Fix: Log and ignore SIGINT and SIGTERM in run_as worker

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>

diff --git a/src/common/runas.c b/src/common/runas.c
index 08979fb79c15bee3bfd9f60bd3d084a141e79d08..fc30a5567774da58b0eb9f96bfda1d38338db9b5 100644 (file)
--- 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;
 
        for (sig = SIGHUP; sig <= SIGUNUSED; sig++) {
                /* Skip unblockable signals. */
@@ -539,8 +539,67 @@ 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
@@ -584,6 +643,8 @@ 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. */