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

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Message-Id: <20190912.133717.257813019167130934.davem@davemloft.net>
Date:   Thu, 12 Sep 2019 13:37:17 +0200 (CEST)
From:   David Miller <davem@...emloft.net>
To:     ap420073@...il.com
Cc:     netdev@...r.kernel.org, j.vosburgh@...il.com, vfalico@...il.com,
        andy@...yhouse.net, jiri@...nulli.us, sd@...asysnail.net,
        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@...onical.com
Subject: Re: [PATCH net v2 01/11] net: core: limit nested device depth

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.