Merge "vts_libsnapshot_test: Fix test flakiness."
diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index 1f54f5b..9fe8e18 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -903,9 +903,9 @@
         // Deal with alternate entries for the same point which are required to be all following
         // each other.
         if (mounted) {
-            LERROR << __FUNCTION__ << "(): skipping fstab dup mountpoint=" << fstab[i].mount_point
-                   << " rec[" << i << "].fs_type=" << fstab[i].fs_type << " already mounted as "
-                   << fstab[*attempted_idx].fs_type;
+            LINFO << __FUNCTION__ << "(): skipping fstab dup mountpoint=" << fstab[i].mount_point
+                  << " rec[" << i << "].fs_type=" << fstab[i].fs_type << " already mounted as "
+                  << fstab[*attempted_idx].fs_type;
             continue;
         }
 
@@ -933,9 +933,9 @@
                 *attempted_idx = i;
                 mounted = true;
                 if (i != start_idx) {
-                    LERROR << __FUNCTION__ << "(): Mounted " << fstab[i].blk_device << " on "
-                           << fstab[i].mount_point << " with fs_type=" << fstab[i].fs_type
-                           << " instead of " << fstab[start_idx].fs_type;
+                    LINFO << __FUNCTION__ << "(): Mounted " << fstab[i].blk_device << " on "
+                          << fstab[i].mount_point << " with fs_type=" << fstab[i].fs_type
+                          << " instead of " << fstab[start_idx].fs_type;
                 }
                 fs_stat &= ~FS_STAT_FULL_MOUNT_FAILED;
                 mount_errno = 0;
diff --git a/init/first_stage_init.cpp b/init/first_stage_init.cpp
index 202a86a..107e99a 100644
--- a/init/first_stage_init.cpp
+++ b/init/first_stage_init.cpp
@@ -295,9 +295,6 @@
     // stage init
     CHECKCALL(mount("tmpfs", kSecondStageRes, "tmpfs", MS_NOEXEC | MS_NOSUID | MS_NODEV,
                     "mode=0755,uid=0,gid=0"))
-
-    // First stage init stores Mainline sepolicy here.
-    CHECKCALL(mkdir("/dev/selinux", 0744));
 #undef CHECKCALL
 
     SetStdioToDevNull(argv);
diff --git a/init/init_test.cpp b/init/init_test.cpp
index 05cf3fd..8362390 100644
--- a/init/init_test.cpp
+++ b/init/init_test.cpp
@@ -280,6 +280,10 @@
 }
 
 TEST(init, StopServiceByApexName) {
+    if (getuid() != 0) {
+        GTEST_SKIP() << "Must be run as root.";
+        return;
+    }
     std::string_view script_template = R"init(
 service apex_test_service /system/bin/yes
     user shell
@@ -291,6 +295,10 @@
 }
 
 TEST(init, StopMultipleServicesByApexName) {
+    if (getuid() != 0) {
+        GTEST_SKIP() << "Must be run as root.";
+        return;
+    }
     std::string_view script_template = R"init(
 service apex_test_service_multiple_a /system/bin/yes
     user shell
@@ -307,6 +315,10 @@
 }
 
 TEST(init, StopServicesFromMultipleApexes) {
+    if (getuid() != 0) {
+        GTEST_SKIP() << "Must be run as root.";
+        return;
+    }
     std::string_view apex_script_template = R"init(
 service apex_test_service_multi_apex_a /system/bin/yes
     user shell
@@ -332,6 +344,10 @@
 }
 
 TEST(init, StopServicesFromApexAndNonApex) {
+    if (getuid() != 0) {
+        GTEST_SKIP() << "Must be run as root.";
+        return;
+    }
     std::string_view apex_script_template = R"init(
 service apex_test_service_apex_a /system/bin/yes
     user shell
@@ -357,6 +373,10 @@
 }
 
