linux/tools/testing/selftests/filesystems/binderfs/binderfs_test.c

// SPDX-License-Identifier: GPL-2.0

#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <sched.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/fsuid.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/sysinfo.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <linux/android/binder.h>
#include <linux/android/binderfs.h>

#include "../../kselftest.h"
#include "../../kselftest_harness.h"

#define DEFAULT_THREADS 4

#define PTR_TO_INT(p) ((int)((intptr_t)(p)))
#define INT_TO_PTR(u) ((void *)((intptr_t)(u)))

#define close_prot_errno_disarm(fd) \
	if (fd >= 0) {              \
		int _e_ = errno;    \
		close(fd);          \
		errno = _e_;        \
		fd = -EBADF;        \
	}

#define log_exit(format, ...)                                                  \
	({                                                                     \
		fprintf(stderr, format "\n", ##__VA_ARGS__);                   \
		exit(EXIT_FAILURE);                                            \
	})

static void change_mountns(void)
{
	int ret;

	ret = unshare(CLONE_NEWNS);
	if (ret < 0)
		ksft_exit_fail_msg("%s - Failed to unshare mount namespace\n",
				   strerror(errno));

	ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0);
	if (ret < 0)
		ksft_exit_fail_msg("%s - Failed to mount / as private\n",
				   strerror(errno));
}

static void rmdir_protect_errno(const char *dir)
{
	int saved_errno = errno;
	(void)rmdir(dir);
	errno = saved_errno;
}

static int __do_binderfs_test(void)
{
	int fd, ret, saved_errno;
	size_t len;
	ssize_t wret;
	struct binderfs_device device = { 0 };
	struct binder_version version = { 0 };
	char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX",
		device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME];

	change_mountns();

	if (!mkdtemp(binderfs_mntpt))
		ksft_exit_fail_msg(
			"%s - Failed to create binderfs mountpoint\n",
			strerror(errno));

	ret = mount(NULL, binderfs_mntpt, "binder", 0, 0);
	if (ret < 0) {
		if (errno != ENODEV)
			ksft_exit_fail_msg("%s - Failed to mount binderfs\n",
					   strerror(errno));

		rmdir_protect_errno(binderfs_mntpt);
		return 1;
	}

	/* binderfs mount test passed */
	ksft_inc_pass_cnt();

	memcpy(device.name, "my-binder", strlen("my-binder"));

	snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt);
	fd = open(device_path, O_RDONLY | O_CLOEXEC);
	if (fd < 0)
		ksft_exit_fail_msg(
			"%s - Failed to open binder-control device\n",
			strerror(errno));

	ret = ioctl(fd, BINDER_CTL_ADD, &device);
	saved_errno = errno;
	close(fd);
	errno = saved_errno;
	if (ret < 0) {
		rmdir_protect_errno(binderfs_mntpt);
		ksft_exit_fail_msg(
			"%s - Failed to allocate new binder device\n",
			strerror(errno));
	}

	ksft_print_msg(
		"Allocated new binder device with major %d, minor %d, and name %s\n",
		device.major, device.minor, device.name);

	/* binder device allocation test passed */
	ksft_inc_pass_cnt();

	snprintf(device_path, sizeof(device_path), "%s/my-binder", binderfs_mntpt);
	fd = open(device_path, O_CLOEXEC | O_RDONLY);
	if (fd < 0) {
		rmdir_protect_errno(binderfs_mntpt);
		ksft_exit_fail_msg("%s - Failed to open my-binder device\n",
				   strerror(errno));
	}

	ret = ioctl(fd, BINDER_VERSION, &version);
	saved_errno = errno;
	close(fd);
	errno = saved_errno;
	if (ret < 0) {
		rmdir_protect_errno(binderfs_mntpt);
		ksft_exit_fail_msg(
			"%s - Failed to open perform BINDER_VERSION request\n",
			strerror(errno));
	}

	ksft_print_msg("Detected binder version: %d\n",
		       version.protocol_version);

	/* binder transaction with binderfs binder device passed */
	ksft_inc_pass_cnt();

	ret = unlink(device_path);
	if (ret < 0) {
		rmdir_protect_errno(binderfs_mntpt);
		ksft_exit_fail_msg("%s - Failed to delete binder device\n",
				   strerror(errno));
	}

	/* binder device removal passed */
	ksft_inc_pass_cnt();

	snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt);
	ret = unlink(device_path);
	if (!ret) {
		rmdir_protect_errno(binderfs_mntpt);
		ksft_exit_fail_msg("Managed to delete binder-control device\n");
	} else if (errno != EPERM) {
		rmdir_protect_errno(binderfs_mntpt);
		ksft_exit_fail_msg(
			"%s - Failed to delete binder-control device but exited with unexpected error code\n",
			strerror(errno));
	}

	/* binder-control device removal failed as expected */
	ksft_inc_xfail_cnt();

on_error:
	ret = umount2(binderfs_mntpt, MNT_DETACH);
	rmdir_protect_errno(binderfs_mntpt);
	if (ret < 0)
		ksft_exit_fail_msg("%s - Failed to unmount binderfs\n",
				   strerror(errno));

