mt76: mt7915: only modify tx buffer list after allocating tx token id

Modifying the tx buffer list too early can leak DMA mappings
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210216135119.23809-2-nbd@nbd.name

drivers/net/wireless/mediatek/mt76/mt7915/mac.c

@@ -967,11 +967,6 @@ int mt7915_tx_prepare_skb(struct mt76_dev *mdev, void *txwi_ptr,
 	}
 	txp->nbuf = nbuf;
 
-	/* pass partial skb header to fw */
-	tx_info->buf[1].len = MT_CT_PARSE_LEN;
-	tx_info->buf[1].skip_unmap = true;
-	tx_info->nbuf = MT_CT_DMA_BUF_NUM;
-
 	txp->flags = cpu_to_le16(MT_CT_INFO_APPLY_TXD | MT_CT_INFO_FROM_HOST);
 
 	if (!key)
@@ -1009,6 +1004,11 @@ int mt7915_tx_prepare_skb(struct mt76_dev *mdev, void *txwi_ptr,
 		txp->rept_wds_wcid = cpu_to_le16(0x3ff);
 	tx_info->skb = DMA_DUMMY_DATA;
 
+	/* pass partial skb header to fw */
+	tx_info->buf[1].len = MT_CT_PARSE_LEN;
+	tx_info->buf[1].skip_unmap = true;
+	tx_info->nbuf = MT_CT_DMA_BUF_NUM;
+
 	return 0;
 }