net: skb_fclone_busy() needs to detect orphaned skb

commit 39bb5e62 upstream.

Some drivers are unable to perform TX completions in a bound time.
They instead call skb_orphan()

Problem is skb_fclone_busy() has to detect this case, otherwise
we block TCP retransmits and can freeze unlucky tcp sessions on
mostly idle hosts.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: 1f3279ae ("tcp: avoid retransmits of TCP packets hanging in host queues")
Signed-off-by: David S. Miller <davem@davemloft.net>
[ luis: backport to 3.16 provided by Eric Dumzet ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

net/ipv4/tcp_output.c

@@ -2082,7 +2082,8 @@ static bool skb_still_in_host_queue(const struct sock *sk,
 	const struct sk_buff *fclone = skb + 1;
 
 	if (unlikely(skb->fclone == SKB_FCLONE_ORIG &&
-		     fclone->fclone == SKB_FCLONE_CLONE)) {
+		     fclone->fclone == SKB_FCLONE_CLONE &&
+		     fclone->sk == sk)) {
 		NET_INC_STATS_BH(sock_net(sk),
 				 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES);
 		return true;