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

[Sakari Ailus <sakari.ailus@linux.intel.com>]

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?

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);
 
-- 
2.30.2