[patch] KVM: make checks stricter in coalesced_mmio_in_range()

[Dan Carpenter]

My testing version of Smatch complains that addr and len come from
the user and they can wrap.  The path is:
  -> kvm_vm_ioctl()
     -> kvm_vm_ioctl_unregister_coalesced_mmio()
        -> coalesced_mmio_in_range()

I don't know what the implications are of wrapping here, but we may
as well fix it, if only to silence the warning.

Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>

diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index a6ec206..88b2fe3 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -28,9 +28,15 @@ static int coalesced_mmio_in_range(struct 
kvm_coalesced_mmio_dev *dev,
         * (addr,len) is fully included in
         * (zone->addr, zone->size)
         */
-
-       return (dev->zone.addr <= addr &&
-               addr + len <= dev->zone.addr + dev->zone.size);
+       if (len < 0)
+               return 0;
+       if (addr + len < addr)
+               return 0;
+       if (addr < dev->zone.addr)
+               return 0;
+       if (addr + len > dev->zone.addr + dev->zone.size)
+               return 0;
+       return 1;
 }
 
 static int coalesced_mmio_has_room(struct kvm_coalesced_mmio_dev *dev)
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