From 683ebc805982a6dbffd94d8a631c75e66c239a67 Mon Sep 17 00:00:00 2001
From: Luis Hector Chavez <lhchavez@google.com>
Date: Tue, 27 Jun 2017 13:49:27 -0700
Subject: [PATCH] init: Terminate gracefully when CAP_SYS_BOOT is absent

This change makes it possible for Android running in a container to
terminate cleanly instead of calling abort() when requested to shut
down.

Bug: 62388055
Test: setprop sys.powerctl reboot makes init terminate nicely

Change-Id: I31c7b475d89d7cbd665e135d9b8951dfd4bca80d
---
 init/reboot.cpp | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/init/reboot.cpp b/init/reboot.cpp
index df7912f96..be1e7607f 100644
--- a/init/reboot.cpp
+++ b/init/reboot.cpp
@@ -21,6 +21,7 @@
 #include <linux/fs.h>
 #include <mntent.h>
 #include <selinux/selinux.h>
+#include <sys/capability.h>
 #include <sys/cdefs.h>
 #include <sys/ioctl.h>
 #include <sys/mount.h>
@@ -39,6 +40,7 @@
 #include <android-base/logging.h>
 #include <android-base/macros.h>
 #include <android-base/properties.h>
+#include <android-base/scopeguard.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
 #include <android-base/unique_fd.h>
@@ -162,9 +164,30 @@ static void LogShutdownTime(UmountStat stat, Timer* t) {
     LOG(WARNING) << "powerctl_shutdown_time_ms:" << std::to_string(t->duration_ms()) << ":" << stat;
 }
 
+static bool IsRebootCapable() {
+    cap_t caps = cap_init();
+    auto scopeguard = android::base::make_scope_guard([&caps] { cap_free(caps); });
+
+    // Assume we have the capability.
+    cap_flag_value_t value = CAP_SET;
+    if (!CAP_IS_SUPPORTED(CAP_SYS_BOOT) ||
+        cap_get_flag(caps, CAP_SYS_BOOT, CAP_EFFECTIVE, &value) != 0) {
+        PLOG(ERROR) << "cap_get_flag(CAP_BOOT, EFFECTIVE) failed";
+    }
+
+    return value == CAP_SET;
+}
+
 static void __attribute__((noreturn))
 RebootSystem(unsigned int cmd, const std::string& rebootTarget) {
     LOG(INFO) << "Reboot ending, jumping to kernel";
+
+    if (!IsRebootCapable()) {
+        // On systems where init does not have the capability of rebooting the
+        // device, just exit cleanly.
+        exit(0);
+    }
+
     switch (cmd) {
         case ANDROID_RB_POWEROFF:
             reboot(RB_POWER_OFF);