
 
@@ -379,16 +380,18 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
 		 ntohs(skb->protocol), skb->len, skb->pkt_type);
 
 	if (hdr->hdr.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
+		unsigned short gso_type = 0;
+
 		pr_debug("GSO!\n");
 		switch (hdr->hdr.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
 		case VIRTIO_NET_HDR_GSO_TCPV4:
-			skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
+			gso_type = SKB_GSO_TCPV4;
 			break;
 		case VIRTIO_NET_HDR_GSO_UDP:
-			skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
+			gso_type = SKB_GSO_UDP;
 			break;
 		case VIRTIO_NET_HDR_GSO_TCPV6:
-			skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
+			gso_type = SKB_GSO_TCPV6;
 			break;
 		default:
 			net_warn_ratelimited("%s: bad gso type %u.\n",
@@ -397,7 +400,7 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
 		}
 
 		if (hdr->hdr.gso_type & VIRTIO_NET_HDR_GSO_ECN)
-			skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
+			gso_type |= SKB_GSO_TCP_ECN;
 
 		skb_shinfo(skb)->gso_size = hdr->hdr.gso_size;
 		if (skb_shinfo(skb)->gso_size == 0) {
@@ -405,6 +408,7 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
 			goto frame_err;
 		}
 
+		skb_shinfo(skb)->gso_type |= gso_type;
 		/* Header must be checked, and gso_segs computed. */
 		skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
 		skb_shinfo(skb)->gso_segs = 0;
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 8b2256e..0259b71 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -307,6 +307,13 @@ enum {
 	SKB_GSO_TCPV6 = 1 << 4,
 
 	SKB_GSO_FCOE = 1 << 5,
+
+	/* This indicates at least one fragment might be overwritten
+	 * (as in vmsplice(), sendfile() ...)
+	 * If we need to compute a TX checksum, we'll need to copy
+	 * all frags to avoid possible bad checksum
+	 */
+	SKB_GSO_SHARED_FRAG = 1 << 6,
 };
 
 #if BITS_PER_LONG > 32
@@ -2201,6 +2208,18 @@ static inline int skb_linearize(struct sk_buff *skb)
 }
 
 /**
+ * skb_has_shared_frag - can any frag be overwritten
+ * @skb: buffer to test
+ *
+ * Return true if the skb has at least one frag that might be modified
+ * by an external entity (as in vmsplice()/sendfile())
+ */
+static inline bool skb_has_shared_frag(const struct sk_buff *skb)
+{
+	return skb_shinfo(skb)->gso_type & SKB_GSO_SHARED_FRAG;
+}
+
+/**
  *	skb_linearize_cow - make sure skb is linear and writable
  *	@skb: buffer to process
  *
diff --git a/net/core/dev.c b/net/core/dev.c
index c69cd87..a83375d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2271,6 +2271,15 @@ int skb_checksum_help(struct sk_buff *skb)
 		return -EINVAL;
 	}
 
+	/* Before computing a checksum, we should make sure no frag could
+	 * be modified by an external entity : checksum could be wrong.
+	 */
+	if (skb_has_shared_frag(skb)) {
+		ret = __skb_linearize(skb);
+		if (ret)
+			goto out;
+	}
+
 	offset = skb_checksum_start_offset(skb);
 	BUG_ON(offset >= skb_headlen(skb));
 	csum = skb_checksum(skb, offset, skb->len - offset, 0);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2568c44..bddc1dd 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2340,6 +2340,8 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len)
 {
 	int pos = skb_headlen(skb);
 
+	skb_shinfo(skb1)->gso_type = skb_shinfo(skb)->gso_type;
+
 	if (len < pos)	/* Split line is inside header. */
 		skb_split_inside_header(skb, skb1, len, pos);
 	else		/* Second chunk has no header, nothing to copy. */
@@ -2845,6 +2847,8 @@ struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features)
 		skb_copy_from_linear_data_offset(skb, offset,
 						 skb_put(nskb, hsize), hsize);
 
+		skb_shinfo(nskb)->gso_type = skb_shinfo(skb)->gso_type;
+
 		while (pos < offset + len && i < nfrags) {
 			*frag = skb_shinfo(skb)->frags[i];
 			__skb_frag_ref(frag);
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 4b70539..49ddca3 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1306,6 +1306,7 @@ static struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 		       SKB_GSO_UDP |
 		       SKB_GSO_DODGY |
 		       SKB_GSO_TCP_ECN |
+		       SKB_GSO_SHARED_FRAG |
 		       0)))
 		goto out;
 
