[PATCH v3] pxa2xx_spi: fix memory corruption

[grant.likely@secretlab.ca (Grant Likely)]

On Sun, Jul 10, 2011 at 06:18:19PM +0300, Vasily Khoruzhick wrote:
> pxa2xx_spi_probe allocates struct driver_data and null_dma_buf
> at same time via spi_alloc_master(), but then calculates
> null_dma_buf pointer incorrectly, and it causes memory corruption
> later if DMA usage is enabled.
> 
> Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
> ---
> v2: - add u8 __null_dma_buf[16] to the end of driver_data structure
>     and use it as null_dma_buf after alignment.
>     - use PTR_ALIGN instead of ALIGN
> v3: - drop (u8 *) cast, use & operator instead, change array name
>  drivers/spi/pxa2xx_spi.c |    9 +++++----
>  1 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/spi/pxa2xx_spi.c b/drivers/spi/pxa2xx_spi.c
> index dc25bee..b25fe27 100644
> --- a/drivers/spi/pxa2xx_spi.c
> +++ b/drivers/spi/pxa2xx_spi.c
> @@ -106,6 +106,7 @@ struct driver_data {
>  	int rx_channel;
>  	int tx_channel;
>  	u32 *null_dma_buf;
> +	u8 null_dma_buf_unaligned[16];

Don't dma buffers need to be cache-line aligned?  How large is the
actual transfer?  Using the __aligned() or __cacheline_aligned
attribute is the correct way to make sure you've got a data buffer
that can be used for DMA mixed with other stuff.  Then you don't need
to fool around with PTR_ALIGN or anything.

g.

>  
>  	/* SSP register addresses */
>  	void __iomem *ioaddr;
> @@ -1543,8 +1544,8 @@ static int __devinit pxa2xx_spi_probe(struct platform_device *pdev)
>  		return -ENODEV;
>  	}
>  
> -	/* Allocate master with space for drv_data and null dma buffer */
> -	master = spi_alloc_master(dev, sizeof(struct driver_data) + 16);
> +	/* Allocate master with space for drv_data */
> +	master = spi_alloc_master(dev, sizeof(struct driver_data));
>  	if (!master) {
>  		dev_err(&pdev->dev, "cannot alloc spi_master\n");
>  		pxa_ssp_free(ssp);
> @@ -1569,8 +1570,8 @@ static int __devinit pxa2xx_spi_probe(struct platform_device *pdev)
>  	master->transfer = transfer;
>  
>  	drv_data->ssp_type = ssp->type;
> -	drv_data->null_dma_buf = (u32 *)ALIGN((u32)(drv_data +
> -						sizeof(struct driver_data)), 8);
> +	drv_data->null_dma_buf =
> +		(u32 *)PTR_ALIGN(&drv_data->null_dma_buf_unaligned, 8);
>  
>  	drv_data->ioaddr = ssp->mmio_base;
>  	drv_data->ssdr_physical = ssp->phys_base + SSDR;
> -- 
> 1.7.5.rc3
>