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

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

[Maud Spierings via B4 Relay]

From: Maud Spierings <maudspierings@gocontroll.com>

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@gocontroll.com/ [1]
Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
---
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.
---
 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

Best regards,
-- 
Maud Spierings <maudspierings@gocontroll.com>

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

[Laurent Pinchart]

Hi Maud,

On Mon, Aug 18, 2025 at 02:31:43PM +0200, Maud Spierings via B4 Relay wrote:
> From: Maud Spierings <maudspierings@gocontroll.com>
> 
> 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@gocontroll.com/ [1]
> Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
> Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
> ---
> 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@ideasonboard.com,
which should fix this issue in a more generic way.

> ---
>  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

-- 
Regards,

Laurent Pinchart

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@gocontroll.com>
>>
>> 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@gocontroll.com/ [1]
>> Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
>> Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
>> ---
>> 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@ideasonboard.com,
> 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
> 

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

[Laurent Pinchart]

On Wed, Aug 20, 2025 at 04:07:55PM +0200, Maud Spierings wrote:
> On 8/20/25 16:01, Laurent Pinchart wrote:
> > On Mon, Aug 18, 2025 at 02:31:43PM +0200, Maud Spierings via B4 Relay wrote:
> >> From: Maud Spierings <maudspierings@gocontroll.com>
> >>
> >> 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@gocontroll.com/ [1]
> >> Fixes: cf21f328fcaf ("media: nxp: Add i.MX8 ISI driver")
> >> Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
> >> ---
> >> 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@ideasonboard.com,
> > 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]

The function documentation states

"returns a pointer to the pad at the remote end of the first found
enabled link, or NULL if no enabled link has been found."

The MUST_CONNECT flag ensures that there is an enabled link, so the
function can't return NULL.

> 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

-- 
Regards,

Laurent Pinchart