From: Willem de Bruijn <willemb@google.com>
Date: Sun, 30 Dec 2018 22:21:05 +0000 (-0500)
Subject: tap: call skb_probe_transport_header after setting skb->dev
X-Git-Tag: v5.0-rc1~49^2~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8c76e77f9069f10505c08e02646c3ee11ad79038;p=thirdparty%2Flinux.git

tap: call skb_probe_transport_header after setting skb->dev

The BPF flow dissector expects either skb->sk or skb->dev set on
all skbs. Delay flow dissection until after skb->dev is set.

This requires calling from within an rcu read-side critical section.
That is fine, see also the call from tun_xdp_one.

Fixes: d0e13a1488ad ("flow_dissector: lookup netns by skb->sk if skb->dev is NULL")
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 443b2694130cd..c0b52e48f0e63 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -1177,8 +1177,6 @@ static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
 			goto err_kfree;
 	}
 
-	skb_probe_transport_header(skb, ETH_HLEN);
-
 	/* Move network header to the right position for VLAN tagged packets */
 	if ((skb->protocol == htons(ETH_P_8021Q) ||
 	     skb->protocol == htons(ETH_P_8021AD)) &&
@@ -1189,6 +1187,7 @@ static int tap_get_user_xdp(struct tap_queue *q, struct xdp_buff *xdp)
 	tap = rcu_dereference(q->tap);
 	if (tap) {
 		skb->dev = tap->dev;
+		skb_probe_transport_header(skb, ETH_HLEN);
 		dev_queue_xmit(skb);
 	} else {
 		kfree_skb(skb);