OpenJDK 17.0.2 - Cgroup v1 initialization causes NullPointerException when cgroup path does not start with the mount root

An_Issue_description.md

When I ran wildfly testsuite on JDK 17 within a podman container, I got NPE for all tests, please refer to NPE.stacktrace.java below on the stack trace, all work fine if I run it on base metal.

It relates to JDK issue: https://bugs.openjdk.java.net/browse/JDK-8272124, but this demostrates another case when the cgroup path does not start with the mount root.

In this case /proc/self/cgroup has the following line:

9:memory:/user.slice/user-1000.slice/session-3.scope

while /proc/self/mountinfo has the following line:

941 931 0:36 /user.slice/user-1000.slice/session-50.scope /sys/fs/cgroup/memory ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,memory

The environment:

• Java version

openjdk version "17.0.2" 2022-01-18
OpenJDK Runtime Environment 21.9 (build 17.0.2+8)
OpenJDK 64-Bit Server VM 21.9 (build 17.0.2+8, mixed mode, sharing)

• RHEL 8.5:

[jenkins@testjenkins ~]$ uname -a
Linux testjenkins 4.18.0-348.el8.x86_64 #1 SMP Mon Oct 4 12:17:22 EDT 2021 x86_64 x86_64 x86_64 GNU/Linux
[jenkins@testjenkins ~]$ cat /etc/redhat-release 
Red Hat Enterprise Linux release 8.5 (Ootpa)

• podman version:

[jenkins@testjenkins ~]$ podman --version
podman version 3.4.2

• podman container inspection Please refer to the podman_container_inspect.json file below.

• The /proc/self/mountinfo within the container Please refer to the proc_self_mountinfo file below

• The /proc/self/cgroup within the container Please refer to the proc_self_cgroup file below

• The /proc/cgroups within the container Please refer to the proc_cgroups file below

• The reproducer Please see the reproducer: Z_cgroup_v1_npe_when_cgrouppath_does_not_start_with_mount_root.patch

NPE.stacktrace.java

```
[ERROR] Failed to execute goal org.wildfly.plugins:wildfly-maven-plugin:2.0.1.Final:execute-commands (apply-elytron) on project wildfly-ts-integ-smoke: Failed to execute commands: Exception in thread "main"
 java.lang.NullPointerException
[ERROR]         at java.base/java.util.Objects.requireNonNull(Objects.java:208)
[ERROR]         at java.base/sun.nio.fs.UnixFileSystem.getPath(UnixFileSystem.java:263)
[ERROR]         at java.base/java.nio.file.Path.of(Path.java:147)
[ERROR]         at java.base/java.nio.file.Paths.get(Paths.java:69)
[ERROR]         at java.base/jdk.internal.platform.CgroupUtil.lambda$readStringValue$1(CgroupUtil.java:67)
[ERROR]         at java.base/java.security.AccessController.doPrivileged(AccessController.java:569)
[ERROR]         at java.base/jdk.internal.platform.CgroupUtil.readStringValue(CgroupUtil.java:69)
[ERROR]         at java.base/jdk.internal.platform.CgroupSubsystemController.getStringValue(CgroupSubsystemController.java:65)
[ERROR]         at java.base/jdk.internal.platform.CgroupSubsystemController.getLongValue(CgroupSubsystemController.java:124)
[ERROR]         at java.base/jdk.internal.platform.cgroupv1.CgroupV1Subsystem.getLongValue(CgroupV1Subsystem.java:175)
[ERROR]         at java.base/jdk.internal.platform.cgroupv1.CgroupV1Subsystem.getHierarchical(CgroupV1Subsystem.java:149)
[ERROR]         at java.base/jdk.internal.platform.cgroupv1.CgroupV1Subsystem.initSubSystem(CgroupV1Subsystem.java:84)
[ERROR]         at java.base/jdk.internal.platform.cgroupv1.CgroupV1Subsystem.getInstance(CgroupV1Subsystem.java:60)
[ERROR]         at java.base/jdk.internal.platform.CgroupSubsystemFactory.create(CgroupSubsystemFactory.java:116)
[ERROR]         at java.base/jdk.internal.platform.CgroupMetrics.getInstance(CgroupMetrics.java:167)
[ERROR]         at java.base/jdk.internal.platform.SystemMetrics.instance(SystemMetrics.java:29)
[ERROR]         at java.base/jdk.internal.platform.Metrics.systemMetrics(Metrics.java:58)
[ERROR]         at java.base/jdk.internal.platform.Container.metrics(Container.java:43)
[ERROR]         at jdk.management/com.sun.management.internal.OperatingSystemImpl.<init>(OperatingSystemImpl.java:182)
[ERROR]         at jdk.management/com.sun.management.internal.PlatformMBeanProviderImpl.getOperatingSystemMXBean(PlatformMBeanProviderImpl.java:280)
[ERROR]         at jdk.management/com.sun.management.internal.PlatformMBeanProviderImpl$3.nameToMBeanMap(PlatformMBeanProviderImpl.java:199)
[ERROR]         at java.management/java.lang.management.ManagementFactory.lambda$getPlatformMBeanServer$0(ManagementFactory.java:488)
[ERROR]         at java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:273)
[ERROR]         at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:179)
[ERROR]         at java.base/java.util.HashMap$ValueSpliterator.forEachRemaining(HashMap.java:1779)
[ERROR]         at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
[ERROR]         at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
[ERROR]         at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
[ERROR]         at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
[ERROR]         at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
[ERROR]         at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596)
[ERROR]         at java.management/java.lang.management.ManagementFactory.getPlatformMBeanServer(ManagementFactory.java:489)
[ERROR]         at org.jboss.modules.ModuleLoader$RealMBeanReg$1.run(ModuleLoader.java:1258)
[ERROR]         at org.jboss.modules.ModuleLoader$RealMBeanReg$1.run(ModuleLoader.java:1256)
[ERROR]         at java.base/java.security.AccessController.doPrivileged(AccessController.java:318)
[ERROR]         at org.jboss.modules.ModuleLoader$RealMBeanReg.<init>(ModuleLoader.java:1256)
[ERROR]         at org.jboss.modules.ModuleLoader$TempMBeanReg.installReal(ModuleLoader.java:1240)
[ERROR]         at org.jboss.modules.ModuleLoader.installMBeanServer(ModuleLoader.java:273)
[ERROR]         at org.jboss.modules.Main.main(Main.java:605)
```

