Re: [PATCH v3] staging: emxx_udc: Add checks for dma_alloc_coherent()

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Jan 19, 2023 at 08:31:19AM +0000, Yuan Can wrote:
> As the dma_alloc_coherent may return NULL, the return value needs to be
> checked to avoid NULL poineter dereference.
> 
> Fixes: 33aa8d45a4fe ("staging: emxx_udc: Add Emma Mobile USB Gadget driver")

This really is not a "fix" as you will never hit this in real life.
I'll drop that tag.

> Signed-off-by: Yuan Can <yuancan@huawei.com>
> ---
> changes in v2:
> - do the null pointer check right before the memcpy().
> changes in v3:
> - do the null pointer check right after the dma_alloc_coherent().
> 
>  drivers/staging/emxx_udc/emxx_udc.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/emxx_udc/emxx_udc.c b/drivers/staging/emxx_udc/emxx_udc.c
> index b4e19174bef2..f9765841c4aa 100644
> --- a/drivers/staging/emxx_udc/emxx_udc.c
> +++ b/drivers/staging/emxx_udc/emxx_udc.c
> @@ -2587,10 +2587,15 @@ static int nbu2ss_ep_queue(struct usb_ep *_ep,
>  		req->unaligned = false;
>  
>  	if (req->unaligned) {
> -		if (!ep->virt_buf)
> +		if (!ep->virt_buf) {
>  			ep->virt_buf = dma_alloc_coherent(udc->dev, PAGE_SIZE,
>  							  &ep->phys_buf,
>  							  GFP_ATOMIC | GFP_DMA);

Wait, why is this asking for GFP_DMA memory?  That's probably a
different bug...

thanks,

greg k-h