linux-kernel - Re: [PATCH] dmaengine: virt-dma: Fix access after free in vcna

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Date:   Fri, 20 Dec 2019 16:50:44 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>,
        "vkoul@...nel.org" <vkoul@...nel.org>
CC:     "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dmaengine: virt-dma: Fix access after free in
 vcna_complete()



On 20/12/2019 16.01, Ardelean, Alexandru wrote:
> On Fri, 2019-12-20 at 15:11 +0200, Peter Ujfalusi wrote:
>> [External]
>>
>> vchan_vdesc_fini() is freeing up 'vd' so the access to vd->tx_result is
>> via already freed up memory.
>>
>> Move the vchan_vdesc_fini() after invoking the callback to avoid this.
>>
> 
> Apologies for seeing this too late: typo in title vcna_complete() ->
> vchan_complete()

Yep, I also noticed after sending it, I hope Vinod is kind enough and
fix it up when applying ;)

- Péter

>> Fixes: 09d5b702b0f97 ("dmaengine: virt-dma: store result on dma
>> descriptor")
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
>> ---
>>  drivers/dma/virt-dma.c | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/dma/virt-dma.c b/drivers/dma/virt-dma.c
>> index ec4adf4260a0..256fc662c500 100644
>> --- a/drivers/dma/virt-dma.c
>> +++ b/drivers/dma/virt-dma.c
>> @@ -104,9 +104,8 @@ static void vchan_complete(unsigned long arg)
>>  		dmaengine_desc_get_callback(&vd->tx, &cb);
>>  
>>  		list_del(&vd->node);
>> -		vchan_vdesc_fini(vd);
>> -
>>  		dmaengine_desc_callback_invoke(&cb, &vd->tx_result);
>> +		vchan_vdesc_fini(vd);
>>  	}
>>  }
>>  


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