vhost: fix end of range for access_ok

During access_ok checks, addr increases as we iterate over the data
structure, thus addr + len - 1 will point beyond the end of region we
are translating.  Harmless since we then verify that the region covers
addr, but let's not waste cpu cycles.

Reported-by: Koichiro Den <den@klaipeden.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Koichiro Den <den@klaipeden.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index d6dbb28..33ac2b1 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1175,7 +1175,7 @@ static int iotlb_access_ok(struct vhost_virtqueue *vq,
 {
        const struct vhost_umem_node *node;
        struct vhost_umem *umem = vq->iotlb;
-       u64 s = 0, size, orig_addr = addr;
+       u64 s = 0, size, orig_addr = addr, last = addr + len - 1;
 
        if (vhost_vq_meta_fetch(vq, addr, len, type))
                return true;
@@ -1183,7 +1183,7 @@ static int iotlb_access_ok(struct vhost_virtqueue *vq,
        while (len > s) {
                node = vhost_umem_interval_tree_iter_first(&umem->umem_tree,
                                                           addr,
-                                                          addr + len - 1);
+                                                          last);
                if (node == NULL || node->start > addr) {
                        vhost_iotlb_miss(vq, addr, access);
                        return false;