netdev - Re: [PATCH 1/3] net: mdio: unexport __init-annotated mdio_bus

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Date:   Mon, 6 Jun 2022 10:09:25 +0200
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] net: mdio: unexport __init-annotated mdio_bus_init()



On 6/6/2022 6:53 AM, 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: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian