netdev - Re: [PATCH net v2 01/11] net: core: limit nested device depth

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Message-ID: <CAMArcTVtv=ah=KbzOb=u_Qyx0V+iGts77kz_X9GhJfEHbGPUSQ@mail.gmail.com>
Date:   Thu, 12 Sep 2019 21:49:44 +0900
From:   Taehee Yoo <ap420073@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Netdev <netdev@...r.kernel.org>, j.vosburgh@...il.com,
        vfalico@...il.com, Andy Gospodarek <andy@...yhouse.net>,
        Jiří Pírko <jiri@...nulli.us>,
        sd@...asysnail.net, Roopa Prabhu <roopa@...ulusnetworks.com>,
        saeedm@...lanox.com, manishc@...vell.com, rahulv@...vell.com,
        kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        sashal@...nel.org, hare@...e.de, varun@...lsio.com,
        ubraun@...ux.ibm.com, kgraul@...ux.ibm.com,
        Jay Vosburgh <jay.vosburgh@...onical.com>
Subject: Re: [PATCH net v2 01/11] net: core: limit nested device depth

On Thu, 12 Sep 2019 at 20:37, David Miller <davem@...emloft.net> wrote:
>
> From: Taehee Yoo <ap420073@...il.com>
> Date: Thu, 12 Sep 2019 19:14:37 +0900
>
> > On Thu, 12 Sep 2019 at 18:38, David Miller <davem@...emloft.net> wrote:
> >>
> >> From: Taehee Yoo <ap420073@...il.com>
> >> Date: Thu, 12 Sep 2019 12:56:19 +0900
> >>
> >> > I tested with this reproducer commands without lockdep.
> >> >
> >> >     ip link add dummy0 type dummy
> >> >     ip link add link dummy0 name vlan1 type vlan id 1
> >> >     ip link set vlan1 up
> >> >
> >> >     for i in {2..200}
> >> >     do
> >> >             let A=$i-1
> >> >
> >> >             ip link add name vlan$i link vlan$A type vlan id $i
> >> >     done
> >> >     ip link del vlan1 <-- this command is added.
> >>
> >> Is there any other device type which allows arbitrary nesting depth
> >> in this manner other than VLAN?  Perhaps it is the VLAN nesting
> >> depth that we should limit instead of all of this extra code.
> >
> > Below device types have the same problem.
> > VLAN, BONDING, TEAM, VXLAN, MACVLAN, and MACSEC.
> > All the below test commands reproduce a panic.
>
> I think then we need to move the traversals over to a iterative
> rather than recursive algorithm.

Just to clarify, I have a question.

There are two recursive routines in the code.
a) netdev_walk_all_{lower/upper}_dev() that are used to traversal
all of their lower or upper devices.
b) VLAN, BONDING, TEAM, VXLAN, MACVLAN, and MACSEC
modules internally handle their lower/upper devices recursively
when an event is received such as unregistering.

what is the routine that you mentioned?