From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net] vhost: synchronize IOTLB message with dev cleanup Date: Fri, 25 May 2018 03:33:55 +0300 Message-ID: <20180525033250-mutt-send-email-mst@kernel.org> References: <1526990337-24892-1-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <1526990337-24892-1-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, May 22, 2018 at 07:58:57PM +0800, Jason Wang wrote: > DaeRyong Jeong reports a race between vhost_dev_cleanup() and > vhost_process_iotlb_msg(): > > Thread interleaving: > CPU0 (vhost_process_iotlb_msg) CPU1 (vhost_dev_cleanup) > (In the case of both VHOST_IOTLB_UPDATE and > VHOST_IOTLB_INVALIDATE) > ===== ===== > vhost_umem_clean(dev->iotlb); > if (!dev->iotlb) { > ret = -EFAULT; > break; > } > dev->iotlb = NULL; > > The reason is we don't synchronize between them, fixing by protecting > vhost_process_iotlb_msg() with dev mutex. > > Reported-by: DaeRyong Jeong > Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API") > Signed-off-by: Jason Wang We should think of a way to have a per-vq lock here, but for now: Acked-by: Michael S. Tsirkin > --- > drivers/vhost/vhost.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index f3bd8e9..f0be5f3 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -981,6 +981,7 @@ static int vhost_process_iotlb_msg(struct vhost_dev *dev, > { > int ret = 0; > > + mutex_lock(&dev->mutex); > vhost_dev_lock_vqs(dev); > switch (msg->type) { > case VHOST_IOTLB_UPDATE: > @@ -1016,6 +1017,8 @@ static int vhost_process_iotlb_msg(struct vhost_dev *dev, > } > > vhost_dev_unlock_vqs(dev); > + mutex_unlock(&dev->mutex); > + > return ret; > } > ssize_t vhost_chr_write_iter(struct vhost_dev *dev, > -- > 2.7.4