From: Jeremy Sowden <jeremy@azazel.net>
Date: Sun, 16 Jun 2019 16:54:37 +0100
Subject: lapb: fixed leak of control-blocks.
Git-commit: 6be8e297f9bcea666ea85ac7a6cd9d52d6deaf92
Patch-mainline: 5.2-rc6
References: networking-stable-19_06_18

lapb_register calls lapb_create_cb, which initializes the control-
block's ref-count to one, and __lapb_insert_cb, which increments it when
adding the new block to the list of blocks.

lapb_unregister calls __lapb_remove_cb, which decrements the ref-count
when removing control-block from the list of blocks, and calls lapb_put
itself to decrement the ref-count before returning.

However, lapb_unregister also calls __lapb_devtostruct to look up the
right control-block for the given net_device, and __lapb_devtostruct
also bumps the ref-count, which means that when lapb_unregister returns
the ref-count is still 1 and the control-block is leaked.

Call lapb_put after __lapb_devtostruct to fix leak.

Reported-by: syzbot+afb980676c836b4a0afa@syzkaller.appspotmail.com
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 net/lapb/lapb_iface.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/lapb/lapb_iface.c
+++ b/net/lapb/lapb_iface.c
@@ -182,6 +182,7 @@ int lapb_unregister(struct net_device *d
 	lapb = __lapb_devtostruct(dev);
 	if (!lapb)
 		goto out;
+	lapb_put(lapb);
 
 	lapb_stop_t1timer(lapb);
 	lapb_stop_t2timer(lapb);