linux-kernel - Re: [PATCH net-next] net: altera_tse: fix init sequence to avoid races with register

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Message-ID: <ZIXrYupBmpviSEW3@shell.armlinux.org.uk>
Date:   Sun, 11 Jun 2023 16:42:26 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
        Andrew Lunn <andrew@...n.ch>, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-arm-kernel@...ts.infradead.org,
        Simon Horman <simon.horman@...igine.com>,
        alexis.lothore@...tlin.com
Subject: Re: [PATCH net-next] net: altera_tse: fix init sequence to avoid
 races with register_netdev

On Sun, Jun 11, 2023 at 12:40:19PM +0200, Maxime Chevallier wrote:
> As reported here[1], the init sequence in altera_tse can be racy should
> any operation on the registered netdev happen after netdev registration
> but before phylink initialization.
> 
> Fix the registering order to avoid such races by making register_netdev
> the last step of the probing sequence.
> 
> [1]: https://lore.kernel.org/netdev/ZH9XK5yEGyoDMIs%2F@shell.armlinux.org.uk/
> 
> Fixes: fef2998203e1 ("net: altera: tse: convert to phylink")
> Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
> ---
> This patch targets net-next as it fixes a commit that is in net-next
> too.

While it fixes the order in which stuff is registered, it introduces
a new bug - register_netdev() is what atomically allocated a netdev
name, and you use the netdev name when creating the PCS MII bus:

	snprintf(mrc.name, MII_BUS_ID_SIZE, "%s-pcs-mii", ndev->name);

This needs to change, because this will end up being "eth%d-pcs-mii".

I am at a loss why you didn't realise this (or in fact recognise that
there are other issues) given that I sent you three patches fixing
this mess.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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