netdev - Re: [PATCH net] bonding: stop the device in bond_setup_by

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Message-ID: <CANn89iLXNnHNdApy3JaOpnq-hkrDyR-vTYjDEiTaU5oJ1uAPTg@mail.gmail.com>
Date: Fri, 10 Nov 2023 09:38:18 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Hangbin Liu <liuhangbin@...il.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Jay Vosburgh <j.vosburgh@...il.com>, 
	Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net] bonding: stop the device in bond_setup_by_slave()

On Fri, Nov 10, 2023 at 4:44 AM Hangbin Liu <liuhangbin@...il.com> wrote:
>
> On Thu, Nov 09, 2023 at 06:01:02PM +0000, Eric Dumazet wrote:
> > Commit 9eed321cde22 ("net: lapbether: only support ethernet devices")
> > has been able to keep syzbot away from net/lapb, until today.
> >
> > In the following splat [1], the issue is that a lapbether device has
> > been created on a bonding device without members. Then adding a non
> > ARPHRD_ETHER member forced the bonding master to change its type.
> >
> > The fix is to make sure we call dev_close() in bond_setup_by_slave()
> > so that the potential linked lapbether devices (or any other devices
> > having assumptions on the physical device) are removed.
> >
> > A similar bug has been addressed in commit 40baec225765
> > ("bonding: fix panic on non-ARPHRD_ETHER enslave failure")
> >
>
> Do we need also do this if the bond changed to ether device from other dev
> type? e.g.
>
>     if (slave_dev->type != ARPHRD_ETHER)
>             bond_setup_by_slave(bond_dev, slave_dev);
>     else
>             bond_ether_setup(bond_dev);

Hmmm... possibly, but as far as I know, nothing can be stacked on top of IPoIB

Note that another way to deal with this in a fine grained way is to
return NOTIFY_BAD
from NETDEV_PRE_TYPE_CHANGE event (vlan, macvlan, ipvlan ...)