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