netdev - Re: [PATCH net 1/2] net: ethernet: ftgmac100: prevent use after free on unregister when using NCSI

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Message-ID: <198a796d5855759ca8561590d848c52028378971.camel@codeconstruct.com.au>
Date: Wed, 30 Oct 2024 08:29:05 +0800
From: Jeremy Kerr <jk@...econstruct.com.au>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Andrew Lunn <andrew@...n.ch>, Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Joel Stanley
 <joel@....id.au>, Jacky Chou <jacky_chou@...eedtech.com>, Jacob Keller
 <jacob.e.keller@...el.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net 1/2] net: ethernet: ftgmac100: prevent use after
 free on unregister when using NCSI

Hi Jakub,

> > As the ordering in ftgmac100_remove() is:
> > 
> > 
> >         if (priv->ndev)
> >                 ncsi_unregister_dev(priv->ndev);
> >         unregister_netdev(netdev);
> > 
> > which, is (I assume intentionally) symmetric with the _probe, which
> > does:
> > 
> >                 priv->ndev = ncsi_register_dev(netdev, ftgmac100_ncsi_handler);
> > 
> >         /* ... */
> > 
> >         register_netdev(netdev)
> 
> To be clear - symmetric means mirror image.

Totally agree with you both on the concept, but I had flipped the
unregister order in my head, sorry!

So, this worth a try with the _remove sequence reordered with respect
to the ncsi device. I'll work on a replacement patch to see if that can
be done without other fallout, and will send a follow-up soon.

Cheers,

Jeremy