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 14:04:03 +0100
From:   Ludovic BARRE <ludovic.barre@...com>
To:     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

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);
> 
>