Test not enough image data

Tests/test_file_xpm.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from io import BytesIO
+
 import pytest
 
 from PIL import Image, XpmImagePlugin
@@ -31,6 +33,14 @@ def test_rgb() -> None:
         assert_image_similar(im, hopper(), 16)
 
 
+def test_not_enough_image_data() -> None:
+    with open(TEST_FILE, "rb") as fp:
+        data = fp.read().split(b"/* pixels */")[0]
+        with Image.open(BytesIO(data)) as im:
+            with pytest.raises(ValueError, match="not enough image data"):
+                im.load()
+
+
 def test_invalid_file() -> None:
     invalid_file = "Tests/images/flower.jpg"
 

src/PIL/XpmImagePlugin.py

@@ -125,11 +125,11 @@ class XpmDecoder(ImageFile.PyDecoder):
         pixel_header = False
         while len(data) < dest_length:
             s = self.fd.readline()
+            if not s:
+                break
             if s.rstrip() == b"/* pixels */" and not pixel_header:
                 pixel_header = True
                 continue
-            if not s:
-                break
             s = b'"'.join(s.split(b'"')[1:-1])
             for i in range(0, len(s), bpp):
                 key = s[i : i + bpp]