snapuserd: Allow connecting to the first-stage daemon.
Currently there is no socket for daemon instances launched during the
selinux phase of init. We don't create any sockets due to the complexity
of the required sepolicy.
This workaround will allow us to create the socket with very minimal
sepolicy changes. init will launch a one-off instance of snapuserd in
"proxy" mode, and then the following steps will occur:
1. The proxy daemon will be given two sockets, the "normal" socket that
snapuserd clients would connect to, and a "proxy" socket.
2. The proxy daemon will listen on the proxy socket.
3. The first-stage daemon will wake up and connect to the proxy daemon
as a client.
4. The proxy will send the normal socket via SCM_RIGHTS, then exit.
5. The first-stage daemon can now listen and accept on the normal
socket.
Ordering of these events is achieved through a snapuserd.proxy_ready
property.
Some special-casing was needed in init to make this work. The snapuserd
socket owned by snapuserd_proxy is placed into a "persist" mode so it
doesn't get deleted when snapuserd_proxy exits. There's also a special
case method to create a Service object around a previously existing pid.
Finally, first-stage init is technically on a different updateable
partition than snapuserd. Thus, we add a way to query snapuserd to see
if it supports socket handoff. If it does, we communicate this
information through an environment variable to second-stage init.
Bug: 193833730
Test: manual test
Change-Id: I1950b31028980f0138bc03578cd455eb60ea4a58
diff --git a/init/init.cpp b/init/init.cpp
index a7325ca..bde8e04 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -725,6 +725,40 @@
}
}
+static Result<void> ConnectEarlyStageSnapuserdAction(const BuiltinArguments& args) {
+ auto pid = GetSnapuserdFirstStagePid();
+ if (!pid) {
+ return {};
+ }
+
+ auto info = GetSnapuserdFirstStageInfo();
+ if (auto iter = std::find(info.begin(), info.end(), "socket"s); iter == info.end()) {
+ // snapuserd does not support socket handoff, so exit early.
+ return {};
+ }
+
+ // Socket handoff is supported.
+ auto svc = ServiceList::GetInstance().FindService("snapuserd");
+ if (!svc) {
+ LOG(FATAL) << "Failed to find snapuserd service entry";
+ }
+
+ svc->SetShutdownCritical();
+ svc->SetStartedInFirstStage(*pid);
+
+ svc = ServiceList::GetInstance().FindService("snapuserd_proxy");
+ if (!svc) {
+ LOG(FATAL) << "Failed find snapuserd_proxy service entry, merge will never initiate";
+ }
+ if (!svc->MarkSocketPersistent("snapuserd")) {
+ LOG(FATAL) << "Could not find snapuserd socket in snapuserd_proxy service entry";
+ }
+ if (auto result = svc->Start(); !result.ok()) {
+ LOG(FATAL) << "Could not start snapuserd_proxy: " << result.error();
+ }
+ return {};
+}
+
int SecondStageMain(int argc, char** argv) {
if (REBOOT_BOOTLOADER_ON_PANIC) {
InstallRebootSignalHandlers();
@@ -852,6 +886,7 @@
am.QueueBuiltinAction(SetupCgroupsAction, "SetupCgroups");
am.QueueBuiltinAction(SetKptrRestrictAction, "SetKptrRestrict");
am.QueueBuiltinAction(TestPerfEventSelinuxAction, "TestPerfEventSelinux");
+ am.QueueBuiltinAction(ConnectEarlyStageSnapuserdAction, "ConnectEarlyStageSnapuserd");
am.QueueEventTrigger("early-init");
// Queue an action that waits for coldboot done so we know ueventd has set up all of /dev...
diff --git a/init/service.cpp b/init/service.cpp
index c3069f5..489dd67 100644
--- a/init/service.cpp
+++ b/init/service.cpp
@@ -269,6 +269,9 @@
// Remove any socket resources we may have created.
for (const auto& socket : sockets_) {
+ if (socket.persist) {
+ continue;
+ }
auto path = ANDROID_SOCKET_DIR "/" + socket.name;
unlink(path.c_str());
}
@@ -409,9 +412,7 @@
}
bool disabled = (flags_ & (SVC_DISABLED | SVC_RESET));
- // Starting a service removes it from the disabled or reset state and
- // immediately takes it out of the restarting state if it was in there.
- flags_ &= (~(SVC_DISABLED|SVC_RESTARTING|SVC_RESET|SVC_RESTART|SVC_DISABLED_START));
+ ResetFlagsForStart();
// Running processes require no additional work --- if they're in the
// process of exiting, we've ensured that they will immediately restart
@@ -622,6 +623,23 @@
return {};
}
+void Service::SetStartedInFirstStage(pid_t pid) {
+ LOG(INFO) << "adding first-stage service '" << name_ << "'...";
+
+ time_started_ = boot_clock::now(); // not accurate, but doesn't matter here
+ pid_ = pid;
+ flags_ |= SVC_RUNNING;
+ start_order_ = next_start_order_++;
+
+ NotifyStateChange("running");
+}
+
+void Service::ResetFlagsForStart() {
+ // Starting a service removes it from the disabled or reset state and
+ // immediately takes it out of the restarting state if it was in there.
