[PATCH] rtl8192ce: avoid accessing the data mapped to streaming DMA

Jia-Ju Bai
2020-10-19T03:09:41Z

In rtl92ce_tx_fill_cmddesc(), skb->data is mapped to streaming DMA on
line 530:
dma_addr_t mapping = dma_map_single(..., skb->data, ...);

On line 533, skb->data is assigned to hdr after cast:
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)(skb->data);

Then hdr->frame_control is accessed on line 534:
__le16 fc = hdr->frame_control;

This DMA access may cause data inconsistency between CPU and hardwre.

To fix this bug, hdr->frame_control is accessed before the DMA mapping.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
drivers/net/wireless/realtek/rtlwifi/rtl8192ce/trx.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8192ce/trx.c b/drivers/net/wireless/realtek/rtlwifi/rtl8192ce/trx.c
index c0635309a92d..4165175cf5c0 100644
--- a/drivers/net/wireless/realtek/rtlwifi/rtl8192ce/trx.c
+++ b/drivers/net/wireless/realtek/rtlwifi/rtl8192ce/trx.c
@@ -527,12 +527,12 @@ void rtl92ce_tx_fill_cmddesc(struct ieee80211_hw *hw,
u8 fw_queue = QSLT_BEACON;
__le32 *pdesc = (__le32 *)pdesc8;

- dma_addr_t mapping = dma_map_single(&rtlpci->pdev->dev, skb->data,
- skb->len, DMA_TO_DEVICE);
-
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)(skb->data);
__le16 fc = hdr->frame_control;

+ dma_addr_t mapping = dma_map_single(&rtlpci->pdev->dev, skb->data,
+ skb->len, DMA_TO_DEVICE);
+
if (dma_mapping_error(&rtlpci->pdev->dev, mapping)) {
rtl_dbg(rtlpriv, COMP_SEND, DBG_TRACE,
"DMA mapping error\n");
--
2.17.1