	/* binderfs unmount test passed */
	ksft_inc_pass_cnt();
	return 0;
}

static int wait_for_pid(pid_t pid)
{
	int status, ret;

again:
	ret = waitpid(pid, &status, 0);
	if (ret == -1) {
		if (errno == EINTR)
			goto again;

		return -1;
	}

	if (!WIFEXITED(status))
		return -1;

	return WEXITSTATUS(status);
}

static int setid_userns_root(void)
{
	if (setuid(0))
		return -1;
	if (setgid(0))
		return -1;

	setfsuid(0);
	setfsgid(0);

	return 0;
}

enum idmap_type {
	UID_MAP,
	GID_MAP,
};

static ssize_t read_nointr(int fd, void *buf, size_t count)
{
	ssize_t ret;
again:
	ret = read(fd, buf, count);
	if (ret < 0 && errno == EINTR)
		goto again;

	return ret;
}

static ssize_t write_nointr(int fd, const void *buf, size_t count)
{
	ssize_t ret;
again:
	ret = write(fd, buf, count);
	if (ret < 0 && errno == EINTR)
		goto again;

	return ret;
}

static int write_id_mapping(enum idmap_type type, pid_t pid, const char *buf,
			    size_t buf_size)
{
	int fd;
	int ret;
	char path[4096];

	if (type == GID_MAP) {
		int setgroups_fd;

		snprintf(path, sizeof(path), "/proc/%d/setgroups", pid);
		setgroups_fd = open(path, O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
		if (setgroups_fd < 0 && errno != ENOENT)
			return -1;

		if (setgroups_fd >= 0) {
			ret = write_nointr(setgroups_fd, "deny", sizeof("deny") - 1);
			close_prot_errno_disarm(setgroups_fd);
			if (ret != sizeof("deny") - 1)
				return -1;
		}
	}

	switch (type) {
	case UID_MAP:
		ret = snprintf(path, sizeof(path), "/proc/%d/uid_map", pid);
		break;
	case GID_MAP:
		ret = snprintf(path, sizeof(path), "/proc/%d/gid_map", pid);
		break;
	default:
		return -1;
	}
	if (ret < 0 || ret >= sizeof(path))
		return -E2BIG;

	fd = open(path, O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
	if (fd < 0)
		return -1;

	ret = write_nointr(fd, buf, buf_size);
	close_prot_errno_disarm(fd);
	if (ret != buf_size)
		return -1;

	return 0;
}

static void change_userns(int syncfds[2])
{
	int ret;
	char buf;

	close_prot_errno_disarm(syncfds[1]);

	ret = unshare(CLONE_NEWUSER);
	if (ret < 0)
		ksft_exit_fail_msg("%s - Failed to unshare user namespace\n",
				   strerror(errno));

	ret = write_nointr(syncfds[0], "1", 1);
	if (ret != 1)
		ksft_exit_fail_msg("write_nointr() failed\n");

	ret = read_nointr(syncfds[0], &buf, 1);
	if (ret != 1)
		ksft_exit_fail_msg("read_nointr() failed\n");

	close_prot_errno_disarm(syncfds[0]);

	if (setid_userns_root())
		ksft_exit_fail_msg("setid_userns_root() failed");
}

static void change_idmaps(int syncfds[2], pid_t pid)
{
	int ret;
	char buf;
	char id_map[4096];

	close_prot_errno_disarm(syncfds[0]);

	ret = read_nointr(syncfds[1], &buf, 1);
	if (ret != 1)
		ksft_exit_fail_msg("read_nointr() failed\n");

	snprintf(id_map, sizeof(id_map), "0 %d 1\n", getuid());
	ret = write_id_mapping(UID_MAP, pid, id_map, strlen(id_map));
	if (ret)
		ksft_exit_fail_msg("write_id_mapping(UID_MAP) failed");

	snprintf(id_map, sizeof(id_map), "0 %d 1\n", getgid());
	ret = write_id_mapping(GID_MAP, pid, id_map, strlen(id_map));
	if (ret)
		ksft_exit_fail_msg("write_id_mapping(GID_MAP) failed");

	ret = write_nointr(syncfds[1], "1", 1);
	if (ret != 1)
		ksft_exit_fail_msg("write_nointr() failed");

	close_prot_errno_disarm(syncfds[1]);
}

static void *binder_version_thread(void *data)
{
	int fd = PTR_TO_INT(data);
	struct binder_version version = { 0 };
	int ret;

	ret = ioctl(fd, BINDER_VERSION, &version);
	if (ret < 0)
		ksft_print_msg("%s - Failed to open perform BINDER_VERSION request\n", strerror(errno));

	pthread_exit(data);
}

/*
 * Regression test:
 * 2669b8b0c798 ("binder: prevent UAF for binderfs devices")
 * f0fe2c0f050d ("binder: prevent UAF for binderfs devices II")
 * 211b64e4b5b6 ("binderfs: use refcount for binder control devices too")
 */
TEST(binderfs_stress)
{
	int fds[1000];
	int syncfds[2];
	pid_t pid;
	int fd, ret;
	size_t len;
	struct binderfs_device device = { 0 };
	char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX",
		device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME];

	ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, syncfds);
	if (ret < 0)
		ksft_exit_fail_msg("%s - Failed to create socket pair", strerror(errno));

	pid = fork();
	if (pid < 0) {
		close_prot_errno_disarm(syncfds[0]);
		close_prot_errno_disarm(syncfds[1]);
		ksft_exit_fail_msg("%s - Failed to fork", strerror(errno));
	}

	if (pid == 0) {
		int i, j, k, nthreads;
		pthread_attr_t attr;
		pthread_t threads[DEFAULT_THREADS];
		change_userns(syncfds);
		change_mountns();

		if (!mkdtemp(binderfs_mntpt))
			log_exit("%s - Failed to create binderfs mountpoint\n",
				 strerror(errno));

		ret = mount(NULL, binderfs_mntpt, "binder", 0, 0);
		if (ret < 0)
			log_exit("%s - Failed to mount binderfs\n", strerror(errno));

		for (int i = 0; i < ARRAY_SIZE(fds); i++) {

			snprintf(device_path, sizeof(device_path),
				 "%s/binder-control", binderfs_mntpt);
			fd = open(device_path, O_RDONLY | O_CLOEXEC);
			if (fd < 0)
				log_exit("%s - Failed to open binder-control device\n", strerror(errno));

			memset(&device, 0, sizeof(device));
			snprintf(device.name, sizeof(device.name), "%d", i);
			ret = ioctl(fd, BINDER_CTL_ADD, &device);
			close_prot_errno_disarm(fd);
			if (ret < 0)
				log_exit("%s - Failed to allocate new binder device\n", strerror(errno));

			snprintf(device_path, sizeof(device_path), "%s/%d",
				 binderfs_mntpt, i);
			fds[i] = open(device_path, O_RDONLY | O_CLOEXEC);
			if (fds[i] < 0)
				log_exit("%s - Failed to open binder device\n", strerror(errno));
		}

		ret = umount2(binderfs_mntpt, MNT_DETACH);
		rmdir_protect_errno(binderfs_mntpt);
		if (ret < 0)
			log_exit("%s - Failed to unmount binderfs\n", strerror(errno));

		nthreads = get_nprocs_conf();
		if (nthreads > DEFAULT_THREADS)
			nthreads = DEFAULT_THREADS;

		pthread_attr_init(&attr);
		for (k = 0; k < ARRAY_SIZE(fds); k++) {
			for (i = 0; i < nthreads; i++) {
				ret = pthread_create(&threads[i], &attr, binder_version_thread, INT_TO_PTR(fds[k]));
				if (ret) {
					ksft_print_msg("%s - Failed to create thread %d\n", strerror(errno), i);
					break;
				}
			}

			for (j = 0; j < i; j++) {
				void *fdptr = NULL;

				ret = pthread_join(threads[j], &fdptr);
				if (ret)
					ksft_print_msg("%s - Failed to join thread %d for fd %d\n", strerror(errno), j, PTR_TO_INT(fdptr));
			}
		}
		pthread_attr_destroy(&attr);

		for (k = 0; k < ARRAY_SIZE(fds); k++)
			close(fds[k]);

		exit(EXIT_SUCCESS);
	}

	change_idmaps(syncfds, pid);

	ret = wait_for_pid(pid);
	if (ret)
		ksft_exit_fail_msg("wait_for_pid() failed");
}

TEST(binderfs_test_privileged)
{
	if (geteuid() != 0)
		XFAIL(return, "Tests are not run as root. Skipping privileged tests");

	if (__do_binderfs_test() == 1)
		XFAIL(return, "The Android binderfs filesystem is not available");
}

TEST(binderfs_test_unprivileged)
{
	int ret;
	int syncfds[2];
	pid_t pid;

	ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, syncfds);
	if (ret < 0)
		ksft_exit_fail_msg("%s - Failed to create socket pair", strerror(errno));

	pid = fork();
	if (pid < 0) {
		close_prot_errno_disarm(syncfds[0]);
		close_prot_errno_disarm(syncfds[1]);
		ksft_exit_fail_msg("%s - Failed to fork", strerror(errno));
	}

	if (pid == 0) {
		change_userns(syncfds);
		if (__do_binderfs_test() == 1)
			exit(2);
		exit(EXIT_SUCCESS);
	}

	change_idmaps(syncfds, pid);

	ret = wait_for_pid(pid);
	if (ret) {
		if (ret == 2)
			XFAIL(return, "The Android binderfs filesystem is not available");
		else
			ksft_exit_fail_msg("wait_for_pid() failed");
	}
}

TEST_HARNESS_MAIN