linux-kernel - Re: [PATCH] xen-netback: fix occasional leak of grant ref mappings under memory pressure

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Date:   Thu, 28 Feb 2019 11:43:46 +0000
From:   Igor Druzhinin <igor.druzhinin@...rix.com>
To:     Paul Durrant <Paul.Durrant@...rix.com>,
        Wei Liu <wei.liu2@...rix.com>
CC:     "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [PATCH] xen-netback: fix occasional leak of grant ref mappings
 under memory pressure

On 28/02/2019 11:21, Paul Durrant wrote:
>>> @@ -1153,6 +1152,10 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
>>>                                 kfree_skb(skb);
>>>                                 continue;
>>>                         }
>>> +
>>> +                       /* Copied all the bits from the frag list. */
>>> +                       skb_frag_list_init(skb);
>>> +                       kfree(nskb);
>>
>> I think you want kfree_skb here?
> 
> No. nskb is the frag list... it is unlinked from skb by the call to skb_frag_list_init() and then it can be freed on its own. The skb is what we need to retain, because that now contains all the data.
> 

Are you saying previous code in xenvif_handle_frag_list() incorrectly
called kfree_skb()?

Igor