Added decompression bomb checks

Tests/test_decompression_bomb.py

@@ -14,6 +14,7 @@ class TestDecompressionBomb(PillowTestCase):
     def test_no_warning_small_file(self):
         # Implicit assert: no warning.
         # A warning would cause a failure.
+        Image.MAX_IMAGE_PIXELS = ORIGINAL_LIMIT
         Image.open(TEST_FILE)
 
     def test_no_warning_no_limit(self):
@@ -41,6 +42,14 @@ class TestDecompressionBomb(PillowTestCase):
 
         self.assertRaises(Image.DecompressionBombError, lambda: Image.open(TEST_FILE))
 
+    def test_exception_ico(self):
+        with self.assertRaises(Image.DecompressionBombError):
+            Image.open("Tests/images/decompression_bomb.ico")
+
+    def test_exception_gif(self):
+        with self.assertRaises(Image.DecompressionBombError):
+            Image.open("Tests/images/decompression_bomb.gif")
+
 
 class TestDecompressionCrop(PillowTestCase):
     def setUp(self):

src/PIL/GifImagePlugin.py

@@ -265,6 +265,7 @@ class GifImageFile(ImageFile.ImageFile):
                 self.dispose = None
             elif self.disposal_method == 2:
                 # replace with background colour
+                Image._decompression_bomb_check(self.size)
                 self.dispose = Image.core.fill("P", self.size, self.info["background"])
             else:
                 # replace with previous contents

src/PIL/IcoImagePlugin.py

@@ -180,6 +180,7 @@ class IcoFile(object):
         else:
             # XOR + AND mask bmp frame
             im = BmpImagePlugin.DibImageFile(self.buf)
+            Image._decompression_bomb_check(im.size)
 
             # change tile dimension to only encompass XOR image
             im._size = (im.size[0], int(im.size[1] / 2))