netdev - Re: [PATCH net v2] ibmvnic: fix ibmvnic_set

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Date:   Thu, 22 Oct 2020 00:34:25 +0200
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     Lijun Pan <ljp@...ux.ibm.com>
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net v2] ibmvnic: fix ibmvnic_set_mac

On Wed, Oct 21, 2020 at 01:07:12AM -0500, Lijun Pan wrote:
> Jakub Kicinski brought up a concern in ibmvnic_set_mac().
> ibmvnic_set_mac() does this:
> 
> 	ether_addr_copy(adapter->mac_addr, addr->sa_data);
> 	if (adapter->state != VNIC_PROBED)
> 		rc = __ibmvnic_set_mac(netdev, addr->sa_data);
> 
> So if state == VNIC_PROBED, the user can assign an invalid address to
> adapter->mac_addr, and ibmvnic_set_mac() will still return 0.
> 
> The fix is to add the handling for "adapter->state == VNIC_PROBED" case,
> which saves the old mac address back to adapter->mac_addr, and
> returns an error code.
> 
> Fixes: 62740e97881c ("net/ibmvnic: Update MAC address settings after adapter reset")
> Cc: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Lijun Pan <ljp@...ux.ibm.com>
> ---
> v2: change the subject from v1's 
>     "ibmvnic: no need to update adapter->mac_addr before it completes"
>     handle adapter->state==VNIC_PROBED case in else statement.
> 
>  drivers/net/ethernet/ibm/ibmvnic.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
> index 4dd3625a4fbc..0d78e1e3d44c 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -1829,8 +1829,12 @@ static int ibmvnic_set_mac(struct net_device *netdev, void *p)
>  
>  	rc = 0;
>  	ether_addr_copy(adapter->mac_addr, addr->sa_data);
> -	if (adapter->state != VNIC_PROBED)
> +	if (adapter->state != VNIC_PROBED) {
>  		rc = __ibmvnic_set_mac(netdev, addr->sa_data);
> +	} else {
> +		ether_addr_copy(adapter->mac_addr, netdev->dev_addr);
> +		rc = -EIO;

Why suddenly you want to change the behavior for case when ibmvnic_set_mac
is called for VNIC_PROBED state?

I went through the previous discussion and I have a feeling that Jakub
meant to simply call the is_valid_ether_addr() on addr->sa_data before the
first ether_addr_copy and then act accordingly based on the validity of
user supplied mac addr.

And instead of yet another write to adapter->mac_addr that you're
introducing you could just move the first ether_addr_copy (if
addr->sa_data is valid) onto the if (adapter->state != VNIC_PROBED)
condition. Right?

> +	}
>  
>  	return rc;
>  }
> -- 
> 2.23.0
>