v4 [PATCH 4/9] ipv6: Check return of dev_set_allmulti

[Wang Chen <wangchen@cn.fujitsu.com>]

allmulti might overflow.
Commit: "netdevice: Fix promiscuity and allmulti overflow" in net-next makes
dev_set_promiscuity/allmulti return error number if overflow happened.

Here, we check the positive increment for allmulti to get error return.

Signed-off-by: Wang Chen <wangchen@cn.fujitsu.com>
Acked-by: Patrick McHardy <kaber@trash.net> 
---
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 1479618..6cd286d 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -603,6 +603,7 @@ static int mif6_add(struct mif6ctl *vifc, int mrtsock)
 	int vifi = vifc->mif6c_mifi;
 	struct mif_device *v = &vif6_table[vifi];
 	struct net_device *dev;
+	int err;
 
 	/* Is vif busy ? */
 	if (MIF_EXISTS(vifi))
@@ -620,6 +621,11 @@ static int mif6_add(struct mif6ctl *vifc, int mrtsock)
 		dev = ip6mr_reg_vif();
 		if (!dev)
 			return -ENOBUFS;
+		err = dev_set_allmulti(dev, 1);
+		if (err) {
+			unregister_netdevice(dev);
+			return err;
+		}
 		break;
 #endif
 	case 0:
@@ -627,13 +633,14 @@ static int mif6_add(struct mif6ctl *vifc, int mrtsock)
 		if (!dev)
 			return -EADDRNOTAVAIL;
 		dev_put(dev);
+		err = dev_set_allmulti(dev, 1);
+		if (err)
+			return err;
 		break;
 	default:
 		return -EINVAL;
 	}
 
-	dev_set_allmulti(dev, 1);
-
 	/*
 	 *	Fill in the VIF structures
 	 */