[PATCH net] tcp: fix a request socket leak

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

While the cited commit fixed a possible deadlock, it added a leak
of the request socket, since reqsk_put() must be called if the BPF
filter decided the ACK packet must be dropped.

Fixes: d624d276d1dd ("tcp: fix possible deadlock in TCP stack vs BPF filter")
Signed-off-by: Eric Dumazet <eduma...@google.com>
---
David, this is a stable candidate (linux-4.13 has this bug)

 net/ipv4/tcp_ipv4.c |    6 +++---
 net/ipv6/tcp_ipv6.c |    6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 
a63486afa7a7e7b4dce88b65bc27cfa872a3ba2f..d9416b5162bc1bdd1acd34fcb4da21cb6b62d0ae
 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1669,9 +1669,9 @@ int tcp_v4_rcv(struct sk_buff *skb)
                 */
                sock_hold(sk);
                refcounted = true;
-               if (tcp_filter(sk, skb))
-                       goto discard_and_relse;
-               nsk = tcp_check_req(sk, skb, req, false);
+               nsk = NULL;
+               if (!tcp_filter(sk, skb))
+                       nsk = tcp_check_req(sk, skb, req, false);
                if (!nsk) {
                        reqsk_put(req);
                        goto discard_and_relse;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 
38f76d8b231e3e5923ad72d05b8d320b6aeb850f..64d94afa427f81fd7a505b1cfd1c0be66c273810
 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1460,9 +1460,9 @@ static int tcp_v6_rcv(struct sk_buff *skb)
                }
                sock_hold(sk);
                refcounted = true;
-               if (tcp_filter(sk, skb))
-                       goto discard_and_relse;
-               nsk = tcp_check_req(sk, skb, req, false);
+               nsk = NULL;
+               if (!tcp_filter(sk, skb))
+                       nsk = tcp_check_req(sk, skb, req, false);
                if (!nsk) {
                        reqsk_put(req);
                        goto discard_and_relse;