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Message-Id: <20251024-work-namespace-nstree-listns-v3-65-b6241981b72b@kernel.org>
Date: Fri, 24 Oct 2025 12:53:34 +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 v3 65/70] selftests/namespace: first threaded active
reference count test
Test that namespace becomes inactive after thread exits. This verifies
active reference counting works with threads, not just processes.
Signed-off-by: Christian Brauner <brauner@...nel.org>
---
.../selftests/namespaces/ns_active_ref_test.c | 138 +++++++++++++++++++++
1 file changed, 138 insertions(+)
diff --git a/tools/testing/selftests/namespaces/ns_active_ref_test.c b/tools/testing/selftests/namespaces/ns_active_ref_test.c
index b7fa973a2572..0c6c4869bb16 100644
--- a/tools/testing/selftests/namespaces/ns_active_ref_test.c
+++ b/tools/testing/selftests/namespaces/ns_active_ref_test.c
@@ -12,9 +12,12 @@
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
+#include <sys/syscall.h>
#include <unistd.h>
+#include <pthread.h>
#include "../kselftest_harness.h"
#include "../filesystems/utils.h"
+#include "wrappers.h"
#ifndef FD_NSFS_ROOT
#define FD_NSFS_ROOT -10003 /* Root of the nsfs filesystem */
@@ -2113,4 +2116,139 @@ TEST(ns_mixed_types_same_owner)
ASSERT_LT(u_fd, 0);
}
+/* Thread test helpers and structures */
+struct thread_ns_info {
+ __u64 ns_id;
+ int pipefd;
+ int syncfd_read;
+ int syncfd_write;
+ int exit_code;
+};
+
+static void *thread_create_namespace(void *arg)
+{
+ struct thread_ns_info *info = (struct thread_ns_info *)arg;
+ int ret;
+
+ /* Create new network namespace */
+ ret = unshare(CLONE_NEWNET);
+ if (ret < 0) {
+ info->exit_code = 1;
+ return NULL;
+ }
+
+ /* Get namespace ID */
+ int fd = open("/proc/thread-self/ns/net", O_RDONLY);
+ if (fd < 0) {
+ info->exit_code = 2;
+ return NULL;
+ }
+
+ ret = ioctl(fd, NS_GET_ID, &info->ns_id);
+ close(fd);
+ if (ret < 0) {
+ info->exit_code = 3;
+ return NULL;
+ }
+
+ /* Send namespace ID to main thread */
+ if (write(info->pipefd, &info->ns_id, sizeof(info->ns_id)) != sizeof(info->ns_id)) {
+ info->exit_code = 4;
+ return NULL;
+ }
+
+ /* Wait for signal to exit */
+ char sync_byte;
+ if (read(info->syncfd_read, &sync_byte, 1) != 1) {
+ info->exit_code = 5;
+ return NULL;
+ }
+
+ info->exit_code = 0;
+ return NULL;
+}
+
+/*
+ * Test that namespace becomes inactive after thread exits.
+ * This verifies active reference counting works with threads, not just processes.
+ */
+TEST(thread_ns_inactive_after_exit)
+{
+ pthread_t thread;
+ struct thread_ns_info info;
+ struct file_handle *handle;
+ int pipefd[2];
+ int syncpipe[2];
+ int ret;
+ char sync_byte;
+ char buf[sizeof(*handle) + MAX_HANDLE_SZ];
+
+ ASSERT_EQ(pipe(pipefd), 0);
+ ASSERT_EQ(pipe(syncpipe), 0);
+
+ info.pipefd = pipefd[1];
+ info.syncfd_read = syncpipe[0];
+ info.syncfd_write = -1;
+ info.exit_code = -1;
+
+ /* Create thread that will create a namespace */
+ ret = pthread_create(&thread, NULL, thread_create_namespace, &info);
+ ASSERT_EQ(ret, 0);
+
+ /* Read namespace ID from thread */
+ __u64 ns_id;
+ ret = read(pipefd[0], &ns_id, sizeof(ns_id));
+ if (ret != sizeof(ns_id)) {
+ sync_byte = 'X';
+ write(syncpipe[1], &sync_byte, 1);
+ pthread_join(thread, NULL);
+ close(pipefd[0]);
+ close(pipefd[1]);
+ close(syncpipe[0]);
+ close(syncpipe[1]);
+ SKIP(return, "Failed to read namespace ID from thread");
+ }
+
+ TH_LOG("Thread created namespace with ID %llu", (unsigned long long)ns_id);
+
+ /* Construct file handle */
+ handle = (struct file_handle *)buf;
+ handle->handle_bytes = sizeof(struct nsfs_file_handle);
+ handle->handle_type = FILEID_NSFS;
+ struct nsfs_file_handle *fh = (struct nsfs_file_handle *)handle->f_handle;
+ fh->ns_id = ns_id;
+ fh->ns_type = 0;
+ fh->ns_inum = 0;
+
+ /* Namespace should be active while thread is alive */
+ TH_LOG("Attempting to open namespace while thread is alive (should succeed)");
+ int nsfd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
+ ASSERT_GE(nsfd, 0);
+ close(nsfd);
+
+ /* Signal thread to exit */
+ TH_LOG("Signaling thread to exit");
+ sync_byte = 'X';
+ ASSERT_EQ(write(syncpipe[1], &sync_byte, 1), 1);
+ close(syncpipe[1]);
+
+ /* Wait for thread to exit */
+ ASSERT_EQ(pthread_join(thread, NULL), 0);
+ close(pipefd[0]);
+ close(pipefd[1]);
+ close(syncpipe[0]);
+
+ if (info.exit_code != 0)
+ SKIP(return, "Thread failed to create namespace");
+
+ TH_LOG("Thread exited, namespace should be inactive");
+
+ /* Namespace should now be inactive */
+ nsfd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
+ ASSERT_LT(nsfd, 0);
+ /* Should fail with ENOENT (inactive) or ESTALE (gone) */
+ TH_LOG("Namespace inactive as expected: %s (errno=%d)", strerror(errno), errno);
+ ASSERT_TRUE(errno == ENOENT || errno == ESTALE);
+}
+
TEST_HARNESS_MAIN
--
2.47.3
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