[PATCH 5.12 087/178] net: ethernet: fix potential use-after-free in ec_bhf_remove

Greg Kroah-Hartman
2021-06-21T16:44:56Z

From: Pavel Skripkin <paskripkin@gmail.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@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.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 46b0dbab8aad..7c992172933b 100644
--- a/drivers/net/ethernet/ec_bhf.c
+++ b/drivers/net/ethernet/ec_bhf.c
@@ -576,10 +576,12 @@ 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