| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 20/71] vhost: make sure used idx is seen before log in vhost_add_used_n() | Date | Mon, 7 Jan 2019 13:32:49 +0100 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Jason Wang <jasowang@redhat.com>
[ 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 <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> --- drivers/vhost/vhost.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -2145,6 +2145,8 @@ int vhost_add_used_n(struct vhost_virtqu 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),
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