linux-kernel - Re: [PATCH 4.9 038/109] dmaengine: stm32-dma: Fix null pointer dereference in stm32_dma_tx

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Date:   Thu, 7 Dec 2017 14:26:54 +0100
From:   Pierre Yves MORDRET <pierre-yves.mordret@...com>
To:     Ludovic BARRE <ludovic.barre@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-kernel@...r.kernel.org>
CC:     <stable@...r.kernel.org>,
        Mboumba Cedric Madianga <cedric.madianga@...il.com>,
        Vinod Koul <vinod.koul@...el.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: Re: [PATCH 4.9 038/109] dmaengine: stm32-dma: Fix null pointer
 dereference in stm32_dma_tx_status


Acked-by: Pierre-Yves MORDRET <pierre-yves.mordret@...com>

~PYM~


On 12/07/2017 02:18 PM, Ludovic BARRE wrote:
> with Pierre Yves mail it's better ;-)
> 
> On 12/07/2017 02:04 PM, Ludovic BARRE wrote:
>> add Pierre-yves Mordret
>>
>> acked-by: Ludovic BARRE <ludovic.barre@...com>
>>
>> On 12/07/2017 01:56 PM, Greg Kroah-Hartman wrote:
>>> 4.9-stable review patch.  If anyone has any objections, please let me 
>>> know.
>>>
>>> ------------------
>>>
>>> From: M'boumba Cedric Madianga <cedric.madianga@...il.com>
>>>
>>>
>>> [ Upstream commit 57b5a32135c813f2ab669039fb4ec16b30cb3305 ]
>>>
>>> chan->desc is always set to NULL when a DMA transfer is complete.
>>> As a DMA transfer could be complete during the call of 
>>> stm32_dma_tx_status,
>>> we need to be sure that chan->desc is not NULL before using this variable
>>> to avoid a null pointer deference issue.
>>>
>>> Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@...il.com>
>>> Reviewed-by: Ludovic BARRE <ludovic.barre@...com>
>>> Signed-off-by: Vinod Koul <vinod.koul@...el.com>
>>> Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
>>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>> ---
>>>   drivers/dma/stm32-dma.c |   10 +++-------
>>>   1 file changed, 3 insertions(+), 7 deletions(-)
>>>
>>> --- a/drivers/dma/stm32-dma.c
>>> +++ b/drivers/dma/stm32-dma.c
>>> @@ -884,7 +884,7 @@ static enum dma_status stm32_dma_tx_stat
>>>       struct virt_dma_desc *vdesc;
>>>       enum dma_status status;
>>>       unsigned long flags;
>>> -    u32 residue;
>>> +    u32 residue = 0;
>>>       status = dma_cookie_status(c, cookie, state);
>>>       if ((status == DMA_COMPLETE) || (!state))
>>> @@ -892,16 +892,12 @@ static enum dma_status stm32_dma_tx_stat
>>>       spin_lock_irqsave(&chan->vchan.lock, flags);
>>>       vdesc = vchan_find_desc(&chan->vchan, cookie);
>>> -    if (cookie == chan->desc->vdesc.tx.cookie) {
>>> +    if (chan->desc && cookie == chan->desc->vdesc.tx.cookie)
>>>           residue = stm32_dma_desc_residue(chan, chan->desc,
>>>                            chan->next_sg);
>>> -    } else if (vdesc) {
>>> +    else if (vdesc)
>>>           residue = stm32_dma_desc_residue(chan,
>>>                            to_stm32_dma_desc(vdesc), 0);
>>> -    } else {
>>> -        residue = 0;
>>> -    }
>>> -
>>>       dma_set_residue(state, residue);
>>>       spin_unlock_irqrestore(&chan->vchan.lock, flags);
>>>
>>>