4.15-stable review patch. If anyone has any objections, please let me know.
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From: Stefan Hajnoczi stefanha@redhat.com
[ Upstream commit d14d2b78090c7de0557362b26a4ca591aa6a9faa ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/vhost/vhost.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
--- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1256,10 +1256,12 @@ static int vq_log_access_ok(struct vhost /* 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); }