Make child processes exit when parent dies

The child processes call prctl() and when their parent process is
killed, they are sent SIGTERM using prctl. This is currently
Linux-specific, for non-Linuxes, a similar effect is achieved by
catching a set of common termination signals and sending SIGTERM to the
process group.

7 files changed, 70 insertions, 1 deletions

diff --git a/server/providers/data_provider.c b/server/providers/data_provider.c
index b9529254..f0ecd30b 100644
--- a/server/providers/data_provider.c
+++ b/server/providers/data_provider.c
@@ -1088,6 +1088,12 @@ int main(int argc, const char *argv[])
     ret = server_setup("sssd[dp]", 0, DP_CONF_ENTRY, &main_ctx);
     if (ret != EOK) return 2;
 
+    ret = die_if_parent_died();
+    if (ret != EOK) {
+        /* This is not fatal, don't return */
+        DEBUG(2, ("Could not set up to exit when parent process does\n"));
+    }
+
     ret = dp_process_init(main_ctx,
                            main_ctx->event_ctx,
                            main_ctx->confdb_ctx);
diff --git a/server/providers/data_provider_be.c b/server/providers/data_provider_be.c
index c93c4531..49885edc 100644
--- a/server/providers/data_provider_be.c
+++ b/server/providers/data_provider_be.c
@@ -1109,6 +1109,12 @@ int main(int argc, const char *argv[])
         return 2;
     }
 
+    ret = die_if_parent_died();
+    if (ret != EOK) {
+        /* This is not fatal, don't return */
+        DEBUG(2, ("Could not set up to exit when parent process does\n"));
+    }
+
     ret = be_process_init(main_ctx,
                           be_name, be_domain,
                           main_ctx->event_ctx,
diff --git a/server/responder/nss/nsssrv.c b/server/responder/nss/nsssrv.c
index 248d5384..418e2f9f 100644
--- a/server/responder/nss/nsssrv.c
+++ b/server/responder/nss/nsssrv.c
@@ -365,6 +365,12 @@ int main(int argc, const char *argv[])
     ret = server_setup("sssd[nss]", 0, NSS_SRV_CONFIG, &main_ctx);
     if (ret != EOK) return 2;
 
+    ret = die_if_parent_died();
+    if (ret != EOK) {
+        /* This is not fatal, don't return */
+        DEBUG(2, ("Could not set up to exit when parent process does\n"));
+    }
+
     ret = nss_process_init(main_ctx,
                            main_ctx->event_ctx,
                            main_ctx->confdb_ctx);
diff --git a/server/responder/pam/pamsrv.c b/server/responder/pam/pamsrv.c
index 92fa4aec..bff2f7cc 100644
--- a/server/responder/pam/pamsrv.c
+++ b/server/responder/pam/pamsrv.c
@@ -227,6 +227,12 @@ int main(int argc, const char *argv[])
     ret = server_setup("sssd[pam]", 0, PAM_SRV_CONFIG, &main_ctx);
     if (ret != EOK) return 2;
 
+    ret = die_if_parent_died();
+    if (ret != EOK) {
+        /* This is not fatal, don't return */
+        DEBUG(2, ("Could not set up to exit when parent process does\n"));
+    }
+
     pam_dp_interface = get_pam_dp_interface();
     sss_cmds = register_sss_cmds();
     ret = sss_process_init(main_ctx,
diff --git a/server/util/server.c b/server/util/server.c
index fd6e4cdc..d20a823c 100644
--- a/server/util/server.c
+++ b/server/util/server.c
@@ -33,6 +33,10 @@
 #include "ldb.h"
 #include "confdb/confdb.h"
 
+#ifdef HAVE_PRCTL
+#include <sys/prctl.h>
+#endif
+
 /*******************************************************************
  Close the low 3 fd's and open dev/null in their place.
 ********************************************************************/
@@ -191,6 +195,21 @@ static void sig_term(int sig)
 	exit(0);
 }
 
+#ifndef HAVE_PRCTL
+static void sig_segv_abrt(int sig)
+{
+#if HAVE_GETPGRP
+	static int done;
+	if (done == 0 && getpgrp() == getpid()) {
+		DEBUG(0,("%s: killing children\n", strsignal(sig)));
+		done = 1;
+		kill(-getpgrp(), SIGTERM);
+	}
+#endif  /* HAVE_GETPGRP */
+    exit(1);
+}
+#endif /* HAVE_PRCTL */
+
 /*
   setup signal masks
 */
@@ -219,6 +238,14 @@ static void setup_signals(void)
 
 	CatchSignal(SIGHUP, sig_hup);
 	CatchSignal(SIGTERM, sig_term);
+
+#ifndef HAVE_PRCTL
+        /* If prctl is not defined on the system, try to handle
+         * some common termination signals gracefully */
+	CatchSignal(SIGSEGV, sig_segv_abrt);
+	CatchSignal(SIGABRT, sig_segv_abrt);
+#endif
+
 }
 
 /*
@@ -244,6 +271,23 @@ static void server_stdin_handler(struct tevent_context *event_ctx,
 /*
  main server helpers.
 */
+
+int die_if_parent_died(void)
+{
+#ifdef HAVE_PRCTL
+    int ret;
+
+    errno = 0;
+    ret = prctl(PR_SET_PDEATHSIG, SIGTERM, 0, 0, 0);
+    if (ret != 0) {
+        ret = errno;
+        DEBUG(2, ("prctl failed [%d]: %s", ret, strerror(ret)));
+        return ret;
+    }
+#endif
+    return EOK;
+}
+
 int server_setup(const char *name, int flags,
                  const char *conf_entry,
                  struct main_context **main_ctx)
diff --git a/server/util/signal.m4 b/server/util/signal.m4
index a778020e..747c7dbf 100644
--- a/server/util/signal.m4
+++ b/server/util/signal.m4
@@ -1 +1 @@
-AC_CHECK_FUNCS(sigprocmask sigblock sigaction getpgrp)
+AC_CHECK_FUNCS(sigprocmask sigblock sigaction getpgrp prctl)
diff --git a/server/util/util.h b/server/util/util.h
index e11bc51c..87965292 100644
--- a/server/util/util.h
+++ b/server/util/util.h
@@ -107,6 +107,7 @@ struct main_context {
     struct confdb_ctx *confdb_ctx;
 };
 
+int die_if_parent_died(void);
 int server_setup(const char *name, int flags,
                  const char *conf_entry,
                  struct main_context **main_ctx);