diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 205384dab89a..57dd6821a8aa 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -752,7 +752,7 @@ static ssize_t enabled_store(struct config_item *item,
 		unregister_netcons_consoles();
 	}
 
-	ret = strnlen(buf, count);
+	ret = count;
 	/* Deferred cleanup */
 	netconsole_process_cleanups();
 out_unlock:
@@ -781,7 +781,7 @@ static ssize_t release_store(struct config_item *item, const char *buf,
 
 	nt->release = release;
 
-	ret = strnlen(buf, count);
+	ret = count;
 out_unlock:
 	dynamic_netconsole_mutex_unlock();
 	return ret;
@@ -807,7 +807,7 @@ static ssize_t extended_store(struct config_item *item, const char *buf,
 		goto out_unlock;
 
 	nt->extended = extended;
-	ret = strnlen(buf, count);
+	ret = count;
 out_unlock:
 	dynamic_netconsole_mutex_unlock();
 	return ret;
@@ -817,6 +817,13 @@ static ssize_t dev_name_store(struct config_item *item, const char *buf,
 		size_t count)
 {
 	struct netconsole_target *nt = to_target(item);
+	size_t len = count;
+
+	/* Account for a trailing newline appended by tools like echo */
+	if (len && buf[len - 1] == '\n')
+		len--;
+	if (len >= IFNAMSIZ)
+		return -ENAMETOOLONG;
 
 	dynamic_netconsole_mutex_lock();
 	if (nt->state == STATE_ENABLED) {
@@ -830,7 +837,7 @@ static ssize_t dev_name_store(struct config_item *item, const char *buf,
 	trim_newline(nt->np.dev_name, IFNAMSIZ);
 
 	dynamic_netconsole_mutex_unlock();
-	return strnlen(buf, count);
+	return count;
 }
 
 static ssize_t local_port_store(struct config_item *item, const char *buf,
@@ -849,7 +856,7 @@ static ssize_t local_port_store(struct config_item *item, const char *buf,
 	ret = kstrtou16(buf, 10, &nt->np.local_port);
 	if (ret < 0)
 		goto out_unlock;
-	ret = strnlen(buf, count);
+	ret = count;
 out_unlock:
 	dynamic_netconsole_mutex_unlock();
 	return ret;
@@ -871,7 +878,7 @@ static ssize_t remote_port_store(struct config_item *item,
 	ret = kstrtou16(buf, 10, &nt->np.remote_port);
 	if (ret < 0)
 		goto out_unlock;
-	ret = strnlen(buf, count);
+	ret = count;
 out_unlock:
 	dynamic_netconsole_mutex_unlock();
 	return ret;
@@ -896,7 +903,7 @@ static ssize_t local_ip_store(struct config_item *item, const char *buf,
 		goto out_unlock;
 	nt->np.ipv6 = !!ipv6;
 
-	ret = strnlen(buf, count);
+	ret = count;
 out_unlock:
 	dynamic_netconsole_mutex_unlock();
 	return ret;
@@ -921,7 +928,7 @@ static ssize_t remote_ip_store(struct config_item *item, const char *buf,
 		goto out_unlock;
 	nt->np.ipv6 = !!ipv6;
 
-	ret = strnlen(buf, count);
+	ret = count;
 out_unlock:
 	dynamic_netconsole_mutex_unlock();
 	return ret;
@@ -957,7 +964,7 @@ static ssize_t remote_mac_store(struct config_item *item, const char *buf,
 		goto out_unlock;
 	memcpy(nt->np.remote_mac, remote_mac, ETH_ALEN);
 
-	ret = strnlen(buf, count);
+	ret = count;
 out_unlock:
 	dynamic_netconsole_mutex_unlock();
 	return ret;
@@ -1072,26 +1079,30 @@ static ssize_t userdatum_value_store(struct config_item *item, const char *buf,
 				     size_t count)
 {
 	struct userdatum *udm = to_userdatum(item);
+	char old_value[MAX_EXTRADATA_VALUE_LEN];
 	struct netconsole_target *nt;
 	struct userdata *ud;
 	ssize_t ret;
 
-	if (count > MAX_EXTRADATA_VALUE_LEN)
+	if (count >= MAX_EXTRADATA_VALUE_LEN)
 		return -EMSGSIZE;
 
 	mutex_lock(&netconsole_subsys.su_mutex);
 	dynamic_netconsole_mutex_lock();
-
-	ret = strscpy(udm->value, buf, sizeof(udm->value));
-	if (ret < 0)
-		goto out_unlock;
+	/* Snapshot for rollback if update_userdata() fails below */
+	strscpy(old_value, udm->value, sizeof(old_value));
+	/* count is bounded above, so strscpy() cannot truncate here */
+	strscpy(udm->value, buf, sizeof(udm->value));
 	trim_newline(udm->value, sizeof(udm->value));
 
 	ud = to_userdata(item->ci_parent);
 	nt = userdata_to_target(ud);
 	ret = update_userdata(nt);
-	if (ret < 0)
+	if (ret < 0) {
+		/* Restore the previous value so it matches the live payload */
+		strscpy(udm->value, old_value, sizeof(udm->value));
 		goto out_unlock;
+	}
 	ret = count;
 out_unlock:
 	dynamic_netconsole_mutex_unlock();
@@ -1133,7 +1144,7 @@ static ssize_t sysdata_msgid_enabled_store(struct config_item *item,
 		disable_sysdata_feature(nt, SYSDATA_MSGID);
 
 unlock_ok:
-	ret = strnlen(buf, count);
+	ret = count;
 	dynamic_netconsole_mutex_unlock();
 	mutex_unlock(&netconsole_subsys.su_mutex);
 	return ret;
@@ -1162,7 +1173,7 @@ static ssize_t sysdata_release_enabled_store(struct config_item *item,
 		disable_sysdata_feature(nt, SYSDATA_RELEASE);
 
 unlock_ok:
-	ret = strnlen(buf, count);
+	ret = count;
 	dynamic_netconsole_mutex_unlock();
 	mutex_unlock(&netconsole_subsys.su_mutex);
 	return ret;
@@ -1191,7 +1202,7 @@ static ssize_t sysdata_taskname_enabled_store(struct config_item *item,
 		disable_sysdata_feature(nt, SYSDATA_TASKNAME);
 
 unlock_ok:
-	ret = strnlen(buf, count);
+	ret = count;
 	dynamic_netconsole_mutex_unlock();
 	mutex_unlock(&netconsole_subsys.su_mutex);
 	return ret;
@@ -1225,7 +1236,7 @@ static ssize_t sysdata_cpu_nr_enabled_store(struct config_item *item,
 		disable_sysdata_feature(nt, SYSDATA_CPU_NR);
 
 unlock_ok:
-	ret = strnlen(buf, count);
+	ret = count;
 	dynamic_netconsole_mutex_unlock();
 	mutex_unlock(&netconsole_subsys.su_mutex);
 	return ret;