V4L/DVB (13831): uvcvideo: Fix oops caused by a race condition in buffer dequeuing

Buffers were marked as done before being removed from the IRQ queue. If
a userspace application dequeued and requeued the buffer fast enough
during that time window, the buffer could end up being deleted twice,
generating an oops in interrupt context.

Add a new state, UVC_BUF_STATE_READY, to mark buffers as ready for reuse
but not yet removed from the queue, and transition to UVC_BUF_STATE_DONE
only when the buffer is removed from the queue.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/media/video/uvc/uvcvideo.h b/drivers/media/video/uvc/uvcvideo.h
index 7ec9a04ced50..2337585001ea 100644
--- a/drivers/media/video/uvc/uvcvideo.h
+++ b/drivers/media/video/uvc/uvcvideo.h
@@ -365,8 +365,9 @@ enum uvc_buffer_state {
         UVC_BUF_STATE_IDLE      = 0,
         UVC_BUF_STATE_QUEUED    = 1,
         UVC_BUF_STATE_ACTIVE    = 2,
-        UVC_BUF_STATE_DONE      = 3,
-        UVC_BUF_STATE_ERROR     = 4,
+        UVC_BUF_STATE_READY     = 3,
+        UVC_BUF_STATE_DONE      = 4,
+        UVC_BUF_STATE_ERROR     = 5,
 };
 
 struct uvc_buffer {