From: Nicholas Bellinger <[email protected]> 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 <[email protected]> Cc: Michael S. Tsirkin <[email protected]> Cc: Asias He <[email protected]> Cc: <[email protected]> # 3.6+ Signed-off-by: Nicholas Bellinger <[email protected]> --- 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 _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
