From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Nicholas A. Bellinger" Subject: [PATCH] vhost/scsi: Fix incorrect usage of get_user_pages_fast write parameter Date: Fri, 25 Oct 2013 18:07:16 +0000 Message-ID: <1382724436-28478-1-git-send-email-nab@linux-iscsi.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: target-devel Cc: kvm-devel , linux-scsi , "Michael S. Tsirkin" , linux-kernel , lf-virt , Stefan Hajnoczi List-Id: virtualization@lists.linuxfoundation.org From: Nicholas Bellinger This patch addresses a long-standing bug where the get_user_pages_fast() write parameter used for setting the underlying page table entry permission bits was incorrectly set to write=1 for data_direction=DMA_TO_DEVICE, and passed into get_user_pages_fast() via vhost_scsi_map_iov_to_sgl(). However, this parameter is intended to signal WRITEs to pinned userspace PTEs for the virtio-scsi DMA_FROM_DEVICE -> READ payload case, and *not* for the virtio-scsi DMA_TO_DEVICE -> WRITE payload case. This bug would manifest itself as random process segmentation faults on KVM host after repeated vhost starts + stops and/or with lots of vhost endpoints + LUNs. Cc: Stefan Hajnoczi Cc: Michael S. Tsirkin Cc: Asias He Cc: # 3.6+ Signed-off-by: Nicholas Bellinger --- drivers/vhost/scsi.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c index ce5221f..e663921 100644 --- a/drivers/vhost/scsi.c +++ b/drivers/vhost/scsi.c @@ -1056,7 +1056,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq) if (data_direction != DMA_NONE) { ret = vhost_scsi_map_iov_to_sgl(cmd, &vq->iov[data_first], data_num, - data_direction == DMA_TO_DEVICE); + data_direction == DMA_FROM_DEVICE); if (unlikely(ret)) { vq_err(vq, "Failed to map iov to sgl\n"); goto err_free; -- 1.7.2.5