netdev - [PATCH net-next] net: mdio_bus: validate "addr" for mdiobus_is_registered

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Message-Id: <E1qNxvu-00111m-1V@rmk-PC.armlinux.org.uk>
Date: Mon, 24 Jul 2023 16:57:14 +0100
From: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
To: Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org
Subject: [PATCH net-next] net: mdio_bus: validate "addr" for
 mdiobus_is_registered_device()

mdiobus_is_registered_device() doesn't checking that "addr" was valid
before dereferencing bus->mdio_map[]. Extract the code that checks
this from mdiobus_get_phy(), and use it here as well.

Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
I've had this patch kicking about for a while - probably a good idea?
It shouldn't cause a regression, but if it does it means we're already
dereferencing the arrray outside its bounds in
mdiobus_is_registered_device().

 drivers/net/phy/mdio_bus.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index bc04048de2fa..25dcaa49ab8b 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -107,16 +107,21 @@ int mdiobus_unregister_device(struct mdio_device *mdiodev)
 }
 EXPORT_SYMBOL(mdiobus_unregister_device);
 
-struct phy_device *mdiobus_get_phy(struct mii_bus *bus, int addr)
+static struct mdio_device *mdiobus_find_device(struct mii_bus *bus, int addr)
 {
 	bool addr_valid = addr >= 0 && addr < ARRAY_SIZE(bus->mdio_map);
-	struct mdio_device *mdiodev;
 
 	if (WARN_ONCE(!addr_valid, "addr %d out of range\n", addr))
 		return NULL;
 
-	mdiodev = bus->mdio_map[addr];
+	return bus->mdio_map[addr];
+}
 
+struct phy_device *mdiobus_get_phy(struct mii_bus *bus, int addr)
+{
+	struct mdio_device *mdiodev;
+
+	mdiodev = mdiobus_find_device(bus, addr);
 	if (!mdiodev)
 		return NULL;
 
@@ -129,7 +134,7 @@ EXPORT_SYMBOL(mdiobus_get_phy);
 
 bool mdiobus_is_registered_device(struct mii_bus *bus, int addr)
 {
-	return bus->mdio_map[addr];
+	return mdiobus_find_device(bus, addr) != NULL;
 }
 EXPORT_SYMBOL(mdiobus_is_registered_device);
 
-- 
2.30.2