From 0d0ba7ee44d652c23e6027fe3b1c1ee8e2f65a25 Mon Sep 17 00:00:00 2001
From: systemd team <systemd-maint@redhat.com>
Date: Mon, 19 Aug 2019 13:51:48 +0200
Subject: [PATCH] Call getgroups() to know size of supplementary groups array
 to allocate

Resolves RHBZ #1743230 - journalctl dumps core when stack limit is reduced to 256 KB
---
 src/shared/util.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/shared/util.c b/src/shared/util.c
index 127a64c3c6..ce6678eb38 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -5097,7 +5097,7 @@ int get_group_creds(const char **groupname, gid_t *gid) {
 
 int in_gid(gid_t gid) {
         gid_t *gids;
-        int ngroups_max, r, i;
+        int ngroups, r, i;
 
         if (getgid() == gid)
                 return 1;
@@ -5105,12 +5105,15 @@ int in_gid(gid_t gid) {
         if (getegid() == gid)
                 return 1;
 
-        ngroups_max = sysconf(_SC_NGROUPS_MAX);
-        assert(ngroups_max > 0);
+        ngroups = getgroups(0, NULL);
+        if (ngroups < 0)
+                return -errno;
+        if (ngroups == 0)
+                return 0;
 
-        gids = alloca(sizeof(gid_t) * ngroups_max);
+        gids = alloca(sizeof(gid_t) * ngroups);
 
-        r = getgroups(ngroups_max, gids);
+        r = getgroups(ngroups, gids);
         if (r < 0)
                 return -errno;