[compiler-rt] [TSan] skip memcpy of ctx when NULL in sighandler (PR #217935)

[via llvm-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

Author: Dan Blackwell (DanBlackwell)

<details>
<summary>Changes</summary>

On some platforms ctx is set to NULL when delivering a signal; this causes a crash when trying to memcpy the contents into __tsan::SignalDesc.

This patch first performs a NULL-check before performing the memcpy in order to avoid the crash.

rdar://168547411

---
Full diff: https://github.com/llvm/llvm-project/pull/217935.diff


1 Files Affected:

- (modified) compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp (+2-1) 


``````````diff
diff --git a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
index e00853bd1b426..6c1523db6b579 100644
--- a/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp
@@ -2343,7 +2343,8 @@ void sighandler(int sig, __sanitizer_siginfo *info, void *ctx) {
   if (signal->armed == false) {
     signal->armed = true;
     internal_memcpy(&signal->siginfo, info, sizeof(*info));
-    internal_memcpy(&signal->ctx, ctx, sizeof(signal->ctx));
+    if (ctx)
+      internal_memcpy(&signal->ctx, ctx, sizeof(signal->ctx));
     atomic_store(&thr->pending_signals, 1, memory_order_relaxed);
   }
 }

``````````

</details>


https://github.com/llvm/llvm-project/pull/217935