[PATCH] net: qcom/emac: fix UAF in emac_remove

adpt is netdev private data and it cannot be
used after free_netdev() call. Using adpt after free_netdev()
can cause UAF bug. Fix it by moving free_netdev() at the end of the
function.

Fixes: 54e19bc74f33 ("net: qcom/emac: do not use devm on internal phy pdev")
Signed-off-by: Pavel Skripkin <redacted>
---
 drivers/net/ethernet/qualcomm/emac/emac.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/qualcomm/emac/emac.c b/drivers/net/ethernet/qualcomm/emac/emac.c
index 8543bf3c3484..ad655f0a4965 100644
--- a/drivers/net/ethernet/qualcomm/emac/emac.c
+++ b/drivers/net/ethernet/qualcomm/emac/emac.c

@@ -735,12 +735,13 @@ static int emac_remove(struct platform_device *pdev)
 
 	put_device(&adpt->phydev->mdio.dev);
 	mdiobus_unregister(adpt->mii_bus);
-	free_netdev(netdev);
 
 	if (adpt->phy.digital)
 		iounmap(adpt->phy.digital);
 	iounmap(adpt->phy.base);
 
+	free_netdev(netdev);
+
 	return 0;
 }
 

-- 
2.32.0

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Fri,  9 Jul 2021 17:24:18 +0300 you wrote:

adpt is netdev private data and it cannot be
used after free_netdev() call. Using adpt after free_netdev()
can cause UAF bug. Fix it by moving free_netdev() at the end of the
function.

Fixes: 54e19bc74f33 ("net: qcom/emac: do not use devm on internal phy pdev")
Signed-off-by: Pavel Skripkin <redacted>

[...]

Here is the summary with links:
  - net: qcom/emac: fix UAF in emac_remove
    https://git.kernel.org/netdev/net/c/ad297cd2db89

You are awesome, thank you!
--
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On Fri, Jul 9, 2021 at 9:24 AM Pavel Skripkin [off-list ref] wrote:

adpt is netdev private data and it cannot be
used after free_netdev() call. Using adpt after free_netdev()
can cause UAF bug. Fix it by moving free_netdev() at the end of the
function.

Please spell out what "UAF" means, thanks.  If you fix that, then

Acked-by: Timur Tabi <timur@kernel.org>

Thanks.

On Sat, 10 Jul 2021 00:02:26 -0500
Timur Tabi [off-list ref] wrote:

On Fri, Jul 9, 2021 at 9:24 AM Pavel Skripkin [off-list ref]
wrote:

quoted

adpt is netdev private data and it cannot be
used after free_netdev() call. Using adpt after free_netdev()
can cause UAF bug. Fix it by moving free_netdev() at the end of the
function.

Please spell out what "UAF" means, thanks.  If you fix that, then

Acked-by: Timur Tabi <timur@kernel.org>

Thanks.

Hi, Timur!

Thank you for feedback. 


David has already applied this pacth. So, should I send v2 or maybe
revert + v2? I haven't been in such situations yet :)




With regards,
Pavel Skripkin

On Sat, Jul 10, 2021 at 1:57 AM Pavel Skripkin [off-list ref] wrote:

David has already applied this pacth. So, should I send v2 or maybe
revert + v2? I haven't been in such situations yet :)

No, don't worry about it.