 TEST(init, StopServicesFromApexMixed) {
+    if (getuid() != 0) {
+        GTEST_SKIP() << "Must be run as root.";
+        return;
+    }
     std::string_view script_template = R"init(
 service apex_test_service_mixed_a /system/bin/yes
     user shell
diff --git a/init/selinux.cpp b/init/selinux.cpp
index be8c554..ab5b0a0 100644
--- a/init/selinux.cpp
+++ b/init/selinux.cpp
@@ -237,9 +237,9 @@
     // If there is an odm partition, precompiled_sepolicy will be in
     // odm/etc/selinux. Otherwise it will be in vendor/etc/selinux.
     static constexpr const char vendor_precompiled_sepolicy[] =
-        "/vendor/etc/selinux/precompiled_sepolicy";
+            "/vendor/etc/selinux/precompiled_sepolicy";
     static constexpr const char odm_precompiled_sepolicy[] =
-        "/odm/etc/selinux/precompiled_sepolicy";
+            "/odm/etc/selinux/precompiled_sepolicy";
     if (access(odm_precompiled_sepolicy, R_OK) == 0) {
         precompiled_sepolicy = odm_precompiled_sepolicy;
     } else if (access(vendor_precompiled_sepolicy, R_OK) == 0) {
@@ -525,6 +525,32 @@
                                              "apex_service_contexts", "apex_seapp_contexts",
                                              "apex_test"};
 
+Result<void> CreateTmpfsDir() {
+    mode_t mode = 0744;
+    struct stat stat_data;
+    if (stat(kTmpfsDir.c_str(), &stat_data) != 0) {
+        if (errno != ENOENT) {
+            return ErrnoError() << "Could not stat " << kTmpfsDir;
+        }
+        if (mkdir(kTmpfsDir.c_str(), mode) != 0) {
+            return ErrnoError() << "Could not mkdir " << kTmpfsDir;
+        }
+    } else {
+        if (!S_ISDIR(stat_data.st_mode)) {
+            return Error() << kTmpfsDir << " exists and is not a directory.";
+        }
+        LOG(WARNING) << "Directory " << kTmpfsDir << " already exists";
+    }
+
+    // Need to manually call chmod because mkdir will create a folder with
+    // permissions mode & ~umask.
+    if (chmod(kTmpfsDir.c_str(), mode) != 0) {
+        return ErrnoError() << "Could not chmod " << kTmpfsDir;
+    }
+
+    return {};
+}
+
 Result<void> PutFileInTmpfs(ZipArchiveHandle archive, const std::string& fileName) {
     ZipEntry entry;
     std::string dstPath = kTmpfsDir + fileName;
@@ -538,7 +564,7 @@
     unique_fd fd(TEMP_FAILURE_RETRY(
             open(dstPath.c_str(), O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, S_IRUSR | S_IWUSR)));
     if (fd == -1) {
-        return Error() << "Failed to open " << dstPath;
+        return ErrnoError() << "Failed to open " << dstPath;
     }
 
     ret = ExtractEntryToFile(archive, &entry, fd);
@@ -568,6 +594,11 @@
 
     auto handle_guard = android::base::make_scope_guard([&handle] { CloseArchive(handle); });
 
+    auto create = CreateTmpfsDir();
+    if (!create.ok()) {
+        return create.error();
+    }
+
     for (const auto& file : kApexSepolicy) {
         auto extract = PutFileInTmpfs(handle, file);
         if (!extract.ok()) {
diff --git a/init/service.cpp b/init/service.cpp
index 99a0367..4cf409c 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -36,6 +36,8 @@
 #include <processgroup/processgroup.h>
 #include <selinux/selinux.h>
 
+#include <string>
+
 #include "lmkd_service.h"
 #include "service_list.h"
 #include "util.h"
@@ -53,6 +55,7 @@
 
 using android::base::boot_clock;
 using android::base::GetBoolProperty;
+using android::base::GetIntProperty;
 using android::base::GetProperty;
 using android::base::Join;
 using android::base::make_scope_guard;
@@ -320,6 +323,20 @@
             mount_namespace_.has_value() && *mount_namespace_ == NS_DEFAULT;
     const bool is_process_updatable = use_default_mount_ns && is_apex_updatable;
 
