From a80ed3053a3b161d23e7bd57bd227671df047ed0 Mon Sep 17 00:00:00 2001
From: =?utf8?q?J=C3=A9r=C3=A9mie=20Galarneau?=
 <jeremie.galarneau@efficios.com>
Date: Tue, 29 Sep 2015 12:19:00 -0400
Subject: [PATCH] Fix: Log and ignore SIGINT and SIGTERM in run_as worker
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The run_as worker is in the same process group as its parent and
will receive both SIGINT and SIGTERM. However, we want to give
the worker a chance to tear itself down gracefully when its
parent closes the command socket.

The run_as worker will now ignore these signals (although it will
log them) and wait for the parent to induce the teardown.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---
 src/common/runas.c | 65 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/src/common/runas.c b/src/common/runas.c
index 2f2c0c7c3..3826c6175 100644
--- a/src/common/runas.c
+++ b/src/common/runas.c
@@ -528,9 +528,9 @@ int run_as_rmdir_recursive(const char *path, uid_t uid, gid_t gid)
 }
 
 static
-void reset_sighandler(void)
+int reset_sighandler(void)
 {
-	int sig;
+	int sig, ret = 0;
 
 	DBG("Resetting run_as worker signal handlers to default");
 	for (sig = SIGHUP; sig <= SIGUNUSED; sig++) {
@@ -540,8 +540,67 @@ void reset_sighandler(void)
 		}
 		if (signal(sig, SIG_DFL) == SIG_ERR) {
 			PERROR("reset signal %d", sig);
+			ret = -1;
+			goto end;
 		}
 	}
+end:
+	return ret;
+}
+
+static
+void worker_sighandler(int sig)
+{
+	const char *signame;
+
+	/*
+	 * The worker will its parent's signals since they are part of the same
+	 * process group. However, in the case of SIGINT and SIGTERM, we want
+	 * to give the worker a chance to teardown gracefully when its parent
+	 * closes the command socket.
+	 */
+	switch (sig) {
+	case SIGINT:
+		signame = "SIGINT";
+		break;
+	case SIGTERM:
+		signame = "SIGTERM";
+		break;
+	default:
+		signame = "Unknown";
+	}
+
+	DBG("run_as worker received signal %s", signame);
+}
+
+static
+int set_worker_sighandlers(void)
+{
+	int ret = 0;
+	sigset_t sigset;
+	struct sigaction sa;
+
+	if ((ret = sigemptyset(&sigset)) < 0) {
+		PERROR("sigemptyset");
+		goto end;
+	}
+
+	sa.sa_handler = worker_sighandler;
+	sa.sa_mask = sigset;
+	sa.sa_flags = 0;
+	if ((ret = sigaction(SIGINT, &sa, NULL)) < 0) {
+		PERROR("sigaction SIGINT");
+		goto end;
+	}
+
+	if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
+		PERROR("sigaction SIGTERM");
+		goto end;
+	}
+
+	DBG("run_as signal handler set for SIGTERM and SIGINT");
+end:
+	return ret;
 }
 
 LTTNG_HIDDEN
@@ -585,6 +644,8 @@ int run_as_create_worker(char *procname)
 
 		reset_sighandler();
 
+		set_worker_sighandlers();
+
 		/* The child has no use for this lock. */
 		pthread_mutex_unlock(&worker_lock);
 		/* Just close, no shutdown. */
-- 
2.34.1