selftests/namespaces: fifth active reference count tests

Test PID namespace active ref tracking

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-27-2e6f823ebdc0@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 396066e641da1463b6bbfd65a9b9c7c86a55572b..f4e92b772f700136c09feea0eedf291cfe8196f7 100644 (file)
--- a/tools/testing/selftests/namespaces/ns_active_ref_test.c
+++ b/tools/testing/selftests/namespaces/ns_active_ref_test.c
@@ -366,4 +366,86 @@ TEST(userns_active_ref_lifecycle)
        ASSERT_TRUE(errno == ENOENT || errno == ESTALE);
 }
 
+/*
+ * Test PID namespace active ref tracking
+ */
+TEST(pidns_active_ref_lifecycle)
+{
+       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];
+
+       ASSERT_EQ(pipe(pipefd), 0);
+
+       pid = fork();
+       ASSERT_GE(pid, 0);
+
+       if (pid == 0) {
+               /* Child process */
+               close(pipefd[0]);
+
+               /* Create new PID namespace */
+               ret = unshare(CLONE_NEWPID);
+               if (ret < 0) {
+                       close(pipefd[1]);
+                       exit(1);
+               }
+
+               /* Fork to actually enter the PID namespace */
+               pid_t child = fork();
+               if (child < 0) {
+                       close(pipefd[1]);
+                       exit(1);
+               }
+
+               if (child == 0) {
+                       /* Grandchild - in new PID namespace */
+                       fd = open("/proc/self/ns/pid", O_RDONLY);
+                       if (fd < 0) {
+                               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) {
+                               exit(1);
+                       }
+
+                       /* Send handle to grandparent */
+                       write(pipefd[1], buf, sizeof(*handle) + handle->handle_bytes);
+                       close(pipefd[1]);
+                       exit(0);
+               }
+
+               /* Wait for grandchild */
+               waitpid(child, NULL, 0);
+               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 after all processes exit */
+       fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
+       ASSERT_LT(fd, 0);
+       ASSERT_TRUE(errno == ENOENT || errno == ESTALE);
+}
+
 TEST_HARNESS_MAIN