1 files changed, 96 insertions, 31 deletions

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 0358e12be54b..35ad69fd0838 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -57,6 +57,19 @@
  * also linked into the probe response struct.
  */
 
+/*
+ * 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	(30 * HZ)
 
 static void bss_free(struct cfg80211_internal_bss *bss)
@@ -137,6 +150,10 @@ static bool __cfg80211_unlink_bss(struct cfg80211_registered_device *rdev,
 
 	list_del_init(&bss->list);
 	rb_erase(&bss->rbn, &rdev->bss_tree);
+	rdev->bss_entries--;
+	WARN_ONCE((rdev->bss_entries == 0) ^ list_empty(&rdev->bss_list),
+		  "rdev bss entries[%d]/list[empty:%d] corruption\n",
+		  rdev->bss_entries, list_empty(&rdev->bss_list));
 	bss_ref_put(rdev, bss);
 	return true;
 }
@@ -163,6 +180,40 @@ static void __cfg80211_bss_expire(struct cfg80211_registered_device *rdev,
 		rdev->bss_generation++;
 }
 
+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;
+}
+
 void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev,
 			   bool send_message)
 {
@@ -352,52 +403,48 @@ void cfg80211_bss_expire(struct cfg80211_registered_device *rdev)
 	__cfg80211_bss_expire(rdev, jiffies - IEEE80211_SCAN_RESULT_EXPIRE);
 }
 
-const u8 *cfg80211_find_ie(u8 eid, const u8 *ies, int len)
+const u8 *cfg80211_find_ie_match(u8 eid, const u8 *ies, int len,
+				 const u8 *match, int match_len,
+				 int match_offset)
 {
-	while (len > 2 && ies[0] != eid) {
+	/* match_offset can't be smaller than 2, unless match_len is
+	 * zero, in which case match_offset must be zero as well.
+	 */
+	if (WARN_ON((match_len && match_offset < 2) ||
+		    (!match_len && match_offset)))
+		return NULL;
+
+	while (len >= 2 && len >= ies[1] + 2) {
+		if ((ies[0] == eid) &&
+		    (ies[1] + 2 >= match_offset + match_len) &&
+		    !memcmp(ies + match_offset, match, match_len))
+			return ies;
+
 		len -= ies[1] + 2;
 		ies += ies[1] + 2;
 	}
-	if (len < 2)
-		return NULL;
-	if (len < 2 + ies[1])
-		return NULL;
-	return ies;
+
+	return NULL;
 }
-EXPORT_SYMBOL(cfg80211_find_ie);
+EXPORT_SYMBOL(cfg80211_find_ie_match);
 
 const u8 *cfg80211_find_vendor_ie(unsigned int oui, int oui_type,
 				  const u8 *ies, int len)
 {
-	struct ieee80211_vendor_ie *ie;
-	const u8 *pos = ies, *end = ies + len;
-	int ie_oui;
+	const u8 *ie;
+	u8 match[] = { oui >> 16, oui >> 8, oui, oui_type };
+	int match_len = (oui_type < 0) ? 3 : sizeof(match);
 
 	if (WARN_ON(oui_type > 0xff))
 		return NULL;
 
-	while (pos < end) {
-		pos = cfg80211_find_ie(WLAN_EID_VENDOR_SPECIFIC, pos,
-				       end - pos);
-		if (!pos)
-			return NULL;
-
-		ie = (struct ieee80211_vendor_ie *)pos;
+	ie = cfg80211_find_ie_match(WLAN_EID_VENDOR_SPECIFIC, ies, len,
+				    match, match_len, 2);
 
-		/* make sure we can access ie->len */
-		BUILD_BUG_ON(offsetof(struct ieee80211_vendor_ie, len) != 1);
-
-		if (ie->len < sizeof(*ie))
-			goto cont;
+	if (ie && (ie[1] < 4))
+		return NULL;
 
-		ie_oui = ie->oui[0] << 16 | ie->oui[1] << 8 | ie->oui[2];
-		if (ie_oui == oui &&
-		    (oui_type < 0 || ie->oui_type == oui_type))
-			return pos;
-cont:
-		pos += 2 + ie->len;
-	}
-	return NULL;
+	return ie;
 }
 EXPORT_SYMBOL(cfg80211_find_vendor_ie);
 
@@ -693,6 +740,7 @@ static bool cfg80211_combine_bsses(struct cfg80211_registered_device *rdev,
 	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))
@@ -716,6 +764,12 @@ static bool cfg80211_combine_bsses(struct cfg80211_registered_device *rdev,
 	/* This is the bad part ... */
 
 	list_for_each_entry(bss, &rdev->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)
@@ -744,6 +798,10 @@ static bool cfg80211_combine_bsses(struct cfg80211_registered_device *rdev,
 				   new->pub.beacon_ies);
 	}
 
+	WARN_ONCE(n_entries != rdev->bss_entries,
+		  "rdev bss entries[%d]/list[len:%d] corruption\n",
+		  rdev->bss_entries, n_entries);
+
 	return true;
 }
 
@@ -898,7 +956,14 @@ cfg80211_bss_update(struct cfg80211_registered_device *rdev,
 			}
 		}
 
+		if (rdev->bss_entries >= bss_entries_limit &&
+		    !cfg80211_bss_expire_oldest(rdev)) {
+			kfree(new);
+			goto drop;
+		}
+
 		list_add_tail(&new->list, &rdev->bss_list);
+		rdev->bss_entries++;
 		rb_insert_bss(rdev, new);
 		found = new;
 	}