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0001 // SPDX-License-Identifier: GPL-2.0
0002 
0003 #define _GNU_SOURCE
0004 #include <errno.h>
0005 #include <fcntl.h>
0006 #include <pthread.h>
0007 #include <sched.h>
0008 #include <stdbool.h>
0009 #include <stdio.h>
0010 #include <stdlib.h>
0011 #include <string.h>
0012 #include <sys/fsuid.h>
0013 #include <sys/ioctl.h>
0014 #include <sys/mount.h>
0015 #include <sys/socket.h>
0016 #include <sys/stat.h>
0017 #include <sys/sysinfo.h>
0018 #include <sys/types.h>
0019 #include <sys/wait.h>
0020 #include <unistd.h>
0021 #include <linux/android/binder.h>
0022 #include <linux/android/binderfs.h>
0023 
0024 #include "../../kselftest_harness.h"
0025 
0026 #define DEFAULT_THREADS 4
0027 
0028 #define PTR_TO_INT(p) ((int)((intptr_t)(p)))
0029 #define INT_TO_PTR(u) ((void *)((intptr_t)(u)))
0030 
0031 #define close_prot_errno_disarm(fd) \
0032     if (fd >= 0) {              \
0033         int _e_ = errno;    \
0034         close(fd);          \
0035         errno = _e_;        \
0036         fd = -EBADF;        \
0037     }
0038 
0039 static void change_mountns(struct __test_metadata *_metadata)
0040 {
0041     int ret;
0042 
0043     ret = unshare(CLONE_NEWNS);
0044     ASSERT_EQ(ret, 0) {
0045         TH_LOG("%s - Failed to unshare mount namespace",
0046             strerror(errno));
0047     }
0048 
0049     ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0);
0050     ASSERT_EQ(ret, 0) {
0051         TH_LOG("%s - Failed to mount / as private",
0052             strerror(errno));
0053     }
0054 }
0055 
0056 static int __do_binderfs_test(struct __test_metadata *_metadata)
0057 {
0058     int fd, ret, saved_errno, result = 1;
0059     size_t len;
0060     ssize_t wret;
0061     struct binderfs_device device = { 0 };
0062     struct binder_version version = { 0 };
0063     char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX",
0064         device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME];
0065     static const char * const binder_features[] = {
0066         "oneway_spam_detection",
0067         "extended_error",
0068     };
0069 
0070     change_mountns(_metadata);
0071 
0072     EXPECT_NE(mkdtemp(binderfs_mntpt), NULL) {
0073         TH_LOG("%s - Failed to create binderfs mountpoint",
0074             strerror(errno));
0075         goto out;
0076     }
0077 
0078     ret = mount(NULL, binderfs_mntpt, "binder", 0, 0);
0079     EXPECT_EQ(ret, 0) {
0080         if (errno == ENODEV)
0081             SKIP(goto out, "binderfs missing");
0082         TH_LOG("%s - Failed to mount binderfs", strerror(errno));
0083         goto rmdir;
0084     }
0085 
0086     /* success: binderfs mounted */
0087 
0088     memcpy(device.name, "my-binder", strlen("my-binder"));
0089 
0090     snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt);
0091     fd = open(device_path, O_RDONLY | O_CLOEXEC);
0092     EXPECT_GE(fd, 0) {
0093         TH_LOG("%s - Failed to open binder-control device",
0094             strerror(errno));
0095         goto umount;
0096     }
0097 
0098     ret = ioctl(fd, BINDER_CTL_ADD, &device);
0099     saved_errno = errno;
0100     close(fd);
0101     errno = saved_errno;
0102     EXPECT_GE(ret, 0) {
0103         TH_LOG("%s - Failed to allocate new binder device",
0104             strerror(errno));
0105         goto umount;
0106     }
0107 
0108     TH_LOG("Allocated new binder device with major %d, minor %d, and name %s",
