V4L/DVB (7556): em28xx: fix locking on vidioc_s_fmt_cap

Currently, vidioc_s_fmt_cap is allowed even if streaming is running on some
other fh. This is likely to cause issues.

Block use of vidioc_s_fmt_cap if someone else has claimed access to the device.

Signed-off-by: Aidan Thornton <makosoft@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
index d6ada62..d3485f5 100644 (file)
--- a/drivers/media/video/em28xx/em28xx-video.c
+++ b/drivers/media/video/em28xx/em28xx-video.c
@@ -947,6 +947,12 @@ static int vidioc_s_fmt_cap(struct file *file, void *priv,
                goto out;
        }
 
+       if (dev->stream_on && !fh->stream_on) {
+               em28xx_errdev("%s device in use by another fh\n", __func__);
+               rc = -EBUSY;
+               goto out;
+       }
+
        /* set new image size */
        dev->width = f->fmt.pix.width;
        dev->height = f->fmt.pix.height;