linux-kernel - [PATCH 2/2] net: vxge: fix use-after-free in vxge_device

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Message-Id: <cf7e28fc0aaac4263564db2e21f22b07928fec87.1628091954.git.paskripkin@gmail.com>
Date:   Wed,  4 Aug 2021 18:52:20 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     davem@...emloft.net, kuba@...nel.org, jdmason@...zu.us,
        jesse.brandeburg@...el.com, colin.king@...onical.com
Cc:     dan.carpenter@...cle.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Pavel Skripkin <paskripkin@...il.com>
Subject: [PATCH 2/2] net: vxge: fix use-after-free in vxge_device_unregister

Smatch says:
drivers/net/ethernet/neterion/vxge/vxge-main.c:3518 vxge_device_unregister() error: Using vdev after free_{netdev,candev}(dev);
drivers/net/ethernet/neterion/vxge/vxge-main.c:3518 vxge_device_unregister() error: Using vdev after free_{netdev,candev}(dev);
drivers/net/ethernet/neterion/vxge/vxge-main.c:3520 vxge_device_unregister() error: Using vdev after free_{netdev,candev}(dev);
drivers/net/ethernet/neterion/vxge/vxge-main.c:3520 vxge_device_unregister() error: Using vdev after free_{netdev,candev}(dev);

Since vdev 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

Fixes: 6cca200362b4 ("vxge: cleanup probe error paths")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---
 drivers/net/ethernet/neterion/vxge/vxge-main.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/neterion/vxge/vxge-main.c b/drivers/net/ethernet/neterion/vxge/vxge-main.c
index 82eef4c72f01..7abd13e69471 100644
--- a/drivers/net/ethernet/neterion/vxge/vxge-main.c
+++ b/drivers/net/ethernet/neterion/vxge/vxge-main.c
@@ -3512,13 +3512,13 @@ static void vxge_device_unregister(struct __vxge_hw_device *hldev)
 
 	kfree(vdev->vpaths);
 
-	/* we are safe to free it now */
-	free_netdev(dev);
-
 	vxge_debug_init(vdev->level_trace, "%s: ethernet device unregistered",
 			buf);
 	vxge_debug_entryexit(vdev->level_trace,	"%s: %s:%d  Exiting...", buf,
 			     __func__, __LINE__);
+
+	/* we are safe to free it now */
+	free_netdev(dev);
 }
 
 /*
-- 
2.32.0