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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id w124sm5726643pfd.71.2020.03.12.16.53.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2020 16:53:18 -0700 (PDT) Date: Thu, 12 Mar 2020 16:53:17 -0700 From: Kees Cook To: Christian Brauner Cc: Greg Kroah-Hartman , Todd Kjos , ard.biesheuvel@linaro.org, ardb@kernel.org, john.stultz@linaro.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, naresh.kamboju@linaro.org, shuah@kernel.org, Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Martijn Coenen , Joel Fernandes , hridya@google.com, kernel-team@android.com Subject: Re: [PATCH 2/3] binderfs: add stress test for binderfs binder devices Message-ID: <202003121652.00BBA1D98@keescook> References: <20200311105309.1742827-1-christian.brauner@ubuntu.com> <20200312131531.3615556-1-christian.brauner@ubuntu.com> <20200312131531.3615556-2-christian.brauner@ubuntu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200312131531.3615556-2-christian.brauner@ubuntu.com> Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Thu, Mar 12, 2020 at 02:15:30PM +0100, Christian Brauner wrote: > 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 Do you care about 80-char line limits? (Or does the selftest tree? There are a few in here...) Otherwise, seems reasonable: Reviewed-by: Kees Cook -Kees > --- > .../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 > -- > 2.25.1 > -- Kees Cook