From 5b697bb08c8e16dcaac428f17b4d95efd7862d07 Mon Sep 17 00:00:00 2001
From: Thiago Macieira <thiago.macieira@intel.com>
Date: Thu, 19 Sep 2024 13:05:35 -0700
Subject: [PATCH] QTest::CrashHandler: allow debugging crashed tests on
 Linux+YAMA

The YAMA LSM by default[1] prevents attaching the debugger to any
process that isn't a child. Since our backtracer comes from a child
process instead (i.e., tracing the parent), we must grant explicit
permission. This also makes QTEST_PAUSE_ON_CRASH=1 work.

[1] https://codebrowser.dev/linux/linux/security/yama/yama_lsm.c.html#ptrace_scope

Change-Id: Ic19d84a7a730c7f8fc0ffffd64e516447e4b1f35
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
(cherry picked from commit 731b1159f9da9d0a5f9871ceaef4b82b657b130c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/testlib/qtestcrashhandler.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/testlib/qtestcrashhandler.cpp b/src/testlib/qtestcrashhandler.cpp
index aabac1c4663..42a715ff865 100644
--- a/src/testlib/qtestcrashhandler.cpp
+++ b/src/testlib/qtestcrashhandler.cpp
@@ -61,6 +61,7 @@
 #include <stdlib.h>
 
 #if defined(Q_OS_LINUX)
+#include <sys/prctl.h>
 #include <sys/types.h>
 #include <fcntl.h>
 #endif
@@ -327,6 +328,11 @@ void generateStackTrace()
     if (debugger == None || alreadyDebugging())
         return;
 
+#  if defined(Q_OS_LINUX) && defined(PR_SET_PTRACER)
+    // allow ourselves to be debugged
+    (void) prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY);
+#  endif
+
 #  if defined(Q_OS_UNIX) && !defined(Q_OS_WASM) && !defined(Q_OS_INTEGRITY) && !defined(Q_OS_VXWORKS)
     writeToStderr("\n=== Stack trace ===\n");