0109         device.major, device.minor, device.name);
0110 
0111     /* success: binder device allocation */
0112 
0113     snprintf(device_path, sizeof(device_path), "%s/my-binder", binderfs_mntpt);
0114     fd = open(device_path, O_CLOEXEC | O_RDONLY);
0115     EXPECT_GE(fd, 0) {
0116         TH_LOG("%s - Failed to open my-binder device",
0117             strerror(errno));
0118         goto umount;
0119     }
0120 
0121     ret = ioctl(fd, BINDER_VERSION, &version);
0122     saved_errno = errno;
0123     close(fd);
0124     errno = saved_errno;
0125     EXPECT_GE(ret, 0) {
0126         TH_LOG("%s - Failed to open perform BINDER_VERSION request",
0127             strerror(errno));
0128         goto umount;
0129     }
0130 
0131     TH_LOG("Detected binder version: %d", version.protocol_version);
0132 
0133     /* success: binder transaction with binderfs binder device */
0134 
0135     ret = unlink(device_path);
0136     EXPECT_EQ(ret, 0) {
0137         TH_LOG("%s - Failed to delete binder device",
0138             strerror(errno));
0139         goto umount;
0140     }
0141 
0142     /* success: binder device removal */
0143 
0144     snprintf(device_path, sizeof(device_path), "%s/binder-control", binderfs_mntpt);
0145     ret = unlink(device_path);
0146     EXPECT_NE(ret, 0) {
0147         TH_LOG("Managed to delete binder-control device");
0148         goto umount;
0149     }
0150     EXPECT_EQ(errno, EPERM) {
0151         TH_LOG("%s - Failed to delete binder-control device but exited with unexpected error code",
0152             strerror(errno));
0153         goto umount;
0154     }
0155 
0156     /* success: binder-control device removal failed as expected */
0157 
0158     for (int i = 0; i < ARRAY_SIZE(binder_features); i++) {
0159         snprintf(device_path, sizeof(device_path), "%s/features/%s",
0160              binderfs_mntpt, binder_features[i]);
0161         fd = open(device_path, O_CLOEXEC | O_RDONLY);
0162         EXPECT_GE(fd, 0) {
0163             TH_LOG("%s - Failed to open binder feature: %s",
0164                 strerror(errno), binder_features[i]);
0165             goto umount;
0166         }
0167         close(fd);
0168     }
0169 
0170     /* success: binder feature files found */
0171     result = 0;
0172 
0173 umount:
0174     ret = umount2(binderfs_mntpt, MNT_DETACH);
0175     EXPECT_EQ(ret, 0) {
0176         TH_LOG("%s - Failed to unmount binderfs", strerror(errno));
0177     }
0178 rmdir:
0179     ret = rmdir(binderfs_mntpt);
0180     EXPECT_EQ(ret, 0) {
0181         TH_LOG("%s - Failed to rmdir binderfs mount", strerror(errno));
0182     }
0183 out:
0184     return result;
0185 }
0186 
0187 static int wait_for_pid(pid_t pid)
0188 {
0189     int status, ret;
0190 
0191 again:
0192     ret = waitpid(pid, &status, 0);
0193     if (ret == -1) {
0194         if (errno == EINTR)
0195             goto again;
0196 
0197         return -1;
0198     }
0199 
0200     if (!WIFEXITED(status))
0201         return -1;
0202 
0203     return WEXITSTATUS(status);
0204 }
0205 
0206 static int setid_userns_root(void)
0207 {
0208     if (setuid(0))
0209         return -1;
0210     if (setgid(0))
0211         return -1;
0212 
0213     setfsuid(0);
0214     setfsgid(0);
0215 
0216     return 0;
0217 }
0218 
0219 enum idmap_type {
0220     UID_MAP,
0221     GID_MAP,
0222 };
0223 
0224 static ssize_t read_nointr(int fd, void *buf, size_t count)
