linux-kernel - Re: [PATCH] dma: ste_dma40: don't dereference free:d descriptor

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Date:	Mon, 17 Feb 2014 14:07:17 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	linux-kernel@...r.kernel.org, Dan Williams <djbw@...com>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	stable@...r.kernel.org
Subject: Re: [PATCH] dma: ste_dma40: don't dereference free:d descriptor

On Thu, Feb 13, 2014 at 10:39:01AM +0100, Linus Walleij wrote:
> It appears that in the DMA40 driver the DMA tasklet will very
> often dereference memory for a descriptor just free:d from the
> DMA40 slab. Nothing happens because no other part of the driver
> has yet had a chance to claim this memory, but it's really
> nasty to dereference free:d memory, so let's check the flag
> before the descriptor is free and store it in a bool variable.
> 
> Cc: stable@...r.kernel.org
> Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>

Applied, thanks

-- 
~Vinod
> ---
>  drivers/dma/ste_dma40.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
> index 00a2de957b23..bf18c786ed40 100644
> --- a/drivers/dma/ste_dma40.c
> +++ b/drivers/dma/ste_dma40.c
> @@ -1641,6 +1641,7 @@ static void dma_tasklet(unsigned long data)
>  	struct d40_chan *d40c = (struct d40_chan *) data;
>  	struct d40_desc *d40d;
>  	unsigned long flags;
> +	bool callback_active;
>  	dma_async_tx_callback callback;
>  	void *callback_param;
>  
> @@ -1668,6 +1669,7 @@ static void dma_tasklet(unsigned long data)
>  	}
>  
>  	/* Callback to client */
> +	callback_active = !!(d40d->txd.flags & DMA_PREP_INTERRUPT);
>  	callback = d40d->txd.callback;
>  	callback_param = d40d->txd.callback_param;
>  
> @@ -1690,7 +1692,7 @@ static void dma_tasklet(unsigned long data)
>  
>  	spin_unlock_irqrestore(&d40c->lock, flags);
>  
> -	if (callback && (d40d->txd.flags & DMA_PREP_INTERRUPT))
> +	if (callback_active && callback)
>  		callback(callback_param);
>  
>  	return;
> -- 
> 1.8.5.3
> 

-- 
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