[all-commits] [llvm/llvm-project] 70cbc6: [libFuzzer] Fix stack overflow detection

[Sebastian Poeplau via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 70cbc6dbef7048d3b1aa89a676d96c6ba075b41b
      https://github.com/llvm/llvm-project/commit/70cbc6dbef7048d3b1aa89a676d96c6ba075b41b
  Author: Sebastian Poeplau <poeplau at code-intelligence.com>
  Date:   2021-05-07 (Fri, 07 May 2021)

  Changed paths:
    M compiler-rt/lib/fuzzer/FuzzerUtilPosix.cpp
    A compiler-rt/test/fuzzer/StackOverflowTest.cpp
    A compiler-rt/test/fuzzer/stack-overflow-with-asan.test

  Log Message:
  -----------
  [libFuzzer] Fix stack overflow detection

Address sanitizer can detect stack exhaustion via its SEGV handler, which is
executed on a separate stack using the sigaltstack mechanism. When libFuzzer is
used with address sanitizer, it installs its own signal handlers which defer to
those put in place by the sanitizer before performing additional actions. In the
particular case of a stack overflow, the current setup fails because libFuzzer
doesn't preserve the flag for executing the signal handler on a separate stack:
when we run out of stack space, the operating system can't run the SEGV handler,
so address sanitizer never reports the issue. See the included test for an
example.

This commit fixes the issue by making libFuzzer preserve the SA_ONSTACK flag
when installing its signal handlers; the dedicated signal-handler stack set up
by the sanitizer runtime appears to be large enough to support the additional
frames from the fuzzer.

Reviewed By: morehouse

Differential Revision: https://reviews.llvm.org/D101824