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

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

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

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2316,6 +2316,12 @@ 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;
 }


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