[PATCH net] tcp: fix a request socket leak

From: Eric Dumazet <edumazet@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 <edumazet@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;

On Fri, Sep 08, 2017 at 12:44:47PM -0700, Eric Dumazet wrote:

From: Eric Dumazet <edumazet@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 <edumazet@google.com>
---
David, this is a stable candidate (linux-4.13 has this bug)

Thanks for the fix
Acked-by: Alexei Starovoitov <ast@kernel.org>
.. since the fix makes sense to me and as a reminder not to forget
to backport it as well :)

From: Alexei Starovoitov <redacted>
Date: Fri, 8 Sep 2017 15:59:23 -0700

On Fri, Sep 08, 2017 at 12:44:47PM -0700, Eric Dumazet wrote:

quoted

From: Eric Dumazet <edumazet@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 <edumazet@google.com>
---
David, this is a stable candidate (linux-4.13 has this bug)

Thanks for the fix
Acked-by: Alexei Starovoitov <ast@kernel.org>
.. since the fix makes sense to me and as a reminder not to forget
to backport it as well :)

Applied and queued up for -stable.