tun: Fix TUN_PKT_STRIP setting

We set the flag TUN_PKT_STRIP if the user buffer provided is too
small to contain the entire packet plus meta-data.  However, this
has been broken ever since we added GSO meta-data.  VLAN acceleration
also has the same problem.

This patch fixes this by taking both into account when setting the
TUN_PKT_STRIP flag.

The fact that this has been broken for six years without anyone
realising means that nobody actually uses this flag.

Fixes: f43798c27684 ("tun: Allow GSO using virtio_net_hdr")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 57e6bf7..9dd3746 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1236,15 +1236,19 @@ static ssize_t tun_put_user(struct tun_struct *tun,
        ssize_t total = 0;
        int vlan_offset = 0, copied;
        int vlan_hlen = 0;
+       int vnet_hdr_sz = 0;
 
        if (vlan_tx_tag_present(skb))
                vlan_hlen = VLAN_HLEN;
 
+       if (tun->flags & TUN_VNET_HDR)
+               vnet_hdr_sz = tun->vnet_hdr_sz;
+
        if (!(tun->flags & TUN_NO_PI)) {
                if ((len -= sizeof(pi)) < 0)
                        return -EINVAL;
 
-               if (len < skb->len) {
+               if (len < skb->len + vlan_hlen + vnet_hdr_sz) {
                        /* Packet will be striped */
                        pi.flags |= TUN_PKT_STRIP;
                }
@@ -1254,9 +1258,9 @@ static ssize_t tun_put_user(struct tun_struct *tun,
                total += sizeof(pi);
        }
 
-       if (tun->flags & TUN_VNET_HDR) {
+       if (vnet_hdr_sz) {
                struct virtio_net_hdr gso = { 0 }; /* no info leak */
-               if ((len -= tun->vnet_hdr_sz) < 0)
+               if ((len -= vnet_hdr_sz) < 0)
                        return -EINVAL;
 
                if (skb_is_gso(skb)) {
@@ -1298,7 +1302,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
                if (unlikely(memcpy_toiovecend(iv, (void *)&gso, total,
                                               sizeof(gso))))
                        return -EFAULT;
-               total += tun->vnet_hdr_sz;
+               total += vnet_hdr_sz;
        }
 
        copied = total;