From ea9053c5f8eaae748683848ed807e7dbf30d85a7 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 17 Nov 2017 13:05:30 +0100
Subject: [PATCH] nspawn: rework mount_systemd_cgroup_writable() a bit

We shouldn't call alloca() as part of function calls, that's not really
defined in C. Hence, let's first do our stack allocations, and then
invoke functions.

Also, some coding style fixes, and minor shuffling around.

No functional changes.
---
 src/nspawn/nspawn-mount.c | 41 ++++++++++++++++++++++++++---------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
index c8c941c..69707cb 100644
--- a/src/nspawn/nspawn-mount.c
+++ b/src/nspawn/nspawn-mount.c
@@ -1213,23 +1213,25 @@ int mount_cgroups(
 
         if (unified_requested >= CGROUP_UNIFIED_ALL)
                 return mount_unified_cgroups(dest);
-        else if (use_cgns)
+        if (use_cgns)
                 return mount_legacy_cgns_supported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
 
         return mount_legacy_cgns_unsupported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
 }
 
-static int mount_systemd_cgroup_writable_one(const char *systemd_own, const char *systemd_root)
-{
+static int mount_systemd_cgroup_writable_one(const char *root, const char *own) {
         int r;
 
+        assert(root);
+        assert(own);
+
         /* Make our own cgroup a (writable) bind mount */
-        r = mount_verbose(LOG_ERR, systemd_own, systemd_own,  NULL, MS_BIND, NULL);
+        r = mount_verbose(LOG_ERR, own, own, NULL, MS_BIND, NULL);
         if (r < 0)
                 return r;
 
         /* And then remount the systemd cgroup root read-only */
-        return mount_verbose(LOG_ERR, NULL, systemd_root, NULL,
+        return mount_verbose(LOG_ERR, NULL, root, NULL,
                              MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL);
 }
 
@@ -1238,6 +1240,7 @@ int mount_systemd_cgroup_writable(
                 CGroupUnified unified_requested) {
 
         _cleanup_free_ char *own_cgroup_path = NULL;
+        const char *root, *own;
         int r;
 
         assert(dest);
@@ -1250,19 +1253,27 @@ int mount_systemd_cgroup_writable(
         if (path_equal(own_cgroup_path, "/"))
                 return 0;
 
-        if (unified_requested >= CGROUP_UNIFIED_ALL)
-                return mount_systemd_cgroup_writable_one(strjoina(dest, "/sys/fs/cgroup", own_cgroup_path),
-                                                         prefix_roota(dest, "/sys/fs/cgroup"));
+        if (unified_requested >= CGROUP_UNIFIED_ALL) {
 
-        if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
-                r = mount_systemd_cgroup_writable_one(strjoina(dest, "/sys/fs/cgroup/unified", own_cgroup_path),
-                                                      prefix_roota(dest, "/sys/fs/cgroup/unified"));
-                if (r < 0)
-                        return r;
+                root = prefix_roota(dest, "/sys/fs/cgroup");
+                own = strjoina(root, own_cgroup_path);
+
+        } else {
+
+                if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
+                        root = prefix_roota(dest, "/sys/fs/cgroup/unified");
+                        own = strjoina(root, own_cgroup_path);
+
+                        r = mount_systemd_cgroup_writable_one(root, own);
+                        if (r < 0)
+                                return r;
+                }
+
+                root = prefix_roota(dest, "/sys/fs/cgroup/systemd");
+                own = strjoina(root, own_cgroup_path);
         }
 
-        return mount_systemd_cgroup_writable_one(strjoina(dest, "/sys/fs/cgroup/systemd", own_cgroup_path),
-                                                 prefix_roota(dest, "/sys/fs/cgroup/systemd"));
+        return mount_systemd_cgroup_writable_one(root, own);
 }
 
 int setup_volatile_state(
-- 
2.7.4