13 files changed, 65 insertions, 15 deletions

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 0f0f9ce3a776..b181dfb3d6d6 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 c81680dc10eb..293ce8dfc9e6 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 701408a1ded6..58914c8ea68f 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 8b2256e880e0..0259b719bebf 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 c69cd8721b28..a83375d3af72 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 2568c449fe36..bddc1dd2e7f2 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 4b7053919976..49ddca31c4da 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 303012adf9e6..af6be70821c4 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 191fc24a745a..8f024d41eefa 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 52271947a471..3ec1f69c5ceb 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 0905997e5873..492c7cfe1453 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 667a6adfccf8..367e2ec01da1 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 f26f0da7f095..d141fc32a2ea 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;