ath10k: drop fragments with multicast DA for PCIe

Fragmentation is not used with multicast frames. Discard unexpected
fragments with multicast DA. This fixes CVE-2020-26145.

Tested-on: QCA6174 hw3.2 PCI WLAN.RM.4.4.1-00110-QCARMSWP-1

Cc: stable@vger.kernel.org
Signed-off-by: Wen Gong <wgong@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20210511200110.5a0bd289bda8.Idd6ebea20038fb1cfee6de924aa595e5647c9eae@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/ath/ath10k/htt_rx.c

@@ -1768,6 +1768,16 @@ static u64 ath10k_htt_rx_h_get_pn(struct ath10k *ar, struct sk_buff *skb,
 	return pn;
 }
 
+static bool ath10k_htt_rx_h_frag_multicast_check(struct ath10k *ar,
+						 struct sk_buff *skb,
+						 u16 offset)
+{
+	struct ieee80211_hdr *hdr;
+
+	hdr = (struct ieee80211_hdr *)(skb->data + offset);
+	return !is_multicast_ether_addr(hdr->addr1);
+}
+
 static bool ath10k_htt_rx_h_frag_pn_check(struct ath10k *ar,
 					  struct sk_buff *skb,
 					  u16 peer_id,
@@ -1839,7 +1849,7 @@ static void ath10k_htt_rx_h_mpdu(struct ath10k *ar,
 	bool is_decrypted;
 	bool is_mgmt;
 	u32 attention;
-	bool frag_pn_check = true;
+	bool frag_pn_check = true, multicast_check = true;
 
 	if (skb_queue_empty(amsdu))
 		return;
@@ -1946,13 +1956,20 @@ static void ath10k_htt_rx_h_mpdu(struct ath10k *ar,
 								      0,
 								      enctype);
 
-		if (!frag_pn_check) {
-			/* Discard the fragment with invalid PN */
+		if (frag)
+			multicast_check = ath10k_htt_rx_h_frag_multicast_check(ar,
+									       msdu,
+									       0);
+
+		if (!frag_pn_check || !multicast_check) {
+			/* Discard the fragment with invalid PN or multicast DA
+			 */
 			temp = msdu->prev;
 			__skb_unlink(msdu, amsdu);
 			dev_kfree_skb_any(msdu);
 			msdu = temp;
 			frag_pn_check = true;
+			multicast_check = true;
 			continue;
 		}