Re: [PATCH] media: nxp: imx8-isi: Check whether pad is non-NULL before access

[Maud Spierings]

On 8/20/25 16:01, Laurent Pinchart wrote:
> Hi Maud,
>
> On Mon, Aug 18, 2025 at 02:31:43PM +0200, Maud Spierings via B4 Relay wrote:
> > From: Maud Spierings <maudspierings@xxxxxxxxxxxxxx>
> >
> > media_pad_remote_pad_first() can return NULL if no valid link is found.
> > Check for this possibility before dereferencing it in the next line.
> >
> > Reported/investigated in [1]:
> >
> > Link: https://lore.kernel.org/all/1536a61b-b405-4762-9fb4-7e257f95e49e@xxxxxxxxxxxxxx/ [1]
> > Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
> > Signed-off-by: Maud Spierings <maudspierings@xxxxxxxxxxxxxx>
> > ---
> > I'm not sure if this should be a dev_dbg(), just following the pattern
> > around it for now, also not sure if EPIPE is the correct error.
>
> I've submitted
> https://lore.kernel.org/linux-media/20250820140021.8026-1-laurent.pinchart@xxxxxxxxxxxxxxxx,
> which should fix this issue in a more generic way.

Saw it, but I think my patch technically is still correct as the 
function documentation states it can potentially return NULL right? [1]

Link: 
https://www.kernel.org/doc/html/latest/driver-api/media/mc-core.html [1]

I will test you patches tomorrow.

> > ---
> >   drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c | 7 +++++++
> >   1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> > index ede6cc74c0234049fa225ad82aaddaad64aa53d7..1ed8b031178b7d934b04a8752747f556bd1fc5a9 100644
> > --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> > +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-crossbar.c
> > @@ -160,6 +160,13 @@ mxc_isi_crossbar_xlate_streams(struct mxc_isi_crossbar *xbar,
> >   	}
> >   
> >   	pad = media_pad_remote_pad_first(&xbar->pads[sink_pad]);
> > +
> > +	if (pad == NULL) {
> > +		dev_dbg(xbar->isi->dev, "no valid link found to pad %u\n",
> > +			sink_pad);
> > +		return ERR_PTR(-EPIPE);
> > +	}
> > +
> >   	sd = media_entity_to_v4l2_subdev(pad->entity);
> >   	if (!sd) {
> >   		dev_dbg(xbar->isi->dev,
> >
> > ---
> > base-commit: 3ac864c2d9bb8608ee236e89bf561811613abfce
> > change-id: 20250818-imx8_isi-954898628bb6