From patchwork Thu Mar 12 13:15:30 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 11434163 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3478B161F for ; Thu, 12 Mar 2020 13:15:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07CA52072F for ; Thu, 12 Mar 2020 13:15:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727363AbgCLNPv (ORCPT ); Thu, 12 Mar 2020 09:15:51 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:38462 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727001AbgCLNPr (ORCPT ); Thu, 12 Mar 2020 09:15:47 -0400 Received: from ip5f5bf7ec.dynamic.kabel-deutschland.de ([95.91.247.236] helo=wittgenstein.fritz.box) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jCNgc-0007TJ-7z; Thu, 12 Mar 2020 13:15:42 +0000 From: Christian Brauner To: Greg Kroah-Hartman , Todd Kjos Cc: ard.biesheuvel@linaro.org, ardb@kernel.org, john.stultz@linaro.org, keescook@chromium.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, naresh.kamboju@linaro.org, shuah@kernel.org, =?utf-8?q?Arve_Hj=C3=B8nnev=C3=A5g?= , Martijn Coenen , Joel Fernandes , hridya@google.com, kernel-team@android.com, Christian Brauner Subject: [PATCH 2/3] binderfs: add stress test for binderfs binder devices Date: Thu, 12 Mar 2020 14:15:30 +0100 Message-Id: <20200312131531.3615556-2-christian.brauner@ubuntu.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200312131531.3615556-1-christian.brauner@ubuntu.com> References: <20200311105309.1742827-1-christian.brauner@ubuntu.com> <20200312131531.3615556-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org 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 --- .../selftests/filesystems/binderfs/Makefile | 2 +- .../filesystems/binderfs/binderfs_test.c | 416 ++++++++++++++---- 2 files changed, 325 insertions(+), 93 deletions(-) diff --git a/tools/testing/selftests/filesystems/binderfs/Makefile b/tools/testing/selftests/filesystems/binderfs/Makefile index 75315d9ba7a9..8af25ae96049 100644 --- a/tools/testing/selftests/filesystems/binderfs/Makefile +++ b/tools/testing/selftests/filesystems/binderfs/Makefile @@ -1,6 +1,6 @@ # SPDX-License-Identifier: GPL-2.0 -CFLAGS += -I../../../../../usr/include/ +CFLAGS += -I../../../../../usr/include/ -pthread TEST_GEN_PROGS := binderfs_test binderfs_test: binderfs_test.c ../../kselftest.h ../../kselftest_harness.h diff --git a/tools/testing/selftests/filesystems/binderfs/binderfs_test.c b/tools/testing/selftests/filesystems/binderfs/binderfs_test.c index d03ed8eed5eb..313ffad15614 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; +#define DEFAULT_THREADS 4 - return ret; -} +#define PTR_TO_INT(p) ((int)((intptr_t)(p))) +#define INT_TO_PTR(u) ((void *)((intptr_t)(u))) -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); - - ret = write_nointr(fd, buf, count); - if (ret < 0) { - if (allowed_errno && (errno == allowed_errno)) { - close(fd); - return; - } - - 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); +#define log_exit(format, ...) \ + ({ \ + fprintf(stderr, format "\n", ##__VA_ARGS__); \ + exit(EXIT_FAILURE); \ + }) - 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)); - - 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; @@ -143,7 +74,7 @@ static void __do_binderfs_test(void) struct binderfs_device device = { 0 }; struct binder_version version = { 0 }; - change_to_mountns(); + change_mountns(); ret = mkdir("/dev/binderfs", 0755); if (ret < 0) { @@ -254,6 +185,283 @@ static void __do_binderfs_test(void) ksft_inc_pass_cnt(); } +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 }; + + 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(); + + ret = mkdir("/tmp/binderfs", 0755); + if (ret < 0 && errno != EEXIST) + log_exit("%s - Failed to create binderfs mountpoint\n", strerror(errno)); + + ret = mount(NULL, "/tmp/binderfs", "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++) { + char path[4096]; + + fd = open("/tmp/binderfs/binder-control", 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(path, sizeof(path), "/tmp/binderfs/%d", i); + fds[i] = open(path, O_RDONLY | O_CLOEXEC); + if (fds[i] < 0) + log_exit("%s - Failed to open binder device\n", strerror(errno)); + } + + ret = umount2("/tmp/binderfs", MNT_DETACH); + 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) @@ -264,8 +472,32 @@ TEST(binderfs_test_privileged) TEST(binderfs_test_unprivileged) { - change_to_userns(); - __do_binderfs_test(); + int ret; + int syncfds[2]; + pid_t pid; + + 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); + __do_binderfs_test(); + exit(EXIT_SUCCESS); + } + + change_idmaps(syncfds, pid); + + ret = wait_for_pid(pid); + if (ret) + ksft_exit_fail_msg("wait_for_pid() failed"); } TEST_HARNESS_MAIN