From b24c89b4df8824ed1b2afc1f6493bff0cc0ea2e5 Mon Sep 17 00:00:00 2001 From: Elliott Hughes Date: Tue, 27 Sep 2022 22:37:03 +0000 Subject: stack_protector_DeathTest#modify_stack_protector: avoid flake. I've never been able to repro the flake myself (in hundreds of thousands of runs), but it's certainly possible that a byte of the cookie is already zero. So let's invert the byte we plan to corrupt rather than set it to zero. Bug: http://b/202948861 Test: treehugger Change-Id: Iccd552fe302d6c01e376819d23c11a308e03acdb (cherry picked from commit 23ce50c1728c6bc6986e12073d5d3c8ab10d05d0) --- tests/stack_protector_test_helper.cpp | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/tests/stack_protector_test_helper.cpp b/tests/stack_protector_test_helper.cpp index fd90b939b..eddd94074 100644 --- a/tests/stack_protector_test_helper.cpp +++ b/tests/stack_protector_test_helper.cpp @@ -19,7 +19,8 @@ __attribute__((noinline)) void modify_stack_protector_test() { // We can't use memset here because it's fortified, and we want to test // the line of defense *after* that. // Without volatile, the generic x86/x86-64 targets don't write to the stack. - volatile char* p; - p = reinterpret_cast(&p + 1); - *p = '\0'; + // We can't make a constant change, since the existing byte might already have + // had that value. + volatile char* p = reinterpret_cast(&p + 1); + *p = ~*p; } -- cgit v1.2.3