Fix heap buffer overflow in decode_png (#7691)

Author: kobrineli

test/assets/toosmall_png/heapbof.png

@@ -32,6 +32,7 @@
 DAMAGED_PNG = os.path.join(IMAGE_ROOT, "damaged_png")
 ENCODE_JPEG = os.path.join(IMAGE_ROOT, "encode_jpeg")
 INTERLACED_PNG = os.path.join(IMAGE_ROOT, "interlaced_png")
+TOOSMALL_PNG = os.path.join(IMAGE_ROOT, "toosmall_png")
 IS_WINDOWS = sys.platform in ("win32", "cygwin")
 PILLOW_VERSION = tuple(int(x) for x in PILLOW_VERSION.split("."))
 
@@ -193,6 +194,8 @@ def test_decode_png_errors():
         decode_png(torch.randint(3, 5, (300,), dtype=torch.uint8))
     with pytest.raises(RuntimeError, match="Out of bound read in decode_png"):
         decode_png(read_file(os.path.join(DAMAGED_PNG, "sigsegv.png")))
+    with pytest.raises(RuntimeError, match="Content is too small for png"):
+        decode_png(read_file(os.path.join(TOOSMALL_PNG, "heapbof.png")))
 
 
 @pytest.mark.parametrize(

test/test_image.py

@@ -49,6 +49,7 @@ torch::Tensor decode_png(
     png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);
     TORCH_CHECK(false, "Internal error.");
   }
+  TORCH_CHECK(datap_len >= 8, "Content is too small for png!")
   auto is_png = !png_sig_cmp(datap, 0, 8);
   TORCH_CHECK(is_png, "Content is not png!")