[net,V3,1/3] vhost: make sure used idx is seen before log in vhost_add_used_n()
diff mbox series

Message ID 20181213025339.14023-2-jasowang@redhat.com
State Accepted
Commit 841df922417eb82c835e93d4b93eb6a68c99d599
Headers show
Series
  • Fix various issue of vhost
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Commit Message

Jason Wang Dec. 13, 2018, 2:53 a.m. UTC
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: 8dd014adfea6f ("vhost-net: mergeable buffers support")
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/vhost/vhost.c | 2 ++
 1 file changed, 2 insertions(+)

Patch
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diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 6b98d8e3a5bf..5915f240275a 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -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),