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 303012a..af6be70 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -738,7 +738,7 @@ drop:
 static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
-	const struct iphdr  *old_iph = ip_hdr(skb);
+	const struct iphdr  *old_iph;
 	const struct iphdr  *tiph;
 	struct flowi4 fl4;
 	u8     tos;
@@ -756,6 +756,8 @@ static netdev_tx_t ipgre_tunnel_xmit(struct sk_buff *skb, struct net_device *dev
 	    skb_checksum_help(skb))
 		goto tx_error;
 
+	old_iph = ip_hdr(skb);
+
 	if (dev->type == ARPHRD_ETHER)
 		IPCB(skb)->flags = 0;
 
diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c
index 191fc24..8f024d4 100644
--- a/net/ipv4/ipip.c
+++ b/net/ipv4/ipip.c
@@ -472,7 +472,7 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	__be16 df = tiph->frag_off;
 	struct rtable *rt;     			/* Route to the other host */
 	struct net_device *tdev;		/* Device to other host */
-	const struct iphdr  *old_iph = ip_hdr(skb);
+	const struct iphdr  *old_iph;
 	struct iphdr  *iph;			/* Our new IP header */
 	unsigned int max_headroom;		/* The extra header space needed */
 	__be32 dst = tiph->daddr;
@@ -486,6 +486,8 @@ static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev)
 	    skb_checksum_help(skb))
 		goto tx_error;
 
+	old_iph = ip_hdr(skb);
+
 	if (tos & 1)
 		tos = old_iph->tos;
 
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 5227194..3ec1f69 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -896,6 +896,8 @@ new_segment:
 			skb_fill_page_desc(skb, i, page, offset, copy);
 		}
 
+		skb_shinfo(skb)->gso_type |= SKB_GSO_SHARED_FRAG;
+
 		skb->len += copy;
 		skb->data_len += copy;
 		skb->truesize += copy;
@@ -3032,6 +3034,7 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb,
 			       SKB_GSO_DODGY |
 			       SKB_GSO_TCP_ECN |
 			       SKB_GSO_TCPV6 |
+			       SKB_GSO_SHARED_FRAG |
 			       0) ||
 			     !(type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))))
 			goto out;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0905997..492c7cf 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1240,13 +1240,13 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
 	 */
 	if (!skb_shinfo(prev)->gso_size) {
 		skb_shinfo(prev)->gso_size = mss;
-		skb_shinfo(prev)->gso_type = sk->sk_gso_type;
+		skb_shinfo(prev)->gso_type |= sk->sk_gso_type;
 	}
 
 	/* CHECKME: To clear or not to clear? Mimics normal skb currently */
 	if (skb_shinfo(skb)->gso_segs <= 1) {
 		skb_shinfo(skb)->gso_size = 0;
-		skb_shinfo(skb)->gso_type = 0;
+		skb_shinfo(skb)->gso_type &= SKB_GSO_SHARED_FRAG;
 	}
 
 	/* Difference in this won't matter, both ACKed by the same cumul. ACK */
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 667a6ad..367e2ec 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1133,6 +1133,7 @@ static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
 static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
 				 unsigned int mss_now)
 {
+	skb_shinfo(skb)->gso_type &= SKB_GSO_SHARED_FRAG;
 	if (skb->len <= mss_now || !sk_can_gso(sk) ||
 	    skb->ip_summed == CHECKSUM_NONE) {
 		/* Avoid the costly divide in the normal
@@ -1140,11 +1141,10 @@ static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb,
 		 */
 		skb_shinfo(skb)->gso_segs = 1;
 		skb_shinfo(skb)->gso_size = 0;
-		skb_shinfo(skb)->gso_type = 0;
 	} else {
 		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
 		skb_shinfo(skb)->gso_size = mss_now;
-		skb_shinfo(skb)->gso_type = sk->sk_gso_type;
+		skb_shinfo(skb)->gso_type |= sk->sk_gso_type;
 	}
 }
 
diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index f26f0da..d141fc3 100644
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -100,6 +100,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 		       SKB_GSO_DODGY |
 		       SKB_GSO_TCP_ECN |
 		       SKB_GSO_TCPV6 |
+		       SKB_GSO_SHARED_FRAG |
 		       0)))
 		goto out;