podman_container_inspect.json

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        "ProcessLabel": "system_u:system_r:container_t:s0:c334,c907",
        "AppArmorProfile": "",
        "EffectiveCaps": null,
        "BoundingCaps": [
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            "CAP_NET_RAW",
            "CAP_SETFCAP",
            "CAP_SETGID",
            "CAP_SETPCAP",
            "CAP_SETUID",
            "CAP_SYS_CHROOT"
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        "ExecIDs": [
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        "Mounts": [
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                "Propagation": "rprivate"
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                "RW": true,
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                "Type": "bind",
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                "Destination": "/var/jenkins_home/.ssh/",
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            "IPAddress": "",
            "IPPrefixLen": 0,
            "IPv6Gateway": "",
            "GlobalIPv6Address": "",
            "GlobalIPv6PrefixLen": 0,
            "MacAddress": "",
            "Bridge": "",
            "SandboxID": "",
            "HairpinMode": false,
            "LinkLocalIPv6Address": "",
            "LinkLocalIPv6PrefixLen": 0,
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            "Env": [
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                "HOSTNAME=1a2b19d89150"
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            "Image": "localhost/automatons:latest",
            "Volumes": null,
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            "Labels": {
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                "1000:1000",
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                "--rm",
                "-v",
                "/home/jenkins/current//jobs/eap-7.4.x-build/builds/7/archive:/parent_job/:ro",
                "--workdir",
                "/var/jenkins_home/workspace/eap-7.4.x-testsuite",
                "-v",
                "/home/jenkins/current/workspace/eap-7.4.x-testsuite:/var/jenkins_home/workspace/eap-7.4.x-testsuite:rw",
                "-v",
                "/opt:/opt:ro",
                "-v",
                "/home/jenkins/.m2/:/var/jenkins_home/.m2/:rw",
                "-v",
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                "-v",
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        "HostConfig": {
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                "/home/jenkins/.gitconfig:/var/jenkins_home/.gitconfig:ro,rprivate,rbind",
                "/home/jenkins/.netrc:/var/jenkins_home/.netrc:ro,rprivate,rbind",
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                "/home/jenkins/current/workspace/eap-7.4.x-testsuite:/var/jenkins_home/workspace/eap-7.4.x-testsuite:rw,rprivate,rbind"
            ],
            "CgroupManager": "cgroupfs",
            "CgroupMode": "host",
            "ContainerIDFile": "",
            "LogConfig": {
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                "Config": null,
                "Path": "/home/jenkins/.local/share/containers/storage/overlay-containers/1a2b19d8915046a04773d7ac350c95d861bcb295d06e9ea2558178eaaa10a1ac/userdata/ctr.log",
                "Tag": "",
                "Size": "0B"
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            "NetworkMode": "slirp4netns",
            "PortBindings": {},
            "RestartPolicy": {
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                "MaximumRetryCount": 0
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            "AutoRemove": true,
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            "VolumesFrom": null,
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            "ExtraHosts": [
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            ],
            "GroupAdd": [],
            "IpcMode": "private",
            "Cgroup": "",
            "Cgroups": "default",
            "Links": null,
            "OomScoreAdj": 0,
            "PidMode": "private",
            "Privileged": false,
            "PublishAllPorts": false,
            "ReadonlyRootfs": false,
            "SecurityOpt": [],
            "Tmpfs": {},
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            "ShmSize": 65536000,
            "Runtime": "oci",
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            "CgroupParent": "",
            "BlkioWeight": 0,
            "BlkioWeightDevice": null,
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            "CpuPeriod": 0,
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            "CpuRealtimeRuntime": 0,
            "CpusetCpus": "",
            "CpusetMems": "",
            "Devices": [],
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            "CpuPercent": 0,
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            "CgroupConf": null
        }
    }
]

