igb: Initialize mailbox message for VF reset

When a MAC address is not assigned to the VF, that portion of the message
sent to the VF is not set. The memory, however, is allocated from the
stack meaning that information may be leaked to the VM. Initialize the
message buffer to 0 so that no information is passed to the VM in this
case.

Fixes: 6ddbc4cf ("igb: Indicate failure on vf reset for empty mac address")
Reported-by: NAkihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: NTony Nguyen <anthony.l.nguyen@intel.com>
Reviewed-by: NAkihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: NLeon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20221212190031.3983342-1-anthony.l.nguyen@intel.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/intel/igb/igb_main.c

@@ -7525,7 +7525,7 @@ static void igb_vf_reset_msg(struct igb_adapter *adapter, u32 vf)
 {
 	struct e1000_hw *hw = &adapter->hw;
 	unsigned char *vf_mac = adapter->vf_data[vf].vf_mac_addresses;
-	u32 reg, msgbuf[3];
+	u32 reg, msgbuf[3] = {};
 	u8 *addr = (u8 *)(&msgbuf[1]);
 
 	/* process all the same items cleared in a function level reset */