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

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: 8dd014adfe ("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>
This commit is contained in:
Jason Wang 2018-12-13 10:53:37 +08:00 committed by David S. Miller
parent 3b076cfe86
commit 841df92241
1 changed files with 2 additions and 0 deletions
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2
drivers/vhost/vhost.c
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@ -2220,6 +2220,8 @@ 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),