proc_cgroups

#subsys_name	hierarchy	num_cgroups	enabled
cpuset	6	4	1
cpu	8	126	1
cpuacct	8	126	1
blkio	11	126	1
memory	9	167	1
devices	3	126	1
freezer	7	4	1
net_cls	5	4	1
perf_event	4	4	1
net_prio	5	4	1
hugetlb	2	4	1
pids	10	159	1
rdma	12	1	1

proc_self_cgroup

12:rdma:/
11:blkio:/system.slice/sshd.service
10:pids:/user.slice/user-1000.slice/session-3.scope
9:memory:/user.slice/user-1000.slice/session-3.scope
8:cpu,cpuacct:/
7:freezer:/
6:cpuset:/
5:net_cls,net_prio:/
4:perf_event:/
3:devices:/system.slice/sshd.service
2:hugetlb:/
1:name=systemd:/user.slice/user-1000.slice/[email protected]/user.slice/podman-637674.scope

proc_self_mountinfo

931 921 0:86 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,context="system_u:object_r:container_file_t:s0:c375,c611",mode=755,uid=100000,gid=100000
932 931 0:26 /user.slice/user-1000.slice/[email protected]/user.slice/podman-637196.scope/2be1ee6e076d20b38a61a1e3289974662d646fb50489ccf22f7fa4e3dc082295 /sys/fs/cgroup/systemd ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd
933 931 0:29 / /sys/fs/cgroup/hugetlb ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,hugetlb
934 931 0:30 /user.slice /sys/fs/cgroup/devices ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,devices
935 931 0:31 / /sys/fs/cgroup/perf_event ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,perf_event
936 931 0:32 / /sys/fs/cgroup/net_cls,net_prio ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,net_cls,net_prio
937 931 0:33 / /sys/fs/cgroup/cpuset ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,cpuset
938 931 0:34 / /sys/fs/cgroup/freezer ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,freezer
940 931 0:35 /user.slice /sys/fs/cgroup/cpu,cpuacct ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,cpu,cpuacct
941 931 0:36 /user.slice/user-1000.slice/session-50.scope /sys/fs/cgroup/memory ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,memory
942 931 0:37 /user.slice/user-1000.slice/session-50.scope /sys/fs/cgroup/pids ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,pids
943 931 0:38 /user.slice /sys/fs/cgroup/blkio ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,blkio
944 931 0:39 / /sys/fs/cgroup/rdma ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,rdma

