s390/qeth: lock the card while changing its hsuid

qeth_l3_dev_hsuid_store() initially checks the card state, but doesn't
take the conf_mutex to ensure that the card stays in this state while
being reconfigured.

Rework the code to take this lock, and drop a redundant state check in a
helper function.

Fixes: b3332930 ("qeth: add support for af_iucv HiperSockets transport")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core_main.c

@@ -3425,11 +3425,6 @@ int qeth_configure_cq(struct qeth_card *card, enum qeth_cq cq)
 			goto out;
 		}
 
-		if (card->state != CARD_STATE_DOWN) {
-			rc = -1;
-			goto out;
-		}
-
 		qeth_free_qdio_queues(card);
 		card->options.cq = cq;
 		rc = 0;

drivers/s390/net/qeth_l3_sys.c

@@ -242,21 +242,33 @@ static ssize_t qeth_l3_dev_hsuid_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t count)
 {
 	struct qeth_card *card = dev_get_drvdata(dev);
+	int rc = 0;
 	char *tmp;
-	int rc;
 
 	if (!IS_IQD(card))
 		return -EPERM;
-	if (card->state != CARD_STATE_DOWN)
-		return -EPERM;
-	if (card->options.sniffer)
-		return -EPERM;
-	if (card->options.cq == QETH_CQ_NOTAVAILABLE)
-		return -EPERM;
+
+	mutex_lock(&card->conf_mutex);
+	if (card->state != CARD_STATE_DOWN) {
+		rc = -EPERM;
+		goto out;
+	}
+
+	if (card->options.sniffer) {
+		rc = -EPERM;
+		goto out;
+	}
+
+	if (card->options.cq == QETH_CQ_NOTAVAILABLE) {
+		rc = -EPERM;
+		goto out;
+	}
 
 	tmp = strsep((char **)&buf, "\n");
-	if (strlen(tmp) > 8)
-		return -EINVAL;
+	if (strlen(tmp) > 8) {
+		rc = -EINVAL;
+		goto out;
+	}
 
 	if (card->options.hsuid[0])
 		/* delete old ip address */
@@ -267,11 +279,13 @@ static ssize_t qeth_l3_dev_hsuid_store(struct device *dev,
 		card->options.hsuid[0] = '\0';
 		memcpy(card->dev->perm_addr, card->options.hsuid, 9);
 		qeth_configure_cq(card, QETH_CQ_DISABLED);
-		return count;
+		goto out;
 	}
 
-	if (qeth_configure_cq(card, QETH_CQ_ENABLED))
-		return -EPERM;
+	if (qeth_configure_cq(card, QETH_CQ_ENABLED)) {
+		rc = -EPERM;
+		goto out;
+	}
 
 	snprintf(card->options.hsuid, sizeof(card->options.hsuid),
 		 "%-8s", tmp);
@@ -280,6 +294,8 @@ static ssize_t qeth_l3_dev_hsuid_store(struct device *dev,
 
 	rc = qeth_l3_modify_hsuid(card, true);
 
+out:
+	mutex_unlock(&card->conf_mutex);
 	return rc ? rc : count;
 }