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 <[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]>

0 files changed, 0 insertions, 0 deletions