selftests/namespaces: fourteenth active reference count tests

Test that user namespace as a child also propagates correctly.
Create user_A -> user_B, verify when user_B is active that user_A
is also active. This is different from non-user namespace children.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-36-2e6f823ebdc0@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 25f06e62306494c2ff3e18762925dbe47f3121f7..430702c041a927d51060c176230204f37058e4df 100644 (file)
--- a/tools/testing/selftests/namespaces/ns_active_ref_test.c
+++ b/tools/testing/selftests/namespaces/ns_active_ref_test.c
@@ -1817,4 +1817,136 @@ TEST(ns_parent_multiple_children_refcount)
        ASSERT_LT(p_fd, 0);
 }
 
+/*
+ * Test that user namespace as a child also propagates correctly.
+ * Create user_A -> user_B, verify when user_B is active that user_A
+ * is also active. This is different from non-user namespace children.
+ */
+TEST(ns_userns_child_propagation)
+{
+       struct file_handle *ua_handle, *ub_handle;
+       int ret, pipefd[2];
+       pid_t pid;
+       int status;
+       __u64 ua_id, ub_id;
+       char ua_buf[sizeof(*ua_handle) + MAX_HANDLE_SZ];
+       char ub_buf[sizeof(*ub_handle) + MAX_HANDLE_SZ];
+
+       ASSERT_EQ(pipe(pipefd), 0);
+       pid = fork();
+       ASSERT_GE(pid, 0);
+
+       if (pid == 0) {
+               close(pipefd[0]);
+
+               /* Create user_A */
+               if (setup_userns() < 0) {
+                       close(pipefd[1]);
+                       exit(1);
+               }
+
+               int ua_fd = open("/proc/self/ns/user", O_RDONLY);
+               if (ua_fd < 0) {
+                       close(pipefd[1]);
+                       exit(1);
+               }
+               if (ioctl(ua_fd, NS_GET_ID, &ua_id) < 0) {
+                       close(ua_fd);
+                       close(pipefd[1]);
+                       exit(1);
+               }
+               close(ua_fd);
+
+               /* Create user_B (child of user_A) */
+               if (setup_userns() < 0) {
+                       close(pipefd[1]);
+                       exit(1);
+               }
+
+               int ub_fd = open("/proc/self/ns/user", O_RDONLY);
+               if (ub_fd < 0) {
+                       close(pipefd[1]);
+                       exit(1);
+               }
+               if (ioctl(ub_fd, NS_GET_ID, &ub_id) < 0) {
+                       close(ub_fd);
+                       close(pipefd[1]);
+                       exit(1);
+               }
+               close(ub_fd);
+
+               /* Send both namespace IDs */
+               write(pipefd[1], &ua_id, sizeof(ua_id));
+               write(pipefd[1], &ub_id, sizeof(ub_id));
+               close(pipefd[1]);
+               exit(0);
+       }
+
+       close(pipefd[1]);
+
+       /* Read both namespace IDs - fixed size, no parsing needed */
+       ret = read(pipefd[0], &ua_id, sizeof(ua_id));
+       if (ret != sizeof(ua_id)) {
+               close(pipefd[0]);
+               waitpid(pid, NULL, 0);
+               SKIP(return, "Failed to read user_A namespace ID");
+       }
+
+       ret = read(pipefd[0], &ub_id, sizeof(ub_id));
+       close(pipefd[0]);
+       if (ret != sizeof(ub_id)) {
+               waitpid(pid, NULL, 0);
+               SKIP(return, "Failed to read user_B namespace ID");
+       }
+
+       /* Construct file handles from namespace IDs */
+       ua_handle = (struct file_handle *)ua_buf;
+       ua_handle->handle_bytes = sizeof(struct nsfs_file_handle);
+       ua_handle->handle_type = FILEID_NSFS;
+       struct nsfs_file_handle *ua_fh = (struct nsfs_file_handle *)ua_handle->f_handle;
+       ua_fh->ns_id = ua_id;
+       ua_fh->ns_type = 0;
+       ua_fh->ns_inum = 0;
+
+       ub_handle = (struct file_handle *)ub_buf;
+       ub_handle->handle_bytes = sizeof(struct nsfs_file_handle);
+       ub_handle->handle_type = FILEID_NSFS;
+       struct nsfs_file_handle *ub_fh = (struct nsfs_file_handle *)ub_handle->f_handle;
+       ub_fh->ns_id = ub_id;
+       ub_fh->ns_type = 0;
+       ub_fh->ns_inum = 0;
+
+       /* Open user_B before child exits */
+       int ub_fd = open_by_handle_at(FD_NSFS_ROOT, ub_handle, O_RDONLY);
+       if (ub_fd < 0) {
+               waitpid(pid, NULL, 0);
+               SKIP(return, "Failed to open user_B");
+       }
+
+       waitpid(pid, &status, 0);
+       ASSERT_TRUE(WIFEXITED(status));
+       ASSERT_EQ(WEXITSTATUS(status), 0);
+
+       /* With user_B active, user_A should also be active */
+       TH_LOG("Testing user_A active when child user_B is active");
+       int ua_fd = open_by_handle_at(FD_NSFS_ROOT, ua_handle, O_RDONLY);
+       ASSERT_GE(ua_fd, 0);
+
+       /* Close user_B */
+       TH_LOG("Closing user_B");
+       close(ub_fd);
+
+       /* user_A should remain active (we hold direct ref) */
+       int ua_fd2 = open_by_handle_at(FD_NSFS_ROOT, ua_handle, O_RDONLY);
+       ASSERT_GE(ua_fd2, 0);
+       close(ua_fd2);
+
+       /* Close user_A - should become inactive */
+       TH_LOG("Closing user_A - should become inactive");
+       close(ua_fd);
+
+       ua_fd = open_by_handle_at(FD_NSFS_ROOT, ua_handle, O_RDONLY);
+       ASSERT_LT(ua_fd, 0);
+}
+
 TEST_HARNESS_MAIN