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

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Message-ID: <9a4a11cf-6505-3434-85fa-262e3e16bc47@gmail.com>
Date:   Thu, 19 Nov 2020 09:54:14 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Larry Finger <Larry.Finger@...inger.net>, pkshih@...ltek.com,
        kvalo@...eaurora.org, davem@...emloft.net, kuba@...nel.org
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] rtlwifi: rtl8188ee: avoid accessing the data
 mapped to streaming DMA

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@...il.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.
>