+#ifdef SEGV_MTEAERR
+    // As a precaution, we only upgrade a service once per reboot, to limit
+    // the potential impact.
+    // TODO(b/244471804): Once we have a kernel API to get sicode, compare it to MTEAERR here.
+    bool should_upgrade_mte = siginfo.si_code != CLD_EXITED && siginfo.si_status == SIGSEGV &&
+                              !upgraded_mte_;
+
+    if (should_upgrade_mte) {
+        LOG(INFO) << "Upgrading service " << name_ << " to sync MTE";
+        once_environment_vars_.emplace_back("BIONIC_MEMTAG_UPGRADE_SECS", "60");
+        upgraded_mte_ = true;
+    }
+#endif
+
     // If we crash > 4 times in 'fatal_crash_window_' minutes or before boot_completed,
     // reboot into bootloader or set crashing property
     boot_clock::time_point now = boot_clock::now();
@@ -484,6 +501,9 @@
         LOG(FATAL) << "Service '" << name_ << "' failed to set up namespaces: " << result.error();
     }
 
+    for (const auto& [key, value] : once_environment_vars_) {
+        setenv(key.c_str(), value.c_str(), 1);
+    }
     for (const auto& [key, value] : environment_vars_) {
         setenv(key.c_str(), value.c_str(), 1);
     }
@@ -628,6 +648,8 @@
         return ErrnoError() << "Failed to fork";
     }
 
+    once_environment_vars_.clear();
+
     if (oom_score_adjust_ != DEFAULT_OOM_SCORE_ADJUST) {
         std::string oom_str = std::to_string(oom_score_adjust_);
         std::string oom_file = StringPrintf("/proc/%d/oom_score_adj", pid);
diff --git a/init/service.h b/init/service.h
index 6d9a0ca..ab19865 100644
--- a/init/service.h
+++ b/init/service.h
@@ -171,6 +171,7 @@
     android::base::boot_clock::time_point time_started_;  // time of last start
     android::base::boot_clock::time_point time_crashed_;  // first crash within inspection window
     int crash_count_;                     // number of times crashed within window
+    bool upgraded_mte_ = false;           // whether we upgraded async MTE -> sync MTE before
     std::chrono::minutes fatal_crash_window_ = 4min;  // fatal() when more than 4 crashes in it
     std::optional<std::string> fatal_reboot_target_;  // reboot target of fatal handler
 
@@ -183,6 +184,8 @@
     std::vector<SocketDescriptor> sockets_;
     std::vector<FileDescriptor> files_;
     std::vector<std::pair<std::string, std::string>> environment_vars_;
+    // Environment variables that only get applied to the next run.
+    std::vector<std::pair<std::string, std::string>> once_environment_vars_;
 
