netdev - Re: [PATCH net-next 09/13] net: axienet: Make missing MAC address non-fatal

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Date:   Mon, 3 Jun 2019 09:49:51 -0600
From:   Robert Hancock <hancock@...systems.ca>
To:     David Laight <David.Laight@...LAB.COM>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:     "anirudh@...inx.com" <anirudh@...inx.com>,
        "John.Linn@...inx.com" <John.Linn@...inx.com>
Subject: Re: [PATCH net-next 09/13] net: axienet: Make missing MAC address
 non-fatal

On 2019-06-03 7:22 a.m., David Laight wrote:
> From: Robert Hancock
>> Sent: 31 May 2019 19:16
>> Failing initialization on a missing MAC address property is excessive.
>> We can just fall back to using a random MAC instead, which at least
>> leaves the interface in a functioning state.
>>
>> Signed-off-by: Robert Hancock <hancock@...systems.ca>
>> ---
>>  drivers/net/ethernet/xilinx/xilinx_axienet_main.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
>> b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
>> index 9949e67..947fa5d 100644
>> --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
>> +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
>> @@ -308,7 +308,7 @@ static void axienet_set_mac_address(struct net_device *ndev,
>>  {
>>  	struct axienet_local *lp = netdev_priv(ndev);
>>
>> -	if (address)
>> +	if (!IS_ERR(address))
>>  		memcpy(ndev->dev_addr, address, ETH_ALEN);
>>  	if (!is_valid_ether_addr(ndev->dev_addr))
>>  		eth_hw_addr_random(ndev);
>> @@ -1730,8 +1730,7 @@ static int axienet_probe(struct platform_device *pdev)
>>  	/* Retrieve the MAC address */
>>  	mac_addr = of_get_mac_address(pdev->dev.of_node);
>>  	if (IS_ERR(mac_addr)) {
>> -		dev_err(&pdev->dev, "could not find MAC address\n");
>> -		goto free_netdev;
>> +		dev_warn(&pdev->dev, "could not find MAC address property\n");
>>  	}
>>  	axienet_set_mac_address(ndev, mac_addr);
> 
> Isn't that going to read from an invalid address on error?
> Seems you didn't test of_get_mac_address() failing :-)

axienet_set_mac_address checks IS_ERR(mac_addr) as well before reading
from it, so the invalid address should not be accessed.

-- 
Robert Hancock
Senior Software Developer
SED Systems, a division of Calian Ltd.
Email: hancock@...systems.ca