ibmvnic: avoid memset null scrq msgs

scrq->msgs could be NULL during device reset, causing Linux to crash.
So, check before memset scrq->msgs.

Fixes: c8b2ad0 ("ibmvnic: Sanitize entire SCRQ buffer on reset")
Signed-off-by: Dany Madden <drt@linux.ibm.com>
Signed-off-by: Lijun Pan <ljp@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/ibm/ibmvnic.c

@@ -2844,15 +2844,26 @@ static int reset_one_sub_crq_queue(struct ibmvnic_adapter *adapter,
 {
 	int rc;
 
+	if (!scrq) {
+		netdev_dbg(adapter->netdev,
+			   "Invalid scrq reset. irq (%d) or msgs (%p).\n",
+			   scrq->irq, scrq->msgs);
+		return -EINVAL;
+	}
+
 	if (scrq->irq) {
 		free_irq(scrq->irq, scrq);
 		irq_dispose_mapping(scrq->irq);
 		scrq->irq = 0;
 	}
-
-	memset(scrq->msgs, 0, 4 * PAGE_SIZE);
-	atomic_set(&scrq->used, 0);
-	scrq->cur = 0;
+	if (scrq->msgs) {
+		memset(scrq->msgs, 0, 4 * PAGE_SIZE);
+		atomic_set(&scrq->used, 0);
+		scrq->cur = 0;
+	} else {
+		netdev_dbg(adapter->netdev, "Invalid scrq reset\n");
+		return -EINVAL;
+	}
 
 	rc = h_reg_sub_crq(adapter->vdev->unit_address, scrq->msg_token,
 			   4 * PAGE_SIZE, &scrq->crq_num, &scrq->hw_irq);