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-rw-r--r--net/wireless/scan.c69
1 files changed, 69 insertions, 0 deletions
diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index b5bd58d0f731..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)
{
@@ -689,6 +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))
@@ -712,6 +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)
@@ -740,6 +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;
}
@@ -894,7 +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;
}