Patch "tcp: release sk_frag.page in tcp_disconnect" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

tcp: release sk_frag.page in tcp_disconnect

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tcp-release-sk_frag.page-in-tcp_disconnect.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Li RongQing <[email protected]>
Date: Fri, 26 Jan 2018 16:40:41 +0800
Subject: tcp: release sk_frag.page in tcp_disconnect

From: Li RongQing <[email protected]>

[ 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

---
 net/ipv4/tcp.c |    6 ++++++
 1 file changed, 6 insertions(+)

@@ -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;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/tcp-release-sk_frag.page-in-tcp_disconnect.patch