From f057aa6bb604845fa10ad569bca306e5e1e8fe0d Mon Sep 17 00:00:00 2001

From: Franck Bui <fbui@suse.com>

Date: Mon, 18 Mar 2019 11:48:34 +0100

Subject: [PATCH] process-util: introduce pid_is_my_child() helper

MIME-Version: 1.0

Content-Type: text/plain; charset=UTF-8

Content-Transfer-Encoding: 8bit

No functional changes.

Thanks Renaud Métrich for backporting this to RHEL.

Resolves: #1744972

---

 src/basic/process-util.c | 14 ++++++++++++++

 src/basic/process-util.h |  1 +

 src/core/cgroup.c        |  7 ++-----

 src/core/service.c       |  8 ++------

 4 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/src/basic/process-util.c b/src/basic/process-util.c

index aa3eff779a..6dbeee9dda 100644

--- a/src/basic/process-util.c

+++ b/src/basic/process-util.c

@@ -903,6 +903,20 @@ int getenv_for_pid(pid_t pid, const char *field, char **ret) {

         return 0;

 }

+int pid_is_my_child(pid_t pid) {

+        pid_t ppid;

+        int r;

+

+        if (pid <= 1)

+                return false;

+

+        r = get_process_ppid(pid, &ppid);

+        if (r < 0)

+                return r;

+

+        return ppid == getpid_cached();

+}

+

 bool pid_is_unwaited(pid_t pid) {

         /* Checks whether a PID is still valid at all, including a zombie */

diff --git a/src/basic/process-util.h b/src/basic/process-util.h

index a5bb072b25..a3bd2851b4 100644

--- a/src/basic/process-util.h

+++ b/src/basic/process-util.h

@@ -68,6 +68,7 @@ int getenv_for_pid(pid_t pid, const char *field, char **_value);

 bool pid_is_alive(pid_t pid);

 bool pid_is_unwaited(pid_t pid);

+int pid_is_my_child(pid_t pid);

 int pid_from_same_root_fs(pid_t pid);

 bool is_main_thread(void);

diff --git a/src/core/cgroup.c b/src/core/cgroup.c

index 62ab41a288..b7ed07e65b 100644

--- a/src/core/cgroup.c

+++ b/src/core/cgroup.c

@@ -1876,7 +1876,7 @@ void unit_prune_cgroup(Unit *u) {

 int unit_search_main_pid(Unit *u, pid_t *ret) {

         _cleanup_fclose_ FILE *f = NULL;

-        pid_t pid = 0, npid, mypid;

+        pid_t pid = 0, npid;

         int r;

         assert(u);

@@ -1889,15 +1889,12 @@ int unit_search_main_pid(Unit *u, pid_t *ret) {

         if (r < 0)

                 return r;

-        mypid = getpid_cached();

         while (cg_read_pid(f, &npid) > 0)  {

-                pid_t ppid;

                 if (npid == pid)

                         continue;

-                /* Ignore processes that aren't our kids */

-                if (get_process_ppid(npid, &ppid) >= 0 && ppid != mypid)

+                if (pid_is_my_child(npid) == 0)

                         continue;

                 if (pid != 0)

diff --git a/src/core/service.c b/src/core/service.c

index 24f167572a..614ba05d89 100644

--- a/src/core/service.c

+++ b/src/core/service.c

@@ -139,8 +139,6 @@ static void service_unwatch_pid_file(Service *s) {

 }

 static int service_set_main_pid(Service *s, pid_t pid) {

-        pid_t ppid;

-

         assert(s);

         if (pid <= 1)

@@ -159,12 +157,10 @@ static int service_set_main_pid(Service *s, pid_t pid) {

         s->main_pid = pid;

         s->main_pid_known = true;

+        s->main_pid_alien = pid_is_my_child(pid) == 0;

-        if (get_process_ppid(pid, &ppid) >= 0 && ppid != getpid_cached()) {

+        if (s->main_pid_alien)

                 log_unit_warning(UNIT(s), "Supervising process "PID_FMT" which is not our child. We'll most likely not notice when it exits.", pid);

-                s->main_pid_alien = true;

-        } else

-                s->main_pid_alien = false;

         return 0;

 }