Z_cgroup_v1_npe_when_cgrouppath_does_not_start_with_mount_root.patch

diff --git a/test/jdk/jdk/internal/platform/cgroup/TestCgroupSubsystemFactory.java b/test/jdk/jdk/internal/platform/cgroup/TestCgroupSubsystemFactory.java
index 369d4244533..a84cb70d7f5 100644
--- a/test/jdk/jdk/internal/platform/cgroup/TestCgroupSubsystemFactory.java
+++ b/test/jdk/jdk/internal/platform/cgroup/TestCgroupSubsystemFactory.java
@@ -43,6 +43,7 @@ import jdk.internal.platform.CgroupSubsystemFactory;
 import jdk.internal.platform.CgroupSubsystemFactory.CgroupTypeResult;
 import jdk.internal.platform.CgroupV1MetricsImpl;
 import jdk.internal.platform.cgroupv1.CgroupV1Subsystem;
+import jdk.internal.platform.cgroupv1.CgroupV1SubsystemController;
 import jdk.internal.platform.Metrics;
 import jdk.test.lib.Utils;
 import jdk.test.lib.util.FileUtils;
@@ -72,8 +73,10 @@ public class TestCgroupSubsystemFactory {
     private Path cgroupv1MntInfoDoubleCpusets;
     private Path cgroupv1MntInfoDoubleCpusets2;
     private Path cgroupv1MntInfoColonsHierarchy;
+    private Path cgroupv1MntInfoPrefix;
     private Path cgroupv1SelfCgroup;
     private Path cgroupv1SelfColons;
+    private Path cgroupv1SelfPrefix;
     private Path cgroupv2SelfCgroup;
     private Path cgroupv1SelfCgroupJoinCtrl;
     private Path cgroupv1CgroupsOnlyCPUCtrl;
@@ -166,6 +169,20 @@ public class TestCgroupSubsystemFactory {
             "42 30 0:38 / /sys/fs/cgroup/cpuset rw,nosuid,nodev,noexec,relatime shared:14 - cgroup none rw,seclabel,cpuset\n" +
             "43 30 0:39 / /sys/fs/cgroup/blkio rw,nosuid,nodev,noexec,relatime shared:15 - cgroup none rw,seclabel,blkio\n" +
             "44 30 0:40 / /sys/fs/cgroup/freezer rw,nosuid,nodev,noexec,relatime shared:16 - cgroup none rw,seclabel,freezer\n";
+    private String mntInfoPrefix =
+            "931 921 0:86 / /sys/fs/cgroup rw,nosuid,nodev,noexec,relatime - tmpfs tmpfs rw,context=\"system_u:object_r:container_file_t:s0:c375,c611\",mode=755,uid=100000,gid=100000\n" +
+            "932 931 0:26 /user.slice/user-1000.slice/[email protected]/user.slice/podman-637196.scope/2be1ee6e076d20b38a61a1e3289974662d646fb50489ccf22f7fa4e3dc082295 /sys/fs/cgroup/systemd ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd\n" +
+            "933 931 0:29 / /sys/fs/cgroup/hugetlb ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,hugetlb\n" +
+            "934 931 0:30 /user.slice /sys/fs/cgroup/devices ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,devices\n" +
+            "935 931 0:31 / /sys/fs/cgroup/perf_event ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,perf_event\n" +
+            "936 931 0:32 / /sys/fs/cgroup/net_cls,net_prio ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,net_cls,net_prio\n" +
+            "937 931 0:33 / /sys/fs/cgroup/cpuset ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,cpuset\n" +
+            "938 931 0:34 / /sys/fs/cgroup/freezer ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,freezer\n" +
+            "940 931 0:35 /user.slice /sys/fs/cgroup/cpu,cpuacct ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,cpu,cpuacct\n" +
+            "941 931 0:36 /user.slice/user-1000.slice/session-50.scope /sys/fs/cgroup/memory ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,memory\n" +
+            "942 931 0:37 /user.slice/user-1000.slice/session-50.scope /sys/fs/cgroup/pids ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,pids\n" +
+            "943 931 0:38 /user.slice /sys/fs/cgroup/blkio ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,blkio\n" +
+            "944 931 0:39 / /sys/fs/cgroup/rdma ro,nosuid,nodev,noexec,relatime - cgroup cgroup rw,seclabel,rdma";
     private String cgroupsNonZeroHierarchy =
             "#subsys_name hierarchy   num_cgroups enabled\n" +
             "cpuset  9   1   1\n" +
@@ -217,6 +234,19 @@ public class TestCgroupSubsystemFactory {
             "2:cpu,cpuacct:/\n" +
             "1:name=systemd:/user.slice/user-1000.slice/[email protected]/apps.slice/apps-org.gnome.Terminal.slice/vte-spawn-3c00b338-5b65-439f-8e97-135e183d135d.scope\n" +
             "0::/user.slice/user-1000.slice/[email protected]/apps.slice/apps-org.gnome.Terminal.slice/vte-spawn-3c00b338-5b65-439f-8e97-135e183d135d.scope\n";
+    private  String cgroupv1SelfPrefixContent =
+            "12:rdma:/\n" +
+            "11:blkio:/system.slice/sshd.service\n" +
+            "10:pids:/user.slice/user-1000.slice/session-3.scope\n" +
+            "9:memory:/user.slice/user-1000.slice/session-3.scope\n" +
+            "8:cpu,cpuacct:/\n" +
+            "7:freezer:/\n" +
+            "6:cpuset:/\n" +
+            "5:net_cls,net_prio:/\n" +
+            "4:perf_event:/\n" +
+            "3:devices:/system.slice/sshd.service\n" +
+            "2:hugetlb:/\n" +
+            "1:name=systemd:/user.slice/user-1000.slice/[email protected]/user.slice/podman-637674.scope";
     private String cgroupv2SelfCgroupContent = "0::/user.slice/user-1000.slice/session-2.scope";
 
