linux-kernel - [PATCH v2] net: hso: do not call unregister if not registered

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Date:   Fri, 2 Oct 2020 13:43:23 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     netdev@...r.kernel.org
Cc:     Tuba Yavuz <tuba@....ufl.edu>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Oliver Neukum <oneukum@...e.com>, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: [PATCH v2] net: hso: do not call unregister if not registered

From: Tuba Yavuz <tuba@....ufl.edu>

On an error path inside the hso_create_net_device function of the hso
driver, hso_free_net_device gets called. This causes a use-after-free
and a double-free if register_netdev has not been called yet as
hso_free_net_device calls unregister_netdev regardless. I think the
driver should distinguish these cases and call unregister_netdev only if
register_netdev has been called.

Signed-off-by: Tuba Yavuz <tuba@....ufl.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
v2: format cleaned up based on feedback from previous review
    Forward to Greg to submit due to email problems on Tuba's side

diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
index 2bb28db89432..e6b56bdf691d 100644
--- a/drivers/net/usb/hso.c
+++ b/drivers/net/usb/hso.c
@@ -2366,7 +2366,8 @@ static void hso_free_net_device(struct hso_device *hso_dev, bool bailout)
 
 	remove_net_device(hso_net->parent);
 
-	if (hso_net->net)
+	if (hso_net->net &&
+	    hso_net->net->reg_state == NETREG_REGISTERED)
 		unregister_netdev(hso_net->net);
 
 	/* start freeing */