     Subcontext* subcontext_;
     Action onrestart_;  // Commands to execute on restart.
diff --git a/init/test_upgrade_mte/Android.bp b/init/test_upgrade_mte/Android.bp
new file mode 100644
index 0000000..1bfc76c
--- /dev/null
+++ b/init/test_upgrade_mte/Android.bp
@@ -0,0 +1,41 @@
+// Copyright (C) 2022 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package {
+    default_applicable_licenses: ["system_core_init_license"],
+}
+
+cc_binary {
+  name: "mte_upgrade_test_helper",
+  srcs: ["mte_upgrade_test_helper.cpp"],
+  sanitize: {
+    memtag_heap: true,
+    diag: {
+      memtag_heap: false,
+    },
+  },
+  init_rc: [
+    "mte_upgrade_test.rc",
+  ],
+}
+
+java_test_host {
+    name: "mte_upgrade_test",
+    libs: ["tradefed"],
+    static_libs: ["frameworks-base-hostutils", "cts-install-lib-host"],
+    srcs:  ["src/**/MteUpgradeTest.java", ":libtombstone_proto-src"],
+    data: [":mte_upgrade_test_helper", "mte_upgrade_test.rc" ],
+    test_config: "AndroidTest.xml",
+    test_suites: ["general-tests"],
+}
diff --git a/init/test_upgrade_mte/AndroidTest.xml b/init/test_upgrade_mte/AndroidTest.xml
new file mode 100644
index 0000000..b89cde8
--- /dev/null
+++ b/init/test_upgrade_mte/AndroidTest.xml
@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2022 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<configuration description="Runs the MTE upgrade tests">
+    <option name="test-suite-tag" value="init_test_upgrade_mte" />
+    <option name="test-suite-tag" value="apct" />
+    <target_preparer class="com.android.tradefed.targetprep.RootTargetPreparer"/>
+    <target_preparer class="com.android.tradefed.targetprep.PushFilePreparer">
+      <option name="cleanup" value="true" />
+      <option name="remount-system" value="true" />
+      <option name="push" value="mte_upgrade_test.rc->/system/etc/init/mte_upgrade_test.rc" />
+      <option name="push" value="mte_upgrade_test_helper->/system/bin/mte_upgrade_test_helper" />
+      <option name="push" value="mte_upgrade_test_helper->/data/local/tmp/app_process64" />
+    </target_preparer>
+    <test class="com.android.tradefed.testtype.HostTest" >
+        <option name="jar" value="mte_upgrade_test.jar" />
+    </test>
+</configuration>
\ No newline at end of file
diff --git a/init/test_upgrade_mte/mte_upgrade_test.rc b/init/test_upgrade_mte/mte_upgrade_test.rc
new file mode 100644
index 0000000..a3e596c
--- /dev/null
+++ b/init/test_upgrade_mte/mte_upgrade_test.rc
@@ -0,0 +1,24 @@
+# Copyright (C) 2022 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+service mte_upgrade_test_helper /system/bin/mte_upgrade_test_helper ${sys.mte_crash_test_uuid}
+  class late_start
+  disabled
+  seclabel u:r:su:s0
+
+service mte_upgrade_test_helper_overridden /system/bin/mte_upgrade_test_helper ${sys.mte_crash_test_uuid}
+  class late_start
+  disabled
+  seclabel u:r:su:s0
+  setenv BIONIC_MEMTAG_UPGRADE_SECS 0
diff --git a/init/test_upgrade_mte/mte_upgrade_test_helper.cpp b/init/test_upgrade_mte/mte_upgrade_test_helper.cpp
new file mode 100644
index 0000000..10af06b
--- /dev/null
+++ b/init/test_upgrade_mte/mte_upgrade_test_helper.cpp
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <linux/prctl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/prctl.h>
+#include <time.h>
+#include <unistd.h>
+
+int MaybeDowngrade() {
+    int res = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+    if (res == -1) return 1;
+    if (static_cast<unsigned long>(res) & PR_MTE_TCF_ASYNC) return 2;
+    time_t t = time(nullptr);
+    while (time(nullptr) - t < 100) {
+        res = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+        if (static_cast<unsigned long>(res) & PR_MTE_TCF_ASYNC) {
+            return 0;
+        }
+        sleep(1);
+    }
+    return 3;
+}
+
+int main(int argc, char** argv) {
+    if (argc == 2 && strcmp(argv[1], "--check-downgrade") == 0) {
+        return MaybeDowngrade();
+    }
+    int res = prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0);
+    if (res == -1) abort();
+    if (argc == 2 && strcmp(argv[1], "--get-mode") == 0) {
+        if (res & PR_MTE_TCF_ASYNC) {
+            return 1;
+        }
+        if (res & PR_MTE_TCF_SYNC) {
+            return 2;
+        }
+        abort();
+    }
+
+    if (res & PR_MTE_TCF_ASYNC && res & PR_MTE_TCF_SYNC) {
+        // Disallow automatic upgrade from ASYNC mode.
+        if (prctl(PR_SET_TAGGED_ADDR_CTRL, res & ~PR_MTE_TCF_SYNC, 0, 0, 0) == -1) abort();
+    }
+    volatile char* f = (char*)malloc(1);
+    f[17] = 'x';
+    char buf[1];
+    read(1, buf, 1);
+    return 0;
+}
diff --git a/init/test_upgrade_mte/src/com/android/tests/init/MteUpgradeTest.java b/init/test_upgrade_mte/src/com/android/tests/init/MteUpgradeTest.java
new file mode 100644
index 0000000..f4e4a9c
--- /dev/null
+++ b/init/test_upgrade_mte/src/com/android/tests/init/MteUpgradeTest.java
@@ -0,0 +1,151 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.tests.init;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import static org.junit.Assume.assumeTrue;
+
+import com.android.server.os.TombstoneProtos.Tombstone;
+import com.android.tradefed.testtype.DeviceJUnit4ClassRunner;
+import com.android.tradefed.testtype.junit4.BaseHostJUnit4Test;
+import com.android.tradefed.util.CommandResult;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.InputStream;
+import java.util.ArrayList;
+
+@RunWith(DeviceJUnit4ClassRunner.class)
+public class MteUpgradeTest extends BaseHostJUnit4Test {
+    @Before
+    public void setUp() throws Exception {
+        CommandResult result =
+                getDevice().executeShellV2Command("/system/bin/mte_upgrade_test_helper --checking");
+        assumeTrue("mte_upgrade_test_binary needs to segfault", result.getExitCode() == 139);
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        // Easier here than in a finally in testCrash, and doesn't really hurt.
