Subject: [PATCH v2] pxa2xx_spi: fix memory corruption

From: [email-masked] (Vasily Khoruzhick)
Date: Sun, 10 Jul 2011 16:09:30 +0300

On Sunday 10 July 2011 15:43:41 Marek Vasut wrote:
> On Sunday, July 10, 2011 02:09:22 PM 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 <[email-masked]>
> > ---
> > 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
> >  
> >  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..25358cd 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[16];
> 
> Ah, please don't name it starting with two underscores.

Ok, what name do you suggest?

> >  	/* 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((u8 *)drv_data->__null_dma_buf, 8);
> 
> Do you need that (u8 *) cast there ?

Yes, cast is necessary here, otherwise:

drivers/spi/pxa2xx_spi.c:1574:10: error: cast specifies array type

> #define PTR_ALIGN(p, a)         ((typeof(p))ALIGN((unsigned long)(p), (a)))
> 
> from linux/kernel.h line 42
> 
> >  	drv_data->ioaddr = ssp->mmio_base;
> >  	drv_data->ssdr_physical = ssp->phys_base + SSDR;