Subject: [PATCH 06/18] tcp: release sk_frag.page in tcp_disconnect

From: Li RongQing <[email-masked]>
Date: Fri, 26 Jan 2018 16:40:41 +0800

[ 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 <[email-masked]>
Cc: Eric Dumazet <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/ipv4/tcp.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 8e053ad7cae2..c821f5d68720 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2434,6 +2434,12 @@ int tcp_disconnect(struct sock *sk, int flags)
 
 	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;
 }
-- 
2.14.3