+        getDevice().executeShellV2Command("stop mte_upgrade_test_helper");
+        getDevice().executeShellV2Command("stop mte_upgrade_test_helper_overridden");
+        getDevice().setProperty("sys.mte_crash_test_uuid", "");
+    }
+
+    Tombstone parseTombstone(String tombstonePath) throws Exception {
+        File tombstoneFile = getDevice().pullFile(tombstonePath);
+        InputStream istr = new FileInputStream(tombstoneFile);
+        Tombstone tombstoneProto;
+        try {
+            tombstoneProto = Tombstone.parseFrom(istr);
+        } finally {
+            istr.close();
+        }
+        return tombstoneProto;
+    }
+
+    @Test
+    public void testCrash() throws Exception {
+        String uuid = java.util.UUID.randomUUID().toString();
+        getDevice().reboot();
+        assertThat(getDevice().setProperty("sys.mte_crash_test_uuid", uuid)).isTrue();
+
+        CommandResult result = getDevice().executeShellV2Command("start mte_upgrade_test_helper");
+        assertThat(result.getExitCode()).isEqualTo(0);
+        java.lang.Thread.sleep(20000);
+        String[] tombstonesAfter = getDevice().getChildren("/data/tombstones");
+        ArrayList<String> segvCodeNames = new ArrayList<String>();
+        for (String tombstone : tombstonesAfter) {
+            if (!tombstone.endsWith(".pb")) {
+                continue;
+            }
+            String tombstoneFilename = "/data/tombstones/" + tombstone;
+            Tombstone tombstoneProto = parseTombstone(tombstoneFilename);
+            if (!tombstoneProto.getCommandLineList().stream().anyMatch(x -> x.contains(uuid))) {
+                continue;
+            }
+            assertThat(tombstoneProto.getSignalInfo().getName()).isEqualTo("SIGSEGV");
+            segvCodeNames.add(tombstoneProto.getSignalInfo().getCodeName());
+            getDevice().deleteFile(tombstoneFilename);
+            // remove the non .pb file as well.
+            getDevice().deleteFile(tombstoneFilename.substring(0, tombstoneFilename.length() - 3));
+        }
+        assertThat(segvCodeNames.size()).isAtLeast(3);
+        assertThat(segvCodeNames.get(0)).isEqualTo("SEGV_MTEAERR");
+        assertThat(segvCodeNames.get(1)).isEqualTo("SEGV_MTESERR");
+        assertThat(segvCodeNames.get(2)).isEqualTo("SEGV_MTEAERR");
+    }
+
+    @Test
+    public void testCrashOverridden() throws Exception {
+        String uuid = java.util.UUID.randomUUID().toString();
+        getDevice().reboot();
+        assertThat(getDevice().setProperty("sys.mte_crash_test_uuid", uuid)).isTrue();
+
+        CommandResult result =
+                getDevice().executeShellV2Command("start mte_upgrade_test_helper_overridden");
+        assertThat(result.getExitCode()).isEqualTo(0);
+        java.lang.Thread.sleep(20000);
+        String[] tombstonesAfter = getDevice().getChildren("/data/tombstones");
+        ArrayList<String> segvCodeNames = new ArrayList<String>();
+        for (String tombstone : tombstonesAfter) {
+            if (!tombstone.endsWith(".pb")) {
+                continue;
+            }
+            String tombstoneFilename = "/data/tombstones/" + tombstone;
+            Tombstone tombstoneProto = parseTombstone(tombstoneFilename);
+            if (!tombstoneProto.getCommandLineList().stream().anyMatch(x -> x.contains(uuid))) {
+                continue;
+            }
+            assertThat(tombstoneProto.getSignalInfo().getName()).isEqualTo("SIGSEGV");
+            segvCodeNames.add(tombstoneProto.getSignalInfo().getCodeName());
+            getDevice().deleteFile(tombstoneFilename);
+            // remove the non .pb file as well.
+            getDevice().deleteFile(tombstoneFilename.substring(0, tombstoneFilename.length() - 3));
+        }
+        assertThat(segvCodeNames.size()).isAtLeast(3);
+        assertThat(segvCodeNames.get(0)).isEqualTo("SEGV_MTEAERR");
+        assertThat(segvCodeNames.get(1)).isEqualTo("SEGV_MTEAERR");
+        assertThat(segvCodeNames.get(2)).isEqualTo("SEGV_MTEAERR");
+    }
+
+    @Test
+    public void testDowngrade() throws Exception {
+        CommandResult result =
+                getDevice()
+                        .executeShellV2Command(
+                                "MEMTAG_OPTIONS=async BIONIC_MEMTAG_UPGRADE_SECS=5"
+                                        + " /system/bin/mte_upgrade_test_helper --check-downgrade");
+        assertThat(result.getExitCode()).isEqualTo(0);
+    }
+
+    @Test
+    public void testAppProcess() throws Exception {
+        CommandResult result =
+                getDevice()
+                        .executeShellV2Command(
+                                "MEMTAG_OPTIONS=async BIONIC_MEMTAG_UPGRADE_SECS=5"
+                                        + " /data/local/tmp/app_process64 --get-mode");
+        assertThat(result.getExitCode()).isEqualTo(1);  // ASYNC
+    }
+}
diff --git a/libcutils/Android.bp b/libcutils/Android.bp
index c8bfb01..fde30ad 100644
--- a/libcutils/Android.bp
+++ b/libcutils/Android.bp
@@ -168,6 +168,9 @@
     target: {
         linux_bionic: {
             enabled: true,
+            static_libs: [
+                "libasync_safe",
+            ],
         },
         not_windows: {
             srcs: libcutils_nonwindows_sources + [
@@ -190,6 +193,9 @@
             ],
         },
         android: {
+            static_libs: [
+                "libasync_safe",
+            ],
             srcs: libcutils_nonwindows_sources + [
                 "android_reboot.cpp",
                 "ashmem-dev.cpp",
diff --git a/libcutils/include/cutils/native_handle.h b/libcutils/include/cutils/native_handle.h
index 4f07456..e46e7cd 100644
--- a/libcutils/include/cutils/native_handle.h
+++ b/libcutils/include/cutils/native_handle.h
@@ -49,18 +49,28 @@
 typedef const native_handle_t* buffer_handle_t;
 
