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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Cc:     Jakub Kicinski <kuba@kernel.org>,
        Lorenzo Bianconi <lorenzo@kernel.org>, netdev@vger.kernel.org,
        linux-wireless@vger.kernel.org, Felix Fietkau <nbd@nbd.name>
Subject: Re: pull-request: wireless-drivers-2021-02-05
References: <20210205163434.14D94C433ED@smtp.codeaurora.org>
        <20210206093537.0bfaf0db@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
        <20210206194325.GA134674@lore-desk>
Date:   Sun, 07 Feb 2021 07:50:06 +0200
In-Reply-To: <20210206194325.GA134674@lore-desk> (Lorenzo Bianconi's message
        of "Sat, 6 Feb 2021 20:43:25 +0100")
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Lorenzo Bianconi <lorenzo.bianconi@redhat.com> writes:

>> On Fri,  5 Feb 2021 16:34:34 +0000 (UTC) Kalle Valo wrote:
>> > Hi,
>> > 
>> > here's a pull request to net tree, more info below. Please let me know if there
>> > are any problems.
>> 
>> Pulled, thanks! One thing to confirm tho..
>> 
>> > ath9k
>> > 
>> > * fix build regression related to LEDS_CLASS
>> > 
>> > mt76
>> > 
>> > * fix a memory leak
>> 
>> Lorenzo, I'm just guessing what this code does, but you're dropping a
>> frag without invalidating the rest of the SKB, which I presume is now
>> truncated? Shouldn't the skb be dropped?
>> 
>
> Hi Jakub,
>
> I agree. We can do something like:
>
> diff --git a/drivers/net/wireless/mediatek/mt76/dma.c b/drivers/net/wireless/mediatek/mt76/dma.c
> index e81dfaf99bcb..6d84533d1df2 100644
> --- a/drivers/net/wireless/mediatek/mt76/dma.c
> +++ b/drivers/net/wireless/mediatek/mt76/dma.c
> @@ -511,8 +511,9 @@ mt76_add_fragment(struct mt76_dev *dev, struct mt76_queue *q, void *data,
>  {
>  	struct sk_buff *skb = q->rx_head;
>  	struct skb_shared_info *shinfo = skb_shinfo(skb);
> +	int nr_frags = shinfo->nr_frags;
>  
> -	if (shinfo->nr_frags < ARRAY_SIZE(shinfo->frags)) {
> +	if (nr_frags < ARRAY_SIZE(shinfo->frags)) {
>  		struct page *page = virt_to_head_page(data);
>  		int offset = data - page_address(page) + q->buf_offset;
>  
> @@ -526,7 +527,10 @@ mt76_add_fragment(struct mt76_dev *dev, struct mt76_queue *q, void *data,
>  		return;
>  
>  	q->rx_head = NULL;
> -	dev->drv->rx_skb(dev, q - dev->q_rx, skb);
> +	if (nr_frags < ARRAY_SIZE(shinfo->frags))
> +		dev->drv->rx_skb(dev, q - dev->q_rx, skb);
> +	else
> +		dev_kfree_skb(skb);
>  }
>  
>
> I do not know if it can occur, but I guess we should even check q->rx_head
> pointer before overwriting it because if the hw does not report more set to
> false for last fragment we will get a memory leak as well. Something like:
>
> @@ -578,6 +582,8 @@ mt76_dma_rx_process(struct mt76_dev *dev, struct mt76_queue *q, int budget)
>  		done++;
>  
>  		if (more) {
> +			if (q->rx_head)
> +				dev_kfree_skb(q->rx_head);
>  			q->rx_head = skb;
>  			continue;
>  		}

So what's the plan? Is there going to be a followup patch? And should
that also go to v5.11 or can it wait v5.12?

-- 
https://patchwork.kernel.org/project/linux-wireless/list/

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