Patch "net: llc: add lock_sock in llc_ui_bind to avoid a race condition" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    net: llc: add lock_sock in llc_ui_bind to avoid a race condition

to the 4.4-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:
     net-llc-add-lock_sock-in-llc_ui_bind-to-avoid-a-race-condition.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Tue Apr 10 10:31:53 CEST 2018
From: linzhang <xiaolou4617@gmail.com>
Date: Thu, 25 May 2017 14:07:18 +0800
Subject: net: llc: add lock_sock in llc_ui_bind to avoid a race condition

From: linzhang <xiaolou4617@gmail.com>


[ Upstream commit 0908cf4dfef35fc6ac12329007052ebe93ff1081 ]

There is a race condition in llc_ui_bind if two or more processes/threads
try to bind a same socket.

If more processes/threads bind a same socket success that will lead to
two problems, one is this action is not what we expected, another is
will lead to kernel in unstable status or oops(in my simple test case,
cause llc2.ko can't unload).

The current code is test SOCK_ZAPPED bit to avoid a process to
bind a same socket twice but that is can't avoid more processes/threads
try to bind a same socket at the same time.

So, add lock_sock in llc_ui_bind like others, such as llc_ui_connect.

Signed-off-by: Lin Zhang <xiaolou4617@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/llc/af_llc.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -309,6 +309,8 @@ static int llc_ui_bind(struct socket *so
 	int rc = -EINVAL;
 
 	dprintk("%s: binding %02X\n", __func__, addr->sllc_sap);
+
+	lock_sock(sk);
 	if (unlikely(!sock_flag(sk, SOCK_ZAPPED) || addrlen != sizeof(*addr)))
 		goto out;
 	rc = -EAFNOSUPPORT;
@@ -380,6 +382,7 @@ static int llc_ui_bind(struct socket *so
 out_put:
 	llc_sap_put(sap);
 out:
+	release_sock(sk);
 	return rc;
 }
 


Patches currently in stable-queue which might be from xiaolou4617@gmail.com are

queue-4.4/net-x25-fix-one-potential-use-after-free-issue.patch
queue-4.4/net-llc-add-lock_sock-in-llc_ui_bind-to-avoid-a-race-condition.patch
queue-4.4/net-ieee802154-fix-net_device-reference-release-too-early.patch