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Manos Koukoutos 0396b732e7 [wasm-gc] read_heap_type should check if index is in module bounds 
read_heap_type did not have knowledge of the module for which the heap
type was being decoded. As a result, callers of read_heap_type (or
read_value_type, which in turn calls read_heap_type) had to check after
the fact that a decoded indexed type (ref, ref null, or rtt) references
a type index within the module's bounds. This was not done consistently,
and was missing (at least) in DecodeLocals.
To avoid such problems in the future, this CL refactors read_heap_type
to accept a module and check the decoded index against it.

Changes:
- Add WasmModule argument to read_heap_type. Do so accordingly to all
  its transitive callers (read_value_type, immediate arguments,
  DecodeLocalDecls, DecodeValue/HeapType in unittests).
- Add index check to read_heap_type and emit an error for an
  out-of-bounds index.
- Remove all other now-redundant index validations. Replace them with
  decoder->ok() if needed (since read_heap_type will now emit an error).
- Fix error message in Validate for BlockTypeImmediate.
- In DecodeLocalDecls in unittests, pass an empty module to
  DecodeLocalDecls in the main code.
- Add a unit test with an invalid index in local type declarations.

Bug: v8:9495
Change-Id: I4ed1204847db80f78b6ae85fa40d300cd2456295
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2569757
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71572}
2020-12-02 16:52:51 +00:00
..
inspector [inspector][fuzzer] Fix termination 2020-11-09 16:02:19 +00:00
json Add json fuzzer 2016-02-02 11:29:01 +00:00
multi_return [turbofan] Add fuzzer to test different signatures for multi-returns 2018-01-12 12:20:27 +00:00
parser Add a library suitable for libfuzzer with a small unit test runner shell 2016-01-26 10:39:03 +00:00
regexp [regexp] add fuzzer support for regexp parser and compiler. 2016-02-01 14:00:38 +00:00
regexp_builtins [regexp] Initial go at a builtins fuzzer 2018-01-18 11:02:57 +00:00
wasm [wasm][fuzzer] Support functions returning i64 2020-09-15 17:23:22 +00:00
wasm_async [wasm][fuzzer] Fix return value of interpreter 2020-08-13 10:08:53 +00:00
wasm_code [wasm] Create a new fuzzer for wasm code. 2016-08-29 13:56:00 +00:00
wasm_compile [wasm] Syntax- and Type-aware Fuzzer 2017-02-17 17:06:29 +00:00
BUILD.gn [inspector][fuzzer] Add inspector fuzzer 2020-11-02 14:29:08 +00:00
DEPS Add a library suitable for libfuzzer with a small unit test runner shell 2016-01-26 10:39:03 +00:00
fuzzer-support.cc [wasm][fuzzer] Enable trap handlers only once 2020-09-01 12:03:59 +00:00
fuzzer-support.h [iwyu] Add missing includes of <memory> for std::unique_ptr 2019-09-13 17:13:36 +00:00
fuzzer.cc [test/fuzzer] Fix cpplint complaints 2017-09-04 10:45:21 +00:00
fuzzer.status Reland "[wasm][fuzzer] Fix exception detection" 2020-08-18 09:00:05 +00:00
inspector-fuzzer.cc [inspector][fuzzer] Allow to overwrite the global 'utils' 2020-12-01 08:57:43 +00:00
json.cc [fuzzer] Fix OOM in v8_json_parser_fuzzer due to unnecessary long input. 2018-07-17 14:25:27 +00:00
multi-return.cc Reland "Reland "[deoptimizer] Change deopt entries into builtins"" 2020-10-21 06:01:38 +00:00
parser.cc [compiler] Fix double error reporting for parser errors 2020-06-10 08:36:41 +00:00
README.md [gyp] move build targets for tests to gypfiles. 2018-01-30 06:31:00 +00:00
regexp-builtins.cc [runtime] Deconfuse Name::Hash() from Name::hash_field() 2020-11-11 12:21:07 +00:00
regexp.cc [regexp] Further narrow public API and restrict includes to regexp.h 2019-06-18 12:23:16 +00:00
testcfg.py [inspector][fuzzer] Add inspector fuzzer 2020-11-02 14:29:08 +00:00
wasm_corpus.tar.gz.sha1 [wasm] Update and run script to generate fuzzer corpus 2020-12-01 16:21:51 +00:00
wasm-async.cc [wasm][fuzzer] Fix data race when setting flags 2020-10-05 16:31:11 +00:00
wasm-code.cc [wasm] Move interpreter to test directory 2020-06-23 08:48:14 +00:00
wasm-compile.cc [config] Add V8_NODISCARD for Scope classes 2020-11-26 11:08:45 +00:00
wasm-fuzzer-common.cc [wasm-gc] read_heap_type should check if index is in module bounds 2020-12-02 16:52:51 +00:00
wasm-fuzzer-common.h [wasm][fuzzer] Fix data race when setting flags 2020-10-05 16:31:11 +00:00
wasm.cc [wasm][fuzzer] Fix data race when setting flags 2020-10-05 16:31:11 +00:00

