[PATCH v2 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 v1:

- Better patch description.

 drivers/media/v4l2-core/v4l2-subdev.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 831c69c958b8..f8ea4afc6cbb 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -2334,11 +2334,13 @@ int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad,
 
 	/* Fallback on .s_stream() if .enable_streams() isn't available. */
 	use_s_stream = !v4l2_subdev_has_op(sd, pad, enable_streams);
-
-	if (!use_s_stream)
+	if (!use_s_stream) {
 		state = v4l2_subdev_lock_and_get_active_state(sd);
-	else
+	} else {
+		if (!v4l2_subdev_has_op(sd, video, s_stream))
+			return -ENOIOCTLCMD;
 		state = NULL;
+	}
 
 	/*
 	 * Verify that the requested streams exist and that they are not
@@ -2435,11 +2437,13 @@ int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad,
 
 	/* Fallback on .s_stream() if .disable_streams() isn't available. */
 	use_s_stream = !v4l2_subdev_has_op(sd, pad, disable_streams);
-
-	if (!use_s_stream)
+	if (!use_s_stream) {
 		state = v4l2_subdev_lock_and_get_active_state(sd);
-	else
+	} else {
+		if (!v4l2_subdev_has_op(sd, video, s_stream))
+			return -ENOIOCTLCMD;
 		state = NULL;
+	}
 
 	/*
 	 * Verify that the requested streams exist and that they are not
-- 
2.47.3