tcp: fix possible sk_priority leak in tcp_v4_send_reset()

When tcp_v4_send_reset() is called with @sk == NULL,
we do not change ctl_sk->sk_priority, which could have been
set from a prior invocation.

Change tcp_v4_send_reset() to set sk_priority and sk_mark
fields before calling ip_send_unicast_reply().

This means tcp_v4_send_reset() and tcp_v4_send_ack()
no longer have to clear ctl_sk->sk_mark after
their call to ip_send_unicast_reply().

Fixes: f6c0f5d ("tcp: honor SO_PRIORITY in TIME_WAIT state")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Antoine Tenart <atenart@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: edumazet

net/ipv4/tcp_ipv4.c

@@ -829,14 +829,16 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
 				   inet_twsk(sk)->tw_priority : sk->sk_priority;
 		transmit_time = tcp_transmit_time(sk);
 		xfrm_sk_clone_policy(ctl_sk, sk);
+	} else {
+		ctl_sk->sk_mark = 0;
+		ctl_sk->sk_priority = 0;
 	}
 	ip_send_unicast_reply(ctl_sk,
 			      skb, &TCP_SKB_CB(skb)->header.h4.opt,
 			      ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
 			      &arg, arg.iov[0].iov_len,
 			      transmit_time);
 
-	ctl_sk->sk_mark = 0;
 	xfrm_sk_free_policy(ctl_sk);
 	sock_net_set(ctl_sk, &init_net);
 	__TCP_INC_STATS(net, TCP_MIB_OUTSEGS);
@@ -935,7 +937,6 @@ static void tcp_v4_send_ack(const struct sock *sk,
 			      &arg, arg.iov[0].iov_len,
 			      transmit_time);
 
-	ctl_sk->sk_mark = 0;
 	sock_net_set(ctl_sk, &init_net);
 	__TCP_INC_STATS(net, TCP_MIB_OUTSEGS);
 	local_bh_enable();