selftests/bpf: Test task storage when local_storage->smap is NULL

The current sk storage test ensures the memory free works when
the local_storage->smap is NULL.

This patch adds a task storage test to ensure the memory free
code path works when local_storage->smap is NULL.

Signed-off-by: Martin KaFai Lau <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/testing/selftests/bpf/prog_tests/test_local_storage.c

···
 /* Fork and exec the provided rm binary and return the exit code of the
  * forked process and its pid.
  */
-static int run_self_unlink(int *monitored_pid, const char *rm_path)
+static int run_self_unlink(struct local_storage *skel, const char *rm_path)
 {
 	int child_pid, child_status, ret;
 	int null_fd;
···
 		dup2(null_fd, STDERR_FILENO);
 		close(null_fd);
 
-		*monitored_pid = getpid();
+		skel->bss->monitored_pid = getpid();
 		/* Use the copied /usr/bin/rm to delete itself
 		 * /tmp/copy_of_rm /tmp/copy_of_rm.
 		 */
···
 			exit(errno);
 	} else if (child_pid > 0) {
 		waitpid(child_pid, &child_status, 0);
+		ASSERT_EQ(skel->data->task_storage_result, 0, "task_storage_result");
 		return WEXITSTATUS(child_status);
 	}
 
···
 	 * unlink its executable. This operation should be denied by the loaded
 	 * LSM program.
 	 */
-	err = run_self_unlink(&skel->bss->monitored_pid, tmp_exec_path);
+	err = run_self_unlink(skel, tmp_exec_path);
 	if (!ASSERT_EQ(err, EPERM, "run_self_unlink"))
 		goto close_prog_rmdir;
 

tools/testing/selftests/bpf/progs/local_storage.c

···
 int monitored_pid = 0;
 int inode_storage_result = -1;
 int sk_storage_result = -1;
+int task_storage_result = -1;
 
 struct local_storage {
 	struct inode *exec_inode;
···
 	__type(value, struct local_storage);
 } task_storage_map SEC(".maps");
 
+struct {
+	__uint(type, BPF_MAP_TYPE_TASK_STORAGE);
+	__uint(map_flags, BPF_F_NO_PREALLOC);
+	__type(key, int);
+	__type(value, struct local_storage);
+} task_storage_map2 SEC(".maps");
+
 SEC("lsm/inode_unlink")
 int BPF_PROG(unlink_hook, struct inode *dir, struct dentry *victim)
 {
 	__u32 pid = bpf_get_current_pid_tgid() >> 32;
+	struct bpf_local_storage *local_storage;
 	struct local_storage *storage;
+	struct task_struct *task;
 	bool is_self_unlink;
 
 	if (pid != monitored_pid)
 		return 0;
 
-	storage = bpf_task_storage_get(&task_storage_map,
-				       bpf_get_current_task_btf(), 0, 0);
-	if (storage) {
-		/* Don't let an executable delete itself */
-		is_self_unlink = storage->exec_inode == victim->d_inode;
-		if (is_self_unlink)
-			return -EPERM;
-	}
+	task = bpf_get_current_task_btf();
+	if (!task)
+		return 0;
 
-	return 0;
+	task_storage_result = -1;
+
+	storage = bpf_task_storage_get(&task_storage_map, task, 0, 0);
+	if (!storage)
+		return 0;
+
+	/* Don't let an executable delete itself */
+	is_self_unlink = storage->exec_inode == victim->d_inode;
+
+	storage = bpf_task_storage_get(&task_storage_map2, task, 0,
+				       BPF_LOCAL_STORAGE_GET_F_CREATE);
+	if (!storage || storage->value)
+		return 0;
+
+	if (bpf_task_storage_delete(&task_storage_map, task))
+		return 0;
+
+	/* Ensure that the task_storage_map is disconnected from the storage.
+	 * The storage memory should not be freed back to the
+	 * bpf_mem_alloc.
+	 */
+	local_storage = task->bpf_storage;
+	if (!local_storage || local_storage->smap)
+		return 0;
+
+	task_storage_result = 0;
+
+	return is_self_unlink ? -EPERM : 0;
 }
 
 SEC("lsm.s/inode_rename")
···
 	if (bpf_sk_storage_delete(&sk_storage_map, sock->sk))
 		return 0;
 
-	/* Ensure that the sk_storage_map is disconnected from the storage.
-	 * The storage memory should not be freed back to the
-	 * bpf_mem_alloc of the sk_bpf_storage_map because
-	 * sk_bpf_storage_map may have been gone.
-	 */
+	/* Ensure that the sk_storage_map is disconnected from the storage. */
 	if (!sock->sk->sk_bpf_storage || sock->sk->sk_bpf_storage->smap)
 		return 0;