[PATCH] dma: ste_dma40: don't dereference free:d descriptor

[PATCH] dma: ste_dma40: don't dereference free:d descriptor

[Linus Walleij]

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@vger.kernel.org
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 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

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

[Vinod Koul]

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@vger.kernel.org
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.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
> 

--