ath10k: drop MPDU which has discard flag set by firmware for SDIO

When the discard flag is set by the firmware for an MPDU, it should be
dropped. This allows a mitigation for CVE-2020-24588 to be implemented
in the firmware.

Tested-on: QCA6174 hw3.2 SDIO WLAN.RMH.4.4.1-00049

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/20210511200110.11968c725b5c.Idd166365ebea2771c0c0a38c78b5060750f90e17@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

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

@@ -2312,6 +2312,11 @@ static bool ath10k_htt_rx_proc_rx_ind_hl(struct ath10k_htt *htt,
 	fw_desc = &rx->fw_desc;
 	rx_desc_len = fw_desc->len;
 
+	if (fw_desc->u.bits.discard) {
+		ath10k_dbg(ar, ATH10K_DBG_HTT, "htt discard mpdu\n");
+		goto err;
+	}
+
 	/* I have not yet seen any case where num_mpdu_ranges > 1.
 	 * qcacld does not seem handle that case either, so we introduce the
 	 * same limitiation here as well.

drivers/net/wireless/ath/ath10k/rx_desc.h

@@ -1282,7 +1282,19 @@ struct fw_rx_desc_base {
 #define FW_RX_DESC_UDP              (1 << 6)
 
 struct fw_rx_desc_hl {
-	u8 info0;
+	union {
+		struct {
+		u8 discard:1,
+		   forward:1,
+		   any_err:1,
+		   dup_err:1,
+		   reserved:1,
+		   inspect:1,
+		   extension:2;
+		} bits;
+		u8 info0;
+	} u;
+
 	u8 version;
 	u8 len;
 	u8 flags;