X-Git-Url: https://git.stricted.de/?a=blobdiff_plain;f=net%2Fwireless%2Fscan.c;h=3e740e937ad11d356471a5f4f912c235afd48802;hb=HEAD;hp=fd99ea495b7e68cd9e5265542a6aa059d0ac7760;hpb=f3c58ceef014ea7f8a253b50b8af81b3b898bc77;p=GitHub%2Fmt8127%2Fandroid_kernel_alcatel_ttab.git

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index fd99ea495b7e..3e740e937ad1 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -55,7 +55,20 @@
  * also linked into the probe response struct.
  */
 
-#define IEEE80211_SCAN_RESULT_EXPIRE	(30 * HZ)
+/*
+ * Limit the number of BSS entries stored in mac80211. Each one is
+ * a bit over 4k at most, so this limits to roughly 4-5M of memory.
+ * If somebody wants to really attack this though, they'd likely
+ * use small beacons, and only one type of frame, limiting each of
+ * the entries to a much smaller size (in order to generate more
+ * entries in total, so overhead is bigger.)
+ */
+static int bss_entries_limit = 1000;
+module_param(bss_entries_limit, int, 0644);
+MODULE_PARM_DESC(bss_entries_limit,
+                 "limit to number of scan BSS entries (per wiphy, default 1000)");
+
+#define IEEE80211_SCAN_RESULT_EXPIRE	(7 * HZ)
 
 static void bss_free(struct cfg80211_internal_bss *bss)
 {
@@ -135,6 +148,10 @@ static bool __cfg80211_unlink_bss(struct cfg80211_registered_device *dev,
 
 	list_del_init(&bss->list);
 	rb_erase(&bss->rbn, &dev->bss_tree);
+	dev->bss_entries--;
+	WARN_ONCE((dev->bss_entries == 0) ^ list_empty(&dev->bss_list),
+		  "rdev bss entries[%d]/list[empty:%d] corruption\n",
+		  dev->bss_entries, list_empty(&dev->bss_list));
 	bss_ref_put(dev, bss);
 	return true;
 }
@@ -253,10 +270,10 @@ void __cfg80211_sched_scan_results(struct work_struct *wk)
 	rdev = container_of(wk, struct cfg80211_registered_device,
 			    sched_scan_results_wk);
 
-	request = rdev->sched_scan_req;
-
 	mutex_lock(&rdev->sched_scan_mtx);
 
+	request = rdev->sched_scan_req;
+
 	/* we don't have sched_scan_req anymore if the scan is stopping */
 	if (request) {
 		if (request->flags & NL80211_SCAN_FLAG_FLUSH) {
@@ -338,6 +355,40 @@ void cfg80211_bss_expire(struct cfg80211_registered_device *dev)
 	__cfg80211_bss_expire(dev, jiffies - IEEE80211_SCAN_RESULT_EXPIRE);
 }
 
+static bool cfg80211_bss_expire_oldest(struct cfg80211_registered_device *rdev)
+{
+	struct cfg80211_internal_bss *bss, *oldest = NULL;
+	bool ret;
+
+	lockdep_assert_held(&rdev->bss_lock);
+
+	list_for_each_entry(bss, &rdev->bss_list, list) {
+		if (atomic_read(&bss->hold))
+			continue;
+
+		if (!list_empty(&bss->hidden_list) &&
+		    !bss->pub.hidden_beacon_bss)
+			continue;
+
+		if (oldest && time_before(oldest->ts, bss->ts))
+			continue;
+		oldest = bss;
+	}
+
+	if (WARN_ON(!oldest))
+		return false;
+
+	/*
+	 * The callers make sure to increase rdev->bss_generation if anything
+	 * gets removed (and a new entry added), so there's no need to also do
+	 * it here.
+	 */
+
+	ret = __cfg80211_unlink_bss(rdev, oldest);
+	WARN_ON(!ret);
+	return ret;
+}
+
 const u8 *cfg80211_find_ie(u8 eid, const u8 *ies, int len)
 {
 	while (len > 2 && ies[0] != eid) {
@@ -622,6 +673,7 @@ static bool cfg80211_combine_bsses(struct cfg80211_registered_device *dev,
 	const u8 *ie;
 	int i, ssidlen;
 	u8 fold = 0;
+	u32 n_entries = 0;
 
 	ies = rcu_access_pointer(new->pub.beacon_ies);
 	if (WARN_ON(!ies))
@@ -645,6 +697,12 @@ static bool cfg80211_combine_bsses(struct cfg80211_registered_device *dev,
 	/* This is the bad part ... */
 
 	list_for_each_entry(bss, &dev->bss_list, list) {
+		/*
+		 * we're iterating all the entries anyway, so take the
+		 * opportunity to validate the list length accounting
+		 */
+		n_entries++;
+
 		if (!ether_addr_equal(bss->pub.bssid, new->pub.bssid))
 			continue;
 		if (bss->pub.channel != new->pub.channel)
@@ -674,6 +732,10 @@ static bool cfg80211_combine_bsses(struct cfg80211_registered_device *dev,
 				   new->pub.beacon_ies);
 	}
 
+	WARN_ONCE(n_entries != dev->bss_entries,
+		  "rdev bss entries[%d]/list[len:%d] corruption\n",
+		  dev->bss_entries, n_entries);
+
 	return true;
 }
 
@@ -818,7 +880,14 @@ cfg80211_bss_update(struct cfg80211_registered_device *dev,
 			}
 		}
 
+		if (dev->bss_entries >= bss_entries_limit &&
+		    !cfg80211_bss_expire_oldest(dev)) {
+			kfree(new);
+			goto drop;
+		}
+
 		list_add_tail(&new->list, &dev->bss_list);
+		dev->bss_entries++;
 		rb_insert_bss(dev, new);
 		found = new;
 	}