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Date: Mon, 6 Jun 2022 09:25:51 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
Eric Dumazet <edumazet@...gle.com>,
Paolo Abeni <pabeni@...hat.com>,
Stephen Rothwell <sfr@...b.auug.org.au>,
Andrew Lunn <andrew@...n.ch>,
Florian Fainelli <f.fainelli@...il.com>,
Heiner Kallweit <hkallweit1@...il.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] net: mdio: unexport __init-annotated mdio_bus_init()
On Mon, Jun 06, 2022 at 01:53:53PM +0900, Masahiro Yamada wrote:
> 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: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Thanks!
--
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