[libfuzzer] Add a sanity check for too big images in libpng_read_fuzzer.

testing/libfuzzer/fuzzers/libpng_read_fuzzer.cc

Index: testing/libfuzzer/fuzzers/libpng_read_fuzzer.cc
diff --git a/testing/libfuzzer/fuzzers/libpng_read_fuzzer.cc b/testing/libfuzzer/fuzzers/libpng_read_fuzzer.cc
index 5d6654e25b4af6255d0ab7f0c8c4b96334e6f1c0..6393c28d52a6f7c3849a2cbbbcab841f1977eb9f 100644
--- a/testing/libfuzzer/fuzzers/libpng_read_fuzzer.cc
+++ b/testing/libfuzzer/fuzzers/libpng_read_fuzzer.cc
@@ -70,7 +70,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
     return 0;
   }
 
-  // Reading
+  // Reading.
   png_read_info(png_ptr, info_ptr);
   png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
   base::ScopedClosureRunner png_deleter(base::Bind(
@@ -91,6 +91,10 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
     return 0;
   }
 
+  // This is going to be too slow.
+  if (height * width > 100000000)

[krasin, 2016/03/17 17:02:48]

what if height * width overflow?

+    return 0;
+
   int passes = png_set_interlace_handling(png_ptr);
   png_start_read_image(png_ptr);