ethtool: rss: prevent rss ctx deletion when in use

ntuple filters can specify an rss context to use for packet hashing
and queue selection. When a filter is referencing an rss context, it
should be invalid for that context to be deleted. A list of active
ntuple filters and their associated rss contexts can be compiled by
querying a device's ethtool_ops.get_rxnfc. This patch checks to see if
any ntuple filters are referencing an rss context during context
deletion, and prevents the deletion if the requested context is still
in use.

Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/ethtool/common.c

@@ -684,6 +684,54 @@ int ethtool_check_max_channel(struct net_device *dev,
 	return 0;
 }
 
+int ethtool_check_rss_ctx_busy(struct net_device *dev, u32 rss_context)
+{
+	const struct ethtool_ops *ops = dev->ethtool_ops;
+	struct ethtool_rxnfc *info;
+	int rc, i, rule_cnt;
+
+	if (!ops->get_rxnfc)
+		return 0;
+
+	rule_cnt = ethtool_get_rxnfc_rule_count(dev);
+	if (!rule_cnt)
+		return 0;
+
+	if (rule_cnt < 0)
+		return -EINVAL;
+
+	info = kvzalloc(struct_size(info, rule_locs, rule_cnt), GFP_KERNEL);
+	if (!info)
+		return -ENOMEM;
+
+	info->cmd = ETHTOOL_GRXCLSRLALL;
+	info->rule_cnt = rule_cnt;
+	rc = ops->get_rxnfc(dev, info, info->rule_locs);
+	if (rc)
+		goto out_free;
+
+	for (i = 0; i < rule_cnt; i++) {
+		struct ethtool_rxnfc rule_info = {
+			.cmd = ETHTOOL_GRXCLSRULE,
+			.fs.location = info->rule_locs[i],
+		};
+
+		rc = ops->get_rxnfc(dev, &rule_info, NULL);
+		if (rc)
+			goto out_free;
+
+		if (rule_info.fs.flow_type & FLOW_RSS &&
+		    rule_info.rss_context == rss_context) {
+			rc = -EBUSY;
+			goto out_free;
+		}
+	}
+
+out_free:
+	kvfree(info);
+	return rc;
+}
+
 int ethtool_check_ops(const struct ethtool_ops *ops)
 {
 	if (WARN_ON(ops->set_coalesce && !ops->supported_coalesce_params))

net/ethtool/common.h

@@ -47,6 +47,7 @@ bool convert_legacy_settings_to_link_ksettings(
 int ethtool_check_max_channel(struct net_device *dev,
 			      struct ethtool_channels channels,
 			      struct genl_info *info);
+int ethtool_check_rss_ctx_busy(struct net_device *dev, u32 rss_context);
 int __ethtool_get_ts_info(struct net_device *dev, struct kernel_ethtool_ts_info *info);
 
 extern const struct ethtool_phy_ops *ethtool_phy_ops;

net/ethtool/ioctl.c

@@ -1462,6 +1462,13 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 		mutex_lock(&dev->ethtool->rss_lock);
 		locked = true;
 	}
+
+	if (rxfh.rss_context && rxfh_dev.rss_delete) {
+		ret = ethtool_check_rss_ctx_busy(dev, rxfh.rss_context);
+		if (ret)
+			goto out;
+	}
+
 	if (create) {
 		if (rxfh_dev.rss_delete) {
 			ret = -EINVAL;