+ flags_ &= ~(SVC_DISABLED | SVC_RESTARTING | SVC_RESET | SVC_RESTART | SVC_DISABLED_START);
+}
+
Result<void> Service::StartIfNotDisabled() {
if (!(flags_ & SVC_DISABLED)) {
return Start();
@@ -792,5 +810,18 @@
nullptr, str_args, false);
}
+// This is used for snapuserd_proxy, which hands off a socket to snapuserd. It's
+// a special case to support the daemon launched in first-stage init. The persist
+// feature is not part of the init language and is only used here.
+bool Service::MarkSocketPersistent(const std::string& socket_name) {
+ for (auto& socket : sockets_) {
+ if (socket.name == socket_name) {
+ socket.persist = true;
+ return true;
+ }
+ }
+ return false;
+}
+
} // namespace init
} // namespace android
diff --git a/init/service.h b/init/service.h
index 043555f..ccf6899 100644
--- a/init/service.h
+++ b/init/service.h
@@ -99,6 +99,8 @@
void AddReapCallback(std::function<void(const siginfo_t& siginfo)> callback) {
reap_callbacks_.emplace_back(std::move(callback));
}
+ void SetStartedInFirstStage(pid_t pid);
+ bool MarkSocketPersistent(const std::string& socket_name);
size_t CheckAllCommands() const { return onrestart_.CheckAllCommands(); }
static bool is_exec_service_running() { return is_exec_service_running_; }
@@ -144,6 +146,7 @@
void StopOrReset(int how);
void KillProcessGroup(int signal, bool report_oneshot = false);
void SetProcessAttributesAndCaps();
+ void ResetFlagsForStart();
static unsigned long next_start_order_;
static bool is_exec_service_running_;
diff --git a/init/service_utils.h b/init/service_utils.h
index 1e0b4bd..9b65dca 100644
--- a/init/service_utils.h
+++ b/init/service_utils.h
@@ -54,6 +54,7 @@
int perm = 0;
std::string context;
bool passcred = false;
+ bool persist = false;
// Create() creates the named unix domain socket in /dev/socket and returns a Descriptor object.
// It should be called when starting a service, before calling fork(), such that the socket is
diff --git a/init/snapuserd_transition.cpp b/init/snapuserd_transition.cpp
index 9a0b3b7..b8c2fd2 100644
--- a/init/snapuserd_transition.cpp
+++ b/init/snapuserd_transition.cpp
@@ -54,6 +54,7 @@
static constexpr char kSnapuserdPath[] = "/system/bin/snapuserd";
static constexpr char kSnapuserdFirstStagePidVar[] = "FIRST_STAGE_SNAPUSERD_PID";
static constexpr char kSnapuserdFirstStageFdVar[] = "FIRST_STAGE_SNAPUSERD_FD";
+static constexpr char kSnapuserdFirstStageInfoVar[] = "FIRST_STAGE_SNAPUSERD_INFO";
static constexpr char kSnapuserdLabel[] = "u:object_r:snapuserd_exec:s0";
static constexpr char kSnapuserdSocketLabel[] = "u:object_r:snapuserd_socket:s0";
@@ -87,6 +88,14 @@
_exit(127);
}
+ auto client = SnapuserdClient::Connect(android::snapshot::kSnapuserdSocket, 10s);
+ if (!client) {
+ LOG(FATAL) << "Could not connect to first-stage snapuserd";
+ }
+ if (client->SupportsSecondStageSocketHandoff()) {
+ setenv(kSnapuserdFirstStageInfoVar, "socket", 1);
+ }
+
setenv(kSnapuserdFirstStagePidVar, std::to_string(pid).c_str(), 1);
LOG(INFO) << "Relaunched snapuserd with pid: " << pid;
@@ -328,5 +337,13 @@
return GetSnapuserdFirstStagePid().has_value();
}
+std::vector<std::string> GetSnapuserdFirstStageInfo() {
+ const char* pid_str = getenv(kSnapuserdFirstStageInfoVar);
+ if (!pid_str) {
+ return {};
+ }
+ return android::base::Split(pid_str, ",");
+}
+
} // namespace init
} // namespace android
diff --git a/init/snapuserd_transition.h b/init/snapuserd_transition.h
index a5ab652..62aee83 100644
--- a/init/snapuserd_transition.h
+++ b/init/snapuserd_transition.h
@@ -76,6 +76,9 @@
// Return the pid of the first-stage instances of snapuserd, if it was started.
std::optional<pid_t> GetSnapuserdFirstStagePid();
+// Return snapuserd info strings that were set during first-stage init.
+std::vector<std::string> GetSnapuserdFirstStageInfo();
+
// Save an open fd to /system/bin (in the ramdisk) into an environment. This is
// used to later execveat() snapuserd.
void SaveRamdiskPathToSnapuserd();