tuntap: reset network header before calling skb_get_rxhash()

Commit 499744209b2c (tuntap: dont use skb after netif_rx_ni(skb))
introduced another bug.

skb_get_rxhash() needs to access the network header, and it was
set for us in netif_rx_ni().

We need to reset network header or else skb_flow_dissect() behavior
is out of control.

Reported-and-tested-by: Kirill A. Shutemov <kirill@shutemov.name>
Tested-by: Daniel Borkmann <daniel.borkmann@tik.ee.ethz.ch>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 255a9f574869..173acf5b369a 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1199,6 +1199,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
                 skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
         }
 
+        skb_reset_network_header(skb);
         rxhash = skb_get_rxhash(skb);
         netif_rx_ni(skb);