Re: [PATCH 1/1] media: v4l: subdev: Make link validation safer

[Hans de Goede <hdegoede@redhat.com>]

Hi Sakari,

On 3/2/23 21:22, Sakari Ailus wrote:
> Link validation currently accesses invalid pointers if the link passed to it
> is not between two sub-devices. This is of course a driver bug.
> 
> Ignore the error but print a debug message, as this is how it used to work
> previously.
> 
> Fixes: a6b995ed03ff ("media: subdev: use streams in v4l2_subdev_link_validate()")
> Reported-by: Hans de Goede <hdegoede@redhat.com>
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
> Hi Hans,
> 
> Could you test this?

Yes, thank you for the fix.

I can confirm that this fixes the oops on my Surface Go 1 and
that it makes the IPU3 attached cameras work again:

Tested-by: Hans de Goede <hdegoede@redhat.com>

or better just replace the Reported-by with:

Reported-and-tested-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans




> The bug is of course in the ImgU driver and this reverts to the old
> pre-streams behaviour. It silently fails instead of oopsing. The ImgU driver
> needs to be fixed and I think we could make this return an error at the same
> time. Right now I can't be sure the ImgU driver is the only one suffering
> from this, but if so, it's likely to be broken anyway.
> 
> - Sakari
> 
>  drivers/media/v4l2-core/v4l2-subdev.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index dff1d9be7841..a6c80096586e 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -1224,6 +1224,17 @@ int v4l2_subdev_link_validate(struct media_link *link)
>  	struct v4l2_subdev_state *source_state, *sink_state;
>  	int ret;
>  
> +	if (!is_media_entity_v4l2_subdev(link->sink->entity)) {
> +		pr_debug("entity \"%s\" not a V4L2 sub-device, driver bug!\n",
> +			 link->sink->entity->name);
> +		return 0;
> +	}
> +	if (!is_media_entity_v4l2_subdev(link->source->entity)) {
> +		pr_debug("entity \"%s\" not a V4L2 sub-device, driver bug!\n",
> +			 link->source->entity->name);
> +		return 0;
> +	}
> +
>  	sink_sd = media_entity_to_v4l2_subdev(link->sink->entity);
>  	source_sd = media_entity_to_v4l2_subdev(link->source->entity);
>