From: Vitaly Buka <vitalybuka@google.com>
Date: Thu, 25 May 2017 01:43:13 +0000 (+0000)
Subject: [libFuzzer] Don't replace custom signal handlers.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=c62411d85945764b9e418b2cdd15531a7002db60;p=llvm

[libFuzzer] Don't replace custom signal handlers.

Summary:
This allows to keep handlers installed by sanitizers.
In other cases third-party code can replace handlers after libFuzzer
initialization anyway.

Reviewers: kcc

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33522

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303828 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Fuzzer/FuzzerUtilPosix.cpp b/lib/Fuzzer/FuzzerUtilPosix.cpp
index 0161309fbf8..bc85264ac18 100644
--- a/lib/Fuzzer/FuzzerUtilPosix.cpp
+++ b/lib/Fuzzer/FuzzerUtilPosix.cpp
@@ -47,8 +47,21 @@ static void FileSizeExceedHandler(int, siginfo_t *, void *) {
 
 static void SetSigaction(int signum,
                          void (*callback)(int, siginfo_t *, void *)) {
-  struct sigaction sigact;
-  memset(&sigact, 0, sizeof(sigact));
+  struct sigaction sigact = {};
+  if (sigaction(signum, nullptr, &sigact)) {
+    Printf("libFuzzer: sigaction failed with %d\n", errno);
+    exit(1);
+  }
+  if (sigact.sa_flags & SA_SIGINFO) {
+    if (sigact.sa_sigaction)
+      return;
+  } else {
+    if (sigact.sa_handler != SIG_DFL && sigact.sa_handler != SIG_IGN &&
+        sigact.sa_handler != SIG_ERR)
+      return;
+  }
+
+  sigact = {};
   sigact.sa_sigaction = callback;
   if (sigaction(signum, &sigact, 0)) {
     Printf("libFuzzer: sigaction failed with %d\n", errno);
diff --git a/lib/Fuzzer/test/fuzzer-segv.test b/lib/Fuzzer/test/fuzzer-segv.test
index b9a6a5ce44c..90f01932f65 100644
--- a/lib/Fuzzer/test/fuzzer-segv.test
+++ b/lib/Fuzzer/test/fuzzer-segv.test
@@ -3,3 +3,5 @@ LIBFUZZER_OWN_SEGV_HANDLER: == ERROR: libFuzzer: deadly signal
 LIBFUZZER_OWN_SEGV_HANDLER: SUMMARY: libFuzzer: deadly signal
 LIBFUZZER_OWN_SEGV_HANDLER: Test unit written to ./crash-
 
+RUN: env ASAN_OPTIONS=handle_segv=1 not LLVMFuzzer-NullDerefTest 2>&1 | FileCheck %s --check-prefix=LIBFUZZER_ASAN_SEGV_HANDLER
+LIBFUZZER_ASAN_SEGV_HANDLER: ERROR: AddressSanitizer: {{SEGV|access-violation}} on unknown address