Commit 60a01f55 authored Oct 25, 2013 by Nicholas Bellinger

vhost/scsi: Fix incorrect usage of get_user_pages_fast write parameter



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 <stefanha@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Asias He <asias@redhat.com>
Cc: <stable@vger.kernel.org> # 3.6+
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

parent 58932e96

drivers/vhost/scsi.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;