linux-kernel - [PATCH 5.4 32/85] net: fec: fix use-after-free in fec_drv

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Date:   Tue, 10 Aug 2021 19:30:05 +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, Dan Carpenter <dan.carpenter@...cle.com>,
        Pavel Skripkin <paskripkin@...il.com>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 32/85] net: fec: fix use-after-free in fec_drv_remove

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

[ Upstream commit 44712965bf12ae1758cec4de53816ed4b914ca1a ]

Smatch says:
	drivers/net/ethernet/freescale/fec_main.c:3994 fec_drv_remove() error: Using fep after free_{netdev,candev}(ndev);
	drivers/net/ethernet/freescale/fec_main.c:3995 fec_drv_remove() error: Using fep after free_{netdev,candev}(ndev);

Since fep pointer is netdev private data, accessing it after free_netdev()
call can cause use-after-free bug. Fix it by moving free_netdev() call at
the end of the function

Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Fixes: a31eda65ba21 ("net: fec: fix clock count mis-match")
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
Reviewed-by: Joakim Zhang <qiangqing.zhang@....com>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@...el.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/freescale/fec_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index b1856552ab81..a53c2d637a97 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -3781,13 +3781,13 @@ fec_drv_remove(struct platform_device *pdev)
 	if (of_phy_is_fixed_link(np))
 		of_phy_deregister_fixed_link(np);
 	of_node_put(fep->phy_node);
-	free_netdev(ndev);
 
 	clk_disable_unprepare(fep->clk_ahb);
 	clk_disable_unprepare(fep->clk_ipg);
 	pm_runtime_put_noidle(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 
+	free_netdev(ndev);
 	return 0;
 }
 
-- 
2.30.2