[PATCH 1/2] ASAN: Support detect_invalid_pointer_pairs=1 with detect_stack_use_after_return=1

[Martin Liška]

Do not crash when AsanThread::GetStackVariableShadowStart does not find
a variable for a pointer on a shadow stack.

Cherry-pick from ad2be02a833e56f7fe280797280b219eb3312621.

Differential Revision: https://reviews.llvm.org/D89552

(cherry picked from commit b69f33f477b9ac38af3c39465600ae74a3554878)
---
 libsanitizer/asan/asan_thread.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libsanitizer/asan/asan_thread.cpp 
b/libsanitizer/asan/asan_thread.cpp
index 6734d9a1668..cb374b28622 100644
--- a/libsanitizer/asan/asan_thread.cpp
+++ b/libsanitizer/asan/asan_thread.cpp
@@ -366,7 +366,9 @@ uptr AsanThread::GetStackVariableShadowStart(uptr addr) {
     bottom = stack_bottom();
   } else if (has_fake_stack()) {
     bottom = fake_stack()->AddrIsInFakeStack(addr);
-    CHECK(bottom);
+    if (bottom == 0) {
+      return 0;
+    }
   } else {
     return 0;
   }
--
2.28.0