     @Before
@@ -257,12 +287,18 @@ public class TestCgroupSubsystemFactory {
             cgroupv1MntInfoColonsHierarchy = Paths.get(existingDirectory.toString(), "mountinfo_colons");
             Files.writeString(cgroupv1MntInfoColonsHierarchy, mntInfoColons);
 
+            cgroupv1MntInfoPrefix = Paths.get(existingDirectory.toString(), "mountinfo-prefix");
+            Files.writeString(cgroupv1MntInfoPrefix, mntInfoPrefix);
+
             cgroupv1SelfCgroup = Paths.get(existingDirectory.toString(), "self_cgroup_cgv1");
             Files.writeString(cgroupv1SelfCgroup, cgroupv1SelfCgroupContent);
 
             cgroupv1SelfColons = Paths.get(existingDirectory.toString(), "self_colons_cgv1");
             Files.writeString(cgroupv1SelfColons, cgroupv1SelfColonsContent);
 
+            cgroupv1SelfPrefix = Paths.get(existingDirectory.toString(), "self_prefix_cgv1");
+            Files.writeString(cgroupv1SelfPrefix, cgroupv1SelfPrefixContent);
+
             cgroupv2SelfCgroup = Paths.get(existingDirectory.toString(), "self_cgroup_cgv2");
             Files.writeString(cgroupv2SelfCgroup, cgroupv2SelfCgroupContent);
 
@@ -393,6 +429,24 @@ public class TestCgroupSubsystemFactory {
         assertEquals(memoryInfo.getMountRoot(), memoryInfo.getCgroupPath());
     }
 
+    @Test
+    public void testMountPrefixCgroupsV1() throws IOException {
+        String cgroups = cgroupv1CgInfoNonZeroHierarchy.toString();
+        String mountInfo = cgroupv1MntInfoPrefix.toString();
+        String selfCgroup = cgroupv1SelfPrefix.toString();
+        Optional<CgroupTypeResult> result = CgroupSubsystemFactory.determineType(mountInfo, cgroups, selfCgroup);
+
+        assertTrue("Expected non-empty cgroup result", result.isPresent());
+        CgroupTypeResult res = result.get();
+        CgroupInfo memoryInfo = res.getInfos().get("memory");
+        assertEquals(memoryInfo.getCgroupPath(), "/user.slice/user-1000.slice/session-3.scope");
+        assertEquals("/sys/fs/cgroup/memory", memoryInfo.getMountPoint());
+        CgroupV1SubsystemController cgroupv1MemoryController = new CgroupV1SubsystemController(memoryInfo.getMountRoot(), memoryInfo.getMountPoint());
+        cgroupv1MemoryController.setPath(memoryInfo.getCgroupPath());
+        // issue to verify: path was not set because the cgroupPath does not start with mount root
+        assertNotNull(cgroupv1MemoryController.path());
+    }
+
     @Test
     public void testZeroHierarchyCgroupsV1() throws IOException {
         String cgroups = cgroupv1CgInfoZeroHierarchy.toString();

OK. I'll consider this when rebooting the PR.