[PATCH 4.19 05/61] lapb: fixed leak of control-blocks.

From: Greg Kroah-Hartman
Date: Thu Jun 20 2019 - 14:10:23 EST

From: Jeremy Sowden <jeremy@xxxxxxxxxx>

[ Upstream commit 6be8e297f9bcea666ea85ac7a6cd9d52d6deaf92 ]

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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Jeremy Sowden <jeremy@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
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);