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In-Reply-To: <Yyt/LhNoEEfjly54@pendragon.ideasonboard.com>
From:   Ricardo Ribalda <ribalda@chromium.org>
Date:   Wed, 21 Sep 2022 23:52:29 +0200
Message-ID: <CANiDSCsSsKk37JtBZjQiuw6MoH+f-iCf47MqU9BH18gbd4EKAg@mail.gmail.com>
Subject: Re: [PATCH v1 1/1] media: uvc: Handle cameras with invalid descriptors
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzbot <syzkaller@googlegroups.com>
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Hi Laurent

On Wed, 21 Sept 2022 at 23:16, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Ricardo,
>
> On Wed, Sep 21, 2022 at 09:51:44AM +0200, Ricardo Ribalda wrote:
> > Do you mean something like this?
> >
> > diff --git a/drivers/media/usb/uvc/uvc_entity.c
> > b/drivers/media/usb/uvc/uvc_entity.c
> > index 7c4d2f93d351..66d1f5da4ec7 100644
> > --- a/drivers/media/usb/uvc/uvc_entity.c
> > +++ b/drivers/media/usb/uvc/uvc_entity.c
> > @@ -37,7 +37,7 @@ static int uvc_mc_create_links(struct uvc_video_chain *chain,
> >                         continue;
> >
> >                 remote = uvc_entity_by_id(chain->dev, entity->baSourceID[i]);
> > -               if (remote == NULL)
> > +               if (remote == NULL || remote->num_pads == 0)
> >                         return -EINVAL;
>
> Yes.
>
> >
> >                 source = (UVC_ENTITY_TYPE(remote) == UVC_TT_STREAMING)
> > @@ -46,6 +46,9 @@ static int uvc_mc_create_links(struct uvc_video_chain *chain,
> >                 if (source == NULL)
> >                         continue;
> >
> > +               if (source->num_pads != remote->num_pads)
> > +                       return -EINVAL;
> > +
>
> But this I would have dropped, as the media_entity num_pads is
> initialized from uvc_entity num_pads and neither are changed after.

Works for me. Shall I send a v2 or you can take it?

Thanks!
>
> >                 remote_pad = remote->num_pads - 1;
> >                 ret = media_create_pad_link(source, remote_pad,
> >                                                sink, i, flags);
> >
> > regarding making a new patch, whatever is easier for you ;)
> >
> >
> > On Wed, 21 Sept 2022 at 02:53, Laurent Pinchart wrote:
> > >
> > > Hi Ricardo,
> > >
> > > Thank you for the patch.
> > >
> > > On Tue, Sep 20, 2022 at 04:04:55PM +0200, Ricardo Ribalda wrote:
> > > > If the source entity does not contain any pads, do not create a link.
> > > >
> > > > Reported-by: syzbot <syzkaller@googlegroups.com>
> > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > >
> > > > diff --git a/drivers/media/usb/uvc/uvc_entity.c b/drivers/media/usb/uvc/uvc_entity.c
> > > > index 7c4d2f93d351..1f730cb72e58 100644
> > > > --- a/drivers/media/usb/uvc/uvc_entity.c
> > > > +++ b/drivers/media/usb/uvc/uvc_entity.c
> > > > @@ -43,7 +43,7 @@ static int uvc_mc_create_links(struct uvc_video_chain *chain,
> > > >               source = (UVC_ENTITY_TYPE(remote) == UVC_TT_STREAMING)
> > > >                      ? (remote->vdev ? &remote->vdev->entity : NULL)
> > > >                      : &remote->subdev.entity;
> > > > -             if (source == NULL)
> > > > +             if (source == NULL || source->num_pads == 0)
> > >
> > > source->num_pads and remote->num_pads should always be identical, but as
> > > the next line uses remote->num_pads, wouldn't it be better to test that
> > > variable ? If so, I'd move the test a file lines earlier, with the
> > > remote == NULL test.
> > >
> > > What do you think ? If you agree I can make that change when applying,
> > > there's no need for a new version. Otherwise I'll keep the patch as-is.
> > >
> > > >                       continue;
> > > >
> > > >               remote_pad = remote->num_pads - 1;
> > > >
>
> --
> Regards,
>
> Laurent Pinchart


-- 
Ricardo Ribalda