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

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Message-ID: <1605666764.7490.1.camel@realtek.com>
Date:   Wed, 18 Nov 2020 02:33:48 +0000
From:   Pkshih <pkshih@...ltek.com>
To:     "baijiaju1990@...il.com" <baijiaju1990@...il.com>,
        "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>
CC:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] rtlwifi: rtl8188ee: avoid accessing the data mapped to streaming DMA

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@...il.com>

This patchset looks good to me.
Thank you.

Acked-by: Ping-Ke Shih <pkshih@...ltek.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");