Re: [PATCH v2] usb: gadget: uvc: Fix ERR_PTR dereference in uvc_v4l2.c

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Aug 15, 2024 at 12:44:16PM +0530, Abhishek Tamboli wrote:
> Fix potential dereferencing of ERR_PTR() in find_format_by_pix()
> and uvc_v4l2_enum_format().
> 
> Fix the following smatch errors:
> 
> drivers/usb/gadget/function/uvc_v4l2.c:124 find_format_by_pix()
> error: 'fmtdesc' dereferencing possible ERR_PTR()
> 
> drivers/usb/gadget/function/uvc_v4l2.c:392 uvc_v4l2_enum_format()
> error: 'fmtdesc' dereferencing possible ERR_PTR()
> 
> Also, fix similar issue in uvc_v4l2_try_format() for potential
> dereferencing of ERR_PTR().
> 
> Fixes: 588b9e85609b ("usb: gadget: uvc: add v4l2 enumeration api calls")
> Fixes: e219a712bc06 ("usb: gadget: uvc: add v4l2 try_format api call")
> Signed-off-by: Abhishek Tamboli <abhishektamboli9@gmail.com>
> ---
> Changes in v2:
> - Add check for dereferencing of ERR_PTR() in uvc_v4l2_try_format()
> 
>  drivers/usb/gadget/function/uvc_v4l2.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c
> index a024aecb76dc..8bb88c864b60 100644
> --- a/drivers/usb/gadget/function/uvc_v4l2.c
> +++ b/drivers/usb/gadget/function/uvc_v4l2.c
> @@ -121,6 +121,9 @@ static struct uvcg_format *find_format_by_pix(struct uvc_device *uvc,
>  	list_for_each_entry(format, &uvc->header->formats, entry) {
>  		const struct uvc_format_desc *fmtdesc = to_uvc_format(format->fmt);
> 
> +		if (IS_ERR(fmtdesc))
> +			continue;
> +
>  		if (fmtdesc->fcc == pixelformat) {
>  			uformat = format->fmt;
>  			break;
> @@ -240,6 +243,7 @@ uvc_v4l2_try_format(struct file *file, void *fh, struct v4l2_format *fmt)
>  	struct uvc_video *video = &uvc->video;
>  	struct uvcg_format *uformat;
>  	struct uvcg_frame *uframe;
> +	const struct uvc_format_desc *fmtdesc;
>  	u8 *fcc;
> 
>  	if (fmt->type != video->queue.queue.type)
> @@ -277,7 +281,10 @@ uvc_v4l2_try_format(struct file *file, void *fh, struct v4l2_format *fmt)
>  		fmt->fmt.pix.height = uframe->frame.w_height;
>  		fmt->fmt.pix.bytesperline = uvc_v4l2_get_bytesperline(uformat, uframe);
>  		fmt->fmt.pix.sizeimage = uvc_get_frame_size(uformat, uframe);
> -		fmt->fmt.pix.pixelformat = to_uvc_format(uformat)->fcc;
> +		fmtdesc = to_uvc_format(uformat);
> +		if (IS_ERR(fmtdesc))
> +			return -EINVAL;

Why not return the error given to you?

> +		fmt->fmt.pix.pixelformat = fmtdesc->fcc;
>  	}
>  	fmt->fmt.pix.field = V4L2_FIELD_NONE;
>  	fmt->fmt.pix.colorspace = V4L2_COLORSPACE_SRGB;
> @@ -389,6 +396,9 @@ uvc_v4l2_enum_format(struct file *file, void *fh, struct v4l2_fmtdesc *f)
>  		return -EINVAL;
> 
>  	fmtdesc = to_uvc_format(uformat);
> +	if (IS_ERR(fmtdesc))
> +		return -EINVAL;

Same here.

thanks,

greg k-h