netdev - [PATCH AUTOSEL 6.10 060/197] net: phy: Check for read errors in SIOCGMIIREG

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Message-ID: <20240925115823.1303019-60-sashal@kernel.org>
Date: Wed, 25 Sep 2024 07:51:19 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Andrew Lunn <andrew@...n.ch>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Jakub Kicinski <kuba@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	hkallweit1@...il.com,
	davem@...emloft.net,
	edumazet@...gle.com,
	pabeni@...hat.com,
	netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 6.10 060/197] net: phy: Check for read errors in SIOCGMIIREG

From: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>

[ Upstream commit 569bf6d481b0b823c3c9c3b8be77908fd7caf66b ]

When reading registers from the PHY using the SIOCGMIIREG IOCTL any
errors returned from either mdiobus_read() or mdiobus_c45_read() are
ignored, and parts of the returned error is passed as the register value
back to user-space.

For example, if mdiobus_c45_read() is used with a bus that do not
implement the read_c45() callback -EOPNOTSUPP is returned. This is
however directly stored in mii_data->val_out and returned as the
registers content. As val_out is a u16 the error code is truncated and
returned as a plausible register value.

Fix this by first checking the return value for errors before returning
it as the register content.

Before this patch,

    # phytool read eth0/0:1/0
    0xffa1

After this change,

    $ phytool read eth0/0:1/0
    error: phy_read (-95)

Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
Reviewed-by: Andrew Lunn <andrew@...n.ch>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
Link: https://patch.msgid.link/20240903171536.628930-1-niklas.soderlund+renesas@ragnatech.se
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/phy/phy.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index c4236564c1cd0..8495b111a524a 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -342,14 +342,19 @@ int phy_mii_ioctl(struct phy_device *phydev, struct ifreq *ifr, int cmd)
 		if (mdio_phy_id_is_c45(mii_data->phy_id)) {
 			prtad = mdio_phy_id_prtad(mii_data->phy_id);
 			devad = mdio_phy_id_devad(mii_data->phy_id);
-			mii_data->val_out = mdiobus_c45_read(
-				phydev->mdio.bus, prtad, devad,
-				mii_data->reg_num);
+			ret = mdiobus_c45_read(phydev->mdio.bus, prtad, devad,
+					       mii_data->reg_num);
+
 		} else {
-			mii_data->val_out = mdiobus_read(
-				phydev->mdio.bus, mii_data->phy_id,
-				mii_data->reg_num);
+			ret = mdiobus_read(phydev->mdio.bus, mii_data->phy_id,
+					   mii_data->reg_num);
 		}
+
+		if (ret < 0)
+			return ret;
+
+		mii_data->val_out = ret;
+
 		return 0;
 
 	case SIOCSMIIREG:
-- 
2.43.0