netdev - Re: [PATCH net v2] vhost: fix a theoretical race in device cleanup

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Date:	Thu, 13 Feb 2014 18:48:25 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	mst@...hat.com
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	virtio-dev@...ts.oasis-open.org,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	jasowang@...hat.com
Subject: Re: [PATCH net v2] vhost: fix a theoretical race in device cleanup

From: "Michael S. Tsirkin" <mst@...hat.com>
Date: Thu, 13 Feb 2014 11:45:11 +0200

> vhost_zerocopy_callback accesses VQ right after it drops a ubuf
> reference.  In theory, this could race with device removal which waits
> on the ubuf kref, and crash on use after free.
> 
> Do all accesses within rcu read side critical section, and synchronize
> on release.
> 
> Since callbacks are always invoked from bh, synchronize_rcu_bh seems
> enough and will help release complete a bit faster.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
> 
> This is was previously posted as part of patch
> series, but it's an independent fix really.
> Theoretical race so not needed for stable I think.

Ok, no -stable, applied.
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