[PATCH 05/10] Input: synaptics-rmi4 - block s_input when F54 queue is busy

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Changing the input (diagnostic report type) mid-stream changes the
report size. Since V4L2 buffers are allocated based on the size at
stream start, changing the input while streaming could lead to a
heap buffer overflow if the new size is larger than the allocated
buffers.

Prevent this by blocking VIDIOC_S_INPUT with -EBUSY if the V4L2 queue
is busy (streaming).

Fixes: 3a762dbd5347 ("[media] Input: synaptics-rmi4 - add support for F54 diagnostics")
Cc: stable@vger.kernel.org
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/input/rmi4/rmi_f54.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/input/rmi4/rmi_f54.c b/drivers/input/rmi4/rmi_f54.c
index aebe74d2032c..e86dfc9ce7d9 100644
--- a/drivers/input/rmi4/rmi_f54.c
+++ b/drivers/input/rmi4/rmi_f54.c
@@ -445,7 +445,12 @@ static int rmi_f54_set_input(struct f54_data *f54, unsigned int i)
 
 static int rmi_f54_vidioc_s_input(struct file *file, void *priv, unsigned int i)
 {
-	return rmi_f54_set_input(video_drvdata(file), i);
+	struct f54_data *f54 = video_drvdata(file);
+
+	if (vb2_is_busy(&f54->queue))
+		return -EBUSY;
+
+	return rmi_f54_set_input(f54, i);
 }
 
 static int rmi_f54_vidioc_g_input(struct file *file, void *priv,
-- 
2.55.0.rc0.799.gd6f94ed593-goog