linux-kernel - [PATCH 4.4 28/57] net: ethernet: fix potential use-after-free in ec_bhf

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Date:   Mon, 28 Jun 2021 10:42:27 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Pavel Skripkin <paskripkin@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 28/57] net: ethernet: fix potential use-after-free in ec_bhf_remove

From: Pavel Skripkin <paskripkin@...il.com>

[ Upstream commit 9cca0c2d70149160407bda9a9446ce0c29b6e6c6 ]

static void ec_bhf_remove(struct pci_dev *dev)
{
...
	struct ec_bhf_priv *priv = netdev_priv(net_dev);

	unregister_netdev(net_dev);
	free_netdev(net_dev);

	pci_iounmap(dev, priv->dma_io);
	pci_iounmap(dev, priv->io);
...
}

priv is netdev private data, but it is used
after free_netdev(). It can cause use-after-free when accessing priv
pointer. So, fix it by moving free_netdev() after pci_iounmap()
calls.

Fixes: 6af55ff52b02 ("Driver for Beckhoff CX5020 EtherCAT master module.")
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/ec_bhf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ec_bhf.c b/drivers/net/ethernet/ec_bhf.c
index f7b42483921c..0ade0c6d81ee 100644
--- a/drivers/net/ethernet/ec_bhf.c
+++ b/drivers/net/ethernet/ec_bhf.c
@@ -589,10 +589,12 @@ static void ec_bhf_remove(struct pci_dev *dev)
 	struct ec_bhf_priv *priv = netdev_priv(net_dev);
 
 	unregister_netdev(net_dev);
-	free_netdev(net_dev);
 
 	pci_iounmap(dev, priv->dma_io);
 	pci_iounmap(dev, priv->io);
+
+	free_netdev(net_dev);
+
 	pci_release_regions(dev);
 	pci_clear_master(dev);
 	pci_disable_device(dev);
-- 
2.30.2