[PATCH v2 1/4] rtlwifi: rtl8188ee: avoid accessing the data mapped to streaming DMA

[PATCH v2 1/4] rtlwifi: rtl8188ee: avoid accessing the data mapped to streaming DMA

[Jia-Ju Bai]

In rtl88ee_tx_fill_cmddesc(), skb->data is mapped to streaming DMA on
line 677:
  dma_addr_t mapping = dma_map_single(..., skb->data, ...);

On line 680, 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 681:
  __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/rtl8188ee/trx.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c b/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
index b9775eec4c54..c948dafa0c80 100644
--- a/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
+++ b/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
@@ -674,12 +674,12 @@ void rtl88ee_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

Re: [PATCH v2 1/4] rtlwifi: rtl8188ee: avoid accessing the data mapped to streaming DMA

[Pkshih]

On Wed, 2020-11-18 at 09:53 +0800, Jia-Ju Bai wrote:
> In rtl88ee_tx_fill_cmddesc(), skb->data is mapped to streaming DMA on
> line 677:
>   dma_addr_t mapping = dma_map_single(..., skb->data, ...);
> 
> On line 680, 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 681:
>   __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>

This patchset looks good to me.
Thank you.

Acked-by: Ping-Ke Shih <pkshih@realtek.com>

> ---
>  drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
> b/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
> index b9775eec4c54..c948dafa0c80 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
> +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
> @@ -674,12 +674,12 @@ void rtl88ee_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");

Re: [PATCH v2 1/4] rtlwifi: rtl8188ee: avoid accessing the data mapped to streaming DMA

[Larry Finger]

On 11/17/20 7:53 PM, Jia-Ju Bai wrote:
> In rtl88ee_tx_fill_cmddesc(), skb->data is mapped to streaming DMA on
> line 677:
>    dma_addr_t mapping = dma_map_single(..., skb->data, ...);
> 
> On line 680, 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 681:
>    __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/rtl8188ee/trx.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)

What changed between v1 and v2?

As outlined in Documentation/process/submitting-patches.rst, you should add a 
'---' marker and descrive what was changed. I usually summarize the changes, but 
it is also possible to provide a diffstat of the changes as the above file shows.

Larry

> 
> diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c b/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
> index b9775eec4c54..c948dafa0c80 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
> +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8188ee/trx.c
> @@ -674,12 +674,12 @@ void rtl88ee_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");
> 

Re: [PATCH v2 1/4] rtlwifi: rtl8188ee: avoid accessing the data mapped to streaming DMA

[Jia-Ju Bai]

Thanks for the advice.
I have added the description of the changes and resent the patches.


Best wishes,
Jia-Ju Bai

On 2020/11/19 1:20, Larry Finger wrote:
> On 11/17/20 7:53 PM, Jia-Ju Bai wrote:
>> In rtl88ee_tx_fill_cmddesc(), skb->data is mapped to streaming DMA on
>> line 677:
>>    dma_addr_t mapping = dma_map_single(..., skb->data, ...);
>>
>> On line 680, 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 681:
>>    __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/rtl8188ee/trx.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> What changed between v1 and v2?
>
> As outlined in Documentation/process/submitting-patches.rst, you 
> should add a '---' marker and descrive what was changed. I usually 
> summarize the changes, but it is also possible to provide a diffstat 
> of the changes as the above file shows.
>