Re: [PATCH] usb: gadget: amd5536udc: fix NULL pointer dereference

[David Cohen]

Hi Sudip,

On Fri, Sep 04, 2015 at 05:12:23PM +0530, Sudip Mukherjee wrote:
> We were checking if dev->regs is NULL but it was done after
> dereferencing it. Lets reset the controller and iounmap dev->regs only
> if it is not NULL.
> free_irq() does not need dev->regs, so unmaping it before freeing the
> irq should not matter.
> 
> Signed-off-by: Sudip Mukherjee <sudip@xxxxxxxxxxxxxxx>
> ---
>  drivers/usb/gadget/udc/amd5536udc.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/amd5536udc.c b/drivers/usb/gadget/udc/amd5536udc.c
> index fdacddb..26066d3 100644
> --- a/drivers/usb/gadget/udc/amd5536udc.c
> +++ b/drivers/usb/gadget/udc/amd5536udc.c
> @@ -3135,11 +3135,12 @@ static void udc_pci_remove(struct pci_dev *pdev)
>  	}
>  
>  	/* reset controller */
> -	writel(AMD_BIT(UDC_DEVCFG_SOFTRESET), &dev->regs->cfg);
> +	if (dev->regs) {
> +		writel(AMD_BIT(UDC_DEVCFG_SOFTRESET), &dev->regs->cfg);
> +		iounmap(dev->regs);

I'm not familiar with the driver, but you're iounmap'ing before freeing
irq. Looks fishy to me.

Br, David

> +	}
>  	if (dev->irq_registered)
>  		free_irq(pdev->irq, dev);
> -	if (dev->regs)
> -		iounmap(dev->regs);
>  	if (dev->mem_region)
>  		release_mem_region(pci_resource_start(pdev, 0),
>  				pci_resource_len(pdev, 0));
> -- 
> 1.9.1
> 
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