linux-kernel - [PATCH] net: dpaa2-eth: fix use-after-free in dpaa2_eth

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Message-Id: <20211113172013.19959-1-paskripkin@gmail.com>
Date:   Sat, 13 Nov 2021 20:20:13 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     ioana.ciornei@....com, davem@...emloft.net, kuba@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Pavel Skripkin <paskripkin@...il.com>, stable@...r.kernel.org,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: [PATCH] net: dpaa2-eth: fix use-after-free in dpaa2_eth_remove

Access to netdev after free_netdev() will cause use-after-free bug.
Move debug log before free_netdev() call to avoid it.

Cc: stable@...r.kernel.org # v4.19+
Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
---

Note about Fixes: tag. The commit introduced it was before this driver
was moved out from staging. I guess, Fixes tag cannot be used here.
Please, let me know if I am wrong.

Cc: Dan Carpenter <dan.carpenter@...cle.com>

@Dan, is there a smatch checker for straigthforward use after free bugs?
Like acessing pointer after free was called? I think, adding
free_netdev() to check list might be good idea

I've skimmed througth smatch source and didn't find one, so can you,
please, point out to it if it exists.

With regards,
Pavel Skripkin

---
 drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index e0c3c58e2ac7..abd833d94eb3 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -4540,10 +4540,10 @@ static int dpaa2_eth_remove(struct fsl_mc_device *ls_dev)

 	fsl_mc_portal_free(priv->mc_io);

-	free_netdev(net_dev);
-
 	dev_dbg(net_dev->dev.parent, "Removed interface %s\n", net_dev->name);

+	free_netdev(net_dev);
+
 	return 0;
 }

-- 
2.33.1