README.md

How to make a libFuzzer fuzzer in V8

This document describes how to make a new libFuzzer fuzzer for V8. A general introduction to libFuzzer can be found here. In short, libFuzzer is an in-process coverage-driven evolutionary fuzzer. libFuzzer serves you with a sequence of byte arrays that you can use to test your code. libFuzzer tries to generate this sequence of byte arrays in a way that maximizes test coverage.

Warning: By itself libFuzzer typically does not generate valid JavaScript code.

Changes to V8

tldr: Do the same as https://codereview.chromium.org/2280623002 to introduce a new fuzzer to V8.

This is a step by step guide on how to make a new fuzzer in V8. In the example the fuzzer is called foo.

  1. Copy one of the existing fuzzer implementations in test/fuzzer/, e.g. cp wasm.cc foo.cc

    • Copying an existing fuzzer is a good idea to get all the required setup, e.g. setting up the isolate

  2. Create a directory called foo in test/fuzzer/ which contains at least one file

    • The file is used by the trybots to check whether the fuzzer actually compiles and runs

  3. Copy the build rules of an existing fuzzer in BUILD.gn, e.g. the build rules for the wasm.cc fuzzer are v8_source_set("wasm_fuzzer") and v8_fuzzer("wasm_fuzzer"). Note that the name has to be the name of the directory created in Step 2 + _fuzzer so that the scripts on the trybots work

  4. Now you can already compile the fuzzer, e.g. with ninja -j 1000 -C out/x64.debug/v8_simple_foo_fuzzer

    • Use this binary to reproduce issues found by cluster fuzz, e.g. out/x64.debug/v8_simple_foo_fuzzer testcase.foo

  5. Copy the binary name and the test directory name in test/fuzzer/fuzzer.isolate

  6. Add the fuzzer to the FuzzerTestSuite in test/fuzzer/testcfg.py

    • This step is needed to run the fuzzer with the files created in Step 2 on the trybots

  7. Commit the changes described above to the V8 repository

Changes to Chromium

tldr: Do the same as https://codereview.chromium.org/2344823002 to add the new fuzzer to cluster fuzz.

  1. Copy the build rules of an existing fuzzer in testing/libfuzzer/fuzzers/BUILD.gn, e.g. the build rule for the wasm.cc fuzzer is v8_wasm_fuzzer. There is no need to set a dictionary , or a seed_corpus. See chromium-fuzzing-getting-started for more information.

  2. Compile the fuzzer in chromium (for different configurations see: https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reference.md):

    • gn gen out/libfuzzer '--args=use_libfuzzer=true is_asan=true is_debug=false enable_nacl=false'

    • ninja -j 1000 -C out/libfuzzer/ v8_foo_fuzzer

  3. Run the fuzzer locally

    • mkdir /tmp/empty_corpus && out/libfuzzer/v8_foo_fuzzer /tmp/empty_corpus