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[24.31.245.230]) by smtp.gmail.com with ESMTPSA id z25sm954928ooj.39.2020.11.18.09.20.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 18 Nov 2020 09:20:25 -0800 (PST) Sender: Larry Finger Subject: Re: [PATCH v2 1/4] rtlwifi: rtl8188ee: avoid accessing the data mapped to streaming DMA To: Jia-Ju Bai , pkshih@realtek.com, kvalo@codeaurora.org, davem@davemloft.net, kuba@kernel.org Cc: linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20201118015314.4979-1-baijiaju1990@gmail.com> From: Larry Finger Message-ID: Date: Wed, 18 Nov 2020 11:20:24 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201118015314.4979-1-baijiaju1990@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org 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 > --- > 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"); >