| From | Kamal Mostafa <> | Subject | [PATCH 3.8 64/91] vhost/scsi: Fix incorrect usage of get_user_pages_fast write parameter | Date | Thu, 7 Nov 2013 18:15:19 -0800 |
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3.8.13.13 -stable review patch. If anyone has any objections, please let me know.
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From: Nicholas Bellinger <nab@linux-iscsi.org>
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 <stefanha@redhat.com> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Asias He <asias@redhat.com> Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org> [ kamal: backport to 3.8 (applied to tcm_vhost.c) ] Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- drivers/vhost/tcm_vhost.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/vhost/tcm_vhost.c b/drivers/vhost/tcm_vhost.c index 22321cf..9412440 100644 --- a/drivers/vhost/tcm_vhost.c +++ b/drivers/vhost/tcm_vhost.c @@ -696,7 +696,7 @@ 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"); break; /* TODO */ -- 1.8.1.2
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