 /*
- * native_handle_close
- * 
- * closes the file descriptors contained in this native_handle_t
- * 
+ * Closes the file descriptors contained in this native_handle_t, which may
+ * either be untagged or tagged for ownership by this native_handle_t via
+ * native_handle_set_tag(). Mixing untagged and tagged fds in the same
+ * native_handle_t is not permitted and triggers an fdsan exception, but
+ * native_handle_set_fdsan_tag() can be used to bring consistency if this is
+ * intentional.
+ *
+ * If it's known that fds are tagged, prefer native_handle_close_with_tag() for
+ * better safety.
+ *
  * return 0 on success, or a negative error code on failure
- * 
  */
 int native_handle_close(const native_handle_t* h);
 
 /*
- * native_handle_init
- *
+ * Equivalent to native_handle_close(), but throws an fdsan exception if the fds
+ * are untagged. Use if it's known that the fds in this native_handle_t were
+ * previously tagged via native_handle_set_tag().
+ */
+int native_handle_close_with_tag(const native_handle_t* h);
+
+/*
  * Initializes a native_handle_t from storage.  storage must be declared with
  * NATIVE_HANDLE_DECLARE_STORAGE.  numFds and numInts must not respectively
  * exceed maxFds and maxInts used to declare the storage.
@@ -68,33 +78,42 @@
 native_handle_t* native_handle_init(char* storage, int numFds, int numInts);
 
