Date:   Fri, 24 Dec 2021 09:48:05 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Jiasheng Jiang <jiasheng@iscas.ac.cn>
Cc:     hminas@synopsys.com, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: dwc2: host: Check for error map
Message-ID: <YcWJRWpmLAmXrnry@kroah.com>
References: <20211224031842.1564705-1-jiasheng@iscas.ac.cn>
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In-Reply-To: <20211224031842.1564705-1-jiasheng@iscas.ac.cn>
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On Fri, Dec 24, 2021 at 11:18:42AM +0800, Jiasheng Jiang wrote:
> For the possible failure of the dma_map_single(), it should be better to
> check the return map address by using dma_mapping_error() to guarantee
> the valid of the map address.
> 
> Fixes: 197ba5f406cc ("Move DWC2 driver out of staging")
> Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
> ---
>  drivers/usb/dwc2/hcd_ddma.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/dwc2/hcd_ddma.c b/drivers/usb/dwc2/hcd_ddma.c
> index a858b5f9c1d6..89ed93a67c8a 100644
> --- a/drivers/usb/dwc2/hcd_ddma.c
> +++ b/drivers/usb/dwc2/hcd_ddma.c
> @@ -143,6 +143,7 @@ static void dwc2_desc_list_free(struct dwc2_hsotg *hsotg, struct dwc2_qh *qh)
>  
>  static int dwc2_frame_list_alloc(struct dwc2_hsotg *hsotg, gfp_t mem_flags)
>  {
> +	dma_addr_t addr;
>  	if (hsotg->frame_list)
>  		return 0;
>  
> @@ -151,9 +152,13 @@ static int dwc2_frame_list_alloc(struct dwc2_hsotg *hsotg, gfp_t mem_flags)
>  	if (!hsotg->frame_list)
>  		return -ENOMEM;
>  
> -	hsotg->frame_list_dma = dma_map_single(hsotg->dev, hsotg->frame_list,
> -					       hsotg->frame_list_sz,
> -					       DMA_TO_DEVICE);
> +	addr = dma_map_single(hsotg->dev, hsotg->frame_list,
> +			      hsotg->frame_list_sz,
> +			      DMA_TO_DEVICE);
> +	if (dma_mapping_error(hsotg->dev, addr))
> +		return -ENOMEM;
> +
> +	hsotg->frame_list_dma = addr;
>  
>  	return 0;
>  }
> -- 
> 2.25.1
> 

As I have said before, I am not going to be taking any changes from you
due to them not being correct and the resulting aftermath of them.

Please start out with doing work in the drivers/staging/ portion of the
kernel to learn kernel development better and get more experience before
going out into other areas which can cause problems to more people.

good luck,

greg k-h