From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [PATCH net V2 1/4] vhost: make sure used idx is seen before log in vhost_add_used_n() Date: Wed, 12 Dec 2018 18:08:16 +0800 Message-ID: <20181212100819.21295-2-jasowang@redhat.com> References: <20181212100819.21295-1-jasowang@redhat.com> To: mst@redhat.com, jasowang@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: In-Reply-To: <20181212100819.21295-1-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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") Signed-off-by: Jason Wang --- drivers/vhost/vhost.c | 2 ++ 1 file changed, 2 insertions(+) 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), -- 2.17.1