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

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 <redacted>
---
 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

On Mon, 2020-10-19 at 11:09 +0800, Jia-Ju Bai wrote:

The changes of the series patches are good to me. 
But, please use 'rtlwifi: ' as subject prefix, like "rtlwifi: rtl8192ce: ...",
and send them as a patchset I think this would be better to maintainer.

Thank you

---
PK

Jia-Ju Bai [off-list ref] wrote:

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 <redacted>

Like Ping said, use "rtlwifi:" prefix and have all rtlwifi patches in
the same patchset.

4 patches set to Changes Requested.

11843533 rtl8192ce: avoid accessing the data mapped to streaming DMA
11843541 rtl8192de: avoid accessing the data mapped to streaming DMA
11843553 rtl8723ae: avoid accessing the data mapped to streaming DMA
11843557 rtl8188ee: avoid accessing the data mapped to streaming DMA

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20201019030931.4796-1-baijiaju1990@gmail.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches