commit 79a1f0ccdbb4ad700590f61b00525b390cb53905
author Hangbin Liu <liuhangbin@gmail.com> Mon Jun 01 11:55:03 2020 +0800
committer David S. Miller <davem@davemloft.net> Mon Jun 01 15:47:04 2020 -0700
tree e7d884a2296980bf2d4103707d86be33ebcddf8c
parent 4c21daae3dbc9f8536cc18e6e53627821fa2c90c

ipv6: fix IPV6_ADDRFORM operation logic

Socket option IPV6_ADDRFORM supports UDP/UDPLITE and TCP at present.
Previously the checking logic looks like:
if (sk->sk_protocol == IPPROTO_UDP || sk->sk_protocol == IPPROTO_UDPLITE)
	do_some_check;
else if (sk->sk_protocol != IPPROTO_TCP)
	break;

After commit b6f6118901d1 ("ipv6: restrict IPV6_ADDRFORM operation"), TCP
was blocked as the logic changed to:
if (sk->sk_protocol == IPPROTO_UDP || sk->sk_protocol == IPPROTO_UDPLITE)
	do_some_check;
else if (sk->sk_protocol == IPPROTO_TCP)
	do_some_check;
	break;
else
	break;

Then after commit 82c9ae440857 ("ipv6: fix restrict IPV6_ADDRFORM operation")
UDP/UDPLITE were blocked as the logic changed to:
if (sk->sk_protocol == IPPROTO_UDP || sk->sk_protocol == IPPROTO_UDPLITE)
	do_some_check;
if (sk->sk_protocol == IPPROTO_TCP)
	do_some_check;

if (sk->sk_protocol != IPPROTO_TCP)
	break;

Fix it by using Eric's code and simply remove the break in TCP check, which
looks like:
if (sk->sk_protocol == IPPROTO_UDP || sk->sk_protocol == IPPROTO_UDPLITE)
	do_some_check;
else if (sk->sk_protocol == IPPROTO_TCP)
	do_some_check;
else
	break;

Fixes: 82c9ae440857 ("ipv6: fix restrict IPV6_ADDRFORM operation")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ipv6_sockglue.c

diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index adbfed6..2c843ff 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -218,14 +218,15 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 					retv = -EBUSY;
 					break;
 				}
-			}
-			if (sk->sk_protocol == IPPROTO_TCP &&
-			    sk->sk_prot != &tcpv6_prot) {
-				retv = -EBUSY;
+			} else if (sk->sk_protocol == IPPROTO_TCP) {
+				if (sk->sk_prot != &tcpv6_prot) {
+					retv = -EBUSY;
+					break;
+				}
+			} else {
 				break;
 			}
-			if (sk->sk_protocol != IPPROTO_TCP)
-				break;
+
 			if (sk->sk_state != TCP_ESTABLISHED) {
 				retv = -ENOTCONN;
 				break;