linux-kernel - [PATCH] media: usbtv: Lock resolution while streaming

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Message-ID: <dd4693d2-3ecb-4081-8227-35e4e89ec7d4@disterhof.eu>
Date: Mon, 28 Apr 2025 20:16:50 +0200
From: Ludwig Disterhof <ludwig@...terhof.eu>
To: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: mchehab@...nel.org, hverkuil@...all.nl
Subject: [PATCH] media: usbtv: Lock resolution while streaming

When an program is streaming (ffplay) and another program (qv4l2)
changes the TV standard from NTSC to PAL, the kernel crashes due to trying
to copy to unmapped memory.

Changing from NTSC to PAL increases the resolution in the usbtv struct,
but the video plane buffer isn't adjusted, so it overflows.

Fixes: 0e0fe3958fdd13d ("[media] usbtv: Add support for PAL video source")

Signed-off-by: Ludwig Disterhof <ludwig@...terhof.eu>
---
 drivers/media/usb/usbtv/usbtv-video.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/media/usb/usbtv/usbtv-video.c b/drivers/media/usb/usbtv/usbtv-video.c
index be22a9697197..965a8ae82afe 100644
--- a/drivers/media/usb/usbtv/usbtv-video.c
+++ b/drivers/media/usb/usbtv/usbtv-video.c
@@ -73,6 +73,10 @@ static int usbtv_configure_for_norm(struct usbtv *usbtv, v4l2_std_id norm)
 	}
 
 	if (params) {
+		if (vb2_is_streaming(&usbtv->vb2q) &&
+		    (usbtv->width != params->cap_width ||
+		     usbtv->height != params->cap_height))
+			return -EBUSY;
 		usbtv->width = params->cap_width;
 		usbtv->height = params->cap_height;
 		usbtv->n_chunks = usbtv->width * usbtv->height
-- 
2.43.0