linux-kernel - Re: [PATCH] media: usb: go7007: Fix warning: passing freed memory 'fw'

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Date:   Fri, 11 Aug 2023 11:58:14 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Madhumitha Prabakaran <madhumithabiw@...il.com>,
        mchehab@...nel.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     skhan@...uxfoundation.org, ivan.orlov0322@...il.com
Subject: Re: [PATCH] media: usb: go7007: Fix warning: passing freed memory
 'fw'

On 09/08/2023 03:00, Madhumitha Prabakaran wrote:
> Fix smatch warning - go7007_loader_probe() warn: passing freed memory 'fw'
> 
> The 'fw' pointer is released using release_firmware(fw) and then being used
> again in another request_firmware() call without being reassigned to a new
> memory allocation. To resolve it, use separate variables for each request.

Hmm, I don't get this smatch warning. And it doesn't appear to be an actual
bug either, so that warning would be a false positive.

I wonder if you tested with an older smatch version?

Regards,

	Hans

> 
> Signed-off-by: Madhumitha Prabakaran <madhumithabiw@...il.com>
> ---
>  drivers/media/usb/go7007/go7007-loader.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/usb/go7007/go7007-loader.c b/drivers/media/usb/go7007/go7007-loader.c
> index 243aa0ad074c..5f5c425f4d45 100644
> --- a/drivers/media/usb/go7007/go7007-loader.c
> +++ b/drivers/media/usb/go7007/go7007-loader.c
> @@ -35,7 +35,7 @@ static int go7007_loader_probe(struct usb_interface *interface,
>  				const struct usb_device_id *id)
>  {
>  	struct usb_device *usbdev;
> -	const struct firmware *fw;
> +	const struct firmware *fw_1, *fw_2;
>  	u16 vendor, product;
>  	const char *fw1, *fw2;
>  	int ret;
> @@ -67,13 +67,13 @@ static int go7007_loader_probe(struct usb_interface *interface,
>  
>  	dev_info(&interface->dev, "loading firmware %s\n", fw1);
>  
> -	if (request_firmware(&fw, fw1, &usbdev->dev)) {
> +	if (request_firmware(&fw_1, fw1, &usbdev->dev)) {
>  		dev_err(&interface->dev,
>  			"unable to load firmware from file \"%s\"\n", fw1);
>  		goto failed2;
>  	}
> -	ret = cypress_load_firmware(usbdev, fw, CYPRESS_FX2);
> -	release_firmware(fw);
> +	ret = cypress_load_firmware(usbdev, fw_1, CYPRESS_FX2);
> +	release_firmware(fw_1);
>  	if (0 != ret) {
>  		dev_err(&interface->dev, "loader download failed\n");
>  		goto failed2;
> @@ -82,13 +82,13 @@ static int go7007_loader_probe(struct usb_interface *interface,
>  	if (fw2 == NULL)
>  		return 0;
>  
> -	if (request_firmware(&fw, fw2, &usbdev->dev)) {
> +	if (request_firmware(&fw_2, fw2, &usbdev->dev)) {
>  		dev_err(&interface->dev,
>  			"unable to load firmware from file \"%s\"\n", fw2);
>  		goto failed2;
>  	}
> -	ret = cypress_load_firmware(usbdev, fw, CYPRESS_FX2);
> -	release_firmware(fw);
> +	ret = cypress_load_firmware(usbdev, fw_2, CYPRESS_FX2);
> +	release_firmware(fw_2);
>  	if (0 != ret) {
>  		dev_err(&interface->dev, "firmware download failed\n");
>  		goto failed2;