Fix Memory DOS in ImageFont

* A corrupt or specially crafted TTF font could have font metrics that
  lead to unreasonably large sizes when rendering text in
  font. ImageFont.py did not check the image size before allocating
  memory for it.
* Found with oss-fuzz
* This dates from the PIL fork

Tests/test_imagefont.py

@@ -997,3 +997,16 @@ def fake_version_module(module):
     # Act / Assert
     with pytest.warns(DeprecationWarning):
         ImageFont.truetype(FONT_PATH, FONT_SIZE)
+
+
+@pytest.mark.parametrize(
+    "test_file",
+    [
+        "Tests/fonts/oom-e8e927ba6c0d38274a37c1567560eb33baf74627.ttf",
+    ],
+)
+def test_oom(test_file):
+    with open(test_file, "rb") as f:
+        font = ImageFont.truetype(BytesIO(f.read()))
+        with pytest.raises(Image.DecompressionBombError):
+            font.getmask("Test Text")

src/PIL/ImageFont.py

@@ -669,6 +669,7 @@ def getmask2(
         )
         size = size[0] + stroke_width * 2, size[1] + stroke_width * 2
         offset = offset[0] - stroke_width, offset[1] - stroke_width
+        Image._decompression_bomb_check(size)
         im = fill("RGBA" if mode == "RGBA" else "L", size, 0)
         self.font.render(
             text, im.id, mode, direction, features, language, stroke_width, ink