 /*
- * native_handle_create
- *
- * creates a native_handle_t and initializes it. must be destroyed with
+ * Creates a native_handle_t and initializes it. Must be destroyed with
  * native_handle_delete(). Note that numFds must be <= NATIVE_HANDLE_MAX_FDS,
  * numInts must be <= NATIVE_HANDLE_MAX_INTS, and both must be >= 0.
- *
  */
 native_handle_t* native_handle_create(int numFds, int numInts);
 
 /*
- * native_handle_clone
- *
- * creates a native_handle_t and initializes it from another native_handle_t.
+ * Updates the fdsan tag for any file descriptors contained in the supplied
+ * handle to indicate that they are owned by this handle and should only be
+ * closed via native_handle_close()/native_handle_close_with_tag(). Each fd in
+ * the handle must have a tag of either 0 (unset) or the tag associated with
+ * this handle, otherwise an fdsan exception will be triggered.
+ */
+void native_handle_set_fdsan_tag(const native_handle_t* handle);
+
+/*
+ * Clears the fdsan tag for any file descriptors contained in the supplied
+ * native_handle_t. Use if this native_handle_t is giving up ownership of its
+ * fds, but the fdsan tags were previously set. Each fd in the handle must have
+ * a tag of either 0 (unset) or the tag associated with this handle, otherwise
+ * an fdsan exception will be triggered.
+ */
+void native_handle_unset_fdsan_tag(const native_handle_t* handle);
+
+/*
+ * Creates a native_handle_t and initializes it from another native_handle_t.
  * Must be destroyed with native_handle_delete().
- *
  */
 native_handle_t* native_handle_clone(const native_handle_t* handle);
 
 /*
- * native_handle_delete
- * 
- * frees a native_handle_t allocated with native_handle_create().
+ * Frees a native_handle_t allocated with native_handle_create().
  * This ONLY frees the memory allocated for the native_handle_t, but doesn't
  * close the file descriptors; which can be achieved with native_handle_close().
- * 
+ *
  * return 0 on success, or a negative error code on failure
- * 
  */
 int native_handle_delete(native_handle_t* h);
 
diff --git a/libcutils/native_handle.cpp b/libcutils/native_handle.cpp
index 5804ab1..b85c93b 100644
--- a/libcutils/native_handle.cpp
+++ b/libcutils/native_handle.cpp
@@ -22,13 +22,74 @@
 #include <string.h>
 #include <unistd.h>
 
