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Message-Id: <20251021-work-namespace-nstree-listns-v1-42-ad44261a8a5b@kernel.org>
Date: Tue, 21 Oct 2025 13:43:48 +0200
From: Christian Brauner <brauner@...nel.org>
To: linux-fsdevel@...r.kernel.org, Josef Bacik <josef@...icpanda.com>,
Jeff Layton <jlayton@...nel.org>
Cc: Jann Horn <jannh@...gle.com>, Mike Yuan <me@...dnzj.com>,
Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>,
Lennart Poettering <mzxreary@...inter.de>,
Daan De Meyer <daan.j.demeyer@...il.com>, Aleksa Sarai <cyphar@...har.com>,
Amir Goldstein <amir73il@...il.com>, Tejun Heo <tj@...nel.org>,
Johannes Weiner <hannes@...xchg.org>, Thomas Gleixner <tglx@...utronix.de>,
Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, bpf@...r.kernel.org,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
netdev@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
Christian Brauner <brauner@...nel.org>
Subject: [PATCH RFC DRAFT 42/50] selftests/namespaces: ninth listns() test
Test that hierarchical active reference propagation keeps parent
user namespaces visible in listns().
Signed-off-by: Christian Brauner <brauner@...nel.org>
---
tools/testing/selftests/namespaces/listns_test.c | 135 +++++++++++++++++++++++
1 file changed, 135 insertions(+)
diff --git a/tools/testing/selftests/namespaces/listns_test.c b/tools/testing/selftests/namespaces/listns_test.c
index 6afffddf9764..ddf4509d5cd6 100644
--- a/tools/testing/selftests/namespaces/listns_test.c
+++ b/tools/testing/selftests/namespaces/listns_test.c
@@ -467,4 +467,139 @@ TEST(listns_multiple_types)
TH_LOG(" [%zd] ns_id: %llu", i, (unsigned long long)ns_ids[i]);
}
+/*
+ * Test that hierarchical active reference propagation keeps parent
+ * user namespaces visible in listns().
+ */
+TEST(listns_hierarchical_visibility)
+{
+ struct ns_id_req req = {
+ .size = sizeof(req),
+ .spare = 0,
+ .ns_id = 0,
+ .ns_type = CLONE_NEWUSER,
+ .spare2 = 0,
+ .user_ns_id = 0,
+ };
+ __u64 parent_ns_id = 0, child_ns_id = 0;
+ int pipefd[2];
+ pid_t pid;
+ int status;
+ int bytes;
+ __u64 ns_ids[100];
+ ssize_t ret;
+ bool found_parent, found_child;
+
+ ASSERT_EQ(pipe(pipefd), 0);
+
+ pid = fork();
+ ASSERT_GE(pid, 0);
+
+ if (pid == 0) {
+ int fd;
+ char buf;
+
+ close(pipefd[0]);
+
+ /* Create parent user namespace */
+ if (setup_userns() < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+
+ fd = open("/proc/self/ns/user", O_RDONLY);
+ if (fd < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+
+ if (ioctl(fd, NS_GET_ID, &parent_ns_id) < 0) {
+ close(fd);
+ close(pipefd[1]);
+ exit(1);
+ }
+ close(fd);
+
+ /* Create child user namespace */
+ if (setup_userns() < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+
+ fd = open("/proc/self/ns/user", O_RDONLY);
+ if (fd < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+
+ if (ioctl(fd, NS_GET_ID, &child_ns_id) < 0) {
+ close(fd);
+ close(pipefd[1]);
+ exit(1);
+ }
+ close(fd);
+
+ /* Send both IDs to parent */
+ write(pipefd[1], &parent_ns_id, sizeof(parent_ns_id));
+ write(pipefd[1], &child_ns_id, sizeof(child_ns_id));
+
+ /* Wait for parent signal */
+ read(pipefd[1], &buf, 1);
+ close(pipefd[1]);
+ exit(0);
+ }
+
+ /* Parent */
+ close(pipefd[1]);
+
+ /* Read both namespace IDs */
+ bytes = read(pipefd[0], &parent_ns_id, sizeof(parent_ns_id));
+ bytes += read(pipefd[0], &child_ns_id, sizeof(child_ns_id));
+
+ if (bytes != (int)(2 * sizeof(__u64))) {
+ close(pipefd[0]);
+ kill(pid, SIGKILL);
+ waitpid(pid, NULL, 0);
+ SKIP(return, "Failed to get namespace IDs from child");
+ }
+
+ TH_LOG("Parent user namespace ID: %llu", (unsigned long long)parent_ns_id);
+ TH_LOG("Child user namespace ID: %llu", (unsigned long long)child_ns_id);
+
+ /* List all user namespaces */
+ ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
+
+ if (ret < 0 && errno == ENOSYS) {
+ close(pipefd[0]);
+ kill(pid, SIGKILL);
+ waitpid(pid, NULL, 0);
+ SKIP(return, "listns() not supported");
+ }
+
+ ASSERT_GE(ret, 0);
+ TH_LOG("Found %zd active user namespaces", ret);
+
+ /* Both parent and child should be visible (active due to child process) */
+ found_parent = false;
+ found_child = false;
+ for (ssize_t i = 0; i < ret; i++) {
+ if (ns_ids[i] == parent_ns_id)
+ found_parent = true;
+ if (ns_ids[i] == child_ns_id)
+ found_child = true;
+ }
+
+ TH_LOG("Parent namespace %s, child namespace %s",
+ found_parent ? "found" : "NOT FOUND",
+ found_child ? "found" : "NOT FOUND");
+
+ ASSERT_TRUE(found_child);
+ /* With hierarchical propagation, parent should also be active */
+ ASSERT_TRUE(found_parent);
+
+ /* Signal child to exit */
+ close(pipefd[0]);
+ waitpid(pid, &status, 0);
+}
+
TEST_HARNESS_MAIN
--
2.47.3
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