[tsan] Don't symbolize stack traces if dl_iterate_phdr is not ready

[thurstond]

When a CHECK() fails during TSan initialization, it may segfault (e.g., google/sanitizers#837 (comment)). This is because a failed CHECK() will attempt to print a symbolized stack trace, which requires dl_iterate_phdr, for which the interceptor may not yet be set up.

This patch fixes the issue by not symbolizing the stack trace if the dl_iterate_phdr interceptor is not ready.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Thurston Dang (thurstond)

Changes

When a CHECK() fails during TSan initialization, it may segfault (e.g., google/sanitizers#837 (comment)). This is because a failed CHECK() will attempt to print a symbolized stack trace, which requires dl_iterate_phdr, for which the interceptor may not yet be set up.

This patch fixes the issue by not symbolizing the stack trace if the dl_iterate_phdr interceptor is not ready.

---

Full diff: https://github.com/llvm/llvm-project/pull/143199.diff

4 Files Affected:

• (modified) compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp (+4)
• (modified) compiler-rt/lib/tsan/rtl/tsan_rtl.cpp (+6)
• (modified) compiler-rt/lib/tsan/rtl/tsan_rtl.h (+2)
• (modified) compiler-rt/lib/tsan/rtl/tsan_rtl_report.cpp (+10-1)

diff --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
index 7c4d23a6a0d74..a4bc3d6cff91a 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
@@ -3085,6 +3085,10 @@ void InitializeInterceptors() {
 #if !SANITIZER_ANDROID
   TSAN_INTERCEPT(dl_iterate_phdr);
 #endif
+
+  // Symbolization indirectly calls dl_iterate_phdr
+  ready_to_symbolize = true;
+
   TSAN_MAYBE_INTERCEPT_ON_EXIT;
   TSAN_INTERCEPT(__cxa_atexit);
   TSAN_INTERCEPT(_exit);
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp b/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
index c83efec8eaca2..d8be21284b934 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
@@ -679,6 +679,12 @@ void CheckUnwind() {
 
 bool is_initialized;
 
+// Symbolization indirectly calls dl_iterate_phdr. If a CHECK() fails early on
+// (prior to the dl_iterate_phdr interceptor setup), resulting in an attempted
+// symbolization, it will segfault.
+// dl_iterate_phdr is not intercepted for Android.
+bool ready_to_symbolize = SANITIZER_ANDROID;
+
 void Initialize(ThreadState *thr) {
   // Thread safe because done before all threads exist.
   if (is_initialized)
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl.h b/compiler-rt/lib/tsan/rtl/tsan_rtl.h
index 4dc5e630c5249..0be53599b6a49 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl.h
@@ -54,6 +54,8 @@
 
 namespace __tsan {
 
+extern bool ready_to_symbolize;
+
 #if !SANITIZER_GO
 struct MapUnmapCallback;
 #  if defined(__mips64) || defined(__aarch64__) || defined(__loongarch__) || \
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl_report.cpp b/compiler-rt/lib/tsan/rtl/tsan_rtl_report.cpp
index 51a98e2f2d5e7..0820bf1adee43 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl_report.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl_report.cpp
@@ -846,7 +846,16 @@ ALWAYS_INLINE USED void PrintCurrentStack(uptr pc, bool fast) {
     ptrace->trace_buffer[i] = ptrace->trace_buffer[ptrace->size - i - 1];
     ptrace->trace_buffer[ptrace->size - i - 1] = tmp;
   }
-  PrintStack(SymbolizeStack(*ptrace));
+
+  if (ready_to_symbolize) {
+    PrintStack(SymbolizeStack(*ptrace));
+  } else {
+    Printf(
+        "WARNING: PrintCurrentStack() has been called too early, before "
+        "symbolization is possible. Printing unsymbolized stack trace:\n");
+    for (unsigned int i = 0; i < ptrace->size; i++)
+      Printf("    #%u: 0x%zx\n", i, ptrace->trace[i]);
+  }
 #endif
 }