linux-kernel - Re: [PATCH] atm: eni: avoid accessing the data mapped to streaming DMA

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Date:   Mon, 03 Aug 2020 15:51:38 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     baijiaju@...nghua.edu.cn
Cc:     3chas3@...il.com, linux-atm-general@...ts.sourceforge.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] atm: eni: avoid accessing the data mapped to streaming
 DMA

From: Jia-Ju Bai <baijiaju@...nghua.edu.cn>
Date: Sun,  2 Aug 2020 17:16:11 +0800

> In do_tx(), skb->data is mapped to streaming DMA on line 1111:
>   paddr = dma_map_single(...,skb->data,DMA_TO_DEVICE);
> 
> Then skb->data is accessed on line 1153:
>   (skb->data[3] & 0xf)
> 
> This access may cause data inconsistency between CPU cache and hardware.
> 
> To fix this problem, skb->data[3] is assigned to a local variable before
> DMA mapping, and then the driver accesses this local variable instead of
> skb->data[3].
> 
> Signed-off-by: Jia-Ju Bai <baijiaju@...nghua.edu.cn>

Applied.