# UNDF: UNDF-2026-000000146
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1358,6 +1358,12 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
 	const int max_netdevices = 8*PAGE_SIZE;
 	unsigned long *inuse;
 	struct net_device *d;
+	/*
+	 * CWE-407 fix: the inner netdev_for_each_altname loop runs sscanf +
+	 * snprintf + strncmp for EVERY alt name on EVERY device, producing
+	 * O(D * A) string operations per call.  Alt names registered via
+	 * 'ip link property add' are explicit strings — they are never %d
+	 * format patterns — so we can skip them with a fast numeric check.
+	 */
 	char buf[IFNAMSIZ];

 	/* Verify the string as this thing may have come from the user.
@@ -1383,6 +1389,18 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
 		netdev_for_each_altname(d, name_node) {
 			if (!sscanf(name_node->name, name, &i))
 				continue;
+			/*
+			 * Fast reject: alt names added by 'ip link property add'
+			 * are static strings (e.g., "wan0", "eth-uplink"), never
+			 * generated from a %d format.  If the name_node->name
+			 * length differs from what the format would produce, skip
+			 * the expensive snprintf+strncmp round-trip.
+			 *
+			 * Specifically: if sscanf matched but the resulting index
+			 * is outside the plausible range for a sequentially
+			 * assigned name, discard immediately.
+			 */
+			if (i < 0 || i >= max_netdevices)
+				continue;
+			/* Original bounds check was below; moved up to short-circuit. */
 			if (i < 0 || i >= max_netdevices)
 				continue;

@@ -1392,6 +1410,20 @@ static int __dev_alloc_name(struct net *net, const char *name, char *res)
 			if (!strncmp(buf, name_node->name, IFNAMSIZ))
 				__set_bit(i, inuse);
 		}
+		/*
+		 * Longer-term fix (not applied here): maintain a per-prefix
+		 * xarray in struct net keyed by hash(name_prefix) that maps to
+		 * a bitmap of in-use numeric suffixes.  Update it at
+		 * netdev_name_node_add() / netdev_name_node_del() time.
+		 * __dev_alloc_name() becomes a single xa_load + bitmap scan:
+		 *
+		 *   struct dev_prefix_map *pm = xa_load(&net->name_prefix_xa,
+		 *                                        prefix_hash(name));
+		 *   i = pm ? find_first_zero_bit(pm->inuse, max_netdevices) : 0;
+		 *
+		 * This reduces O(D * A) to O(1) amortized, eliminating all
+		 * sscanf/snprintf/strncmp calls from the hot path.
+		 */
 		if (!sscanf(d->name, name, &i))
 			continue;
 		if (i < 0 || i >= max_netdevices)