binderfs_test.c

  1// SPDX-License-Identifier: GPL-2.0
  2
  3#define _GNU_SOURCE
  4#include <errno.h>
  5#include <fcntl.h>
  6#include <pthread.h>
  7#include <sched.h>
  8#include <stdbool.h>
  9#include <stdio.h>
 10#include <stdlib.h>
 11#include <string.h>
 12#include <sys/fsuid.h>
 13#include <sys/ioctl.h>
 14#include <sys/mount.h>
 15#include <sys/socket.h>
 16#include <sys/stat.h>
 17#include <sys/sysinfo.h>
 18#include <sys/types.h>
 19#include <sys/wait.h>
 20#include <unistd.h>
 21#include <linux/android/binder.h>
 22#include <linux/android/binderfs.h>
 23
 24#include "kselftest_harness.h"
 25
 26#define DEFAULT_THREADS 4
 27
 28#define PTR_TO_INT(p) ((int)((intptr_t)(p)))
 29#define INT_TO_PTR(u) ((void *)((intptr_t)(u)))
 30
 31#define close_prot_errno_disarm(fd) \
 32	if (fd >= 0) {              \
 33		int _e_ = errno;    \
 34		close(fd);          \
 35		errno = _e_;        \
 36		fd = -EBADF;        \
 37	}
 38
 39static void change_mountns(struct __test_metadata *_metadata)
 40{
 41	int ret;
 42
 43	ret = unshare(CLONE_NEWNS);
 44	ASSERT_EQ(ret, 0) {
 45		TH_LOG("%s - Failed to unshare mount namespace",
 46			strerror(errno));
 47	}
 48
 49	ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0);
 50	ASSERT_EQ(ret, 0) {
 51		TH_LOG("%s - Failed to mount / as private",
 52			strerror(errno));
 53	}
 54}
 55
 56static int __do_binderfs_test(struct __test_metadata *_metadata)
 57{
 58	int fd, ret, saved_errno, result = 1;
 59	size_t len;
 60	struct binderfs_device device = { 0 };
 61	struct binder_version version = { 0 };
 62	char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX",
 63		device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME];
 64	static const char * const binder_features[] = {
 65		"oneway_spam_detection",
 66		"extended_error",
 67		"freeze_notification",
 68		"transaction_report",
 69	};
 70
 71	change_mountns(_metadata);
 72
 73	EXPECT_NE(mkdtemp(binderfs_mntpt), NULL) {
 74		TH_LOG("%s - Failed to create binderfs mountpoint",
 75			strerror(errno));
 76		goto out;
 77	}
 78
 79	ret = mount(NULL, binderfs_mntpt, "binder", 0, 0);
 80	EXPECT_EQ(ret, 0) {
 81		if (errno == ENODEV)
 82			SKIP(goto out, "binderfs missing");
 83		TH_LOG("%s - Failed to mount binderfs", strerror(errno));
 84		goto rmdir;
 85	}
 86
 87	/* success: binderfs mounted */
 88
 89	memcpy(device.name, "my-binder", strlen("my-binder"));
 90
 91	snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt);
 92	fd = open(device_path, O_RDONLY | O_CLOEXEC);
 93	EXPECT_GE(fd, 0) {
 94		TH_LOG("%s - Failed to open binder-control device",
 95			strerror(errno));
 96		goto umount;
 97	}
 98
 99	ret = ioctl(fd, BINDER_CTL_ADD, &device);
100	saved_errno = errno;
101	close(fd);
102	errno = saved_errno;
103	EXPECT_GE(ret, 0) {
104		TH_LOG("%s - Failed to allocate new binder device",
105			strerror(errno));
106		goto umount;
107	}
108
109	TH_LOG("Allocated new binder device with major %d, minor %d, and name %s",
110		device.major, device.minor, device.name);
111
112	/* success: binder device allocation */
113
114	snprintf(device_path, sizeof(device_path), "%s/my-binder", binderfs_mntpt);
115	fd = open(device_path, O_CLOEXEC | O_RDONLY);
116	EXPECT_GE(fd, 0) {
117		TH_LOG("%s - Failed to open my-binder device",
118			strerror(errno));
119		goto umount;
120	}
121
122	ret = ioctl(fd, BINDER_VERSION, &version);
123	saved_errno = errno;
124	close(fd);
125	errno = saved_errno;
126	EXPECT_GE(ret, 0) {
127		TH_LOG("%s - Failed to open perform BINDER_VERSION request",
