linux-kernel - [PATCH 5.4 357/411] net: mdio: unexport __init-annotated mdio_bus

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Message-Id: <20220613094939.401437878@linuxfoundation.org>
Date:   Mon, 13 Jun 2022 12:10:30 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stephen Rothwell <sfr@...b.auug.org.au>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 357/411] net: mdio: unexport __init-annotated mdio_bus_init()

From: Masahiro Yamada <masahiroy@...nel.org>

[ Upstream commit 35b42dce619701f1300fb8498dae82c9bb1f0263 ]

EXPORT_SYMBOL and __init is a bad combination because the .init.text
section is freed up after the initialization. Hence, modules cannot
use symbols annotated __init. The access to a freed symbol may end up
with kernel panic.

modpost used to detect it, but it has been broken for a decade.

Recently, I fixed modpost so it started to warn it again, then this
showed up in linux-next builds.

There are two ways to fix it:

  - Remove __init
  - Remove EXPORT_SYMBOL

I chose the latter for this case because the only in-tree call-site,
drivers/net/phy/phy_device.c is never compiled as modular.
(CONFIG_PHYLIB is boolean)

Fixes: 90eff9096c01 ("net: phy: Allow splitting MDIO bus/device support from PHYs")
Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/phy/mdio_bus.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index b0a439248ff6..05c24db507a2 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -753,7 +753,6 @@ int __init mdio_bus_init(void)
 
 	return ret;
 }
-EXPORT_SYMBOL_GPL(mdio_bus_init);
 
 #if IS_ENABLED(CONFIG_PHYLIB)
 void mdio_bus_exit(void)
-- 
2.35.1