[dm-devel] [PATCH] multipathd: avoid crash in uevent_cleanup()

[Martin Wilck]

lixiaokeng,

did this fix your "crash on exit" issue?

Martin

On Thu, 2021-01-28 at 22:08 +0100, mwilck at suse.com wrote:
> From: Martin Wilck <mwilck at suse.com>
> 
> Crashes have been observed in the unwinder stack of uevent_listen().
> This can only be explained by "udev" not being a valid object at that
> time. Be sure to pass a valid pointer, and don't call udev_unref() if
> it has been set to NULL already.
> 
> I'm not quite sure how this would come to pass, as we join the
> threads
> before setting udev to NULL, but this is unwinder code, so I guess it
> might actually be executed after the thread has terminated.
> 
> Signed-off-by: Martin Wilck <mwilck at suse.com>
> ---
>  libmultipath/uevent.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
> index d3061bf..4e662ff 100644
> --- a/libmultipath/uevent.c
> +++ b/libmultipath/uevent.c
> @@ -397,10 +397,11 @@ service_uevq(struct list_head *tmpq)
>  
>  static void uevent_cleanup(void *arg)
>  {
> -       struct udev *udev = arg;
> +       struct udev **pudev = arg;
>  
> +       if (*pudev)
> +               udev_unref(*pudev);
>         condlog(3, "Releasing uevent_listen() resources");
> -       udev_unref(udev);
>  }
>  
>  static void monitor_cleanup(void *arg)
> @@ -560,7 +561,7 @@ int uevent_listen(struct udev *udev)
>                 return 1;
>         }
>         udev_ref(udev);
> -       pthread_cleanup_push(uevent_cleanup, udev);
> +       pthread_cleanup_push(uevent_cleanup, &udev);
>  
>         monitor = udev_monitor_new_from_netlink(udev, "udev");
>         if (!monitor) {