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Message-Id: <20251021-work-namespace-nstree-listns-v1-29-ad44261a8a5b@kernel.org>
Date: Tue, 21 Oct 2025 13:43:35 +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 29/50] selftests/namespaces: eleventh active
reference count tests
Test that different namespace types with same owner all contribute
active references to the owning user namespace.
Signed-off-by: Christian Brauner <brauner@...nel.org>
---
.../selftests/namespaces/ns_active_ref_test.c | 178 +++++++++++++++++++++
1 file changed, 178 insertions(+)
diff --git a/tools/testing/selftests/namespaces/ns_active_ref_test.c b/tools/testing/selftests/namespaces/ns_active_ref_test.c
index 15d001df981c..3c2f99b25067 100644
--- a/tools/testing/selftests/namespaces/ns_active_ref_test.c
+++ b/tools/testing/selftests/namespaces/ns_active_ref_test.c
@@ -1353,4 +1353,182 @@ TEST(ns_multiple_children_same_parent)
}
}
+/*
+ * Test that different namespace types with same owner all contribute
+ * active references to the owning user namespace.
+ */
+TEST(ns_different_types_same_owner)
+{
+ struct file_handle *u_handle, *n_handle, *ut_handle;
+ int ret, pipefd[2];
+ pid_t pid;
+ int status;
+ __u64 u_id, n_id, ut_id;
+ char u_buf[sizeof(*u_handle) + MAX_HANDLE_SZ];
+ char n_buf[sizeof(*n_handle) + MAX_HANDLE_SZ];
+ char ut_buf[sizeof(*ut_handle) + MAX_HANDLE_SZ];
+
+ ASSERT_EQ(pipe(pipefd), 0);
+ pid = fork();
+ ASSERT_GE(pid, 0);
+
+ if (pid == 0) {
+ close(pipefd[0]);
+
+ /* Create user namespace */
+ if (setup_userns() < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+
+ int u_fd = open("/proc/self/ns/user", O_RDONLY);
+ if (u_fd < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+ if (ioctl(u_fd, NS_GET_ID, &u_id) < 0) {
+ close(u_fd);
+ close(pipefd[1]);
+ exit(1);
+ }
+ close(u_fd);
+
+ /* Create network namespace (owned by user namespace) */
+ if (unshare(CLONE_NEWNET) < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+
+ int n_fd = open("/proc/self/ns/net", O_RDONLY);
+ if (n_fd < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+ if (ioctl(n_fd, NS_GET_ID, &n_id) < 0) {
+ close(n_fd);
+ close(pipefd[1]);
+ exit(1);
+ }
+ close(n_fd);
+
+ /* Create UTS namespace (also owned by user namespace) */
+ if (unshare(CLONE_NEWUTS) < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+
+ int ut_fd = open("/proc/self/ns/uts", O_RDONLY);
+ if (ut_fd < 0) {
+ close(pipefd[1]);
+ exit(1);
+ }
+ if (ioctl(ut_fd, NS_GET_ID, &ut_id) < 0) {
+ close(ut_fd);
+ close(pipefd[1]);
+ exit(1);
+ }
+ close(ut_fd);
+
+ /* Send all namespace IDs */
+ write(pipefd[1], &u_id, sizeof(u_id));
+ write(pipefd[1], &n_id, sizeof(n_id));
+ write(pipefd[1], &ut_id, sizeof(ut_id));
+ close(pipefd[1]);
+ exit(0);
+ }
+
+ close(pipefd[1]);
+
+ /* Read all three namespace IDs - fixed size, no parsing needed */
+ ret = read(pipefd[0], &u_id, sizeof(u_id));
+ if (ret != sizeof(u_id)) {
