[PATCH 3/3] inet: fix improper empty comparison

[Stefan Bader]

From: Josef Bacik <jbacik at fb.com>

BugLink: http://bugs.launchpad.net/bugs/1722702

When doing my reuseport rework I screwed up and changed a

if (hlist_empty(&tb->owners))

to

if (!hlist_empty(&tb->owners))

This is obviously bad as all of the reuseport/reuse logic was reversed,
which caused weird problems like allowing an ipv4 bind conflict if we
opened an ipv4 only socket on a port followed by an ipv6 only socket on
the same port.

Fixes: b9470c27607b ("inet: kill smallest_size and smallest_port")
Reported-by: Cole Robinson <crobinso at redhat.com>
Signed-off-by: Josef Bacik <jbacik at fb.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry-picked from commit fbed24bcc69d3e48c5402c371f19f5c7688871e5)
Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
---
 net/ipv4/inet_connection_sock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index ff8b15a..14469b6 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -321,7 +321,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 			goto fail_unlock;
 	}
 success:
-	if (!hlist_empty(&tb->owners)) {
+	if (hlist_empty(&tb->owners)) {
 		tb->fastreuse = reuse;
 		if (sk->sk_reuseport) {
 			tb->fastreuseport = FASTREUSEPORT_ANY;
-- 
2.7.4