Re: [PATCH] net: ethernet: mediatek: add NULL check on of_match_device() return value

From: Gustavo A. R. Silva
Date: Fri Jul 07 2017 - 16:09:04 EST

Hi Andrew,

Quoting Andrew Lunn <andrew@xxxxxxx>:

On Fri, Jul 07, 2017 at 02:11:35AM -0500, Gustavo A. R. Silva wrote:
Check return value from call to of_match_device()
in order to prevent a NULL pointer dereference.

In case of NULL print error message and return -ENODEV

Signed-off-by: Gustavo A. R. Silva <garsilva@xxxxxxxxxxxxxx>
drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index adaaafc..6a77dea 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -2408,6 +2408,11 @@ static int mtk_probe(struct platform_device *pdev)
int i;

match = of_match_device(of_mtk_match, &pdev->dev);
+ if (!match) {
+ dev_err(&pdev->dev, "failed to match device\n");
+ return -ENODEV;
+ }
soc = (struct mtk_soc_data *)match->data;

Hi Gustavo

I think you are fixing the wrong thing. The soc variable is unused. Also,

const struct of_device_id of_mtk_match[] = {
{ .compatible = "mediatek,mt2701-eth" },

So match->data is NULL. This code is all pointless and should be
removed, rather than try to avoid a NULL pointer dereference which can
not actually happen.

You are right. Thank you for pointing it out. I'll remove that code and send a new patch shortly.

Gustavo A. R. Silva