0225 {
0226     ssize_t ret;
0227 again:
0228     ret = read(fd, buf, count);
0229     if (ret < 0 && errno == EINTR)
0230         goto again;
0231 
0232     return ret;
0233 }
0234 
0235 static ssize_t write_nointr(int fd, const void *buf, size_t count)
0236 {
0237     ssize_t ret;
0238 again:
0239     ret = write(fd, buf, count);
0240     if (ret < 0 && errno == EINTR)
0241         goto again;
0242 
0243     return ret;
0244 }
0245 
0246 static int write_id_mapping(enum idmap_type type, pid_t pid, const char *buf,
0247                 size_t buf_size)
0248 {
0249     int fd;
0250     int ret;
0251     char path[4096];
0252 
0253     if (type == GID_MAP) {
0254         int setgroups_fd;
0255 
0256         snprintf(path, sizeof(path), "/proc/%d/setgroups", pid);
0257         setgroups_fd = open(path, O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
0258         if (setgroups_fd < 0 && errno != ENOENT)
0259             return -1;
0260 
0261         if (setgroups_fd >= 0) {
0262             ret = write_nointr(setgroups_fd, "deny", sizeof("deny") - 1);
0263             close_prot_errno_disarm(setgroups_fd);
0264             if (ret != sizeof("deny") - 1)
0265                 return -1;
0266         }
0267     }
0268 
0269     switch (type) {
0270     case UID_MAP:
0271         ret = snprintf(path, sizeof(path), "/proc/%d/uid_map", pid);
0272         break;
0273     case GID_MAP:
0274         ret = snprintf(path, sizeof(path), "/proc/%d/gid_map", pid);
0275         break;
0276     default:
0277         return -1;
0278     }
0279     if (ret < 0 || ret >= sizeof(path))
0280         return -E2BIG;
0281 
0282     fd = open(path, O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
0283     if (fd < 0)
0284         return -1;
0285 
0286     ret = write_nointr(fd, buf, buf_size);
0287     close_prot_errno_disarm(fd);
0288     if (ret != buf_size)
0289         return -1;
0290 
0291     return 0;
0292 }
0293 
0294 static void change_userns(struct __test_metadata *_metadata, int syncfds[2])
0295 {
0296     int ret;
0297     char buf;
0298 
0299     close_prot_errno_disarm(syncfds[1]);
0300 
0301     ret = unshare(CLONE_NEWUSER);
0302     ASSERT_EQ(ret, 0) {
0303         TH_LOG("%s - Failed to unshare user namespace",
0304             strerror(errno));
0305     }
0306 
0307     ret = write_nointr(syncfds[0], "1", 1);
0308     ASSERT_EQ(ret, 1) {
0309         TH_LOG("write_nointr() failed");
0310     }
0311 
0312     ret = read_nointr(syncfds[0], &buf, 1);
0313     ASSERT_EQ(ret, 1) {
0314         TH_LOG("read_nointr() failed");
0315     }
0316 
0317     close_prot_errno_disarm(syncfds[0]);
0318 
0319     ASSERT_EQ(setid_userns_root(), 0) {
0320         TH_LOG("setid_userns_root() failed");
0321     }
0322 }
0323 
0324 static void change_idmaps(struct __test_metadata *_metadata, int syncfds[2], pid_t pid)
0325 {
0326     int ret;
0327     char buf;
0328     char id_map[4096];
0329 
0330     close_prot_errno_disarm(syncfds[0]);
0331 
0332     ret = read_nointr(syncfds[1], &buf, 1);
0333     ASSERT_EQ(ret, 1) {
0334         TH_LOG("read_nointr() failed");
0335     }
0336 
0337     snprintf(id_map, sizeof(id_map), "0 %d 1\n", getuid());
0338     ret = write_id_mapping(UID_MAP, pid, id_map, strlen(id_map));
0339     ASSERT_EQ(ret, 0) {
0340         TH_LOG("write_id_mapping(UID_MAP) failed");
0341     }
0342 
0343     snprintf(id_map, sizeof(id_map), "0 %d 1\n", getgid());
