close file in case of failures

PIL/Image.py

@@ -2391,6 +2391,7 @@ def open(fp, mode="r"):
     if mode != "r":
         raise ValueError("bad mode %r" % mode)
 
+    exclusive_fp = False
     filename = ""
     if isPath(fp):
         filename = fp
@@ -2404,11 +2405,13 @@ def open(fp, mode="r"):
 
     if filename:
         fp = builtins.open(filename, "rb")
+        exclusive_fp = True
 
     try:
         fp.seek(0)
     except (AttributeError, io.UnsupportedOperation):
         fp = io.BytesIO(fp.read())
+        exclusive_fp = True
 
     prefix = fp.read(16)
 
@@ -2439,6 +2442,8 @@ def open(fp, mode="r"):
     if im:
         return im
 
+    if exclusive_fp:
+        fp.close()
     raise IOError("cannot identify image file %r"
                   % (filename if filename else fp))
 

PIL/ImageFile.py

@@ -88,10 +88,12 @@ class ImageFile(Image.Image):
             # filename
             self.fp = open(fp, "rb")
             self.filename = fp
+            self._exclusive_fp = True
         else:
             # stream
             self.fp = fp
             self.filename = filename
+            self._exclusive_fp = False
 
         try:
             self._open()
@@ -100,6 +102,9 @@ class ImageFile(Image.Image):
                 KeyError,  # unsupported mode
                 EOFError,  # got header but not the first frame
                 struct.error) as v:
+            # close the file only if we have opened it this constructor
+            if self._exclusive_fp:
+                self.fp.close()
             raise SyntaxError(v)
 
         if not self.mode or self.size[0] <= 0: