linux-kernel - Re: [PATCH] usb: gadget: uvc: Fix ERR_PTR dereference in uvc

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Message-ID: <2024081321-kiwi-gibberish-d065@gregkh>
Date: Tue, 13 Aug 2024 10:11:48 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Abhishek Tamboli <abhishektamboli9@...il.com>
Cc: laurent.pinchart@...asonboard.com, dan.scally@...asonboard.com,
	skhan@...uxfoundation.org, dan.carpenter@...aro.org,
	rbmarliere@...il.com,
	linux-kernel-mentees@...ts.linuxfoundation.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: uvc: Fix ERR_PTR dereference in uvc_v4l2.c

On Fri, Aug 02, 2024 at 11:32:47PM +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()
> 
> Signed-off-by: Abhishek Tamboli <abhishektamboli9@...il.com>
> ---
>  drivers/usb/gadget/function/uvc_v4l2.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c
> index a024aecb76dc..9dd602a742c4 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;
> @@ -389,6 +392,9 @@ 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;
> +
>  	f->pixelformat = fmtdesc->fcc;

You are now only checking 2 of the responses here, not all of them,
which feels odd.

Either fix all calls to this function, or none of them :)

thanks,

greg k-h