Commit 2510d91b authored Dec 13, 2018 by Jason Wang Committed by Greg Kroah-Hartman Jan 09, 2019

vhost: make sure used idx is seen before log in vhost_add_used_n()



[ Upstream commit 841df922417eb82c835e93d4b93eb6a68c99d599 ]

We miss a write barrier that guarantees used idx is updated and seen
before log. This will let userspace sync and copy used ring before
used idx is update. Fix this by adding a barrier before log_write().

Fixes: 8dd014ad ("vhost-net: mergeable buffers support")
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 3009452f

drivers/vhost/vhost.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -2231,6 +2231,8 @@ int vhost_add_used_n(struct vhost_virtqueue vq, struct vring_used_elem heads,
		return -EFAULT;
		}
		if (unlikely(vq->log_used)) {
		/* Make sure used idx is seen before log. */
		smp_wmb();
		/* Log used index update. */
		log_write(vq->log_base,
		vq->log_addr + offsetof(struct vring_used, idx),