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[libpng16] Another attempt to defeat the fuzzer optimizer

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Glenn Randers-Pehrson 2017-09-24 09:25:12 -05:00
parent 8eb79b3435
commit 346cbf2c2a
1 changed files with 10 additions and 1 deletions
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11
contrib/oss-fuzz/libpng_read_fuzzer.cc
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@ -169,14 +169,23 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
int passes = png_set_interlace_handling(png_handler.png_ptr); int passes = png_set_interlace_handling(png_handler.png_ptr);
png_start_read_image(png_handler.png_ptr); png_start_read_image(png_handler.png_ptr);
/* To do: prevent the optimizer from removing this code entirely */ /* prevent the optimizer from removing this code entirely */
int max_sample = 0;
for (int pass = 0; pass < passes; ++pass) { for (int pass = 0; pass < passes; ++pass) {
for (png_uint_32 y = 0; y < height; ++y) { for (png_uint_32 y = 0; y < height; ++y) {
png_read_row(png_handler.png_ptr, png_read_row(png_handler.png_ptr,
static_cast<png_bytep>(png_handler.row_ptr), nullptr); static_cast<png_bytep>(png_handler.row_ptr), nullptr);
max_sample = png_handler.row_ptr[0] > max_sample ?
png_handler.row_ptr[0] : max_sample;
} }
} }
/* I hope the compiler doesn't figure out that this cannot happen */
if (max_sample > 255) {
PNG_CLEANUP
return 0;
}
png_read_end(png_handler.png_ptr, png_handler.end_info_ptr); png_read_end(png_handler.png_ptr, png_handler.end_info_ptr);
PNG_CLEANUP PNG_CLEANUP