main: set PR_SET_CHILD_REAPER for MANAGER_USER

Become the reaper for all children part of the user session. Tested
with several forking services.

2 files changed, 13 insertions, 0 deletions

diff --git a/src/core/main.c b/src/core/main.c
index c7a7a87e7a..1326b94f68 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -1500,6 +1500,15 @@ int main(int argc, char *argv[]) {
                 }
         }
 
+        if (arg_running_as == MANAGER_USER) {
+                /* Become reaper of our children */
+                r = prctl(PR_SET_CHILD_SUBREAPER, 1);
+                if (r < 0)
+                        log_error("Failed to prctl(PR_SET_CHILD_SUBREAPER): %s", strerror(-r));
+                if (r == -EINVAL)
+                        log_error("Perhaps the kernel version is too old (< 3.4?)");
+        }
+
         r = manager_new(arg_running_as, &m);
         if (r < 0) {
                 log_error("Failed to allocate manager object: %s", strerror(-r));
diff --git a/src/shared/missing.h b/src/shared/missing.h
index e600acc0b1..df3fd0e839 100644
--- a/src/shared/missing.h
+++ b/src/shared/missing.h
@@ -190,3 +190,7 @@ static inline pid_t gettid(void) {
 #ifndef PR_SET_NO_NEW_PRIVS
 #define PR_SET_NO_NEW_PRIVS 38
 #endif
+
+#ifndef PR_SET_CHILD_SUBREAPER
+#define PR_SET_CHILD_SUBREAPER 36
+#endif