linux-kernel - [PATCH 5.4 51/64] phylib: fix potential use-after-free

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Date:   Mon, 31 Jan 2022 11:56:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Marek Behún <kabel@...nel.org>,
        Andrew Lunn <andrew@...n.ch>, Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 51/64] phylib: fix potential use-after-free

From: Marek Behún <kabel@...nel.org>

[ Upstream commit cbda1b16687580d5beee38273f6241ae3725960c ]

Commit bafbdd527d56 ("phylib: Add device reset GPIO support") added call
to phy_device_reset(phydev) after the put_device() call in phy_detach().

The comment before the put_device() call says that the phydev might go
away with put_device().

Fix potential use-after-free by calling phy_device_reset() before
put_device().

Fixes: bafbdd527d56 ("phylib: Add device reset GPIO support")
Signed-off-by: Marek Behún <kabel@...nel.org>
Reviewed-by: Andrew Lunn <andrew@...n.ch>
Link: https://lore.kernel.org/r/20220119162748.32418-1-kabel@kernel.org
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/phy/phy_device.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 35ade5d21de51..78b918dcd5472 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1433,6 +1433,9 @@ void phy_detach(struct phy_device *phydev)
 	    phy_driver_is_genphy_10g(phydev))
 		device_release_driver(&phydev->mdio.dev);
 
+	/* Assert the reset signal */
+	phy_device_reset(phydev, 1);
+
 	/*
 	 * The phydev might go away on the put_device() below, so avoid
 	 * a use-after-free bug by reading the underlying bus first.
@@ -1444,9 +1447,6 @@ void phy_detach(struct phy_device *phydev)
 		ndev_owner = dev->dev.parent->driver->owner;
 	if (ndev_owner != bus->owner)
 		module_put(bus->owner);
-
-	/* Assert the reset signal */
-	phy_device_reset(phydev, 1);
 }
 EXPORT_SYMBOL(phy_detach);
 
-- 
2.34.1