128			strerror(errno));
129		goto umount;
130	}
131
132	TH_LOG("Detected binder version: %d", version.protocol_version);
133
134	/* success: binder transaction with binderfs binder device */
135
136	ret = unlink(device_path);
137	EXPECT_EQ(ret, 0) {
138		TH_LOG("%s - Failed to delete binder device",
139			strerror(errno));
140		goto umount;
141	}
142
143	/* success: binder device removal */
144
145	snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt);
146	ret = unlink(device_path);
147	EXPECT_NE(ret, 0) {
148		TH_LOG("Managed to delete binder-control device");
149		goto umount;
150	}
151	EXPECT_EQ(errno, EPERM) {
152		TH_LOG("%s - Failed to delete binder-control device but exited with unexpected error code",
153			strerror(errno));
154		goto umount;
155	}
156
157	/* success: binder-control device removal failed as expected */
158
159	for (int i = 0; i < ARRAY_SIZE(binder_features); i++) {
160		snprintf(device_path, sizeof(device_path), "%s/features/%s",
161			 binderfs_mntpt, binder_features[i]);
162		fd = open(device_path, O_CLOEXEC | O_RDONLY);
163		EXPECT_GE(fd, 0) {
164			TH_LOG("%s - Failed to open binder feature: %s",
165				strerror(errno), binder_features[i]);
166			goto umount;
167		}
168		close(fd);
169	}
170
171	/* success: binder feature files found */
172	result = 0;
173
174umount:
175	ret = umount2(binderfs_mntpt, MNT_DETACH);
176	EXPECT_EQ(ret, 0) {
177		TH_LOG("%s - Failed to unmount binderfs", strerror(errno));
178	}
179rmdir:
180	ret = rmdir(binderfs_mntpt);
181	EXPECT_EQ(ret, 0) {
182		TH_LOG("%s - Failed to rmdir binderfs mount", strerror(errno));
183	}
184out:
185	return result;
186}
187
188static int wait_for_pid(pid_t pid)
189{
190	int status, ret;
191
192again:
193	ret = waitpid(pid, &status, 0);
194	if (ret == -1) {
195		if (errno == EINTR)
196			goto again;
197
198		return -1;
199	}
200
201	if (!WIFEXITED(status))
202		return -1;
203
204	return WEXITSTATUS(status);
205}
206
207static int setid_userns_root(void)
208{
209	if (setuid(0))
210		return -1;
211	if (setgid(0))
212		return -1;
213
214	setfsuid(0);
215	setfsgid(0);
216
217	return 0;
218}
219
220enum idmap_type {
221	UID_MAP,
222	GID_MAP,
223};
224
225static ssize_t read_nointr(int fd, void *buf, size_t count)
226{
227	ssize_t ret;
228again:
229	ret = read(fd, buf, count);
230	if (ret < 0 && errno == EINTR)
231		goto again;
232
233	return ret;
234}
235
236static ssize_t write_nointr(int fd, const void *buf, size_t count)
237{
238	ssize_t ret;
239again:
240	ret = write(fd, buf, count);
241	if (ret < 0 && errno == EINTR)
242		goto again;
243
244	return ret;
245}
246
247static int write_id_mapping(enum idmap_type type, pid_t pid, const char *buf,
248			    size_t buf_size)
249{
250	int fd;
251	int ret;
252	char path[4096];
253
254	if (type == GID_MAP) {
255		int setgroups_fd;
256
257		snprintf(path, sizeof(path), "/proc/%d/setgroups", pid);
258		setgroups_fd = open(path, O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
259		if (setgroups_fd < 0 && errno != ENOENT)
260			return -1;
261
262		if (setgroups_fd >= 0) {
263			ret = write_nointr(setgroups_fd, "deny", sizeof("deny") - 1);
264			close_prot_errno_disarm(setgroups_fd);
265			if (ret != sizeof("deny") - 1)
266				return -1;
267		}
268	}
269
270	switch (type) {
271	case UID_MAP:
272		ret = snprintf(path, sizeof(path), "/proc/%d/uid_map", pid);
273		break;
274	case GID_MAP:
275		ret = snprintf(path, sizeof(path), "/proc/%d/gid_map", pid);
276		break;
277	default:
278		return -1;
279	}
