| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.10 32/74] vhost/scsi: Fix incorrect usage of get_user_pages_fast write parameter | Date | Fri, 8 Nov 2013 22:51:37 -0800 |
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3.10-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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/vhost/scsi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/vhost/scsi.c +++ b/drivers/vhost/scsi.c @@ -1017,7 +1017,7 @@ static void vhost_scsi_handle_vq(struct 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;
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