+// Needs to come after stdlib includes to capture the __BIONIC__ definition
+#ifdef __BIONIC__
+#include <android/fdsan.h>
+#endif
+
+namespace {
+
+#if !defined(__BIONIC__)
+// fdsan stubs when not linked against bionic
+#define ANDROID_FDSAN_OWNER_TYPE_NATIVE_HANDLE 0
+
+uint64_t android_fdsan_create_owner_tag(int /*type*/, uint64_t /*tag*/) {
+    return 0;
+}
+uint64_t android_fdsan_get_owner_tag(int /*fd*/) {
+    return 0;
+}
+int android_fdsan_close_with_tag(int fd, uint64_t /*tag*/) {
+    return close(fd);
+}
+void android_fdsan_exchange_owner_tag(int /*fd*/, uint64_t /*expected_tag*/, uint64_t /*tag*/) {}
+#endif  // !__BIONIC__
+
+uint64_t get_fdsan_tag(const native_handle_t* handle) {
+    return android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_NATIVE_HANDLE,
+                                          reinterpret_cast<uint64_t>(handle));
+}
+
+int close_internal(const native_handle_t* h, bool allowUntagged) {
+    if (!h) return 0;
+
+    if (h->version != sizeof(native_handle_t)) return -EINVAL;
+
+    const int numFds = h->numFds;
+    uint64_t tag;
+    if (allowUntagged && numFds > 0 && android_fdsan_get_owner_tag(h->data[0]) == 0) {
+        tag = 0;
+    } else {
+        tag = get_fdsan_tag(h);
+    }
+    int saved_errno = errno;
+    for (int i = 0; i < numFds; ++i) {
+        android_fdsan_close_with_tag(h->data[i], tag);
+    }
+    errno = saved_errno;
+    return 0;
+}
+
+void swap_fdsan_tags(const native_handle_t* handle, uint64_t expected_tag, uint64_t new_tag) {
+    if (!handle || handle->version != sizeof(native_handle_t)) return;
+
+    for (int i = 0; i < handle->numFds; i++) {
+        // allow for idempotence to make the APIs easier to use
+        if (android_fdsan_get_owner_tag(handle->data[i]) != new_tag) {
+            android_fdsan_exchange_owner_tag(handle->data[i], expected_tag, new_tag);
+        }
+    }
+}
+
+}  // anonymous namespace
+
 native_handle_t* native_handle_init(char* storage, int numFds, int numInts) {
-    if ((uintptr_t) storage % alignof(native_handle_t)) {
+    if ((uintptr_t)storage % alignof(native_handle_t)) {
         errno = EINVAL;
         return NULL;
     }
 
-    native_handle_t* handle = (native_handle_t*) storage;
+    native_handle_t* handle = (native_handle_t*)storage;
     handle->version = sizeof(native_handle_t);
     handle->numFds = numFds;
     handle->numInts = numInts;
@@ -52,6 +113,14 @@
     return h;
 }
 
+void native_handle_set_fdsan_tag(const native_handle_t* handle) {
+    swap_fdsan_tags(handle, 0, get_fdsan_tag(handle));
+}
+
+void native_handle_unset_fdsan_tag(const native_handle_t* handle) {
+    swap_fdsan_tags(handle, get_fdsan_tag(handle), 0);
+}
+
 native_handle_t* native_handle_clone(const native_handle_t* handle) {
     native_handle_t* clone = native_handle_create(handle->numFds, handle->numInts);
     if (clone == NULL) return NULL;
@@ -81,15 +150,9 @@
 }
 
 int native_handle_close(const native_handle_t* h) {
-    if (!h) return 0;
+    return close_internal(h, /*allowUntagged=*/true);
+}
 
-    if (h->version != sizeof(native_handle_t)) return -EINVAL;
-
-    int saved_errno = errno;
-    const int numFds = h->numFds;
-    for (int i = 0; i < numFds; ++i) {
-        close(h->data[i]);
-    }
-    errno = saved_errno;
-    return 0;
+int native_handle_close_with_tag(const native_handle_t* h) {
+    return close_internal(h, /*allowUntagged=*/false);
 }