From: Mike Yuan <me@yhndnzj.com>
Date: Sun, 16 Mar 2025 21:05:41 +0000 (+0100)
Subject: core/namespace: remove wonky fallback in mount_private_apivfs()
X-Git-Tag: v258-rc1~952^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0cba5bdcf102649741d83734c1c5c9e0bedfdfeb;p=thirdparty%2Fsystemd.git

core/namespace: remove wonky fallback in mount_private_apivfs()

Let's avoid dropping opts willy-nilly, especially that we already
carry the logic of determining availability prior to mount (but
make sure we respect the result though, and don't assume things
are available if the check fails).
---

diff --git a/src/core/namespace.c b/src/core/namespace.c
index aecc827797f..7e131b14250 100644
--- a/src/core/namespace.c
+++ b/src/core/namespace.c
@@ -1319,16 +1319,6 @@ static int mount_private_apivfs(
                 return r;
 
         r = mount_nofollow_verbose(LOG_DEBUG, fstype, temporary_mount, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, opts);
-        if (r == -EINVAL && opts)
-                /* If this failed with EINVAL then this likely means either:
-                 * 1. the textual hidepid= stuff for procfs is not supported by the kernel, and thus the
-                 *    per-instance hidepid= neither, which means we really don't want to use it, since it
-                 *    would affect our host's /proc mount.
-                 * 2. nsdelegate for cgroup2 is not supported by the kernel even though CLONE_NEWCGROUP
-                 *    is supported.
-                 *
-                 * Hence let's gracefully fallback to a classic, unrestricted version. */
-                r = mount_nofollow_verbose(LOG_DEBUG, fstype, temporary_mount, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, /* opts = */ NULL);
         if (ERRNO_IS_NEG_PRIVILEGE(r)) {
                 /* When we do not have enough privileges to mount a new instance, fall back to use an
                  * existing mount. */
@@ -1347,8 +1337,8 @@ static int mount_private_apivfs(
                         return r;
 
                 return 1;
-
-        } else if (r < 0)
+        }
+        if (r < 0)
                 return r;
 
         /* OK. We have a new mount instance. Let's clear an existing mount and its submounts. */
@@ -1404,14 +1394,14 @@ static int mount_procfs(const MountEntry *m, const NamespaceParameters *p) {
                  * fsopen()/fsconfig() was also backported on some distros which allows us to detect
                  * hidepid=/subset= support in even more scenarios. */
 
-                if (mount_option_supported("proc", "hidepid", hpv) != 0) {
+                if (mount_option_supported("proc", "hidepid", hpv) > 0) {
                         opts = strjoin("hidepid=", hpv);
                         if (!opts)
                                 return -ENOMEM;
                 }
 
                 if (p->proc_subset == PROC_SUBSET_PID &&
-                    mount_option_supported("proc", "subset", "pid") != 0)
+                    mount_option_supported("proc", "subset", "pid") > 0)
                         if (!strextend_with_separator(&opts, ",", "subset=pid"))
                                 return -ENOMEM;
         }