Revert "wireless: Use first phyX name available when registering phy devices."

This reverts commit 5a254ffe.

The commit failed to take into account that allocated wireless devices
(wiphys) are not added into the device list upon allocation, but only
when they are registered. Therefore, it opened up a race between
allocating and registering a name, so that if two processes allocate and
register concurrently ("alloc, alloc, register, register" rather than
"alloc, register, alloc, register") the code will attempt to use the
same name twice.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/core.c

@@ -178,10 +178,26 @@ int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
 			char *newname)
 {
 	struct cfg80211_registered_device *rdev2;
-	int result;
+	int wiphy_idx, taken = -1, result, digits;
 
 	assert_cfg80211_lock();
 
+	/* prohibit calling the thing phy%d when %d is not its number */
+	sscanf(newname, PHY_NAME "%d%n", &wiphy_idx, &taken);
+	if (taken == strlen(newname) && wiphy_idx != rdev->wiphy_idx) {
+		/* count number of places needed to print wiphy_idx */
+		digits = 1;
+		while (wiphy_idx /= 10)
+			digits++;
+		/*
+		 * deny the name if it is phy<idx> where <idx> is printed
+		 * without leading zeroes. taken == strlen(newname) here
+		 */
+		if (taken == strlen(PHY_NAME) + digits)
+			return -EINVAL;
+	}
+
+
 	/* Ignore nop renames */
 	if (strcmp(newname, dev_name(&rdev->wiphy.dev)) == 0)
 		return 0;
@@ -189,7 +205,7 @@ int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
 	/* Ensure another device does not already have this name. */
 	list_for_each_entry(rdev2, &cfg80211_rdev_list, list)
 		if (strcmp(newname, dev_name(&rdev2->wiphy.dev)) == 0)
-			return -EEXIST;
+			return -EINVAL;
 
 	result = device_rename(&rdev->wiphy.dev, newname);
 	if (result)
@@ -304,11 +320,9 @@ static void cfg80211_event_work(struct work_struct *work)
 struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
 {
 	static int wiphy_counter;
-	int i;
-	struct cfg80211_registered_device *rdev, *rdev2;
+
+	struct cfg80211_registered_device *rdev;
 	int alloc_size;
-	char nname[IFNAMSIZ + 1];
-	bool found = false;
 
 	WARN_ON(ops->add_key && (!ops->del_key || !ops->set_default_key));
 	WARN_ON(ops->auth && (!ops->assoc || !ops->deauth || !ops->disassoc));
@@ -332,37 +346,17 @@ struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
 
 	if (unlikely(!wiphy_idx_valid(rdev->wiphy_idx))) {
 		wiphy_counter--;
-		goto too_many_devs;
-	}
-
-	/* 64k wiphy devices is enough for anyone! */
-	for (i = 0; i < 0xFFFF; i++) {
-		found = false;
-		snprintf(nname, sizeof(nname)-1, PHY_NAME "%d", i);
-		nname[sizeof(nname)-1] = 0;
-		list_for_each_entry(rdev2, &cfg80211_rdev_list, list)
-			if (strcmp(nname, dev_name(&rdev2->wiphy.dev)) == 0) {
-				found = true;
-				break;
-			}
-
-		if (!found)
-			break;
-	}
-
-	if (unlikely(found)) {
-too_many_devs:
 		mutex_unlock(&cfg80211_mutex);
-		/* ugh, too many devices already! */
+		/* ugh, wrapped! */
 		kfree(rdev);
 		return NULL;
 	}
 
-	/* give it a proper name */
-	dev_set_name(&rdev->wiphy.dev, "%s", nname);
-
 	mutex_unlock(&cfg80211_mutex);
 
+	/* give it a proper name */
+	dev_set_name(&rdev->wiphy.dev, PHY_NAME "%d", rdev->wiphy_idx);
+
 	mutex_init(&rdev->mtx);
 	mutex_init(&rdev->devlist_mtx);
 	INIT_LIST_HEAD(&rdev->netdev_list);