linux-kernel - [PATCH 4.9 093/117] lapb: fixed leak of control-blocks.

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Date:   Thu, 20 Jun 2019 19:57:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+afb980676c836b4a0afa@...kaller.appspotmail.com,
        Jeremy Sowden <jeremy@...zel.net>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.9 093/117] lapb: fixed leak of control-blocks.

From: Jeremy Sowden <jeremy@...zel.net>

[ 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@...kaller.appspotmail.com
Signed-off-by: Jeremy Sowden <jeremy@...zel.net>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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);