linux-kernel - [PATCH v3 2/3] net: phy: fixed_phy: fix use-after-free when checking link GPIO

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Message-Id: <20200103010320.245675-3-dmitry.torokhov@gmail.com>
Date:   Thu,  2 Jan 2020 17:03:19 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org>,
        linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: [PATCH v3 2/3] net: phy: fixed_phy: fix use-after-free when checking link GPIO

If we fail to locate GPIO for any reason other than deferral or
not-found-GPIO, we try to print device tree node info, however if might
be freed already as we called of_node_put() on it.

Acked-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---

 drivers/net/phy/fixed_phy.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/net/phy/fixed_phy.c b/drivers/net/phy/fixed_phy.c
index 7c5265fd2b94d..4190f9ed5313d 100644
--- a/drivers/net/phy/fixed_phy.c
+++ b/drivers/net/phy/fixed_phy.c
@@ -212,16 +212,13 @@ static struct gpio_desc *fixed_phy_get_gpiod(struct device_node *np)
 	 */
 	gpiod = gpiod_get_from_of_node(fixed_link_node, "link-gpios", 0,
 				       GPIOD_IN, "mdio");
-	of_node_put(fixed_link_node);
-	if (IS_ERR(gpiod)) {
-		if (PTR_ERR(gpiod) == -EPROBE_DEFER)
-			return gpiod;
-
+	if (IS_ERR(gpiod) && PTR_ERR(gpiod) != -EPROBE_DEFER) {
 		if (PTR_ERR(gpiod) != -ENOENT)
 			pr_err("error getting GPIO for fixed link %pOF, proceed without\n",
 			       fixed_link_node);
 		gpiod = NULL;
 	}
+	of_node_put(fixed_link_node);
 
 	return gpiod;
 }
-- 
2.24.1.735.g03f4e72817-goog