selftests/namespaces: eigth active reference count tests

Test that bind mounts keep namespaces in the tree even when inactive

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-30-2e6f823ebdc0@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/namespaces/ns_active_ref_test.c b/tools/testing/selftests/namespaces/ns_active_ref_test.c
index 60876965dd71c21cbba88dc0e5bb1b6710a917c3..55a741d32b085e6c21250f4f6fba915ef34082c0 100644 (file)
--- a/tools/testing/selftests/namespaces/ns_active_ref_test.c
+++ b/tools/testing/selftests/namespaces/ns_active_ref_test.c
@@ -825,4 +825,121 @@ TEST(ns_parent_always_reachable)
        ASSERT_TRUE(errno == ENOENT || errno == ESTALE);
 }
 
+/*
+ * Test that bind mounts keep namespaces in the tree even when inactive
+ */
+TEST(ns_bind_mount_keeps_in_tree)
+{
+       struct file_handle *handle;
+       int mount_id;
+       int ret;
+       int fd;
+       int pipefd[2];
+       pid_t pid;
+       int status;
+       char buf[sizeof(*handle) + MAX_HANDLE_SZ];
+       char tmpfile[] = "/tmp/ns-test-XXXXXX";
+       int tmpfd;
+
+       /* Create temporary file for bind mount */
+       tmpfd = mkstemp(tmpfile);
+       if (tmpfd < 0) {
+               SKIP(return, "Cannot create temporary file");
+       }
+       close(tmpfd);
+
+       ASSERT_EQ(pipe(pipefd), 0);
+
+       pid = fork();
+       ASSERT_GE(pid, 0);
+
+       if (pid == 0) {
+               /* Child process */
+               close(pipefd[0]);
+
+               /* Unshare mount namespace and make mounts private to avoid propagation */
+               ret = unshare(CLONE_NEWNS);
+               if (ret < 0) {
+                       close(pipefd[1]);
+                       unlink(tmpfile);
+                       exit(1);
+               }
+               ret = mount(NULL, "/", NULL, MS_PRIVATE | MS_REC, NULL);
+               if (ret < 0) {
+                       close(pipefd[1]);
+                       unlink(tmpfile);
+                       exit(1);
+               }
+
+               /* Create new network namespace */
+               ret = unshare(CLONE_NEWNET);
+               if (ret < 0) {
+                       close(pipefd[1]);
+                       unlink(tmpfile);
+                       exit(1);
+               }
+
+               /* Bind mount the namespace */
+               ret = mount("/proc/self/ns/net", tmpfile, NULL, MS_BIND, NULL);
+               if (ret < 0) {
+                       close(pipefd[1]);
+                       unlink(tmpfile);
+                       exit(1);
+               }
+
+               /* Get file handle */
+               fd = open("/proc/self/ns/net", O_RDONLY);
+               if (fd < 0) {
+                       umount(tmpfile);
+                       close(pipefd[1]);
+                       unlink(tmpfile);
+                       exit(1);
+               }
+
+               handle = (struct file_handle *)buf;
+               handle->handle_bytes = MAX_HANDLE_SZ;
+               ret = name_to_handle_at(fd, "", handle, &mount_id, AT_EMPTY_PATH);
+               close(fd);
+
+               if (ret < 0) {
+                       umount(tmpfile);
+                       close(pipefd[1]);
+                       unlink(tmpfile);
+                       exit(1);
+               }
+
+               /* Send handle to parent */
+               write(pipefd[1], buf, sizeof(*handle) + handle->handle_bytes);
+               close(pipefd[1]);
+               exit(0);
+       }
+
+       /* Parent */
+       close(pipefd[1]);
+       ret = read(pipefd[0], buf, sizeof(buf));
+       close(pipefd[0]);
+
+       waitpid(pid, &status, 0);
+       ASSERT_TRUE(WIFEXITED(status));
+       ASSERT_EQ(WEXITSTATUS(status), 0);
+
+       ASSERT_GT(ret, 0);
+       handle = (struct file_handle *)buf;
+
+       /*
+        * Namespace should be inactive but still in tree due to bind mount.
+        * Reopening should fail with ENOENT (inactive) not ESTALE (not in tree).
+        */
+       fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
+       ASSERT_LT(fd, 0);
+       /* Should be ENOENT (inactive) since bind mount keeps it in tree */
+       if (errno != ENOENT && errno != ESTALE) {
+               TH_LOG("Unexpected error: %d", errno);
+       }
+
+       /* Cleanup */
+       umount(tmpfile);
+       unlink(tmpfile);
+}
+
 TEST_HARNESS_MAIN