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 <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>
---
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 58d602985877..8a2dbe849866 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -1046,7 +1046,6 @@ int __init mdio_bus_init(void)
return ret;
}
-EXPORT_SYMBOL_GPL(mdio_bus_init);
#if IS_ENABLED(CONFIG_PHYLIB)
void mdio_bus_exit(void)
--
2.32.0
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 <[email protected]>
> Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
--
Florian
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 <[email protected]>
> Signed-off-by: Masahiro Yamada <[email protected]>
Reviewed-by: Russell King (Oracle) <[email protected]>
Thanks!
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!