Index: compiler-rt/lib/msan/tests/msan_test.cc
===================================================================
--- compiler-rt/lib/msan/tests/msan_test.cc
+++ compiler-rt/lib/msan/tests/msan_test.cc
@@ -3502,6 +3502,21 @@
     EXPECT_NOT_POISONED(gids[i]);
 }
 
+TEST(MemorySanitizer, getgroups_zero) {
+  gid_t group;
+  int n = getgroups(0, &group);
+  ASSERT_GE(n, 0);
+}
+
+TEST(MemorySanitizer, getgroups_negative) {
+  gid_t group;
+  int n = getgroups(-1, 0);
+  ASSERT_EQ(-1, n);
+
+  n = getgroups(-1, 0);
+  ASSERT_EQ(-1, n);
+}
+
 TEST(MemorySanitizer, wordexp) {
   wordexp_t w;
   int res = wordexp("a b c", &w, 0);
Index: compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
+++ compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc
@@ -3420,7 +3420,8 @@
   // its metadata. See
   // https://github.com/google/sanitizers/issues/321.
   int res = REAL(getgroups)(size, lst);
-  if (res && lst) COMMON_INTERCEPTOR_WRITE_RANGE(ctx, lst, res * sizeof(*lst));
+  if (res >= 0 && lst && size > 0)
+    COMMON_INTERCEPTOR_WRITE_RANGE(ctx, lst, res * sizeof(*lst));
   return res;
 }
 #define INIT_GETGROUPS COMMON_INTERCEPT_FUNCTION(getgroups);