From: Nicholas Bellinger Date: Fri, 25 Oct 2013 17:44:15 +0000 (-0700) Subject: vhost/scsi: Fix incorrect usage of get_user_pages_fast write parameter X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=722b78bc8a42b6910c291266e87abe2e63dc750f;p=linux-edison.git vhost/scsi: Fix incorrect usage of get_user_pages_fast write parameter commit 60a01f558af9c48b0bb31f303c479e32721add3f upstream. 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 Signed-off-by: Nicholas Bellinger Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c index 70142029722..962c7e3c3ba 100644 --- a/drivers/vhost/scsi.c +++ b/drivers/vhost/scsi.c @@ -1017,7 +1017,7 @@ static void vhost_scsi_handle_vq(struct vhost_scsi *vs, if (data_direction != DMA_NONE) { ret = vhost_scsi_map_iov_to_sgl(tv_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;