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

39
static 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

56
static 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

174
umount:
175
	ret = umount2(binderfs_mntpt, MNT_DETACH);
176
	EXPECT_EQ(ret, 0) {
177
		TH_LOG("%s - Failed to unmount binderfs", strerror(errno));
178
	}
179
rmdir:
180
	ret = rmdir(binderfs_mntpt);
181
	EXPECT_EQ(ret, 0) {
182
		TH_LOG("%s - Failed to rmdir binderfs mount", strerror(errno));
183
	}
184
out:
185
	return result;
186
}
187

188
static int wait_for_pid(pid_t pid)
189
{
190
	int status, ret;
191

192
again:
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

207
static 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

220
enum idmap_type {
221
	UID_MAP,
222
	GID_MAP,
223
};
224

225
static ssize_t read_nointr(int fd, void *buf, size_t count)
226
{
227
	ssize_t ret;
228
again:
229
	ret = read(fd, buf, count);
230
	if (ret < 0 && errno == EINTR)
231
		goto again;
232

233
	return ret;
234
}
235

236
static ssize_t write_nointr(int fd, const void *buf, size_t count)
237
{
238
	ssize_t ret;
239
again:
240
	ret = write(fd, buf, count);
241
	if (ret < 0 && errno == EINTR)
242
		goto again;
243

244
	return ret;
245
}
246

247
static 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

295
static 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

325
static 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

358
struct __test_metadata *_thread_metadata;
359
static 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
 */
380
TEST(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

495
TEST(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

504
TEST(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

541
TEST_HARNESS_MAIN
542

543