netdev - Re: [PATCH net] team: fix null-ptr-deref when team device type is changed

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Date: Mon, 4 Sep 2023 13:00:08 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Hangbin Liu <liuhangbin@...il.com>
Cc: Ziyang Xuan <william.xuanziyang@...wei.com>, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH net] team: fix null-ptr-deref when team device type is
 changed

Mon, Sep 04, 2023 at 12:23:15PM CEST, liuhangbin@...il.com wrote:
>Hi Ziyang,
>
>On Sat, Sep 02, 2023 at 05:20:07PM +0800, Ziyang Xuan wrote:
>> $ teamd -t team0 -d -c '{"runner": {"name": "loadbalance"}}'
>> $ ip link add name t-dummy type dummy
>> $ ip link add link t-dummy name t-dummy.100 type vlan id 100
>> $ ip link add name t-nlmon type nlmon
>> $ ip link set t-nlmon master team0
>> $ ip link set t-nlmon nomaster
>> $ ip link set t-dummy up
>> $ ip link set team0 up
>> $ ip link set t-dummy.100 down
>> $ ip link set t-dummy.100 master team0
>> 
>> When enslave a vlan device to team device and team device type is changed
>> from non-ether to ether, header_ops of team device is changed to
>> vlan_header_ops. That is incorrect and will trigger null-ptr-deref
>> for vlan->real_dev in vlan_dev_hard_header() because team device is not
>> a vlan device.
>> 
>> Use ether_setup() for team device when its type is changed from non-ether
>> to ether to fix the bug.
>> 
>> Fixes: 1d76efe1577b ("team: add support for non-ethernet devices")
>> Signed-off-by: Ziyang Xuan <william.xuanziyang@...wei.com>
>> ---
>>  drivers/net/team/team.c | 21 +++++++++++++--------
>>  1 file changed, 13 insertions(+), 8 deletions(-)
>> 
>> diff --git a/drivers/net/team/team.c b/drivers/net/team/team.c
>> index d3dc22509ea5..560e04860aa7 100644
>> --- a/drivers/net/team/team.c
>> +++ b/drivers/net/team/team.c
>> @@ -2127,14 +2127,19 @@ static const struct ethtool_ops team_ethtool_ops = {
>>  static void team_setup_by_port(struct net_device *dev,
>>  			       struct net_device *port_dev)
>>  {
>> -	dev->header_ops	= port_dev->header_ops;
>> -	dev->type = port_dev->type;
>> -	dev->hard_header_len = port_dev->hard_header_len;
>> -	dev->needed_headroom = port_dev->needed_headroom;
>> -	dev->addr_len = port_dev->addr_len;
>> -	dev->mtu = port_dev->mtu;
>> -	memcpy(dev->broadcast, port_dev->broadcast, port_dev->addr_len);
>> -	eth_hw_addr_inherit(dev, port_dev);
>> +	if (port_dev->type == ARPHRD_ETHER) {
>> +		ether_setup(dev);
>> +		eth_hw_addr_random(dev);
>> +	} else {
>> +		dev->header_ops	= port_dev->header_ops;
>> +		dev->type = port_dev->type;
>> +		dev->hard_header_len = port_dev->hard_header_len;
>> +		dev->needed_headroom = port_dev->needed_headroom;
>> +		dev->addr_len = port_dev->addr_len;
>> +		dev->mtu = port_dev->mtu;
>> +		memcpy(dev->broadcast, port_dev->broadcast, port_dev->addr_len);
>> +		eth_hw_addr_inherit(dev, port_dev);
>> +	}
>>  
>>  	if (port_dev->flags & IFF_POINTOPOINT) {
>>  		dev->flags &= ~(IFF_BROADCAST | IFF_MULTICAST);
>
>Thanks for the report. This fix is similar with what I do in my PATCHv3 [1].
>And this will go back to the discussion of MTU update. How about just update
>the header_ops for ARPHRD_ETHER? e.g.
>
>	if (port_dev->type == ARPHRD_ETHER)
>		dev->header_ops	= &eth_header_ops;
>	else
>		dev->header_ops	= port_dev->header_ops;

Yes, this sounds better.


>
>[1] https://lore.kernel.org/netdev/20230718101741.2751799-3-liuhangbin@gmail.com/
>
>Thanks
>Hangbin