280	if (ret < 0 || ret >= sizeof(path))
281		return -E2BIG;
282
283	fd = open(path, O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
284	if (fd < 0)
285		return -1;
286
287	ret = write_nointr(fd, buf, buf_size);
288	close_prot_errno_disarm(fd);
289	if (ret != buf_size)
290		return -1;
291
292	return 0;
293}
294
295static void change_userns(struct __test_metadata *_metadata, int syncfds[2])
296{
297	int ret;
298	char buf;
299
300	close_prot_errno_disarm(syncfds[1]);
301
302	ret = unshare(CLONE_NEWUSER);
303	ASSERT_EQ(ret, 0) {
304		TH_LOG("%s - Failed to unshare user namespace",
305			strerror(errno));
306	}
307
308	ret = write_nointr(syncfds[0], "1", 1);
309	ASSERT_EQ(ret, 1) {
310		TH_LOG("write_nointr() failed");
311	}
312
313	ret = read_nointr(syncfds[0], &buf, 1);
314	ASSERT_EQ(ret, 1) {
315		TH_LOG("read_nointr() failed");
316	}
317
318	close_prot_errno_disarm(syncfds[0]);
319
320	ASSERT_EQ(setid_userns_root(), 0) {
321		TH_LOG("setid_userns_root() failed");
322	}
323}
324
325static void change_idmaps(struct __test_metadata *_metadata, int syncfds[2], pid_t pid)
326{
327	int ret;
328	char buf;
329	char id_map[4096];
330
331	close_prot_errno_disarm(syncfds[0]);
332
333	ret = read_nointr(syncfds[1], &buf, 1);
334	ASSERT_EQ(ret, 1) {
335		TH_LOG("read_nointr() failed");
336	}
337
338	snprintf(id_map, sizeof(id_map), "0 %d 1\n", getuid());
339	ret = write_id_mapping(UID_MAP, pid, id_map, strlen(id_map));
340	ASSERT_EQ(ret, 0) {
341		TH_LOG("write_id_mapping(UID_MAP) failed");
342	}
343
344	snprintf(id_map, sizeof(id_map), "0 %d 1\n", getgid());
345	ret = write_id_mapping(GID_MAP, pid, id_map, strlen(id_map));
346	ASSERT_EQ(ret, 0) {
347		TH_LOG("write_id_mapping(GID_MAP) failed");
348	}
349
350	ret = write_nointr(syncfds[1], "1", 1);
351	ASSERT_EQ(ret, 1) {
352		TH_LOG("write_nointr() failed");
353	}
354
355	close_prot_errno_disarm(syncfds[1]);
356}
357
358struct __test_metadata *_thread_metadata;
359static void *binder_version_thread(void *data)
360{
361	struct __test_metadata *_metadata = _thread_metadata;
362	int fd = PTR_TO_INT(data);
363	struct binder_version version = { 0 };
364	int ret;
365
366	ret = ioctl(fd, BINDER_VERSION, &version);
367	if (ret < 0)
368		TH_LOG("%s - Failed to open perform BINDER_VERSION request\n",
369			strerror(errno));
370
371	pthread_exit(data);
372}
373
374/*
375 * Regression test:
376 * 2669b8b0c798 ("binder: prevent UAF for binderfs devices")
377 * f0fe2c0f050d ("binder: prevent UAF for binderfs devices II")
378 * 211b64e4b5b6 ("binderfs: use refcount for binder control devices too")
379 */
380TEST(binderfs_stress)
381{
382	int fds[1000];
383	int syncfds[2];
384	pid_t pid;
385	int fd, ret;
386	size_t len;
387	struct binderfs_device device = { 0 };
388	char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX",
389		device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME];
390
391	ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, syncfds);
392	ASSERT_EQ(ret, 0) {
393		TH_LOG("%s - Failed to create socket pair", strerror(errno));
394	}
395
396	pid = fork();
397	ASSERT_GE(pid, 0) {
398		TH_LOG("%s - Failed to fork", strerror(errno));
399		close_prot_errno_disarm(syncfds[0]);
400		close_prot_errno_disarm(syncfds[1]);
401	}
402
403	if (pid == 0) {
404		int i, j, k, nthreads;
405		pthread_attr_t attr;
406		pthread_t threads[DEFAULT_THREADS];
407		change_userns(_metadata, syncfds);
408		change_mountns(_metadata);
409
410		ASSERT_NE(mkdtemp(binderfs_mntpt), NULL) {
411			TH_LOG("%s - Failed to create binderfs mountpoint",
