[PATCH 4.15 06/23] tcp: release sk_frag.page in tcp_disconnect

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Li RongQing <lirongqing@baidu.com>


[ Upstream commit 9b42d55a66d388e4dd5550107df051a9637564fc ]

socket can be disconnected and gets transformed back to a listening
socket, if sk_frag.page is not released, which will be cloned into
a new socket by sk_clone_lock, but the reference count of this page
is increased, lead to a use after free or double free issue

Signed-off-by: Li RongQing <lirongqing@baidu.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/tcp.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2434,6 +2434,12 @@ int tcp_disconnect(struct sock *sk, int
 
 	WARN_ON(inet->inet_num && !icsk->icsk_bind_hash);
 
+	if (sk->sk_frag.page) {
+		put_page(sk->sk_frag.page);
+		sk->sk_frag.page = NULL;
+		sk->sk_frag.offset = 0;
+	}
+
 	sk->sk_error_report(sk);
 	return err;
 }