[PATCH 4.14 21/52] tcp: use IPCB instead of TCP_SKB_CB in inet_exact_dif_match()

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Ahern <dsahern@xxxxxxxxx>


[ Usptream commit b4d1605a8ea608fd7dc45b926a05d75d340bde4b ]

After this fix : ("tcp: add tcp_v4_fill_cb()/tcp_v4_restore_cb()"),
socket lookups happen while skb->cb[] has not been mangled yet by TCP.

Fixes: a04a480d4392 ("net: Require exact match for TCP socket lookups if dif is l3mdev")
Signed-off-by: David Ahern <dsahern@xxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 include/net/tcp.h |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -874,12 +874,11 @@ static inline int tcp_v6_sdif(const stru
 }
 #endif
 
-/* TCP_SKB_CB reference means this can not be used from early demux */
 static inline bool inet_exact_dif_match(struct net *net, struct sk_buff *skb)
 {
 #if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
 	if (!net->ipv4.sysctl_tcp_l3mdev_accept &&
-	    skb && ipv4_l3mdev_skb(TCP_SKB_CB(skb)->header.h4.flags))
+	    skb && ipv4_l3mdev_skb(IPCB(skb)->flags))
 		return true;
 #endif
 	return false;