netdev - [PATCH 1/2] net/x25: Fix x25_neigh refcnt leak when x25

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Message-Id: <1587618822-13544-1-git-send-email-xiyuyang19@fudan.edu.cn>
Date:   Thu, 23 Apr 2020 13:13:40 +0800
From:   Xiyu Yang <xiyuyang19@...an.edu.cn>
To:     Andrew Hendry <andrew.hendry@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Martin Schiller <ms@....tdt.de>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-x25@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, kjlu@....edu,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH 1/2] net/x25: Fix x25_neigh refcnt leak when x25_connect() fails

x25_connect() invokes x25_get_neigh(), which returns a reference of the
specified x25_neigh object to "x25->neighbour" with increased refcnt.

When x25_connect() returns, local variable "x25" and "x25->neighbour"
become invalid, so the refcount should be decreased to keep refcount
balanced.

The reference counting issue happens in one exception handling path of
x25_connect(). When sock state is not TCP_ESTABLISHED and its flags
include O_NONBLOCK, the function forgets to decrease the refcnt
increased by x25_get_neigh(), causing a refcnt leak.

Fix this issue by jumping to "out_put_neigh" label when x25_connect()
fails.

Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 net/x25/af_x25.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index d5b09bbff375..e6571c56209b 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -816,7 +816,7 @@ static int x25_connect(struct socket *sock, struct sockaddr *uaddr,
 	/* Now the loop */
 	rc = -EINPROGRESS;
 	if (sk->sk_state != TCP_ESTABLISHED && (flags & O_NONBLOCK))
-		goto out;
+		goto out_put_neigh;

 	rc = x25_wait_for_connection_establishment(sk);
 	if (rc)
-- 
2.7.4