From 04a1c4080cbfade5b445e15d0e64dc98e32fe484 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Thu, 13 Dec 2018 10:53:37 +0800 Subject: 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: 8dd014adfea6f ("vhost-net: mergeable buffers support") Acked-by: Michael S. Tsirkin Signed-off-by: Jason Wang Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- drivers/vhost/vhost.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/vhost') diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index c54d388310f0..2ed0a356d1d3 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1550,6 +1550,8 @@ 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), -- cgit v1.2.3