Do not block SIGTERM in init's child processes

Previously, unless the process unblocks the signal by itself,
the signal was never delivered to the process. This caused at
least one CTS test failure.

Bug: 72453675
Test: 'kill -TERM app_pid' terminates the app process

Change-Id: I3977cac75e2673b52c5cf91d34d7a9c258c1a0e4

1 files changed, 17 insertions, 0 deletions

diff --git a/init/init.cpp b/init/init.cpp
index 79623c333..bd09e4bcc 100644
--- a/init/init.cpp
+++ b/init/init.cpp
@@ -19,6 +19,7 @@
 #include <dirent.h>
 #include <fcntl.h>
 #include <paths.h>
+#include <pthread.h>
 #include <seccomp_policy.h>
 #include <signal.h>
 #include <stdlib.h>
@@ -491,6 +492,16 @@ static void HandleSigtermSignal() {
     HandlePowerctlMessage("shutdown,container");
 }
 
+static void UnblockSigterm() {
+    sigset_t mask;
+    sigemptyset(&mask);
+    sigaddset(&mask, SIGTERM);
+
+    if (sigprocmask(SIG_UNBLOCK, &mask, nullptr) == -1) {
+        PLOG(FATAL) << "failed to unblock SIGTERM for PID " << getpid();
+    }
+}
+
 static void InstallSigtermHandler() {
     sigset_t mask;
     sigemptyset(&mask);
@@ -500,6 +511,12 @@ static void InstallSigtermHandler() {
         PLOG(FATAL) << "failed to block SIGTERM";
     }
 
+    // Register a handler to unblock SIGTERM in the child processes.
+    const int result = pthread_atfork(nullptr, nullptr, &UnblockSigterm);
+    if (result != 0) {
+        LOG(FATAL) << "Failed to register a fork handler: " << strerror(result);
+    }
+
     sigterm_signal_fd = signalfd(-1, &mask, SFD_CLOEXEC);
     if (sigterm_signal_fd == -1) {
         PLOG(FATAL) << "failed to create signalfd for SIGTERM";