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

Abhishek Tamboli
2024-08-15T09:21:14Z

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@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?
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