[PATCH net v3] ibmvnic: fix ibmvnic_set_mac

[Lijun Pan <ljp@linux.ibm.com>]

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 validate ethernet address at the beginning of
ibmvnic_set_mac(), and move the ether_addr_copy to
the case of "adapter->state != VNIC_PROBED".

Fixes: 62740e97881c ("net/ibmvnic: Update MAC address settings after adapter reset")
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Lijun Pan <ljp@linux.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.
v3: take Maciej Fijalkowski's advice.

 drivers/net/ethernet/ibm/ibmvnic.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 4dd3625a4fbc..660761538c55 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1828,9 +1828,13 @@ static int ibmvnic_set_mac(struct net_device *netdev, void *p)
 	int rc;
 
 	rc = 0;
-	ether_addr_copy(adapter->mac_addr, addr->sa_data);
-	if (adapter->state != VNIC_PROBED)
+	if (!is_valid_ether_addr(addr->sa_data))
+		return -EADDRNOTAVAIL;
+
+	if (adapter->state != VNIC_PROBED) {
+		ether_addr_copy(adapter->mac_addr, addr->sa_data);
 		rc = __ibmvnic_set_mac(netdev, addr->sa_data);
+	}
 
 	return rc;
 }
-- 
2.23.0