[PATCH 1/1] media: v4l2-subdev: Fail {enable,disable}_streams and s_streaming nicely

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

If a sub-device does not set enable_streams() and disable_streams() pad
ops while it sets the s_stream() video op to
v4l2_subdev_s_stream_helper(), enabling or disabling streaming either way
on the sub-device will result calling v4l2_subdev_s_stream_helper() and
v4l2_subdev_{enable,disable}_streams() recursively, exhausting the stack.
Return -ENOIOCTLCMD in this case to handle the situation gracefully.

Reported-by: David Heidelberg <david@ixit.cz>
Fixes: b62949ddaa52 ("media: subdev: Support single-stream case in v4l2_subdev_enable/disable_streams()")
Cc: stable@vger.kernel.org
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
since v2:

- Move the check, with checking the pad ops, to
  v4l2_subdev_s_stream_helper().

 drivers/media/v4l2-core/v4l2-subdev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 831c69c958b8..3b726f044d3f 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -2504,6 +2504,10 @@ int v4l2_subdev_s_stream_helper(struct v4l2_subdev *sd, int enable)
 	u64 source_mask = 0;
 	int pad_index = -1;
 
+	if (WARN_ON_ONCE(!v4l2_subdev_has_op(sd, pad, enable_streams) ||
+			 !v4l2_subdev_has_op(sd, pad, disable_streams)))
+		return -ENOIOCTLCMD;
+
 	/*
 	 * Find the source pad. This helper is meant for subdevs that have a
 	 * single source pad, so failures shouldn't happen, but catch them
-- 
2.47.3