staging: rtlwifi: rtl8822b: fix a missing check of alloc_skb

__netdev_alloc_skb() return NULl when it fails. skb_put() further uses
it even when the allocation fails, leading to NULL pointer dereference.
The fix inserts a check for the return value of __netdev_alloc_skb().

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtlwifi/rtl8822be/fw.c

@@ -486,6 +486,8 @@ bool rtl8822b_halmac_cb_write_data_h2c(struct rtl_priv *rtlpriv, u8 *buf,
 
 	/* without GFP_DMA, pci_map_single() may not work */
 	skb = __netdev_alloc_skb(NULL, size, GFP_ATOMIC | GFP_DMA);
+	if (!skb)
+		return false;
 	memcpy((u8 *)skb_put(skb, size), buf, size);
 
 	return _rtl8822be_send_bcn_or_cmd_packet(rtlpriv->hw, skb, H2C_QUEUE);