0344     ret = write_id_mapping(GID_MAP, pid, id_map, strlen(id_map));
0345     ASSERT_EQ(ret, 0) {
0346         TH_LOG("write_id_mapping(GID_MAP) failed");
0347     }
0348 
0349     ret = write_nointr(syncfds[1], "1", 1);
0350     ASSERT_EQ(ret, 1) {
0351         TH_LOG("write_nointr() failed");
0352     }
0353 
0354     close_prot_errno_disarm(syncfds[1]);
0355 }
0356 
0357 struct __test_metadata *_thread_metadata;
0358 static void *binder_version_thread(void *data)
0359 {
0360     struct __test_metadata *_metadata = _thread_metadata;
0361     int fd = PTR_TO_INT(data);
0362     struct binder_version version = { 0 };
0363     int ret;
0364 
0365     ret = ioctl(fd, BINDER_VERSION, &version);
0366     if (ret < 0)
0367         TH_LOG("%s - Failed to open perform BINDER_VERSION request\n",
0368             strerror(errno));
0369 
0370     pthread_exit(data);
0371 }
0372 
0373 /*
0374  * Regression test:
0375  * 2669b8b0c798 ("binder: prevent UAF for binderfs devices")
0376  * f0fe2c0f050d ("binder: prevent UAF for binderfs devices II")
0377  * 211b64e4b5b6 ("binderfs: use refcount for binder control devices too")
0378  */
0379 TEST(binderfs_stress)
0380 {
0381     int fds[1000];
0382     int syncfds[2];
0383     pid_t pid;
0384     int fd, ret;
0385     size_t len;
0386     struct binderfs_device device = { 0 };
0387     char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX",
0388         device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME];
0389 
0390     ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, syncfds);
0391     ASSERT_EQ(ret, 0) {
0392         TH_LOG("%s - Failed to create socket pair", strerror(errno));
0393     }
0394 
0395     pid = fork();
0396     ASSERT_GE(pid, 0) {
0397         TH_LOG("%s - Failed to fork", strerror(errno));
0398         close_prot_errno_disarm(syncfds[0]);
0399         close_prot_errno_disarm(syncfds[1]);
0400     }
0401 
0402     if (pid == 0) {
0403         int i, j, k, nthreads;
0404         pthread_attr_t attr;
0405         pthread_t threads[DEFAULT_THREADS];
0406         change_userns(_metadata, syncfds);
0407         change_mountns(_metadata);
0408 
0409         ASSERT_NE(mkdtemp(binderfs_mntpt), NULL) {
0410             TH_LOG("%s - Failed to create binderfs mountpoint",
0411                 strerror(errno));
0412         }
0413 
0414         ret = mount(NULL, binderfs_mntpt, "binder", 0, 0);
0415         ASSERT_EQ(ret, 0) {
0416             TH_LOG("%s - Failed to mount binderfs, check if CONFIG_ANDROID_BINDERFS is enabled in the running kernel",
0417                 strerror(errno));
0418         }
0419 
0420         for (int i = 0; i < ARRAY_SIZE(fds); i++) {
0421 
0422             snprintf(device_path, sizeof(device_path),
0423                  "%s/binder-control", binderfs_mntpt);
0424             fd = open(device_path, O_RDONLY | O_CLOEXEC);
0425             ASSERT_GE(fd, 0) {
0426                 TH_LOG("%s - Failed to open binder-control device",
0427                     strerror(errno));
0428             }
0429 
0430             memset(&device, 0, sizeof(device));
0431             snprintf(device.name, sizeof(device.name), "%d", i);
0432             ret = ioctl(fd, BINDER_CTL_ADD, &device);
0433             close_prot_errno_disarm(fd);
0434             ASSERT_EQ(ret, 0) {
0435                 TH_LOG("%s - Failed to allocate new binder device",
0436                     strerror(errno));
