From: Sean Anderson Date: Mon, 16 Mar 2026 15:58:22 +0000 (-0400) Subject: media: uvcvideo: Fix deadlock if uvc_status_stop is called from async_ctrl.work X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=6d27f92c54ce28cfbd2a8a479a96d6f4a781b7d2;p=thirdparty%2Fkernel%2Flinux.git media: uvcvideo: Fix deadlock if uvc_status_stop is called from async_ctrl.work If a UVC camera has an asynchronous control, uvc_status_stop may be called from async_ctrl.work: uvc_ctrl_status_event_work() uvc_ctrl_status_event() uvc_ctrl_clear_handle() uvc_pm_put() uvc_status_put() uvc_status_stop() cancel_work_sync() This will cause a deadlock, since cancel_work_sync will wait for uvc_ctrl_status_event_work to complete before returning. Fix this by returning early from uvc_status_stop if we are currently in the work function. flush_status now remains false until uvc_status_start is called again, ensuring that uvc_ctrl_status_event_work won't resubmit the URB. Fixes: a32d9c41bdb8 ("media: uvcvideo: Make power management granular") Cc: stable@vger.kernel.org Closes: https://lore.kernel.org/all/6733bdfb-3e88-479f-8956-ab09c04c433e@linux.dev/ Signed-off-by: Sean Anderson Link: https://patch.msgid.link/20260316155823.1855434-1-sean.anderson@linux.dev Reviewed-by: Ricardo Ribalda Tested-by: Ricardo Ribalda Reviewed-by: Laurent Pinchart Signed-off-by: Hans de Goede Signed-off-by: Hans Verkuil --- diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c index 65f5356bebb3..b632cf5e3fe9 100644 --- a/drivers/media/usb/uvc/uvc_status.c +++ b/drivers/media/usb/uvc/uvc_status.c @@ -316,6 +316,16 @@ static int uvc_status_start(struct uvc_device *dev, gfp_t flags) if (!dev->int_urb) return 0; + /* + * If the previous uvc_status_stop() call was from the async work, + * the work may still be running. Wait for it to finish before we submit + * the urb. + */ + flush_work(&dev->async_ctrl.work); + + /* Clear the flush status if we were previously stopped. */ + smp_store_release(&dev->flush_status, false); + return usb_submit_urb(dev->int_urb, flags); } @@ -336,6 +346,15 @@ static void uvc_status_stop(struct uvc_device *dev) */ smp_store_release(&dev->flush_status, true); + /* + * If we are called from the event work function, the URB is guaranteed + * to not be in flight as it has completed and has not been resubmitted. + * There's no need to cancel the work (which would deadlock), or to kill + * the URB. + */ + if (current_work() == &w->work) + return; + /* * Cancel any pending asynchronous work. If any status event was queued, * process it synchronously. @@ -354,15 +373,6 @@ static void uvc_status_stop(struct uvc_device *dev) */ if (cancel_work_sync(&w->work)) uvc_ctrl_status_event(w->chain, w->ctrl, w->data); - - /* - * From this point, there are no events on the queue and the status URB - * is dead. No events will be queued until uvc_status_start() is called. - * The barrier is needed to make sure that flush_status is visible to - * uvc_ctrl_status_event_work() when uvc_status_start() will be called - * again. - */ - smp_store_release(&dev->flush_status, false); } int uvc_status_resume(struct uvc_device *dev)