net: ethernet: bcmasp: fix possible OOB write in bcmasp_netfilt_get_all_active()

rule_locs is allocated in ethtool_get_rxnfc and the size is determined by
rule_cnt from user space. So rule_cnt needs to be check before using
rule_locs to avoid OOB writing or NULL pointer dereference.

Fixes: c5d511c4 ("net: bcmasp: Add support for wake on net filters")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/asp2/bcmasp.c

@@ -528,13 +528,16 @@ void bcmasp_netfilt_suspend(struct bcmasp_intf *intf)
 				  ASP_RX_FILTER_BLK_CTRL);
 }
 
-void bcmasp_netfilt_get_all_active(struct bcmasp_intf *intf, u32 *rule_locs,
+int bcmasp_netfilt_get_all_active(struct bcmasp_intf *intf, u32 *rule_locs,
 				  u32 *rule_cnt)
 {
 	struct bcmasp_priv *priv = intf->parent;
 	int j = 0, i;
 
 	for (i = 0; i < NUM_NET_FILTERS; i++) {
+		if (j == *rule_cnt)
+			return -EMSGSIZE;
+
 		if (!priv->net_filters[i].claimed ||
 		    priv->net_filters[i].port != intf->port)
 			continue;
@@ -548,6 +551,8 @@ void bcmasp_netfilt_get_all_active(struct bcmasp_intf *intf, u32 *rule_locs,
 	}
 
 	*rule_cnt = j;
+
+	return 0;
 }
 
 int bcmasp_netfilt_get_active(struct bcmasp_intf *intf)

drivers/net/ethernet/broadcom/asp2/bcmasp.h

@@ -577,7 +577,7 @@ void bcmasp_netfilt_release(struct bcmasp_intf *intf,
 
 int bcmasp_netfilt_get_active(struct bcmasp_intf *intf);
 
-void bcmasp_netfilt_get_all_active(struct bcmasp_intf *intf, u32 *rule_locs,
+int bcmasp_netfilt_get_all_active(struct bcmasp_intf *intf, u32 *rule_locs,
 				  u32 *rule_cnt);
 
 void bcmasp_netfilt_suspend(struct bcmasp_intf *intf);

drivers/net/ethernet/broadcom/asp2/bcmasp_ethtool.c

@@ -335,7 +335,7 @@ static int bcmasp_get_rxnfc(struct net_device *dev, struct ethtool_rxnfc *cmd,
 		err = bcmasp_flow_get(intf, cmd);
 		break;
 	case ETHTOOL_GRXCLSRLALL:
-		bcmasp_netfilt_get_all_active(intf, rule_locs, &cmd->rule_cnt);
+		err = bcmasp_netfilt_get_all_active(intf, rule_locs, &cmd->rule_cnt);
 		cmd->data = NUM_NET_FILTERS;
 		break;
 	default: