Hi Laurent
Thanks for the prompt reply :)
On Wed, 1 Dec 2021 at 03:37, Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Tue, Nov 30, 2021 at 03:50:25PM +0000, Ricardo Ribalda wrote:
> > If mappings points to an invalid memory, we will be invalid accessing
> > it.
> > Solve it by initializing the value of the variable mapping and by
> > changing the order in the conditional statement (to avoid accessing
> > mapping->id if not needed).
> >
> > Fix:
> > kasan: GPF could be caused by NULL-ptr deref or user memory access
> > general protection fault: 0000 [#1] PREEMPT SMP KASAN NOPTI
> >
> > Fixes: 6350d6a4ed487 ("media: uvcvideo: Set error_idx during ctrl_commit errors")
> > Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> > ---
> > drivers/media/usb/uvc/uvc_ctrl.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 30bfe9069a1fb..f7b7add3cfa59 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -852,8 +852,8 @@ static void __uvc_find_control(struct uvc_entity *entity, u32 v4l2_id,
> > return;
> > }
> >
> > - if ((*mapping == NULL || (*mapping)->id > map->id) &&
> > - (map->id > v4l2_id) && next) {
> > + if (next && (map->id > v4l2_id) &&
> > + (*mapping == NULL || (*mapping)->id > map->id)) {
> > *control = ctrl;
> > *mapping = map;
> > }
> > @@ -1638,7 +1638,7 @@ static int uvc_ctrl_find_ctrl_idx(struct uvc_entity *entity,
> > struct v4l2_ext_controls *ctrls,
> > struct uvc_control *uvc_control)
> > {
> > - struct uvc_control_mapping *mapping;
> > + struct uvc_control_mapping *mapping = NULL;
>
> It seems to me that either change will fix the bug, we don't need both,
> is that right ? If so I'd drop the change to __uvc_find_control(), as it
> seems quite fragile to allow mapping to be uninitialized.
Just wanted to be extra paranoid. I have just sent a v2 of the patch.
Thanks!
>
> > struct uvc_control *ctrl_found;
> > unsigned int i;
> >
>
> --
> Regards,
>
> Laurent Pinchart
--
Ricardo Ribalda
