From 5611fa78caf6aac69ab774f37d7eb921337019bb Mon Sep 17 00:00:00 2001
From: Evgenii Stepanov <eugenis@google.com>
Date: Wed, 3 Jun 2020 18:50:47 -0700
Subject: [PATCH] Clean MTE and GWP-ASan runtime flags after use.

A check in ZygoteHooks_nativePostForkChild expects runtime_flags to be
empty. Clear the flags that have been used and are not needed any
longer.

Bug: 157939523
Test: adb logcat | grep "Unknown bits set in runtime_flags"
Change-Id: Ifade5e2437cbf24ae1d3909032a98bd60fc8a148
---
 core/jni/com_android_internal_os_Zygote.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/core/jni/com_android_internal_os_Zygote.cpp b/core/jni/com_android_internal_os_Zygote.cpp
index 3d8cae8e74d07..5c444bda18386 100644
--- a/core/jni/com_android_internal_os_Zygote.cpp
+++ b/core/jni/com_android_internal_os_Zygote.cpp
@@ -1744,6 +1744,8 @@ static void SpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray gids,
       heap_tagging_level = M_HEAP_TAGGING_LEVEL_NONE;
   }
   android_mallopt(M_SET_HEAP_TAGGING_LEVEL, &heap_tagging_level, sizeof(heap_tagging_level));
+  // Now that we've used the flag, clear it so that we don't pass unknown flags to the ART runtime.
+  runtime_flags &= ~RuntimeFlags::MEMORY_TAG_LEVEL_MASK;
 
   bool forceEnableGwpAsan = false;
   switch (runtime_flags & RuntimeFlags::GWP_ASAN_LEVEL_MASK) {
@@ -1756,6 +1758,8 @@ static void SpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray gids,
       case RuntimeFlags::GWP_ASAN_LEVEL_LOTTERY:
           android_mallopt(M_INITIALIZE_GWP_ASAN, &forceEnableGwpAsan, sizeof(forceEnableGwpAsan));
   }
+  // Now that we've used the flag, clear it so that we don't pass unknown flags to the ART runtime.
+  runtime_flags &= ~RuntimeFlags::GWP_ASAN_LEVEL_MASK;
 
   if (NeedsNoRandomizeWorkaround()) {
     // Work around ARM kernel ASLR lossage (http://b/5817320).