diff --git a/test/unit/test_disk_tensor.py b/test/unit/test_disk_tensor.py
index 36f087221c..41b91299ba 100644
--- a/test/unit/test_disk_tensor.py
+++ b/test/unit/test_disk_tensor.py
@@ -383,6 +383,38 @@ class TestDiskTensor(unittest.TestCase):
     np.testing.assert_equal(t1.numpy(), np.arange(128, dtype=np.uint8))
     np.testing.assert_equal(t2.numpy(), np.arange(64, dtype=np.uint8))
 
+  def test_disk_open_failure_state(self):
+    from tinygrad.runtime.ops_disk import DiskDevice
+    fn = pathlib.Path(temp("dt_open_failure"))
+    fn.unlink(missing_ok=True)
+    fn.write_bytes(bytes(range(256)))
+    os.chmod(fn, 0o000)
+    try:
+      t = Tensor.empty(100, device=f"disk:{fn}", dtype=dtypes.uint8)
+      t.numpy()
+    except PermissionError: pass
+    # device state should be clean after failed open
+    disk_device = Device[f"DISK:{fn}"]
+    assert isinstance(disk_device, DiskDevice)
+    assert disk_device.size is None, "size should be None after failed open"
+    assert not hasattr(disk_device, "mem"), "mem should not exist after failed open"
+    # should be able to open with any size after failure
+    os.chmod(fn, 0o644)
+    t2 = Tensor.empty(200, device=f"disk:{fn}", dtype=dtypes.uint8)
+    t2.to("CPU").realize()
+    assert disk_device.size == 200
+
+  def test_disk_permission_error(self):
+    fn = pathlib.Path(temp("dt_permission"))
+    fn.unlink(missing_ok=True)
+    fn.write_bytes(bytes(range(256)))
+    os.chmod(fn, 0o000)
+    try:
+      with self.assertRaises(PermissionError):
+        Tensor.empty(100, device=f"disk:{fn}", dtype=dtypes.uint8).numpy()
+    finally:
+      os.chmod(fn, 0o644)
+
 class TestPathTensor(unittest.TestCase):
   def setUp(self):
     self.temp_dir = tempfile.TemporaryDirectory()
diff --git a/tinygrad/runtime/ops_disk.py b/tinygrad/runtime/ops_disk.py
index 2725b6d103..89475a1957 100644
--- a/tinygrad/runtime/ops_disk.py
+++ b/tinygrad/runtime/ops_disk.py
@@ -22,17 +22,17 @@ class DiskDevice(Compiled):
       self.count += 1
       return
     filename = self.device[len("disk:"):]
-    self.size = size
 
     if sys.platform != "win32" and filename.startswith("shm:"):
       fd = _posixshmem.shm_open("/"+filename[4:].lstrip("/"), os.O_RDWR, 0o600)
-      self.mem = mmap.mmap(fd, self.size, mmap.MAP_SHARED | MAP_POPULATE | MAP_LOCKED)
+      self.mem = mmap.mmap(fd, size, mmap.MAP_SHARED | MAP_POPULATE | MAP_LOCKED)
       os.close(fd)
     else:
       try: self.fd = os.open(filename, os.O_RDWR|os.O_CREAT|getattr(os, "O_DIRECT", 0))
       except OSError: self.fd = os.open(filename, os.O_RDWR|os.O_CREAT)
-      if not pathlib.Path(filename).is_block_device() and os.fstat(self.fd).st_size < self.size: os.ftruncate(self.fd, self.size)
-      self.mem = mmap.mmap(self.fd, self.size)
+      if not pathlib.Path(filename).is_block_device() and os.fstat(self.fd).st_size < size: os.ftruncate(self.fd, size)
+      self.mem = mmap.mmap(self.fd, size)
+    self.size = size
     if hasattr(self.mem, 'madvise') and (hp := getattr(mmap, "MADV_HUGEPAGE", None)) is not None:
       with contextlib.suppress(OSError): self.mem.madvise(hp) # some systems have transparent_hugepage disabled
     self.count += 1