ipv6: tcp: add rcu locking in tcp_v6_send_synack()

When first SYNACK is sent, we already hold rcu_read_lock(), but this is not true if a SYNACK is retransmitted, as a timer (soft) interrupt does not hold rcu_read_lock() Fixes: 45f6fad ("ipv6: add complete rcu protection around np->opt") Reported-by: Dave Jones <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Signed-off-by: David S. Miller <[email protected]>
akeromi · Jan 11, 2016 · 3e4006f · 3e4006f
1 parent 320f1a4
commit 3e4006f
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
@@ -462,8 +462,10 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
 		if (np->repflow && ireq->pktopts)
 			fl6->flowlabel = ip6_flowlabel(ipv6_hdr(ireq->pktopts));
 
+		rcu_read_lock();
 		err = ip6_xmit(sk, skb, fl6, rcu_dereference(np->opt),
 			       np->tclass);
+		rcu_read_unlock();
 		err = net_xmit_eval(err);
 	}