Ensure that the Centipede runner writes the failure atomically and on…

…ly once.

The atomicity is needed because the function `WriteFailureDescription()` may
be called from multiple threads: from the main thread, e.g. for a GoogleTest
assertion failure, and from the watchdog thread, e.g. for an OOM.

The function should write the failure only once because for failures like stack
overflow, it gets called twice: the first time for the stack overflow itself,
and the second time from the SIGABRT handler handling the abort that follows the
detected stack overflow.

PiperOrigin-RevId: 695434225

centipede/runner.cc

@@ -104,21 +104,25 @@ __thread ThreadLocalRunnerState tls;
 static void WriteFailureDescription(const char *description) {
   // TODO(b/264715830): Remove I/O error logging once the bug is fixed?
   if (state.failure_description_path == nullptr) return;
-  FILE *f = fopen(state.failure_description_path, "w");
-  if (f == nullptr) {
-    perror("FAILURE: fopen()");
-    return;
-  }
-  const auto len = strlen(description);
-  if (fwrite(description, 1, len, f) != len) {
-    perror("FAILURE: fwrite()");
-  }
-  if (fflush(f) != 0) {
-    perror("FAILURE: fflush()");
-  }
-  if (fclose(f) != 0) {
-    perror("FAILURE: fclose()");
-  }
+  // Make sure that the write is atomic and only happens once.
+  [[maybe_unused]] static int write_once = [=] {
+    FILE *f = fopen(state.failure_description_path, "w");
+    if (f == nullptr) {
+      perror("FAILURE: fopen()");
+      return 0;
+    }
+    const auto len = strlen(description);
+    if (fwrite(description, 1, len, f) != len) {
+      perror("FAILURE: fwrite()");
+    }
+    if (fflush(f) != 0) {
+      perror("FAILURE: fflush()");
+    }
+    if (fclose(f) != 0) {
+      perror("FAILURE: fclose()");
+    }
+    return 0;
+  }();
 }
 
 void ThreadLocalRunnerState::TraceMemCmp(uintptr_t caller_pc, const uint8_t *s1,

e2e_tests/corpus_database_test.cc

@@ -27,6 +27,7 @@
 namespace fuzztest::internal {
 namespace {
 
+using ::testing::ContainsRegex;
 using ::testing::HasSubstr;
 
 class UpdateCorpusDatabaseTest : public testing::Test {
@@ -88,7 +89,8 @@ absl::NoDestructor<std::string> UpdateCorpusDatabaseTest::centipede_std_err_{};
 
 TEST_F(UpdateCorpusDatabaseTest, RunsFuzzTests) {
   EXPECT_THAT(GetCentipedeStdErr(),
-              HasSubstr("Fuzzing FuzzTest.FailsInTwoWays"));
+              AllOf(HasSubstr("Fuzzing FuzzTest.FailsInTwoWays"),
+                    HasSubstr("Fuzzing FuzzTest.FailsWithStackOverflow")));
 }
 
 TEST_F(UpdateCorpusDatabaseTest, UsesMultipleShardsForFuzzingAndDistillation) {
@@ -99,5 +101,13 @@ TEST_F(UpdateCorpusDatabaseTest, UsesMultipleShardsForFuzzingAndDistillation) {
             HasSubstr("DISTILL[S.1]: Distilling to output shard 1")));
 }
 
+TEST_F(UpdateCorpusDatabaseTest, FindsAllCrashes) {
+  EXPECT_THAT(
+      GetCentipedeStdErr(),
+      AllOf(ContainsRegex(R"re(Failure\s*: GoogleTest assertion failure)re"),
+            ContainsRegex(R"re(Failure\s*: heap-buffer-overflow)re"),
+            ContainsRegex(R"re(Failure\s*: stack-limit-exceeded)re")));
+}
+
 }  // namespace
 }  // namespace fuzztest::internal

e2e_tests/testdata/fuzz_tests_for_corpus_database_testing.cc

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <cstddef>
+
 #include "gtest/gtest.h"
 #include "./fuzztest/fuzztest.h"
 
@@ -29,4 +31,20 @@ void FailsInTwoWays(const std::vector<int>& v) {
 }
 FUZZ_TEST(FuzzTest, FailsInTwoWays);
 
+int ReachStackOverflow(int n) {
+  // Use volatile to prevent the compiler from inlining the recursion.
+  volatile auto f = ReachStackOverflow;
+  return n > 0 ? 1 + f(n - 1) : 0;
+}
+
+// Stack frame consists of at least one word.
+constexpr size_t kStackFrameSizeLowerBound = sizeof(void*);
+// Default stack limit is 128 KiB.
+constexpr int kDepthToReachStackOverflow =
+    128 * 1024 / kStackFrameSizeLowerBound;
+
+void FailsWithStackOverflow(int n) { ReachStackOverflow(n); }
+FUZZ_TEST(FuzzTest, FailsWithStackOverflow)
+    .WithDomains(fuzztest::Just(kDepthToReachStackOverflow));
+
 }  // namespace