linux-kernel - Re: [PATCH] p54: avoid accessing the data mapped to streaming DMA

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Message-Id: <20200818124147.27D1DC43391@smtp.codeaurora.org>
Date:   Tue, 18 Aug 2020 12:41:47 +0000 (UTC)
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Jia-Ju Bai <baijiaju@...nghua.edu.cn>
Cc:     chunkeey@...glemail.com, davem@...emloft.net, kuba@...nel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jia-Ju Bai <baijiaju@...nghua.edu.cn>
Subject: Re: [PATCH] p54: avoid accessing the data mapped to streaming DMA

Jia-Ju Bai <baijiaju@...nghua.edu.cn> wrote:

> In p54p_tx(), skb->data is mapped to streaming DMA on line 337:
>   mapping = pci_map_single(..., skb->data, ...);
> 
> Then skb->data is accessed on line 349:
>   desc->device_addr = ((struct p54_hdr *)skb->data)->req_id;
> 
> This access may cause data inconsistency between CPU cache and hardware.
> 
> To fix this problem, ((struct p54_hdr *)skb->data)->req_id is stored in
> a local variable before DMA mapping, and then the driver accesses this
> local variable instead of skb->data.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju@...nghua.edu.cn>

Can someone review this?

-- 
https://patchwork.kernel.org/patch/11696391/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches