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>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
index d6ada6226b54..d3485f500c5e 100644
--- 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;