[all-commits] [llvm/llvm-project] 62e4dc: [libFuzzer] Fix off-by-one error in ApplyDictionar...

[Matt Morehouse via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 62e4dca94e25668c9f70abc7e524328fd5c6d5c9
      https://github.com/llvm/llvm-project/commit/62e4dca94e25668c9f70abc7e524328fd5c6d5c9
  Author: Fabian Meumertzheim <meumertzheim at code-intelligence.com>
  Date:   2021-05-03 (Mon, 03 May 2021)

  Changed paths:
    M compiler-rt/lib/fuzzer/FuzzerMutate.cpp

  Log Message:
  -----------
  [libFuzzer] Fix off-by-one error in ApplyDictionaryEntry

In the overwrite branch of MutationDispatcher::ApplyDictionaryEntry in
FuzzerMutate.cpp, the index Idx at which W.size() bytes are overwritten
with the word W is chosen uniformly at random in the interval
[0, Size - W.size()). This means that Idx + W.size() will always be
strictly less than Size, i.e., the last byte of the current unit will
never be overwritten.

This is fixed by adding 1 to the exclusive upper bound.

Addresses https://bugs.llvm.org/show_bug.cgi?id=49989.

Reviewed By: morehouse

Differential Revision: https://reviews.llvm.org/D101625


  Commit: ac512890b47032fcee167a702ab14da59137723c
      https://github.com/llvm/llvm-project/commit/ac512890b47032fcee167a702ab14da59137723c
  Author: Matt Morehouse <mascasa at google.com>
  Date:   2021-05-03 (Mon, 03 May 2021)

  Changed paths:
    M compiler-rt/test/fuzzer/EntropicScalePerExecTimeTest.cpp
    M compiler-rt/test/fuzzer/entropic-scale-per-exec-time.test

  Log Message:
  -----------
  [libFuzzer] Deflake entropic exec-time test.


Compare: https://github.com/llvm/llvm-project/compare/89a94be16b01...ac512890b470