mac80211: add fragment cache to sta_info

commit 3a11ce08c45b50d69c891d71760b7c5b92074709 upstream.

Prior patches protected against fragmentation cache attacks
by coloring keys, but this shows that it can lead to issues
when multiple stations use the same sequence number. Add a
fragment cache to struct sta_info (in addition to the one in
the interface) to separate fragments for different stations
properly.

This then automatically clear most of the fragment cache when a
station disconnects (or reassociates) from an AP, or when client
interfaces disconnect from the network, etc.

On the way, also fix the comment there since this brings us in line
with the recommendation in 802.11-2016 ("An AP should support ...").
Additionally, remove a useless condition (since there's no problem
purging an already empty list).

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210511200110.fc35046b0d52.I1ef101e3784d13e8f6600d83de7ec9a3a45bcd52@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 30 insertions, 11 deletions

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 23c1e6529900..a93dd83b77af 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1738,19 +1738,34 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 	return result;
 }
 
+void ieee80211_init_frag_cache(struct ieee80211_fragment_cache *cache)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(cache->entries); i++)
+		skb_queue_head_init(&cache->entries[i].skb_list);
+}
+
+void ieee80211_destroy_frag_cache(struct ieee80211_fragment_cache *cache)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(cache->entries); i++)
+		__skb_queue_purge(&cache->entries[i].skb_list);
+}
+
 static inline struct ieee80211_fragment_entry *
-ieee80211_reassemble_add(struct ieee80211_sub_if_data *sdata,
+ieee80211_reassemble_add(struct ieee80211_fragment_cache *cache,
 			 unsigned int frag, unsigned int seq, int rx_queue,
 			 struct sk_buff **skb)
 {
 	struct ieee80211_fragment_entry *entry;
 
-	entry = &sdata->fragments[sdata->fragment_next++];
-	if (sdata->fragment_next >= IEEE80211_FRAGMENT_MAX)
-		sdata->fragment_next = 0;
+	entry = &cache->entries[cache->next++];
+	if (cache->next >= IEEE80211_FRAGMENT_MAX)
+		cache->next = 0;
 
-	if (!skb_queue_empty(&entry->skb_list))
-		__skb_queue_purge(&entry->skb_list);
+	__skb_queue_purge(&entry->skb_list);
 
 	__skb_queue_tail(&entry->skb_list, *skb); /* no need for locking */
 	*skb = NULL;
@@ -1765,14 +1780,14 @@ ieee80211_reassemble_add(struct ieee80211_sub_if_data *sdata,
 }
 
 static inline struct ieee80211_fragment_entry *
-ieee80211_reassemble_find(struct ieee80211_sub_if_data *sdata,
+ieee80211_reassemble_find(struct ieee80211_fragment_cache *cache,
 			  unsigned int frag, unsigned int seq,
 			  int rx_queue, struct ieee80211_hdr *hdr)
 {
 	struct ieee80211_fragment_entry *entry;
 	int i, idx;
 
-	idx = sdata->fragment_next;
+	idx = cache->next;
 	for (i = 0; i < IEEE80211_FRAGMENT_MAX; i++) {
 		struct ieee80211_hdr *f_hdr;
 
@@ -1780,7 +1795,7 @@ ieee80211_reassemble_find(struct ieee80211_sub_if_data *sdata,
 		if (idx < 0)
 			idx = IEEE80211_FRAGMENT_MAX - 1;
 
-		entry = &sdata->fragments[idx];
+		entry = &cache->entries[idx];
 		if (skb_queue_empty(&entry->skb_list) || entry->seq != seq ||
 		    entry->rx_queue != rx_queue ||
 		    entry->last_frag + 1 != frag)
@@ -1820,6 +1835,7 @@ static bool requires_sequential_pn(struct ieee80211_rx_data *rx, __le16 fc)
 static ieee80211_rx_result debug_noinline
 ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
 {
+	struct ieee80211_fragment_cache *cache = &rx->sdata->frags;
 	struct ieee80211_hdr *hdr;
 	u16 sc;
 	__le16 fc;
@@ -1842,6 +1858,9 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
 		goto out_no_led;
 	}
 
+	if (rx->sta)
+		cache = &rx->sta->frags;
+
 	if (likely(!ieee80211_has_morefrags(fc) && frag == 0))
 		goto out;
 
@@ -1860,7 +1879,7 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
 
 	if (frag == 0) {
 		/* This is the first fragment of a new frame. */
-		entry = ieee80211_reassemble_add(rx->sdata, frag, seq,
+		entry = ieee80211_reassemble_add(cache, frag, seq,
 						 rx->seqno_idx, &(rx->skb));
 		if (requires_sequential_pn(rx, fc)) {
 			int queue = rx->security_idx;
@@ -1888,7 +1907,7 @@ ieee80211_rx_h_defragment(struct ieee80211_rx_data *rx)
 	/* This is a fragment for a frame that should already be pending in
 	 * fragment cache. Add this fragment to the end of the pending entry.
 	 */
-	entry = ieee80211_reassemble_find(rx->sdata, frag, seq,
+	entry = ieee80211_reassemble_find(cache, frag, seq,
 					  rx->seqno_idx, hdr);
 	if (!entry) {
 		I802_DEBUG_INC(rx->local->rx_handlers_drop_defrag);