From e48d117436082217a22bee58760f101ae1f48fee Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Fri, 13 Mar 2020 16:24:20 +0100 Subject: binderfs: add stress test for binderfs binder devices This adds a stress test that should hopefully help us catch regressions for [1], [2], and [3]. [1]: 2669b8b0c798 ("binder: prevent UAF for binderfs devices") [2]: f0fe2c0f050d ("binder: prevent UAF for binderfs devices II") [3]: 211b64e4b5b6 ("binderfs: use refcount for binder control devices too") Signed-off-by: Christian Brauner Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/20200313152420.138777-3-christian.brauner@ubuntu.com Signed-off-by: Greg Kroah-Hartman --- .../selftests/filesystems/binderfs/binderfs_test.c | 426 ++++++++++++++++----- 1 file changed, 333 insertions(+), 93 deletions(-) (limited to 'tools/testing/selftests/filesystems/binderfs/binderfs_test.c') diff --git a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c index 818eb49f8125..8a6b507e34a8 100644 --- a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c +++ b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c @@ -3,15 +3,20 @@ #define _GNU_SOURCE #include #include +#include #include #include #include #include #include +#include #include #include +#include #include +#include #include +#include #include #include #include @@ -19,100 +24,26 @@ #include "../../kselftest.h" #include "../../kselftest_harness.h" -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 void write_to_file(const char *filename, const void *buf, size_t count, - int allowed_errno) -{ - int fd, saved_errno; - ssize_t ret; - - fd = open(filename, O_WRONLY | O_CLOEXEC); - if (fd < 0) - ksft_exit_fail_msg("%s - Failed to open file %s\n", - strerror(errno), filename); +#define DEFAULT_THREADS 4 - ret = write_nointr(fd, buf, count); - if (ret < 0) { - if (allowed_errno && (errno == allowed_errno)) { - close(fd); - return; - } +#define PTR_TO_INT(p) ((int)((intptr_t)(p))) +#define INT_TO_PTR(u) ((void *)((intptr_t)(u))) - goto on_error; +#define close_prot_errno_disarm(fd) \ + if (fd >= 0) { \ + int _e_ = errno; \ + close(fd); \ + errno = _e_; \ + fd = -EBADF; \ } - if ((size_t)ret != count) - goto on_error; - - close(fd); - return; - -on_error: - saved_errno = errno; - close(fd); - errno = saved_errno; - - if (ret < 0) - ksft_exit_fail_msg("%s - Failed to write to file %s\n", - strerror(errno), filename); - - ksft_exit_fail_msg("Failed to write to file %s\n", filename); -} - -static void change_to_userns(void) -{ - int ret; - uid_t uid; - gid_t gid; - /* {g,u}id_map files only allow a max of 4096 bytes written to them */ - char idmap[4096]; - - uid = getuid(); - gid = getgid(); - - ret = unshare(CLONE_NEWUSER); - if (ret < 0) - ksft_exit_fail_msg("%s - Failed to unshare user namespace\n", - strerror(errno)); - - write_to_file("/proc/self/setgroups", "deny", strlen("deny"), ENOENT); - - ret = snprintf(idmap, sizeof(idmap), "0 %d 1", uid); - if (ret < 0 || (size_t)ret >= sizeof(idmap)) - ksft_exit_fail_msg("%s - Failed to prepare uid mapping\n", - strerror(errno)); - - write_to_file("/proc/self/uid_map", idmap, strlen(idmap), 0); - - ret = snprintf(idmap, sizeof(idmap), "0 %d 1", gid); - if (ret < 0 || (size_t)ret >= sizeof(idmap)) - ksft_exit_fail_msg("%s - Failed to prepare uid mapping\n", - strerror(errno)); - - write_to_file("/proc/self/gid_map", idmap, strlen(idmap), 0); - - ret = setgid(0); - if (ret) - ksft_exit_fail_msg("%s - Failed to setgid(0)\n", - strerror(errno)); +#define log_exit(format, ...) \ + ({ \ + fprintf(stderr, format "\n", ##__VA_ARGS__); \ + exit(EXIT_FAILURE); \ + }) - ret = setuid(0); - if (ret) - ksft_exit_fail_msg("%s - Failed to setgid(0)\n", - strerror(errno)); -} - -static void change_to_mountns(void) +static void change_mountns(void) { int ret; @@ -144,7 +75,7 @@ static int __do_binderfs_test(void) char binderfs_mntpt[] = P_tmpdir "/binderfs_XXXXXX", device_path[sizeof(P_tmpdir "/binderfs_XXXXXX/") + BINDERFS_MAX_NAME]; - change_to_mountns(); + change_mountns(); if (!mkdtemp(binderfs_mntpt)) ksft_exit_fail_msg( @@ -253,6 +184,288 @@ on_error: 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) @@ -264,10 +477,37 @@ TEST(binderfs_test_privileged) TEST(binderfs_test_unprivileged) { - change_to_userns(); + int ret; + int syncfds[2]; + pid_t pid; - if (__do_binderfs_test() == 1) - XFAIL(return, "The Android binderfs filesystem is not available"); + 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 -- cgit v1.2.3-59-g8ed1b