linux-kernel - Re: [PATCH v2] usb: gadget: uvc: Fix ERR_PTR dereference in uvc

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Message-ID: <Zr3IKD4LCrlke+8H@embed-PC.myguest.virtualbox.org>
Date: Thu, 15 Aug 2024 14:49:36 +0530
From: Abhishek Tamboli <abhishektamboli9@...il.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: dan.scally@...asonboard.com, laurent.pinchart@...asonboard.com,
	dan.carpenter@...aro.org, linux-usb@...r.kernel.org,
	skhan@...uxfoundation.org, rbmarliere@...il.com,
	linux-kernel-mentees@...ts.linuxfoundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] usb: gadget: uvc: Fix ERR_PTR dereference in
 uvc_v4l2.c

Hi Greg,
Thank you for the feedback.

On Thu, Aug 15, 2024 at 10:00:27AM +0200, Greg KH wrote:
> 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@...il.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?
Returning -EINVAL directly was based on the current implementation of to_uvc_format(), 
which only returns ERR_PTR(-EINVAL) in case of error.
> 
> > +		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.
If you'd like me to make the changes to use PTR_ERR()? 
I'll update the patch.

Regards,
Abhishek