Re: [PATCH] virtio_balloon: initialize wakeup_lock before virtqueues are set up

[sashiko-bot@kernel.org]

> Since c578123e63da ("virtio_balloon: Treat stats requests as wakeup
> events") the stats_request() virtqueue callback takes vb->wakeup_lock
> via start_wakeup_event().  init_vqs() registers that callback and even
> primes and kicks the stats queue, so the lock is reachable from irq
> context as soon as init_vqs() returns, long before the driver sets
> DRIVER_OK: vring_interrupt() dispatches to the callback without any
> DRIVER_OK check unless CONFIG_VIRTIO_HARDEN_NOTIFICATION is set, and
> that option depends on BROKEN.  syzbot hit it from a threaded irq:
> 
>   INFO: trying to register non-static key in stats_request
>   ...
>   assign_lock_key
>   register_lock_class
>   lock_acquire
>   rt_spin_lock
> [ ... ]
> 
> Fixes: c578123e63da ("virtio_balloon: Treat stats requests as wakeup events")
> Reported-by: syzbot+13df72e0dc4be5c62215@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=13df72e0dc4be5c62215
> Signed-off-by: Mingbing Zhai <zhaimingbing@cmss.chinamobile.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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