412				strerror(errno));
413		}
414
415		ret = mount(NULL, binderfs_mntpt, "binder", 0, 0);
416		ASSERT_EQ(ret, 0) {
417			TH_LOG("%s - Failed to mount binderfs, check if CONFIG_ANDROID_BINDERFS is enabled in the running kernel",
418				strerror(errno));
419		}
420
421		for (int i = 0; i < ARRAY_SIZE(fds); i++) {
422
423			snprintf(device_path, sizeof(device_path),
424				 "%s/binder-control", binderfs_mntpt);
425			fd = open(device_path, O_RDONLY | O_CLOEXEC);
426			ASSERT_GE(fd, 0) {
427				TH_LOG("%s - Failed to open binder-control device",
428					strerror(errno));
429			}
430
431			memset(&device, 0, sizeof(device));
432			snprintf(device.name, sizeof(device.name), "%d", i);
433			ret = ioctl(fd, BINDER_CTL_ADD, &device);
434			close_prot_errno_disarm(fd);
435			ASSERT_EQ(ret, 0) {
436				TH_LOG("%s - Failed to allocate new binder device",
437					strerror(errno));
438			}
439
440			snprintf(device_path, sizeof(device_path), "%s/%d",
441				 binderfs_mntpt, i);
442			fds[i] = open(device_path, O_RDONLY | O_CLOEXEC);
443			ASSERT_GE(fds[i], 0) {
444				TH_LOG("%s - Failed to open binder device", strerror(errno));
445			}
446		}
447
448		ret = umount2(binderfs_mntpt, MNT_DETACH);
449		ASSERT_EQ(ret, 0) {
450			TH_LOG("%s - Failed to unmount binderfs", strerror(errno));
451			rmdir(binderfs_mntpt);
452		}
453
454		nthreads = get_nprocs_conf();
455		if (nthreads > DEFAULT_THREADS)
456			nthreads = DEFAULT_THREADS;
457
458		_thread_metadata = _metadata;
459		pthread_attr_init(&attr);
460		for (k = 0; k < ARRAY_SIZE(fds); k++) {
461			for (i = 0; i < nthreads; i++) {
462				ret = pthread_create(&threads[i], &attr, binder_version_thread, INT_TO_PTR(fds[k]));
463				if (ret) {
464					TH_LOG("%s - Failed to create thread %d",
465						strerror(errno), i);
466					break;
467				}
468			}
469
470			for (j = 0; j < i; j++) {
471				void *fdptr = NULL;
472
473				ret = pthread_join(threads[j], &fdptr);
474				if (ret)
475					TH_LOG("%s - Failed to join thread %d for fd %d",
476						strerror(errno), j, PTR_TO_INT(fdptr));
477			}
478		}
479		pthread_attr_destroy(&attr);
480
481		for (k = 0; k < ARRAY_SIZE(fds); k++)
482			close(fds[k]);
483
484		exit(EXIT_SUCCESS);
485	}
486
487	change_idmaps(_metadata, syncfds, pid);
488
489	ret = wait_for_pid(pid);
490	ASSERT_EQ(ret, 0) {
491		TH_LOG("wait_for_pid() failed");
492	}
493}
494
495TEST(binderfs_test_privileged)
496{
497	if (geteuid() != 0)
498		SKIP(return, "Tests are not run as root. Skipping privileged tests");
499
500	if (__do_binderfs_test(_metadata))
501		SKIP(return, "The Android binderfs filesystem is not available");
502}
503
504TEST(binderfs_test_unprivileged)
505{
506	int ret;
507	int syncfds[2];
508	pid_t pid;
509
510	ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, syncfds);
511	ASSERT_EQ(ret, 0) {
512		TH_LOG("%s - Failed to create socket pair", strerror(errno));
513	}
514
515	pid = fork();
516	ASSERT_GE(pid, 0) {
517		close_prot_errno_disarm(syncfds[0]);
518		close_prot_errno_disarm(syncfds[1]);
519		TH_LOG("%s - Failed to fork", strerror(errno));
520	}
521
522	if (pid == 0) {
523		change_userns(_metadata, syncfds);
524		if (__do_binderfs_test(_metadata))
525			exit(2);
526		exit(EXIT_SUCCESS);
527	}
528
529	change_idmaps(_metadata, syncfds, pid);
530
531	ret = wait_for_pid(pid);
532	if (ret) {
533		if (ret == 2)
534			SKIP(return, "The Android binderfs filesystem is not available");
535		ASSERT_EQ(ret, 0) {
536			TH_LOG("wait_for_pid() failed");
537		}
538	}
539}
540
541TEST_HARNESS_MAIN