linux-kernel - Re: [PATCH] rtl8180: avoid accessing the data mapped to streaming DMA

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Message-ID: <20201019114319.1b699ffa@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 19 Oct 2020 11:43:19 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     kvalo@...eaurora.org, davem@...emloft.net,
        vaibhavgupta40@...il.com, christophe.jaillet@...adoo.fr,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtl8180: avoid accessing the data mapped to streaming
 DMA

On Mon, 19 Oct 2020 10:54:20 +0800 Jia-Ju Bai wrote:
> +	if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ) {
> +		if (info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT)
> +			priv->seqno += 0x10;
> +		hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
> +		hdr->seq_ctrl |= cpu_to_le16(priv->seqno);
> +	}
> +
>  	mapping = dma_map_single(&priv->pdev->dev, skb->data, skb->len,
>  				 DMA_TO_DEVICE);
>  
> @@ -534,13 +541,6 @@ static void rtl8180_tx(struct ieee80211_hw *dev,
>  
>  	spin_lock_irqsave(&priv->lock, flags);
>  
> -	if (info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ) {
> -		if (info->flags & IEEE80211_TX_CTL_FIRST_FRAGMENT)
> -			priv->seqno += 0x10;

You're taking the priv->seqno access and modification from under
priv->lock. Is that okay?