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vhost: fix vhost_vq_access_ok() log check

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Commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ("vhost: validate log
when IOTLB is enabled") introduced a regression.  The logic was
originally:

  if (vq->iotlb)
      return 1;
  return A && B;

After the patch the short-circuit logic for A was inverted:

  if (A || vq->iotlb)
      return A;
  return B;

This patch fixes the regression by rewriting the checks in the obvious
way, no longer returning A when vq->iotlb is non-NULL (which is hard to
understand).

Reported-by: syzbot+65a84dde0214b0387ccd@syzkaller.appspotmail.com
Cc: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stefan Hajnoczi 2018-04-11 10:35:40 +08:00 committed by David S. Miller
parent 7ced6c98c7
commit d14d2b7809
1 changed files with 5 additions and 3 deletions
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8
drivers/vhost/vhost.c
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@ -1244,10 +1244,12 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq,
/* Caller should have vq mutex and device mutex */
int vhost_vq_access_ok(struct vhost_virtqueue *vq)
{
int ret = vq_log_access_ok(vq, vq->log_base);
if (!vq_log_access_ok(vq, vq->log_base))
return 0;
if (ret || vq->iotlb)
return ret;
/* Access validation occurs at prefetch time with IOTLB */
if (vq->iotlb)
return 1;
return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
}