+ close(pipefd[0]);
+ waitpid(pid, NULL, 0);
+ SKIP(return, "Failed to read user namespace ID");
+ }
+
+ ret = read(pipefd[0], &n_id, sizeof(n_id));
+ if (ret != sizeof(n_id)) {
+ close(pipefd[0]);
+ waitpid(pid, NULL, 0);
+ SKIP(return, "Failed to read network namespace ID");
+ }
+
+ ret = read(pipefd[0], &ut_id, sizeof(ut_id));
+ close(pipefd[0]);
+ if (ret != sizeof(ut_id)) {
+ waitpid(pid, NULL, 0);
+ SKIP(return, "Failed to read UTS namespace ID");
+ }
+
+ /* Construct file handles from namespace IDs */
+ u_handle = (struct file_handle *)u_buf;
+ u_handle->handle_bytes = sizeof(struct nsfs_file_handle);
+ u_handle->handle_type = FILEID_NSFS;
+ struct nsfs_file_handle *u_fh = (struct nsfs_file_handle *)u_handle->f_handle;
+ u_fh->ns_id = u_id;
+ u_fh->ns_type = 0;
+ u_fh->ns_inum = 0;
+
+ n_handle = (struct file_handle *)n_buf;
+ n_handle->handle_bytes = sizeof(struct nsfs_file_handle);
+ n_handle->handle_type = FILEID_NSFS;
+ struct nsfs_file_handle *n_fh = (struct nsfs_file_handle *)n_handle->f_handle;
+ n_fh->ns_id = n_id;
+ n_fh->ns_type = 0;
+ n_fh->ns_inum = 0;
+
+ ut_handle = (struct file_handle *)ut_buf;
+ ut_handle->handle_bytes = sizeof(struct nsfs_file_handle);
+ ut_handle->handle_type = FILEID_NSFS;
+ struct nsfs_file_handle *ut_fh = (struct nsfs_file_handle *)ut_handle->f_handle;
+ ut_fh->ns_id = ut_id;
+ ut_fh->ns_type = 0;
+ ut_fh->ns_inum = 0;
+
+ /* Open both non-user namespaces before process exits */
+ int n_fd = open_by_handle_at(FD_NSFS_ROOT, n_handle, O_RDONLY);
+ int ut_fd = open_by_handle_at(FD_NSFS_ROOT, ut_handle, O_RDONLY);
+
+ if (n_fd < 0 || ut_fd < 0) {
+ if (n_fd >= 0) close(n_fd);
+ if (ut_fd >= 0) close(ut_fd);
+ waitpid(pid, NULL, 0);
+ SKIP(return, "Failed to open namespaces");
+ }
+
+ waitpid(pid, &status, 0);
+ ASSERT_TRUE(WIFEXITED(status));
+ if (WEXITSTATUS(status) != 0) {
+ close(n_fd);
+ close(ut_fd);
+ SKIP(return, "Child failed");
+ }
+
+ /*
+ * Both network and UTS namespaces are active.
+ * User namespace should be active (gets 2 active refs).
+ */
+ TH_LOG("Both net and uts active - user namespace should be active");
+ int u_fd = open_by_handle_at(FD_NSFS_ROOT, u_handle, O_RDONLY);
+ ASSERT_GE(u_fd, 0);
+ close(u_fd);
+
+ /* Close network namespace - user namespace should STILL be active */
+ TH_LOG("Closing network ns - user ns should still be active (uts still active)");
+ close(n_fd);
+ u_fd = open_by_handle_at(FD_NSFS_ROOT, u_handle, O_RDONLY);
+ ASSERT_GE(u_fd, 0);
+ close(u_fd);
+
+ /* Close UTS namespace - user namespace should become inactive */
+ TH_LOG("Closing uts ns - user ns should become inactive");
+ close(ut_fd);
+ u_fd = open_by_handle_at(FD_NSFS_ROOT, u_handle, O_RDONLY);
+ if (u_fd >= 0) {
+ close(u_fd);
+ TH_LOG("Warning: User namespace still active after all owned namespaces inactive");
+ }
+}
+
TEST_HARNESS_MAIN
--
2.47.3
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