wifi: mwifiex: avoid possible NULL skb pointer dereference

In 'mwifiex_handle_uap_rx_forward()', always check the value
returned by 'skb_copy()' to avoid potential NULL pointer
dereference in 'mwifiex_uap_queue_bridged_pkt()', and drop
original skb in case of copying failure.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 838e4f44 ("mwifiex: improve uAP RX handling")
Acked-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230814095041.16416-1-dmantipov@yandex.ru

drivers/net/wireless/marvell/mwifiex/uap_txrx.c

@@ -253,7 +253,15 @@ int mwifiex_handle_uap_rx_forward(struct mwifiex_private *priv,
 
 	if (is_multicast_ether_addr(ra)) {
 		skb_uap = skb_copy(skb, GFP_ATOMIC);
-		mwifiex_uap_queue_bridged_pkt(priv, skb_uap);
+		if (likely(skb_uap)) {
+			mwifiex_uap_queue_bridged_pkt(priv, skb_uap);
+		} else {
+			mwifiex_dbg(adapter, ERROR,
+				    "failed to copy skb for uAP\n");
+			priv->stats.rx_dropped++;
+			dev_kfree_skb_any(skb);
+			return -1;
+		}
 	} else {
 		if (mwifiex_get_sta_entry(priv, ra)) {
 			/* Requeue Intra-BSS packet */