0437             }
0438 
0439             snprintf(device_path, sizeof(device_path), "%s/%d",
0440                  binderfs_mntpt, i);
0441             fds[i] = open(device_path, O_RDONLY | O_CLOEXEC);
0442             ASSERT_GE(fds[i], 0) {
0443                 TH_LOG("%s - Failed to open binder device", strerror(errno));
0444             }
0445         }
0446 
0447         ret = umount2(binderfs_mntpt, MNT_DETACH);
0448         ASSERT_EQ(ret, 0) {
0449             TH_LOG("%s - Failed to unmount binderfs", strerror(errno));
0450             rmdir(binderfs_mntpt);
0451         }
0452 
0453         nthreads = get_nprocs_conf();
0454         if (nthreads > DEFAULT_THREADS)
0455             nthreads = DEFAULT_THREADS;
0456 
0457         _thread_metadata = _metadata;
0458         pthread_attr_init(&attr);
0459         for (k = 0; k < ARRAY_SIZE(fds); k++) {
0460             for (i = 0; i < nthreads; i++) {
0461                 ret = pthread_create(&threads[i], &attr, binder_version_thread, INT_TO_PTR(fds[k]));
0462                 if (ret) {
0463                     TH_LOG("%s - Failed to create thread %d",
0464                         strerror(errno), i);
0465                     break;
0466                 }
0467             }
0468 
0469             for (j = 0; j < i; j++) {
0470                 void *fdptr = NULL;
0471 
0472                 ret = pthread_join(threads[j], &fdptr);
0473                 if (ret)
0474                     TH_LOG("%s - Failed to join thread %d for fd %d",
0475                         strerror(errno), j, PTR_TO_INT(fdptr));
0476             }
0477         }
0478         pthread_attr_destroy(&attr);
0479 
0480         for (k = 0; k < ARRAY_SIZE(fds); k++)
0481             close(fds[k]);
0482 
0483         exit(EXIT_SUCCESS);
0484     }
0485 
0486     change_idmaps(_metadata, syncfds, pid);
0487 
0488     ret = wait_for_pid(pid);
0489     ASSERT_EQ(ret, 0) {
0490         TH_LOG("wait_for_pid() failed");
0491     }
0492 }
0493 
0494 TEST(binderfs_test_privileged)
0495 {
0496     if (geteuid() != 0)
0497         SKIP(return, "Tests are not run as root. Skipping privileged tests");
0498 
0499     if (__do_binderfs_test(_metadata))
0500         SKIP(return, "The Android binderfs filesystem is not available");
0501 }
0502 
0503 TEST(binderfs_test_unprivileged)
0504 {
0505     int ret;
0506     int syncfds[2];
0507     pid_t pid;
0508 
0509     ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, syncfds);
0510     ASSERT_EQ(ret, 0) {
0511         TH_LOG("%s - Failed to create socket pair", strerror(errno));
0512     }
0513 
0514     pid = fork();
0515     ASSERT_GE(pid, 0) {
0516         close_prot_errno_disarm(syncfds[0]);
0517         close_prot_errno_disarm(syncfds[1]);
0518         TH_LOG("%s - Failed to fork", strerror(errno));
0519     }
0520 
0521     if (pid == 0) {
0522         change_userns(_metadata, syncfds);
0523         if (__do_binderfs_test(_metadata))
0524             exit(2);
0525         exit(EXIT_SUCCESS);
0526     }
0527 
0528     change_idmaps(_metadata, syncfds, pid);
0529 
0530     ret = wait_for_pid(pid);
0531     if (ret) {
0532         if (ret == 2)
0533             SKIP(return, "The Android binderfs filesystem is not available");
0534         ASSERT_EQ(ret, 0) {
0535             TH_LOG("wait_for_pid() failed");
0536         }
0537     }
0538 }
0539 
0540 TEST_HARNESS_MAIN
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